March 20-21 Potential - STORM MODE THREAD

[snowmagnet]

23 minutes ago, psuhoffman said:

Stop it with ground temp talk. We have had significant snowstorms the day after it was 70 before. We have had accumulating snow the last week of march several times. Colorado has the same radiation as us. Denver is at our latitude and they get big snows in early fall when it's been 75 the whole week before and soil temps are above 50*. This is the dumbest thing ever. Knock it off. 

I said that in banter.  We have had some of our best storms s day or 2 after it was 60 or 70. 

[BTRWx's Thanks Giving]

1 minute ago, snowmagnet said:

I said that in banter.  We have had some of our best storms s day or 2 after it was 60 or 70. 

I think the original argument was how low ground temps were relative to the air with the March we've had so far overall.

[clskinsfan]

Pretty interesting bufkit data from the 18Z runs. The snow ratio's once the coastal kicks off are really good.Like 12-13 to 1. I dont know how accurate that is. But it could pile up very quickly in the heavier bands with ratio's like that.

[eurojosh]

1 minute ago, clskinsfan said:

Pretty interesting bufkit data from the 18Z runs. The snow ratio's once the coastal kicks off are really good.Like 12-13 to 1. I dont know how accurate that is. But it could pile up very quickly in the heavier bands with ratio's like that.

Correct me if I'm wrong, but while the models account for temp, dps, saturation, etc, they don't account for sun angle.  At the risk of getting told that's a cliche, I wouldn't expect those sorts of ratios on accumulation when the sun is at this angle even through the clouds.

[clskinsfan]

1 minute ago, eurojosh said:

Correct me if I'm wrong, but while the models account for temp, dps, saturation, etc, they don't account for sun angle.  At the risk of getting told that's a cliche, I wouldn't expect those sorts of ratios on accumulation when the sun is at this angle even through the clouds.

I honestly dont know? I would think as long as the lift and temps are good than the ratio's would be as well. But I am sure one of the more educated minds in here will let us know.

[RDM]

Things are starting to get dynamic in the mid-west and south.  Nrn half of Alabama is under a tornado watch that extends up into central TN.  T-Strms are exploding along the fetch from the gulf.

[snowmagnet]

6 minutes ago, clskinsfan said:

Pretty interesting bufkit data from the 18Z runs. The snow ratio's once the coastal kicks off are really good.Like 12-13 to 1. I dont know how accurate that is. But it could pile up very quickly in the heavier bands with ratio's like that.

Bob explained the other day that the dynamics of a closed Low on the coast can lead to very high snow ratios.  So it may be accurate.  

[BTRWx's Thanks Giving]

3 minutes ago, snowmagnet said:

Bob explained the other day that the dynamics of a closed Low on the coast can lead to very high snow ratios.  So it may be accurate.  

for a time at least

[BristowWx]

6 minutes ago, eurojosh said:

Correct me if I'm wrong, but while the models account for temp, dps, saturation, etc, they don't account for sun angle.  At the risk of getting told that's a cliche, I wouldn't expect those sorts of ratios on accumulation when the sun is at this angle even through the clouds.

Sun angle impacts how long the snow will stay on the ground after it stops but has nothing to do with ratios.  That’s a function of the atmosphere.  Below freezing is below freezing.  We have issues with ratios in January.  Not worth the mental energy to fret about that.  We can’t change the calendar.  

[Maestrobjwa]

1 minute ago, snowmagnet said:

Bob explained the other day that the dynamics of a closed Low on the coast can lead to very high snow ratios.  So it may be accurate.  

 

10 minutes ago, clskinsfan said:

Pretty interesting bufkit data from the 18Z runs. The snow ratio's once the coastal kicks off are really good.Like 12-13 to 1. I dont know how accurate that is. But it could pile up very quickly in the heavier bands with ratio's like that.

Wondering if we should start a thread looking at the previous March snowstorms and how those HECS-level accumulations were achieved...If nothing else, those storms show that it CAN happen under the rigjt dynamics!

[Cobalt]

Just now, Maestrobjwa said:

 

Wondering if we should start a thread looking at the previous March snowstorms and how those HECS-level accumulations were achieved...If nothing else, those storms show that it CAN happen under the rigjt dynamics!

This is a great idea! 

[yoda]

Upgrade from WWA to WSW

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
755 PM EDT Mon Mar 19 2018

MDZ502-WVZ050-055-502-504-200800-
/O.UPG.KLWX.WW.Y.0018.180320T1000Z-180320T2200Z/
/O.EXA.KLWX.WS.W.0006.180320T0900Z-180321T0000Z/
/O.CON.KLWX.WS.A.0004.180321T0000Z-180321T2100Z/
Central and Eastern Allegany-Hampshire-Hardy-Eastern Grant-
Eastern Mineral-
755 PM EDT Mon Mar 19 2018

...WINTER STORM WARNING IN EFFECT FROM 5 AM TO 8 PM EDT TUESDAY...
...WINTER STORM WATCH REMAINS IN EFFECT FROM TUESDAY EVENING
THROUGH WEDNESDAY AFTERNOON...

* WHAT...Wet snow expected Tuesday, with wet snow and sleet
  accumulation 3 to 6 inches and a thin layer of ice. Additional
  snow accumulation of 5 or more inches will be possible Tuesday
  night and Wednesday.

* WHERE...Portions of the Potomac Highlands.

[Fozz]

Here's an updated LWX map (and yes, this one actually is up to date and not from 8 hours ago  )

8-12" for the northern crowd.

[psuhoffman]

@mappy @HighStakes @showmethesnow 

And the rest of the northern tier...

I think we're safe for a solid snowfall but the difference between a standard 4-6" snow and perhaps pushing for double digits will come down to 2 factors.

1. How much accumulation we can squeeze out of the waa precip. I think some sleet is unavoidable and probably a lot of it. But if we can get enough cooling in some heavy bands to pick up 2-4" with that vs just 1" of sleet tomorrow we will be off to a good start. I'm 50/50 on that. Nams are warm. Most other guidance says we are close enough to get snow in heavier bands.  It's close. 

2.  How the banding sets up with the ccb. There is no way to pin that BUT this track and our location usually works. We often see that back edge deform band set up right across our area. There were strong hints of that on the euro. And models always undergo qpf and ratios in that band.  If we get into such a band early Wednesday and pile up some snow before radiation starts to fight back mid morning things could snowball our way. 

Get both of those to break our way and 10"+ is very possible. Get one and 6-8" is very possible. Both those fail and we're looking at 3-6". That's my thoughts right now. If I had to forecast I would go 4-8 to split the difference between all those options. 

[Sparky]

3 minutes ago, psuhoffman said:

@mappy @HighStakes @showmethesnow 

And the rest of the northern tier...

I think we're safe for a solid snowfall but the difference between a standard 4-6" snow and perhaps pushing for double digits will come down to 2 factors.

1. How much accumulation we can squeeze out of the waa precip. I think some sleet is unavoidable and probably a lot of it. But if we can get enough cooling in some heavy bands to pick up 2-4" with that vs just 1" of sleet tomorrow we will be off to a good start. I'm 50/50 on that. Nams are warm. Most other guidance says we are close enough to get snow in heavier bands.  It's close. 

2.  How the banding sets up with the ccb. There is no way to pin that BUT this track and our location usually works. We often see that back edge deform band set up right across our area. There were strong hints of that on the euro. And models always undergo qpf and ratios in that band.  If we get into such a band early Wednesday and pile up some snow before radiation starts to fight back mid morning things could snowball our way. 

Get both of those to break our way and 10"+ is very possible. Get one and 6-8" is very possible. Both those fail and we're looking at 3-6". That's my thoughts right now. If I had to forecast I would go 4-8 to split the difference between all those options. 

Hoping Parr's Ridge grabs onto that ccb and holds onto it like grim death.

[ErinInTheSky]

9 minutes ago, Fozz said:

Here's an updated LWX map (and yes, this one actually is up to date and not from 8 hours ago  )

8-12" for the northern crowd.

I'm REAL close to that 6-8" line. I'd be thrilled.

[mappy]

7 minutes ago, psuhoffman said:

@mappy @HighStakes @showmethesnow 

And the rest of the northern tier...

I think we're safe for a solid snowfall but the difference between a standard 4-6" snow and perhaps pushing for double digits will come down to 2 factors.

1. How much accumulation we can squeeze out of the waa precip. I think some sleet is unavoidable and probably a lot of it. But if we can get enough cooling in some heavy bands to pick up 2-4" with that vs just 1" of sleet tomorrow we will be off to a good start. I'm 50/50 on that. Nams are warm. Most other guidance says we are close enough to get snow in heavier bands.  It's close. 

2.  How the banding sets up with the ccb. There is no way to pin that BUT this track and our location usually works. We often see that back edge deform band set up right across our area. There were strong hints of that on the euro. And models always undergo qpf and ratios in that band.  If we get into such a band early Wednesday and pile up some snow before radiation starts to fight back mid morning things could snowball our way. 

Get both of those to break our way and 10"+ is very possible. Get one and 6-8" is very possible. Both those fail and we're looking at 3-6". That's my thoughts right now. If I had to forecast I would go 4-8 to split the difference between all those options. 

Thanks! Appreciate you taking the time to break it down for us. 

[WeathermanB]

Like i said a few days back... As long as we're close to the rain snow line, i wouldn't see why not that if the rain starts coming down really heavy and is very close to the rain/snow, i have a gut feeling that the temps in the column up to 850 mb would crash, changing over to very heavy snow. 

Actually i think i've seen this happen maybe once or twice this winter. Usually works if you are really close to the LP off the coast of OC, and 850's are just at 0C.

I don't know too much. That's all. That's at least from my standpoint of it.

[osfan24]

LWX is pretty aggressive. I was surprised to see Cranky went 6-12 over basically the entire region.

I wish we could get this low to crank just a little bit earlier so it got going south of us. Worried that we miss some of the best stuff and the duration of the best stuff and that it ends up more Philly to Central Jersey.

[Maestrobjwa]

11 minutes ago, Fozz said:

Here's an updated LWX map (and yes, this one actually is up to date and not from 8 hours ago  )

8-12" for the northern crowd.

The fact that they put Baltimore in the 6-8" range...I s 6" becoming the bottom end even for Baltimore CITY?...Not sure I can believe it fully, but I suppose it's possible!

[WEATHER53]

Tonight is not an example of low dews and favorable winds but colder air will filter in by dawn tomorrow 

[HighStakes]

16 minutes ago, psuhoffman said:

@mappy @HighStakes @showmethesnow 

And the rest of the northern tier...

I think we're safe for a solid snowfall but the difference between a standard 4-6" snow and perhaps pushing for double digits will come down to 2 factors.

1. How much accumulation we can squeeze out of the waa precip. I think some sleet is unavoidable and probably a lot of it. But if we can get enough cooling in some heavy bands to pick up 2-4" with that vs just 1" of sleet tomorrow we will be off to a good start. I'm 50/50 on that. Nams are warm. Most other guidance says we are close enough to get snow in heavier bands.  It's close. 

2.  How the banding sets up with the ccb. There is no way to pin that BUT this track and our location usually works. We often see that back edge deform band set up right across our area. There were strong hints of that on the euro. And models always undergo qpf and ratios in that band.  If we get into such a band early Wednesday and pile up some snow before radiation starts to fight back mid morning things could snowball our way. 

Get both of those to break our way and 10"+ is very possible. Get one and 6-8" is very possible. Both those fail and we're looking at 3-6". That's my thoughts right now. If I had to forecast I would go 4-8 to split the difference between all those options. 

I have been so busy working since the windstorm and today I was swamped so I've only been checking in occassionally.

I'm in total agreement with your thoughts. I'm trying not to get overly excited but I can see how we can score a foot here. I really can see the ccb setting up here and getting enhanced by parrs ridge. I am nervous though about the initial thump. Not real confident with that for the same reasons you touched on.

 

[Amped]

All 18z models dug were more amped with the trough in ARK.  If 00z comes west again we are going to have an even more strung out mess. And the jet streak is just coming onshore now.

[clskinsfan]

21 minutes ago, Fozz said:

Here's an updated LWX map (and yes, this one actually is up to date and not from 8 hours ago  )

8-12" for the northern crowd.

 

Holy crap! 8-12. That is about as bullish as I have ever seen them.

[nj2va]

HRRR has DC flipping from rain to sleet late tomorrow morning. 18z NAM had it a few hours later.  I’d be happy with any frozen precip from Wave 1.

[Fozz]

8 minutes ago, Maestrobjwa said:

The fact that they put Baltimore in the 6-8" range...I s 6" becoming the bottom end even for Baltimore CITY?...Not sure I can believe it fully, but I suppose it's possible!

Yeah I'm not so sure 6" is the low end for Baltimore proper, but I guess that's what they're going with. I think 3-6" is more reasonable, with potentially more in the burbs.

[Fozz]

HRRRX looks very snowy tomorrow morning for those of us north of I-70.

[clskinsfan]

Their thoughts on max potential. Lets hope they bust low!!!

[Fozz]

1 minute ago, clskinsfan said:

Their thoughts on max potential. Lets hope they bust low!!!

Yeah this is ungodly... probably would require the WAA to be all snow and for the CCB on Wednesday to be like Feb 10, 2010. Then maybe we'd see these totals.

[psuhoffman]

36 minutes ago, snowmagnet said:

Bob explained the other day that the dynamics of a closed Low on the coast can lead to very high snow ratios.  So it may be accurate.  

Banding in the CCB can have very high ratios. Towards the end of the feb 10, 2010 storm in such a band I was pulling off over 20-1. 15/18-1 is common. March might knock that down to 12-1 but higher then 10 is possible in those bands if it's coming down hard enough to overcome radiation 

31 minutes ago, Maestrobjwa said:

 

Wondering if we should start a thread looking at the previous March snowstorms and how those HECS-level accumulations were achieved...If nothing else, those storms show that it CAN happen under the rigjt dynamics!

It's a combo of one or more of 3 factors. Rates. Timing luck. Anomalous arctic cold. 

Forger the arctic cold this time. Although the next threat might incorporate that!

If we can get this going early Wednesday morning and put down solid accumulation before 9 am it would help a lot. The timing here isn't perfect with best snow coming during 2 daylight periods. 

Rates rates rates!!!! If it's 31 and snowing 1/3" an hour at noon it's not going to stick at all. If it's snowing 2" an hour at 31 it will overcome radiation.  Late march 58 and 42 did it with heavy rates and marginal temps. We will have to win that way here. 

Time of year is going to take its pound of flesh here. I would be expecting 18-24" along 95 if this was January. Instead 3-6 seems likely with upside potential. I could see a death band dumping and a shock 10". And I could see it break wrong and a slushy 1-3". These are tough to nail down. In winter where bands set up is the difference between 18" or 28". Because light to moderate snow won't accumulate well now that can be the difference between 10" or 2".  Banding won't be known until nowcast time.

7 minutes ago, mappy said:

Thanks! Appreciate you taking the time to break it down for us. 

I expect some awesome pics!!!