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Richmond Metro/Hampton Roads Discussion


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9 minutes ago, eaglesin2011 said:

Ha there is already is a nice coating of ice/snow on almost all of the trees....This is why it's not going to take much to cause issues... That DT guy gets way to wrapped up in the modles ..

Anyone with half a brain can see if we get frozen precip on what has already fallen it will cause issues..

 

I think he’s down playing getting that much ice because some models are showing temps at 32 for some areas so will be close. First ever ice storm warning issued by Wakefield and they are usually conservative so they must see this as a significant event 

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13 minutes ago, RVASnowLover said:

I think he’s down playing getting that much ice because some models are showing temps at 32 for some areas so will be close. First ever ice storm warning issued by Wakefield and they are usually conservative so they must see this as a significant event 

Even if that's the case... light plain rain, could also put weight on the limbs that already snow covered at first...

To me....if there wasn't already snow on my of the lines and limbs, it wouldn't be that big of deal.. But there is... 

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1 minute ago, eaglesin2011 said:

Even if that's the case light plain rain could also put weight on some limbs that already snow covered at first...

To me if there wasn't already snow on my of the lines and limbs it wouldn't be that big of deal.. But there is... 

I agree. Not sure why he’s downplaying it 

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1 hour ago, RVASnowLover said:

I read that too and it confused me. Not sure what data he’s looking at. Almost all the short range models are showing at least .25 of ice 

The guy ends up being like some weird mad scientist or something sometimes. He feels like he got burned by the European and other models in Europe the last couple weeks so now he just thinks everything is a nonevent. It’s very strange. 

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11 minutes ago, wasnow215 said:

The guy ends up being like some weird mad scientist or something sometimes. He feels like he got burned by the European and other models in Europe the last couple weeks so now he just thinks everything is a nonevent. It’s very strange. 

Yeah ever since the model let him down and he got burned by it it’s like he’s angry at the models now and doesn’t want to trust them. Now he’s not saying there won’t be ice but he is downplaying the ice storm warning 

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Just now, wasnow215 said:

Also 18z gfs colder during freezing rain than 12z. That’s the thing also. Some of the places north and west of Richmond proper could get a little less QPF but could be two or 3° colder than those south and east even though they are still freezing. This is going to be a problem

Agreed. And Wakefield is all in. 

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February 12, 2021

this Friday afternoon

510 PM EST

 

Quite an interesting event coming up!!  Here's what the latest forecast models from Friday show:

Both of the higher definition forecast models indicate this SHOULD remain mostly a FREEZING RAIN event, in their hour-by-hour indications.

This morning's NAM MOS vs. GFS MOS had a discrepancy in their Saturday afternoon temperatures, whereby Nam kept FREEZING TEMPS at 32°, and GFS MOS went ABOVE freezing to 33° at 1 PM onward in Richmond.  

HOWEVER.... newest GFS LAMP guidance from 21Z this afternoon is REVISING these hour-by-hour Saturday AFTERNOON temperatures DOWNWARD, indicating a temperature between 30° - 32° from 7 AM to 4 PM Saturday, through the afternoon.

Looking at the forecast precipitation TYPE.... All models I reviewed are unanimous at pointing towards freezing rain, and ICING for the Richmond area.  I do think there will be some periods of SLEET or ice pellets mixed in, and in any outlying areas, where temperatures hover at 33°, then that will yield a cold rain, at a surface temp of 33°, and above.

The amounts rendered are the following:

FREEZING RAIN / ICE amounts for Richmond --

HRRR --  18Z Fri fcst iteration -->>  0.31" of ice, (freezing rain).  TIMING  3 AM Saturday -- 7 PM Saturday night

GFS -- 12Z Fri. fcst -->>  0.46" of ice; freezing rain ;  Timing  3 AM Saturday thru 10 PM Saturday night

GFS --  18Z Fri. fcst -->>  0.26" of ice; freezing rain

WRF --  12Z Fri. fcst -->>  0.56" of ice; freezing rain ; TIMING  4 AM Saturday -- 9 PM Saturday night.

NAM --  12z Fri. fcst -->>  0.37" of ice; freezing rain;  TIMING 1 AM Saturday -- 7 AM Sunday.   (That's stretching it!)

NAM -- 18z Fri. fcst -->>  0.44" of ice, freezing rain

 

This yields an AVERAGE consensus of:  0.4"  (4/10").  That is significant icing which will topple trees & tree branches, and cause power lines to sag.  It is also enough significant ICING to completely CRIPPLE & DISABLE the entire road infrastructure, both secondary roads and primary roads.  I can't emphasize enough to STAY OFF the MOTORWAYS, and avoid driving, starting late tonight, through all of Saturday, Saturday night & Sunday morning.

 

The fortunate GOOD news out of this is that WIND SPEED forecasts are expected to REMAIN BELOW 15 mph.

On the ice damage index, very damaging ice storms occur when WIND SPEEDS GET OVER 15 mph, and winds are forecast to stay below that.

 

Not to let your guard down, though, because lessons learned from the Dallas interstate 75 -100 car pile-up occurred in only light icing.  When I checked back at all the observations at the 3 airports in Dallas - Ft. Worth, Dallas Love Field's ICE ACCRETION sensor ONLY RECORDED just 0.08" of ice accumulation ; LESS than 1/10", but still tragedy of lost control of vehicles occurred so early in the morning on a bridge pitched at a slight decline was enough to send chaos through the air.  Also, yesterday, storm reports in Central Texas near Austin, during their ice storm showed surrounding communities of 40,000 left with NO POWER, when icing of 1/4" to 1/2" was encountered yesterday there.

So now, just think about the STEEP & ARCHED curvature to the infrastructure INSIDE the Richmond city limits on Interstates 64 and 95.  Everyone should AVOID travelling on the roads, period.  Just think of that infamous "stay-at-home" order you'd seen issued a little less than a year ago, and let this ICING event from yesterday in Dallas, be a reminder for tomorrow, in Richmond & surround areas, to STAY OFF THE ROADS altogether, from EARLY Saturday morning, all day Saturday, Saturday night & Sunday morning.

Bridges, hills & curves on the roads are especially dangerous, and Richmond's got plenty of them.  Just stay at home and don't drive, from Saturday morning through Sunday morning.

 

How to inspect the icing??   Go look at THIN tree branches, and feel for the icing.  It should be SLICK.  The tree branches will SQUEAK in the wind or as you pull on them.  Also, chain link fences & antennas on vehicles are other good places to inspect icing.  Many vehicles on their undersides, and on SIDE MIRRORS will often show hanging icicles, if out in exposed weather, away from garages and overhangs.  

 

Here are the corresponding attachments that supplement this writing, supporting the ICING AMOUNT TOTALS....

 

--  cyclogenesis

 

Freezing Rain vs. Rain environment Sat. PM, ARW.JPG

HRRR fcst for Freezing Rain Amounts, from 18Z Fri, for RIC.JPG

GFS LAMP.JPG

Ice Damage Index.JPG

WRF fcst freezing rain amounts, from 12Z Fri.JPG

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16 minutes ago, cyclogenesis said:

February 12, 2021

this Friday afternoon

510 PM EST

 

Quite an interesting event coming up!!  Here's what the latest forecast models from Friday show:

Both of the higher definition forecast models indicate this SHOULD remain mostly a FREEZING RAIN event, in their hour-by-hour indications.

This morning's NAM MOS vs. GFS MOS had a discrepancy in their Saturday afternoon temperatures, whereby Nam kept FREEZING TEMPS at 32°, and GFS MOS went ABOVE freezing to 33° at 1 PM onward in Richmond.  

HOWEVER.... newest GFS LAMP guidance from 21Z this afternoon is REVISING these hour-by-hour Saturday AFTERNOON temperatures DOWNWARD, indicating a temperature between 30° - 32° from 7 AM to 4 PM Saturday, through the afternoon.

Looking at the forecast precipitation TYPE.... All models I reviewed are unanimous at pointing towards freezing rain, and ICING for the Richmond area.  I do think there will be some periods of SLEET or ice pellets mixed in, and in any outlying areas, where temperatures hover at 33°, then that will yield a cold rain, at a surface temp of 33°, and above.

The amounts rendered are the following:

FREEZING RAIN / ICE amounts for Richmond --

HRRR --  18Z Fri fcst iteration -->>  0.31" of ice, (freezing rain).  TIMING  3 AM Saturday -- 7 PM Saturday night

GFS -- 12Z Fri. fcst -->>  0.46" of ice; freezing rain ;  Timing  3 AM Saturday thru 10 PM Saturday night

GFS --  18Z Fri. fcst -->>  0.26" of ice; freezing rain

WRF --  12Z Fri. fcst -->>  0.56" of ice; freezing rain ; TIMING  4 AM Saturday -- 9 PM Saturday night.

NAM --  12z Fri. fcst -->>  0.37" of ice; freezing rain;  TIMING 1 AM Saturday -- 7 AM Sunday.   (That's stretching it!)

NAM -- 18z Fri. fcst -->>  0.44" of ice, freezing rain

 

This yields an AVERAGE consensus of:  0.4"  (4/10").  That is significant icing which will topple trees & tree branches, and cause power lines to sag.  It is also enough significant ICING to completely CRIPPLE & DISABLE the entire road infrastructure, both secondary roads and primary roads.  I can't emphasize enough to STAY OFF the MOTORWAYS, and avoid driving, starting late tonight, through all of Saturday, Saturday night & Sunday morning.

 

The fortunate GOOD news out of this is that WIND SPEED forecasts are expected to REMAIN BELOW 15 mph.

On the ice damage index, very damaging ice storms occur when WIND SPEEDS GET OVER 15 mph, and winds are forecast to stay below that.

 

Not to let your guard down, though, because lessons learned from the Dallas interstate 75 -100 car pile-up occurred in only light icing.  When I checked back at all the observations at the 3 airports in Dallas - Ft. Worth, Dallas Love Field's ICE ACCRETION sensor ONLY RECORDED just 0.08" of ice accumulation ; LESS than 1/10", but still tragedy of lost control of vehicles occurred so early in the morning on a bridge pitched at a slight decline was enough to send chaos through the air.  Also, yesterday, storm reports in Central Texas near Austin, during their ice storm showed surrounding communities of 40,000 left with NO POWER, when icing of 1/4" to 1/2" was encountered yesterday there.

So now, just think about the STEEP & ARCHED curvature to the infrastructure INSIDE the Richmond city limits on Interstates 64 and 95.  Everyone should AVOID travelling on the roads, period.  Just think of that infamous "stay-at-home" order you'd seen issued a little less than a year ago, and let this ICING event from yesterday in Dallas, be a reminder for tomorrow, in Richmond & surround areas, to STAY OFF THE ROADS altogether, from EARLY Saturday morning, all day Saturday, Saturday night & Sunday morning.

Bridges, hills & curves on the roads are especially dangerous, and Richmond's got plenty of them.  Just stay at home and don't drive, from Saturday morning through Sunday morning.

 

How to inspect the icing??   Go look at THIN tree branches, and feel for the icing.  It should be SLICK.  The tree branches will SQUEAK in the wind or as you pull on them.  Also, chain link fences & antennas on vehicles are other good places to inspect icing.  Many vehicles on their undersides, and on SIDE MIRRORS will often show hanging icicles, if out in exposed weather, away from garages and overhangs.  

 

Here are the corresponding attachments that supplement this writing, supporting the ICING AMOUNT TOTALS....

 

--  cyclogenesis

 

Freezing Rain vs. Rain environment Sat. PM, ARW.JPG

HRRR fcst for Freezing Rain Amounts, from 18Z Fri, for RIC.JPG

GFS LAMP.JPG

Ice Damage Index.JPG

WRF fcst freezing rain amounts, from 12Z Fri.JPG

My man! Thanks!

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17 minutes ago, cyclogenesis said:

February 12, 2021

this Friday afternoon

510 PM EST

 

Quite an interesting event coming up!!  Here's what the latest forecast models from Friday show:

Both of the higher definition forecast models indicate this SHOULD remain mostly a FREEZING RAIN event, in their hour-by-hour indications.

This morning's NAM MOS vs. GFS MOS had a discrepancy in their Saturday afternoon temperatures, whereby Nam kept FREEZING TEMPS at 32°, and GFS MOS went ABOVE freezing to 33° at 1 PM onward in Richmond.  

HOWEVER.... newest GFS LAMP guidance from 21Z this afternoon is REVISING these hour-by-hour Saturday AFTERNOON temperatures DOWNWARD, indicating a temperature between 30° - 32° from 7 AM to 4 PM Saturday, through the afternoon.

Looking at the forecast precipitation TYPE.... All models I reviewed are unanimous at pointing towards freezing rain, and ICING for the Richmond area.  I do think there will be some periods of SLEET or ice pellets mixed in, and in any outlying areas, where temperatures hover at 33°, then that will yield a cold rain, at a surface temp of 33°, and above.

The amounts rendered are the following:

FREEZING RAIN / ICE amounts for Richmond --

HRRR --  18Z Fri fcst iteration -->>  0.31" of ice, (freezing rain).  TIMING  3 AM Saturday -- 7 PM Saturday night

GFS -- 12Z Fri. fcst -->>  0.46" of ice; freezing rain ;  Timing  3 AM Saturday thru 10 PM Saturday night

GFS --  18Z Fri. fcst -->>  0.26" of ice; freezing rain

WRF --  12Z Fri. fcst -->>  0.56" of ice; freezing rain ; TIMING  4 AM Saturday -- 9 PM Saturday night.

NAM --  12z Fri. fcst -->>  0.37" of ice; freezing rain;  TIMING 1 AM Saturday -- 7 AM Sunday.   (That's stretching it!)

NAM -- 18z Fri. fcst -->>  0.44" of ice, freezing rain

 

This yields an AVERAGE consensus of:  0.4"  (4/10").  That is significant icing which will topple trees & tree branches, and cause power lines to sag.  It is also enough significant ICING to completely CRIPPLE & DISABLE the entire road infrastructure, both secondary roads and primary roads.  I can't emphasize enough to STAY OFF the MOTORWAYS, and avoid driving, starting late tonight, through all of Saturday, Saturday night & Sunday morning.

 

The fortunate GOOD news out of this is that WIND SPEED forecasts are expected to REMAIN BELOW 15 mph.

On the ice damage index, very damaging ice storms occur when WIND SPEEDS GET OVER 15 mph, and winds are forecast to stay below that.

 

Not to let your guard down, though, because lessons learned from the Dallas interstate 75 -100 car pile-up occurred in only light icing.  When I checked back at all the observations at the 3 airports in Dallas - Ft. Worth, Dallas Love Field's ICE ACCRETION sensor ONLY RECORDED just 0.08" of ice accumulation ; LESS than 1/10", but still tragedy of lost control of vehicles occurred so early in the morning on a bridge pitched at a slight decline was enough to send chaos through the air.  Also, yesterday, storm reports in Central Texas near Austin, during their ice storm showed surrounding communities of 40,000 left with NO POWER, when icing of 1/4" to 1/2" was encountered yesterday there.

So now, just think about the STEEP & ARCHED curvature to the infrastructure INSIDE the Richmond city limits on Interstates 64 and 95.  Everyone should AVOID travelling on the roads, period.  Just think of that infamous "stay-at-home" order you'd seen issued a little less than a year ago, and let this ICING event from yesterday in Dallas, be a reminder for tomorrow, in Richmond & surround areas, to STAY OFF THE ROADS altogether, from EARLY Saturday morning, all day Saturday, Saturday night & Sunday morning.

Bridges, hills & curves on the roads are especially dangerous, and Richmond's got plenty of them.  Just stay at home and don't drive, from Saturday morning through Sunday morning.

 

How to inspect the icing??   Go look at THIN tree branches, and feel for the icing.  It should be SLICK.  The tree branches will SQUEAK in the wind or as you pull on them.  Also, chain link fences & antennas on vehicles are other good places to inspect icing.  Many vehicles on their undersides, and on SIDE MIRRORS will often show hanging icicles.  

 

Here are the corresponding attachments that supplement this writing, supporting the ICING AMOUNT TOTALS....

 

--  cyclogenesis

 

Freezing Rain vs. Rain environment Sat. PM, ARW.JPG

HRRR fcst for Freezing Rain Amounts, from 18Z Fri, for RIC.JPG

GFS LAMP.JPG

Ice Damage Index.JPG

WRF fcst freezing rain amounts, from 12Z Fri.JPG

I remember living in NYC I believe it was 1994 and even tho temps rose above 32° it took awhile for the freezing rain to become “rain” on the actual surfaces because it was landing on ice that had already accumulated. So I think it may take a little while on Sunday to get back to normal even if temps go 33° or 34°.

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23 minutes ago, cyclogenesis said:

February 12, 2021

this Friday afternoon

510 PM EST

 

Quite an interesting event coming up!!  Here's what the latest forecast models from Friday show:

Both of the higher definition forecast models indicate this SHOULD remain mostly a FREEZING RAIN event, in their hour-by-hour indications.

This morning's NAM MOS vs. GFS MOS had a discrepancy in their Saturday afternoon temperatures, whereby Nam kept FREEZING TEMPS at 32°, and GFS MOS went ABOVE freezing to 33° at 1 PM onward in Richmond.  

HOWEVER.... newest GFS LAMP guidance from 21Z this afternoon is REVISING these hour-by-hour Saturday AFTERNOON temperatures DOWNWARD, indicating a temperature between 30° - 32° from 7 AM to 4 PM Saturday, through the afternoon.

Looking at the forecast precipitation TYPE.... All models I reviewed are unanimous at pointing towards freezing rain, and ICING for the Richmond area.  I do think there will be some periods of SLEET or ice pellets mixed in, and in any outlying areas, where temperatures hover at 33°, then that will yield a cold rain, at a surface temp of 33°, and above.

The amounts rendered are the following:

FREEZING RAIN / ICE amounts for Richmond --

HRRR --  18Z Fri fcst iteration -->>  0.31" of ice, (freezing rain).  TIMING  3 AM Saturday -- 7 PM Saturday night

GFS -- 12Z Fri. fcst -->>  0.46" of ice; freezing rain ;  Timing  3 AM Saturday thru 10 PM Saturday night

GFS --  18Z Fri. fcst -->>  0.26" of ice; freezing rain

WRF --  12Z Fri. fcst -->>  0.56" of ice; freezing rain ; TIMING  4 AM Saturday -- 9 PM Saturday night.

NAM --  12z Fri. fcst -->>  0.37" of ice; freezing rain;  TIMING 1 AM Saturday -- 7 AM Sunday.   (That's stretching it!)

NAM -- 18z Fri. fcst -->>  0.44" of ice, freezing rain

 

This yields an AVERAGE consensus of:  0.4"  (4/10").  That is significant icing which will topple trees & tree branches, and cause power lines to sag.  It is also enough significant ICING to completely CRIPPLE & DISABLE the entire road infrastructure, both secondary roads and primary roads.  I can't emphasize enough to STAY OFF the MOTORWAYS, and avoid driving, starting late tonight, through all of Saturday, Saturday night & Sunday morning.

 

The fortunate GOOD news out of this is that WIND SPEED forecasts are expected to REMAIN BELOW 15 mph.

On the ice damage index, very damaging ice storms occur when WIND SPEEDS GET OVER 15 mph, and winds are forecast to stay below that.

 

Not to let your guard down, though, because lessons learned from the Dallas interstate 75 -100 car pile-up occurred in only light icing.  When I checked back at all the observations at the 3 airports in Dallas - Ft. Worth, Dallas Love Field's ICE ACCRETION sensor ONLY RECORDED just 0.08" of ice accumulation ; LESS than 1/10", but still tragedy of lost control of vehicles occurred so early in the morning on a bridge pitched at a slight decline was enough to send chaos through the air.  Also, yesterday, storm reports in Central Texas near Austin, during their ice storm showed surrounding communities of 40,000 left with NO POWER, when icing of 1/4" to 1/2" was encountered yesterday there.

So now, just think about the STEEP & ARCHED curvature to the infrastructure INSIDE the Richmond city limits on Interstates 64 and 95.  Everyone should AVOID travelling on the roads, period.  Just think of that infamous "stay-at-home" order you'd seen issued a little less than a year ago, and let this ICING event from yesterday in Dallas, be a reminder for tomorrow, in Richmond & surround areas, to STAY OFF THE ROADS altogether, from EARLY Saturday morning, all day Saturday, Saturday night & Sunday morning.

Bridges, hills & curves on the roads are especially dangerous, and Richmond's got plenty of them.  Just stay at home and don't drive, from Saturday morning through Sunday morning.

 

How to inspect the icing??   Go look at THIN tree branches, and feel for the icing.  It should be SLICK.  The tree branches will SQUEAK in the wind or as you pull on them.  Also, chain link fences & antennas on vehicles are other good places to inspect icing.  Many vehicles on their undersides, and on SIDE MIRRORS will often show hanging icicles, if out in exposed weather, away from garages and overhangs.  

 

Here are the corresponding attachments that supplement this writing, supporting the ICING AMOUNT TOTALS....

 

--  cyclogenesis

This is great, I was wondering when you were going to come back in here, been a while! 

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It should be noted that the Ice Storm Warning is a product that didn't exist back when the AKQ WFO last needed it. NWS creates new products and discontinues others based on feedback from the public. For instance, Blizzard Watch and Freeze Watch, along with others, are no longer used as of a year or two ago. So, just because AKQ is using it for the first time, doesn't mean they wouldn't have back in 1998, 1994, etc.

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14 minutes ago, wasnow215 said:

I remember living in NYC I believe it was 1994 and even tho temps rose above 32° it took awhile for the freezing rain to become “rain” on the actual surfaces because it was landing on ice that had already accumulated. So I think it may take a little while on Sunday to get back to normal even if temps go 33° or 34°.

 

19 minutes ago, Rvarookie said:

My man! Thanks!

 

wasnow215  ---   Yes, you are correct; it  WILL  take a while on Sunday to get back to normal.   In fact, to the casual onlooker, it may "appear" as though it's simply raining, but after a while, there will be ICE ACCRETION that collects.  The MOST DAMAGING effects will be to anyone out on the road.  People can NOT take a chance with this one.  Just stay at home, and don't risk mangling your vehicle off the roadway or ramming in to someone else.    Although there could be some POWER OUTAGES in spots across the metro Richmond area, and especially outer-lying rural areas, the PRIMARY DANGERS are outside on the road way.  Avoid driving altogether, and call-off from work.  It's what I had to do in Dallas back in the 1990s, during an ice storm there.  

As another appended note:   BE ESPECIALLY CAREFUL walking outside.  A BAD SLIP & FALL DOWN, especially to the elderly, could send a person in the HOSPITAL, from SLICK, ICY sidewalks or stairways, either up or down from an apartment or home.

Take this time NOW to SAND or SALT your outside walkways & sidewalks from your HOME, if you even need to walk outside.    

So, ya, I'd say wait until LATE Sunday afternoon, when temperatures get WELL-ABOVE freezing to go out again.  Any LAST MINUTE preparations to get food, or run errands needs to be RUSHED to COMPLETION BEFORE 12 AM Midnight tonight, on Friday night.  

 

--  cyclogenesis

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8 minutes ago, RIC Airport said:

This is great, I was wondering when you were going to come back in here, been a while! 

RIC Airport --   I moved out of Virginia in June 2020.  I moved down South, to the Gulf coast, so it'll be a rare occurrence that I write again, on any future events, for Richmond, beyond this one.

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4 minutes ago, cyclogenesis said:

RIC Airport --   I moved out of Virginia in June 2020.  I moved down South, to the Gulf coast, so it'll be a rare occurrence that I write again, on any future events, for Richmond, beyond this one.

Ah, that explains it. Well, feel free to chime in when you can the next time we get a notable weather event. Hope you like where you're living now. 

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7 hours ago, RIC Airport said:

RIC has now gone 752 consecutive days with high temperatures above 32°F. This is the longest stretch on record.

The last day to NOT rise above freezing was January 31, 2019 when the high temperature was 32°F.  It will be interesting to see whether today or tomorrow can stay below freezing at the airport to end this streak. 

Screenshot 2021-02-12 103041.jpg

By the way, the average number of days with subfreezing highs for the 1991-2020 period of record is 5 days. 2020 and 2012 were the only two years with NO subfreezing highs. 

The high at RIC was only 31°F, which happened at 2:06am. So the record streak above freezing is over!

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February 12, 2021

this Friday night

856 PM EST

 

So, now that everyone know WHAT to expect and WHEN to expect it, I thought I’d open with the topic of UNDERSTANDING the MECHANICS of what’s going on here.

First, we take a LOOK at the mechanics in play:  How does the TEMPERATURE profile change WITH HEIGHT?  That tells the KEY as to what precipitation type you’re going to get.  That is what this attached visual graphic I’m producing here details.

The pink-traced line is a forecast temperature that goes UPWARD in HEIGHT, centered at 7 AM on Saturday morning, over Richmond, Virginia, just after the start of the freezing rain event.

The background of thin, black lines is the skewed temperature scale that angles right-ward with height.

If the pink-traced line STAYS LEFT of the 0°C thin, black line, this means the temperature stays freezing all the way upward in height, if the pink traced line LIES to the LEFT of the 0°C thin black line.  In such a case, precipitation would fall as snow.  If the pink-traced line STAYS RIGHT of the 0°C thin, black line all the way up, staying RIGHT of it, then it all falls as rain. 

But what happens if the pink-traced, (forecast temperature line), crosses over between above-freezing and below freezing??   Then, it can either be FREEZING RAIN, (in this case for tomorrow), or in other times as sleet or even snow some other times.

The DEPTH of the above-freezing layer aloft and the MAGNITUDE, of HOW WARM dictate as to whether it converts to freezing rain, sleet, or snow. 

For tomorrow’s case in Richmond, VA on Feb. 13th, I’ve calculated the ABOVE-FREEZING LAYER DEPTH to be 1,650 meters, which is about 5,414 feet in DEPTH, ALOFT, of above-freezing temperatures.  (Refer to my visual attachment of the Skew-T).

From ground level, up to 1,935 ft, temperatures are forecast to STAY either BELOW FREEZING or right at Freezing, 32°F.  Then between 1,935 ft altitude on upward to ~ 7,349 ft, the temperature goes ABOVE freezing, with the WARMEST peaking at 4°C to 4.5°C between the 900 mb to 850 mb layer about 12 Noon, midday.  This layer depth of above-freezing temperatures neither grows nor shrinks in depth throughout the day Saturday, except that the magnitude gets just a little warmer at the 900 to 850 mb layer. 

So what happens??  Take it from the top!  Falls first as snow, ABOVE 7,500 ft, then begins melting to liquid cold rain in that 775 mb to 950 mb layer of ABOVE-FREEZING temperatures, between 7,349 ft to 1,935 ft.  (Refer to my visual attachment of the Skew-T). Then in that last 1,900 ft down to the surface it HITS on contact as freezing rain, SO LONG AS THE SURFACE temperature stays either BELOW or AT 32°.  (But why doesn’t it freeze back to snow or sleet between 1,900 ft and the surface??)  Great question!  The problem here is that the warm layer depth is so deep whose magnitude gets as warm as 4°C, that there isn’t time for the rain drops to freeze back to snow.  If the boundary layer temperature was WAY BELOW freezing in the lowest 2,000 ft, as in like mid 20’s or lower, then MAYBE you could get some sleet out of it.  There is a pronounced layer right at 975 mb that gets briefly near there, so it’s possible to get a few ice pellets, but predominantly will be freezing rain. 

(What determines freezing rain in this case??)   So, the depth measurement of the above-freezing layer is about 1,650 meters, and the AVERAGE temperature within that above-freezing layer is running about 1.7°C, almost 2°C.  (Refer to my visual attachment of the Skew-T). It does briefly peak to as warm as 4.0 to 4.5°C around midday and afternoon Saturday.  With that depth & mean virtual temperature on the Tau Technique, at 1,650 meters & 1.7°C, this equates to a translation of FREEZING RAIN as the dominant type of precipitation, AS LONG AS YOUR SURFACE temperature is at least 32° or below.  As soon as the temperature flips to 33° and above, then the jig is up!  All the modeling data that I reviewed from Friday points to this being mostly an icing, freezing rain event; however you may occasionally observe some liquid rain mixed in, especially in the afternoon, and some ice pellets, or sleet during the morning.  Mostly, should be rain freezing on contact, and may take time to see the ice accretion build by late morning.

That RED-SHADED AREA is that layer DEPTH that is ABOVE-FREEZING, located between an altitude of 1,935 ft and 7,349 ft above ground level.   

--  cyclogenesis

mechanics.jpg

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13 minutes ago, cyclogenesis said:

February 12, 2021

this Friday night

856 PM EST

 

So, now that everyone know WHAT to expect and WHEN to expect it, I thought I’d open with the topic of UNDERSTANDING the MECHANICS of what’s going on here.

First, we take a LOOK at the mechanics in play:  How does the TEMPERATURE profile change WITH HEIGHT?  That tells the KEY as to what precipitation type you’re going to get.  That is what this attached visual graphic I’m producing here details.

The pink-traced line is a forecast temperature that goes UPWARD in HEIGHT, centered at 7 AM on Saturday morning, over Richmond, Virginia, just after the start of the freezing rain event.

The background of thin, black lines is the skewed temperature scale that angles right-ward with height.

If the pink-traced line STAYS LEFT of the 0°C thin, black line, this means the temperature stays freezing all the way upward in height, if the pink traced line LIES to the LEFT of the 0°C thin black line.  In such a case, precipitation would fall as snow.  If the pink-traced line STAYS RIGHT of the 0°C thin, black line all the way up, staying RIGHT of it, then it all falls as rain. 

But what happens if the pink-traced, (forecast temperature line), crosses over between above-freezing and below freezing??   Then, it can either be FREEZING RAIN, (in this case for tomorrow), or in other times as sleet or even snow some other times.

The DEPTH of the above-freezing layer aloft and the MAGNITUDE, of HOW WARM dictate as to whether it converts to freezing rain, sleet, or snow. 

For tomorrow’s case in Richmond, VA on Feb. 13th, I’ve calculated the ABOVE-FREEZING LAYER DEPTH to be 1,650 meters, which is about 5,414 feet in DEPTH, ALOFT, of above-freezing temperatures.  (Refer to my visual attachment of the Skew-T).

From ground level, up to 1,935 ft, temperatures are forecast to STAY either BELOW FREEZING or right at Freezing, 32°F.  Then between 1,935 ft altitude on upward to ~ 7,349 ft, the temperature goes ABOVE freezing, with the WARMEST peaking at 4°C to 4.5°C between the 900 mb to 850 mb layer about 12 Noon, midday.  This layer depth of above-freezing temperatures neither grows nor shrinks in depth throughout the day Saturday, except that the magnitude gets just a little warmer at the 900 to 850 mb layer. 

So what happens??  Take it from the top!  Falls first as snow, ABOVE 7,500 ft, then begins melting to liquid cold rain in that 775 mb to 950 mb layer of ABOVE-FREEZING temperatures, between 7,349 ft to 1,935 ft.  (Refer to my visual attachment of the Skew-T). Then in that last 1,900 ft down to the surface it HITS on contact as freezing rain, SO LONG AS THE SURFACE temperature stays either BELOW or AT 32°.  (But why doesn’t it freeze back to snow or sleet between 1,900 ft and the surface??)  Great question!  The problem here is that the warm layer depth is so deep whose magnitude gets as warm as 4°C, that there isn’t time for the rain drops to freeze back to snow.  If the boundary layer temperature was WAY BELOW freezing in the lowest 2,000 ft, as in like mid 20’s or lower, then MAYBE you could get some sleet out of it.  There is a pronounced layer right at 975 mb that gets briefly near there, so it’s possible to get a few ice pellets, but predominantly will be freezing rain. 

(What determines freezing rain in this case??)   So, the depth measurement of the above-freezing layer is about 1,650 meters, and the AVERAGE temperature within that above-freezing layer is running about 1.7°C, almost 2°C.  (Refer to my visual attachment of the Skew-T). It does briefly peak to as warm as 4.0 to 4.5°C around midday and afternoon Saturday.  With that depth & mean virtual temperature on the Tau Technique, at 1,650 meters & 1.7°C, this equates to a translation of FREEZING RAIN as the dominant type of precipitation, AS LONG AS YOUR SURFACE temperature is at least 32° or below.  As soon as the temperature flips to 33° and above, then the jig is up!  All the modeling data that I reviewed from Friday points to this being mostly an icing, freezing rain event; however you may occasionally observe some liquid rain mixed in, especially in the afternoon, and some ice pellets, or sleet during the morning.  Mostly, should be rain freezing on contact, and may take time to see the ice accretion build by late morning.

That RED-SHADED AREA is that layer DEPTH that is ABOVE-FREEZING, located between an altitude of 1,935 ft and 7,349 ft above ground level.   

--  cyclogenesis

mechanics.jpg

Thanks for dropping the knowledge! Awesome write up 

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