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Wintry Jan 15-16 Winter Storm Discussion & Obs

griteater said:
I'd like to see these snow maps verify as well, but reality is that warm air is going to be pouring in aloft from the SE. A lot of these snow map algorithms are tinted toward promotion....like "hey, let's count the last 6 hours of precip as snow even though it changed from snow to sleet at hour 1". If the heavy damming holds like this, this will be a major winter storm no doubt, but you'll need to dig into the soundings to investigate the time of precip type changeover etc. The snow maps are going to be tilted on the high side east of the mountains in cases like this of damming and warm air moving in rapidly aloft
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Yep, when it comes to snow east of the mountains, are hope is a big column cooling 850mb-700mb FGEN band which can allow heavy snow for some hours, this chance especially increases along the 85 corridor and NW in this deep cold CAD setup, and many deep cold CAD setups in the past, there’s a big reason why CLT/GSO has a bigger snow average from Miller Bs vs Miller As
 
KCAE's discussion is alarming, tbh. And it was written before the 12z Euro:

000
FXUS62 KCAE 111917
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
217 PM EST Tue Jan 11 2022

.LONG TERM /SATURDAY THROUGH TUESDAY/...

-- Changed Discussion --
...Potentially Impactful Winter Weather on tap Saturday through

Sunday Night...

=======================
SYNOPTIC OVERVIEW
=======================

Synoptic flow through this period can be classified as meridional,
as the shortwave trough on Thursday digs through the region and
ushers in broad northwesterly flow across the eastern CONUS. As this
500 hPa trough deepens off the US east coast, a strong surface high
pressure system will begin moving from the prairies of Canada
towards southeastern Canada and the northeastern US. This will
begin to ridge into the Mid-Atlantic and Carolinas by Friday,
and even more so on Saturday. Models are in very good agreement
overall with this initial progression of features, with
Ensemble and Deterministic models agree on this progression.
Meanwhile, model guidance has come into fairly good agreement on
the location and strength of another mid/upper level shortwave.
This positively tilted trough is forecast to dig into the
southern MS Valley by Saturday morning, and will push towards
our region Saturday night and into Sunday. Ensemble means and
deterministic models are all showing this in some similar form,
with a surface low of varying strength developing across the
Gulf Coast states and traversing from there and into the
southern GA/northern FL. Ahead of this, the strong surface
wedging looks to be in place across the region, with cool air
already locked into place. From a pattern recognition
standpoint, this is a favorable synoptic set up for wintry
weather around the region. Precipitation is expected to increase
in earnest on Saturday night ahead of this as isentropic lift
increases across the area atop the surface wedging. Guidance is
mixed in terms of p-type, and it is a bit early to get into
these details. However, the pattern would suggest rain, snow,
sleet, and freezing rain all being possible during this event.
Behind this system, high pressure and dry air push back into the
region to start the next work week.

=======================
MODEL DISCUSSION
=======================

We have increasing concern that a wintry mix of rain, sleet,
freezing rain, and snow may impact the region this weekend. Model
guidance is in somewhat remarkable agreement with the overall
pattern and even some details of the pattern. The ECMWF begun
this trend yesterday, and since, the GFS and Canadian have
pushed towards that, along with their ensembles. Ensemble means
are impressive, showing trends towards a deeper and more
amplified shortwave over the MS Delta region as it pushes a
surface low towards us. The ECM is the weakest with the 500 hPa
shortwave, keeping it as a fairly progressive, open wave. The
GFS and Canadian have quickly trended towards a closed 500 hPa
low tracking near the region on Saturday night. The ECM would
suggest more of a frozen precip type, but the trend in the 00z
GFS/Can & 12z GFS is concerning, pushing strong warm air
advection atop a cold layer & resulting in some ice. Model
trends and agreement, both in the deterministic and ensembles,
are certainly concerning and bear watching over the coming days.
Models are fairly uniform in showing the precip generally
starting after midnight on Sunday and lasting through Sunday
evening. Leaning towards the stronger solutions given the trend
towards them within the ensemble guidance. Model guidance did a
similar thing (though withing 48h of the event itself) on Jan
2nd-3rd, when they quickly picked up on a deepening and closed
low. One other trend to note in the 12z guidance is that the
surface high ahead of this is slightly further south and
slightly more intense across our region immediately ahead of the
surface low.

=======================
FORECASTER CONFIDENCE
=======================

Forecaster confidence is increasing in some kind of winter weather
event impacting the Carolinas on Saturday night and Sunday. So that
answers two of the four big questions ("Where?" and "When?"). The
"What?" and "How Much?" is still TBD at this point. A couple of
things to note:

- This could still trend away from a winter weather event. We are
several days out from this event, and there is a lot of uncertainty
involved in a forecast where precipitation types look to be an
issue.
- While forecaster confidence is increasing in something happening
this weekend, confidence in p=type, amounts, and impacts is not high
at this time. Depending on "What?" falls and "How Much?" actually
occurs will determine overall impacts of this event.
- Guidance is notoriously poor at predicting when and how long a
wedge situation will set up across our region. They are usually too
quick to scour it out, and usually push us out of a wedge too early.
This is important because this set up will be driving any wintry
precip that occurs across the area.

Given all that I have outlined, I am most confident that areas along
and north of I-20 are under the greatest threat for a wintry mix of
precipitation this weekend. This doesn`t mean future model trends
won`t push in a different direction, but given the weight of the
ensemble & deterministic guidance at this point, that is the area of
greatest confidence. I want to reiterate - this is a forecast with
high variance and several potential outcomes at this point. Stay
abreast of latest forecasts over the coming days as details come
into clearer view about potential wintry weather across the Midlands
and CSRA.
-- End Changed Discussion --
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SD said:
Here are all the members locations. Kind of strangethe mean seems to be weighted a little E of the clustering View attachment 103900
Click to expand...

The mean is definitely east of the OP which would lean towards a flatter solution vs straight up the coast . Not that you don't already know that


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1641929632302.png
Decided to make my first probability map about SEEING snowfall. Not a accumulation map by no means. Just how confident I feel that we will get some accumulating snow. Pretty easy, if you're in the western NC mountains you're probably almost guaranteed to see accumulating snow at this point. I don't want to go higher than 60% since we are at day 5 but definitely feel it is very likely at this point. Along and north of 85 I think will see accumulations but I don't want to go above 40% right now. Definitely probably going to switch to sleet and ZR at some point while finishing with snow. Could easily get a really good swath of 2-6" before a changeover to ice and then another changeover back to snow for a few more inches in this region. The next 2 regions I think we could see some front end and backend thumping snow but I am really worried more about the ice potential here.
 
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As we get closer the wind forecast is gonna be a big deal. Could it actually be possible to get a blizzard warning. Maybe! But the amount of power outages is going to be huge with this storm I feel like


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ryan1234 said:
Exactly. Took the words right out of my mouth. We know if we get the precip falling when temps are that cold, it's going to stay COLD thorough the duration of the event. Been through wayyyy too many CAD setups to fall for things warming up like some models tend to depict.
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You certainly can warm that much when you have 850s in the 40s over head. I'm not trying to be snotty, but it's called an Exothermic Process.

1641929735940.png


And at that exact same time frame, you've lost the press from the HP up north and thus your cold air feed.

1641929921500.png

The end result is you release the heat that the water absorbed higher up, and release it into the low levels, and with no fresh air supply, you slowly warm.
 
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