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Jan 15-16 Winter Storm


Brick Tamland
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11 minutes ago, wncsnow said:

One big different between GFS and NAM is the front end thump is much heavier precip on GFS which gives mountains and foothills more snow. 

GFS has been unbelievably consistent with this for several days now. I feel like if NAM ends up correcting toward a GFS type synoptic solution the thermals will adjust accordingly within reason as well. Kinda silly to see the GFS all snow in certain areas the NAM has PL/ZR, when it has one of the worst resolutions for CAD purposes.

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13 minutes ago, DAWGNKITTEN said:

 

Here's what concerns me.  No one is talking about the possible ice in Rabun County,but it sure shows up here.  Should we be worried about it or ?  

Should be more sleet than freezing rain based on soundings. If it keeps trending that way then maybe worry, but for now it should still be more snow/sleet and glazing of ice.

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12 minutes ago, Buddy1987 said:

@BornAgain13I wouldnt even look at the Canadian if I were you man. There's nothing positive that came out of it. Cut your snow totals in half and has the freezing precip vs rain line very close. 

This went to heck in a hurry! I'll say by tomorrow 12z models will probably have us going above freezing Sunday! And earlier today it look like low 20s during the storm... lol 

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9 minutes ago, wxduncan said:

So with the talks I'm seeing everyone might be looking at nothing to advisory level type stuff? If so what happen I thought everything was good? I'm in Morganton now I wonder if I get anything? 

Looks like front end snow for you and then a sleet fest. As for MBY, it’s a freezing rain storm. Ready for some power outages.

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GSP overnight

.NEAR TERM /THROUGH TONIGHT/...
As of 345 AM EST Saturday: Forecast for the overnight hours is
simple in comparison to the next 30 hours.  Largely anticipate quasi-
zonal flow aloft with weak northeasterly flow at the surface.
Profiles remain dry through perhaps sunrise Saturday, with only high
cirrus filtering in before dawn.  High pressure settles across New
England on Saturday, and strengthens the developing northeasterly
flow, prompting the developing of a cold-air damming situation east
of the Appalachians.  Increasing low-level WAA after 12Z suggests
that moist upglide will gradually tick upward throughout the day,
which will result in enhanced low- to mid-level cloud cover.  A few
of the CAMs are advertising spotty showers from late morning onward,
but profiles indicate continued dry advection in the boundary layer
(courtesy of sustained northeast winds) will keep precipitation from
reaching the ground in lieu of simply strengthening the cold wedge.

Saturday night, impacts from an approaching winter storm will begin
in earnest.  By 21Z, the models depict a closed upper low shifting
east out of the ArkLaTex region and steering a rapidly developing
surface cyclone northeast out of the Deep South.  Models are now
in excellent agreement that the low will track across the southern
Upstate and produce widespread wintry precipitation.  With the
cold wedge still intact and ~850mb WAA enhancing a warm nose aloft,
a developing rain-freezing rain mix will further enhance the CAD.
How far north and west this warm nose will extend remains a topic of
contention among the models still, but the trend over the last 24
hours has been for the CAMs to bring the warm nose farther inland,
resulting in more widespread ice across the Upstate and even into
parts of the Piedmont.

As the 850mb low tracks north and east of our CWA, low-level flow
will rapidly turn easterly by perhaps 12Z Sunday.  850mb WAA becomes
increasingly anemic and the warm nose begins to diminish by Sunday
evening.  By this point in time, however, profiles will starting
to dry, as dry cool-sector air filters into the area, scouring out
the wedge.  This drying should gradually deactivate ice nuclei,
decreasing precip rates overall and allowing a transition back to a
light, patchy, snow-sleet mix across most of the Piedmont and
Upstate.  The mountains, meanwhile are on track for a mostly-snow
forecast.  The warm nose should not penetrate into the Appalachians.
Profiles here appear to remain well-saturated and sub-freezing
through most of the event, allowing for an easy transition from
a rain-snow mix to all snow from Saturday night onward.

Precipitation intensity and coverage should drop off significantly
past mid-afternoon Sunday.  Patchy snow and sleet warrants slight
PoPs across the area through 00Z Monday and beyond, however,
especially in the mountains where NW flow snow will likely already
be developing in the wake of the system.

 

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Nice discussion from CAE

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Impactful winter storm set to impact the northern half of the
forecast area, bringing with it widespread freezing rain and gusty
winds.

=======================
   SYNOPTIC SET UP
=======================

Challenging forecast is on tap across the forecast area as we get
into this period, with a potential ice storm developing late
Saturday night and Sunday morning across portions of the forecast
area. Synoptically impressive event will be taking shape and
overspreading the area, as a sharp & positively tilted 500 hPa
trough digs into the lower MS Valley at the beginning of this
period. Deepening moisture in the atmosphere will be noted ahead
of this by increasing cloud cover across the FA. Meanwhile,
convergence across the Mid-Atlantic region will foster the
southward ridging of a strong Canadian high pressure system. As
a result, surface wedging will develop during the day on
Saturday and continue to build into the region via cold air
advection and northeasterly flow Saturday night. This will
continue to take shape through the night as a surface low
deepens along the Gulf Coast and moves south of this wedge. In
addition to some cold air advection noted with the wedge, dry
low-level air is expected to push into the region, with surface
dewpoint depressions of ~8-12F in place by 1a Sunday.

Impressive forcing for ascent is expected to push into the region
between 1a and 4a. Of note will be a developing dual upper level jet
structure, with the FA placed underneath the coupled right-entrance
region and exit region of 250 hPa jet streaks. This will result in a
strong response in the 850 hpa jet, with a 50+ knot low-level jet
pushing over the region Sunday morning. Strong isentropic lift will
overspread the region as a result, and precipitation will blossom
over the region after 1a Sunday. The surface low is expected to
approach and pass through/around the region (depending on the
strength of the surface wedge) by 1p on Sunday. As this interacts
with the wedge, a strong surface pressure gradient will develop
between 4a and 10a on Sunday, and should result in gusty winds. By
1p on Sunday, the mid/upper level closed low will begin to take on a
negative tilt and push to the north and northeast of the area, with
a dry slot likely ending widespread precipitation from south to
north on Sunday afternoon. Some light showers may persist into
Sunday evening, but these aren`t likely to result in widespread
issues.

=======================
   MESOCALE DETAILS
=======================

As previously outlined, this is a challenging forecast across the
region. Evening guidance has shifted slightly warmer with the
surface wedging, while morning/midday guidance yesterday was
slightly cooler with it. This back and forth is making the forecast
difficult, especially in the areas that area closest to the
freezing line in the central Midlands. There are some things to
keep in mind today as we approach this event:

1. Models still seem to be struggling with the strength of the
wedge. This is usually the case with wedging events, and it is
usually underestimated. It is leading to lower confidence in how
temperatures will play out. If the wedge is stronger, more
freezing rain can be expected further south. If weaker, the area
of freezing rain will shrink northward.

2. Dewpoints will be important watch as we get into this afternoon
and tonight. Models are split on this, but the lower the dewpoints
get ahead of this, the more evaporative cooling potential we will
see when precip quickly increases across the region. Slight differences
can make a large impact and can be illustrated by looking at the HREF
and NAM. The HREF has lower dewpoints at precip onset and results
in a more widespread & significant event. The wetbulb temperature
will be key in where the rain/freezing rain line eventually sets
up.

3. Temperatures are expected to rise above freezing across the area,
starting between 8a and 10a across the central Midlands, and then
between 10a and 12p across the northern Midlands. The CSRA and
southern Midlands will likely remain above freezing for the bulk of
the event.

4. Precipitation rate will likely be heavy, and this will have an
impact on overall ice accumulation efficiency. As previously
mentioned, synoptic scale ascent is very impressive in the 4a to 1p
Sunday timeframe. With PWs approaching 175-200% of normal, this will
result in moderate to heavy rainfall. This is expected to keep
freezing rain accumulation lower than the overall forecast QPF may
suggest otherwise.

All of that being said, this event is going to come down to some
nowcasting later today and tonight. This is going to be a tight
forecast across the central Midlands. Forecast soundings have a
deep warm layer, indicating that rain to freezing rain back to
rain is the likely P-type progression. The time spend with
freezing rain is unknown, but highest confidence in a long
duration freezing rain event is across the northern Midlands.
Model guidance should continue to get a clearer and better
picture through the day today, but with a forecast as tight as
this one will be, watching observations is going to help clear
up a lot of the uncertainty that we have right now.

===========================
  EXPECTATIONS/CONFIDENCE
===========================

Current areas in headlines look good for now. We will keep the Ice
Storm Warning unchanged, even if some sleet may mix up there at the
onset of precipitation. Will transition Winter Storm Watch areas to
a Winter Weather Advisory for now, and expand the advisory one tier
of counties south to account for possible light accumulations of
ice. Expect 0.20"-0.40" of ice accumulation in the Ice Storm Warning
area, with 0.01"-0.20" of ice accumulation in the Advisory area.
Timing of greatest impacts & freezing rain looks to be from 5a
through 9a across the Advisory area, and 3a to 11a across the
Warning area. Trees and powerlines are expected to be strained by
the ice accumulation, which may result in some down tree limbs and
power outages. Be prepared for potential power outages,
especially in the Ice Storm Warning area. Confidence is
certainly highest that the Warning area will see highest ice
accumulation, with confidence lower across the Advisory. There
is too much uncertainty at this point to justify upgrading to a
warning, though that could be necessary if some of the cooler
model guidance verifies tonight. Keep abreast of the latest
forecasts today!
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Hrrr and RAP are really blowing in the cold/dry air with the wedge ahead of our storm. 

It may be a little too early to say this, but it's pretty clear the ole goofy GFS has once again dropped the ball on surface temps/dew points under classic CAD.  Very little chance the temperatures it's been spitting out for CAD regions of GA/SC the last few days come close to verifying. 

As such, this is looking like one heck of an ice storm for places like Elberton, Greenwood, Abbeville, Laurens, Irmo, up to South Charlotte.  

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The 06z Hrrr had GSP at 38/25 at midnight. The latest 11z run has GSP at 37/22 for midnight.

06z had Greenwood at 39/30, 11z is at 41/22.

So even the Hi-Res models showing super cold/dry air are trending colder/drier at appears. This could be bad news for the Columbia area in terms of power outages.

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9 hours ago, Snowacane said:

The best storms in the Triangle over the past 20+ years have been the ones that were not forecasted. I'll never forget Fish in the early 2000's saying that we were looking down the barrel of a gun and we were supposed to have over a foot. Next day was clear and sunny.

Special, special storm. Was a senior at NC State and taking “Intro to Weather and Climatology.” It was a M,W,F class. So, we got to watch the “winter hurricane” slowly evolve from a “chance” of snow to a dump fest. It was awesome watching the professor’s inner child blossom by Friday’s class. With spit building up in the corners of his dry mouth and disheveled hair, constantly manipulated by his fidgety hands, he was in awe of what could be and what was a once in lifetime triangle storm…I can still see the SLP epically develop right off the coast of southern SC, windup into an atmospheric bowling ball and to then stall off the SOBX, creating mesoscale snow banding right over Wake Co. And it.just.wouldn’t.stop!…We can always dream…

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33 minutes ago, burrel2 said:

The 06z Hrrr had GSP at 38/25 at midnight. The latest 11z run has GSP at 37/22 for midnight.

06z had Greenwood at 39/30, 11z is at 41/22.

So even the Hi-Res models showing super cold/dry air are trending colder/drier at appears. This could be bad news for the Columbia area in terms of power outages.

How do the mid and upper layers look for I-85 in the Upstate with those two models? Still a mix or now mostly snow now? 

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32 minutes ago, burrel2 said:

Hrrr and RAP are really blowing in the cold/dry air with the wedge ahead of our storm. 

It may be a little too early to say this, but it's pretty clear the ole goofy GFS has once again dropped the ball on surface temps/dew points under classic CAD.  Very little chance the temperatures it's been spitting out for CAD regions of GA/SC the last few days come close to verifying. 

As such, this is looking like one heck of an ice storm for places like Elberton, Greenwood, Abbeville, Laurens, Irmo, up to South Charlotte.  

I know you haven't gotten a ton response on these posts, but I think they are wise and on point.

On the one hand, the model consistency on this storm has been breathtaking.

On the other hand, if there is going to be a surprise, it's not going to be on track (a track which hasn't budged, for the most part, for 3 days), it's going to be old Larry Cosgrove-esque CAD over- (or under-) performance. 

You and I have been on these boards a long time and two things always seem to happen: 1) The CAD is underestimated 2) So is the warm nose.

That could be a particularly ugly combination with this sucker. 

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2 minutes ago, lilj4425 said:

How do the mid and upper layers look for I-85 in the Upstate? Still a mix or now mostly snow? 

IMO, we should be mostly/all snow until 6-7am at the earliest. That gives us a 3-4 hour window for accumulations. If the initial fronto band can really perform for us we can get 3-5 inches I think before the changeover to sleet.  Time will tell.

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I know you haven't gotten a ton response on these posts, but I think they are wise and on point.
On the one hand, the model consistency on this storm has been breathtaking.
On the other hand, if there is going to be a surprise, it's not going to be on track (a track which hasn't budged, for the most part, for 3 days), it's going to be old Larry Cosgrove-esque CAD over- (or under-) performance. 
You and I have been on these boards a long time and two things always seem to happen: 1) The CAD is underestimated 2) So is the warm nose.
That could be a particularly ugly combination with this sucker. 

And one will win this micro battle round here.


.
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IMO, we should be mostly/all snow until 6-7am at the earliest. That gives us a 3-4 hour window for accumulations. If the initial fronto band can really perform for us we can get 3-5 inches I think before the changeover to sleet.  Time will tell.

Saw up here with maybe a few hours later before change over ( mid-late morning) then switching back to snow around 2 Ish Sunday.


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I know you haven't gotten a ton response on these posts, but I think they are wise and on point.
On the one hand, the model consistency on this storm has been breathtaking.
On the other hand, if there is going to be a surprise, it's not going to be on track (a track which hasn't budged, for the most part, for 3 days), it's going to be old Larry Cosgrove-esque CAD over- (or under-) performance. 
You and I have been on these boards a long time and two things always seem to happen: 1) The CAD is underestimated 2) So is the warm nose.
That could be a particularly ugly combination with this sucker. 

The last thing I’m doing tonight and the first thing I’m doing tomorrow morning is checking out dews upstream of us and how they’re verifying on Iowa state meteogram.

I spoke on this yesterday, I think there’s a few more things with storm than usual that could erode our CAD, and if it hangs on/overperforms then It solidifies itself as the dominant forecasting feature for winter storms.

One last thing I’ll touch on since I saw some chatter about it, Jan 2000 was both cool, and could also never happen again. Our tools are a bit better today than the TI-89 graphing calculators they were using to run models back then.
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55 minutes ago, eyewall said:

December 2002 is a reasonable comparison although that ended up a blizzard where I was at the time in the NYC Metro. They won't see much this go around.

For the CLT area …. My then 12yr old Self has memories of my dad Waking me up at 2AM leaving for work and it looking like 4th of July with transformers blowing so I certainly hope not

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Couple quick points watching from afar:

1. No one should be using the global models (GFS/Euro/Canadian etc.) from this point forward for surface temps and dew points. The hi-res models will do a much better job of handling the shallow cold airmass associated with the CAD. The HRRR, NAM, and other hi-res variations are what people should be paying attention to. 
 

2. From experience growing up in this area and having been through many winter storms, the warm nose almost always overperforms, and I’d say the synoptic setup with the upper low passing overhead or to the west only argues for that scenario even more. Expect mostly sleet or freezing rain outside the mountains, and even there I wouldn’t be surprised if mixing occurs at times. 
 

3. As far as impacts go, there is a HUGE difference between freezing rain at 32 degrees and freezing rain at 30 and below. This has me concerned for the I-85 corridor near Charlotte where temps will be below 30 for the majority of the precipitation. The biggest limiting factor will be precipitation rates as heavy freezing rain does not accrete as efficiently as a light to moderate rainfall. Most of the precipitation should fall quick and fast in a 6-10 hour window, which may help limit max accretion potential. Still, a I think there will be a swath of 0.5-0.75” of accretion somewhere near the Charlotte area when all is said and done. 

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