The January 5/6 Thing

[yoda]

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
328 AM EST Sat Jan 4 2025

VAZ025-026-036>038-050-056-504-507-508-WVZ506-041630-
/O.NEW.KLWX.WS.A.0002.250105T2100Z-250107T0300Z/
Augusta-Rockingham-Nelson-Albemarle-Greene-Orange-Spotsylvania-
Eastern Highland-Northern Virginia Blue Ridge-Central Virginia
Blue Ridge-Eastern Pendleton-
328 AM EST Sat Jan 4 2025

...WINTER STORM WATCH IN EFFECT FROM SUNDAY AFTERNOON THROUGH MONDAY
EVENING...

* WHAT...Heavy snow, sleet, and freezing rain possible. Total snow
  and sleet accumulations of 5 inches or greater and ice
  accumulations up to one quarter of an inch possible. A localized
  band with up to 10 inches of snow is possible.

* WHERE...Portions of central, northwest, and western Virginia and
  eastern West Virginia.

* WHEN...From Sunday afternoon through Monday evening.

* IMPACTS...Travel could be very difficult. The hazardous conditions
  could impact the Monday morning and evening commutes.

[yoda]

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
328 AM EST Sat Jan 4 2025

DCZ001-MDZ013-014-016>018-502>504-VAZ027>031-039-040-051-053>055-057-
501-502-505-506-526-527-WVZ050>053-055-502-504-041630-
/O.NEW.KLWX.WS.A.0002.250106T0000Z-250107T0600Z/
District of Columbia-Prince Georges-Anne Arundel-Charles-St.
Marys-Calvert-Central and Eastern Allegany-Northwest Montgomery-
Central and Southeast Montgomery-Shenandoah-Frederick VA-Page-
Warren-Clarke-Madison-Rappahannock-Culpeper-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-King George-Northern
Fauquier-Southern Fauquier-Western Loudoun-Eastern Loudoun-
Northwest Prince William-Central and Southeast Prince
William/Manassas/Manassas Park-Hampshire-Morgan-Berkeley-
Jefferson-Hardy-Eastern Grant-Eastern Mineral-
328 AM EST Sat Jan 4 2025

...WINTER STORM WATCH IN EFFECT FROM SUNDAY EVENING THROUGH LATE
MONDAY NIGHT...

* WHAT...Heavy snow possible, with potential for some sleet and
  freezing rain. Total snow and sleet accumulations of 5 inches or
  greater and ice accumulations up to one tenth of an inch possible.
  A localized band with up to 10 inches of snow is possible.

* WHERE...Washington DC, and portions of central, southern, and
  western Maryland, central, northern, and northwest Virginia, and
  eastern West Virginia.

* WHEN...From Sunday evening through late Monday night.

* IMPACTS...Travel could be very difficult. The hazardous conditions
  could impact the Monday morning and evening commutes.

[yoda]

All of MD (excluding SE MD)/S PA/DE clean up well.  reason why DC metro and most of VA being don't do as well is because there is a warm nose centered around 800mb that shows up

[MillvilleWx]

There's notable difference in the handling of the thermals by the NAM Nest and the parent 12km. The Nest does a good job with the physical nature of evaporative cooling in the column when heavier precip moves overhead as the soundings between 850-750 drop to isothermal or colder, maintaining snow for longer periods of time. Only when the precip starts to lighten up the afternoon a touch does the thermal profile become more favorable for IP chances. Even so, the areal extent does not get much further than US50 in MD to DC and stays mostly snow in the Northern neck of VA. The second part of the storm is still to go as well on the Nest since it only goes out to 18z Mon and the trough is still all the way back into KY. It's a pretty formidable shortwave, so a pass underneath would likely spark the second round of precip which would be higher ratio fluff before exiting the area. You can tack on 1-4" with that feature alone bringing totals to 6-10" between I-66 to I-70, then along and north of I-70, totals would be 8-12" with local to 15" most likely, verbatim. This run was similar to my thoughts on how this storm might play out with multiple banding features across the region. The 85H FGEN panels are sick and would likely allow for one hell of a scene on Monday morning in these parts. Of course, will have to see how the runs hold, but this is a time frame to now take interest in the Nest. Yes it's at range, but this model has a history of scoping out thermal progressions in these setups and has the resolution to fine tune these types of details as we get closer to game time. A slight south adjustment would still make almost everyone in here happy to some degree. Good run

[MillvilleWx]

850mb FGEN on the 06z Nam Nest

[yoda]

I thought 7H FGEN was better to look at then 85H in regards to rates?

[MillvilleWx]

Pretty incredible beat down for many in here. Even a slight south shift would pay dividends. Incredible that there is still more storm left with the trough back in KY

[MillvilleWx]

Just now, yoda said:

I thought 7H FGEN was better to look at then 85H in regards to rates?

Both are useful! There's some 7H FGEN in there as well but the 85H was just incredibly impressive, so wanted to share. 

[MillvilleWx]

Last but not least, some precip panels from the 06z NAM Nest

Total QPF thru 18z Monday (Still more storm left!)

Kuchera Snowfall thru 18z Monday

[MDstorm]

3 hours ago, nj2va said:

Oh my.

Look at the snow fall distribution.  The Euro must really be feeling the effects from the developing 50/50 low/convergence.  This "squashes" the snow fall from NE to SW.  We will see over the next 12 -24 hours as the 50/50 low sets up if the perceived effect of the 50/50 low is being over-estimated allowing heavier snow to creep more northeast.  

[wasnow215]

3 hours ago, wawarriors4 said:

So true. The sleet always finds its way to FXBG.

12/19-12/20 2009? Maybe a bit but man that was pure as far as I recall

[yoda]

FXUS61 KLWX 040904
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
404 AM EST Sat Jan 4 2025

.SYNOPSIS...
High pressure will briefly build in by tonight. A strong low
pressure system will bring wintry precipitation late Sunday into
Monday. Below normal temperatures continue through next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Strong high pressure is building southeastward from central
Canada with low pressure situated over Quebec. Broad troughing
encompasses the eastern US. Upslope snows are dwindling this
morning with additional accumulations of an inch or two at most.
However, winds are still strong which will reduce visibility in
falling snow and result in blowing/drifting of the snow on the
ground. A Cold Weather Advisory also remains in effect for the
high peaks due to wind chills less than -10.

Elsewhere, expect cold and blustery conditions today, with winds
gusting 20-35 mph. This will result in wind chills in the teens
and 20s through the day with highs only in the upper 20s and
mid 30s. Stratocumulus may tend to expand across the northern
half of the area through the day before clouds finally retreat
tonight.

Temperatures will drop into the teens to lower 20s tonight for
much of the area with single digits in the Alleghenies.
Additional Cold Weather Advisories for the high Alleghenies may
need to be considered, although winds will be gradually
diminishing.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The focus for Sunday and Monday will be the potent low pressure
system moving from the Mid Mississippi Valley to the east coast.
Precipitation will spread into the area late Sunday afternoon
and into the evening (perhaps not reaching northeast Maryland
until late Sunday night). While not a classic cold air damming
set up, the antecedent cold airmass will be plenty supportive
of wintry precipitation across the entire area. With 00Z
guidance, there are essentially two camps, although both offer
the potential for a heavy frontogenetic snow band to the north
of the warm nose. A northern solution would result in mixed
precipitation up to the Potomac River/US-50 or so, with the
heaviest snow across the northern half of the area (and close to
a quarter inch of ice south of I-64). A southern solution would
result in the heaviest snow across the southern half of the
area, with far northern/northeast Maryland receiving a minimum
of snow. It`s also worth noting temperatures could warm enough
Monday for Nelson and St. Marys Counties to change to rain. In
the end, there`s a strong signal for the potential of heavy snow
and/or a mix that includes significant sleet and freezing rain
across most of the forecast area. Therefore, Winter Storm
Watches have been issued. For worst-case scenario planning, the
potential band of 8-12 inches of snow could set up nearly
anywhere within the forecast area. Precipitation will wind down
Monday night. However, there is an increasing signal for wrap-
around snow. Steepening lapse rates through the dendritic snow
zone in a cooling column could result in another round of
locally heavy, fluffy snow on the back end. Hopefully some of
these details can be refined in the next 24 hours.

[WesternFringe]

7 minutes ago, MillvilleWx said:

Last but not least, some precip panels from the 06z NAM Nest

Total QPF thru 18z Monday (Still more storm left!)

Kuchera Snowfall thru 18z Monday

NAM nest says “what snow?”  here in Augusta County whereas the Euro and Ukie drop 12-15”. Lol

This is going to be ‘fun’ to track on the way in!

[Deck Pic]

44 minutes ago, yoda said:

All of MD (excluding SE MD)/S PA/DE clean up well.  reason why DC metro and most of VA being don't do as well is because there is a warm nose centered around 800mb that shows up

there is a slight warm nose at 800mb at hour 53 that might even be all snow. As @MillvilleWx points out the 3k is pretty fucking sick even for me and you when it truncates.  

Maybe on Sunday they'll run the 1.33km over the mid atlantic

[yoda]

06z ICON took a 50 mile jog north with its snowfall totals compared to 00z FWIW (i.e. increased them in C MD)

[Ji]

06z ICON took a 50 mile jog north with its snowfall totals compared to 00z FWIW

Oooh?

[Deck Pic]

6z gfs out in 5...might as well stay up

[yoda]

06z RGEM is all snow for DC metro once again

[MDstorm]

6 minutes ago, yoda said:

06z ICON took a 50 mile jog north with its snowfall totals compared to 00z FWIW (i.e. increased them in C MD)

[Ji]

06z RGEM is all snow for DC metro once again

Did it tick a certain direction ?

[yoda]

2 minutes ago, Ji said:

Did it tick a certain direction ?

north with its snowfall totals.  I only have the regional view though.  Will post 00z and 06z in a min.  Also increased amounts

[Ji]

6z gfs out in 5...might as well stay up

Assuming you get 10 inches…will dc finish season over 20? You all were pretty high on seasonal forecasts right? I think you said Feb would be our best month

[Deck Pic]

3 minutes ago, Ji said:

Did it tick a certain direction ?

[Deck Pic]

1 minute ago, Ji said:

Assuming you get 10 inches…will dc finish season over 20? You all were pretty high on seasonal forecasts right? I think you said Feb would be our best month

yes

[yoda]

06z RGEM 

 

00z RGEM 

 

[Ji]

06z RGEM 

 
00z RGEM 

 

We need to juice this up more

[yoda]

Snow moves into DC metro around 05z MON on 06z GFS

[yoda]

Ripping snow at 09z MON... thermals all systems go

[Deck Pic]

Just now, yoda said:

Ripping snow at 09z MON... thermals all systems go

this is a pretty obscene run.  

[yoda]

all snow DC metro through 15z MON.  thermals touch 0c at 800mb at 15z... precip is lighter... so maybe some sleet in there... but should still be snow