12/10-11 Disco / Obs - Rain/Snow/Wind Event

[Eskimo Joe]

37 minutes ago, Jersey Andrew said:

Are there any recent examples of December fronts kicking off snowfall after significant rainfall in the DC metro area?

Dec 5, 2009

[NorthArlington101]

EURO holds.

10:1

Snow Depth  - for the fun haters 

[nj2va]

Euro beats my snowfall total all of last winter.  

[rjvanals]

Euro looks somewhat sleety in the metros w a change to snow looking at soundings.

[Chris78]

2 minutes ago, NorthArlington101 said:

EURO holds.

10:1

Snow Depth  - for the fun haters 

Might be a fun drive to work over the Catoctins on Monday morning 

[300 square feet]

Serious question here from someone wanting to learn. 
 

You all remember last winter, I think it was near the end of winter, there was a strong cold front moving through and all the models were calling for anafrontal snow? It went from a prediction of nothing to several inches even in the metros shortly before the event, and we ended up getting nothing.

Is there something about this setup that’s different? Growing up in this area, I know how difficult it is for us to get anafrontal snow, and I’m trying not to get my hopes up. 

[TSSN+]

1 minute ago, 300 square feet said:

Serious question here from someone wanting to learn. 
 

You all remember last winter, I think it was near the end of winter, there was a strong cold front moving through and all the models were calling for anafrontal snow? It went from a prediction of nothing to several inches even in the metros shortly before the event, and we ended up getting nothing.

Is there something about this setup that’s different? Growing up in this area, I know how difficult it is for us to get anafrontal snow, and I’m trying not to get my hopes up. 

This one has a trailing low too 

[psuhoffman]

It’’s amazing how consistent the euro has been for 5 runs. There has been a slight trend to go more negative the last 2 runs (good) but overall the euros been a rock with all other guidance converging on it. 

This is one of the reasons I still find the euro useful in short range. I’ll use the high res to pick out meso features but this lends confidence that the general idea here is becoming pretty locked in. Of course this is a very marginal setup wrt Tempe so now cast issues with the exact Tempe and banding will have a huge impact. 1-2 degrees and where a meso band sets up is the difference between 1-2” of wet paste and white rain. But this consistency combined with the meso models converging towards it makes me confident the idea of a more amplified negative tilt wave is correct. So at least we are in the game.  Like I said I use it as a baseline to judge everything else. 
 

BTW 1-3” of wet snow is better than 2-4” of dry snow imo. The wet snow sits on top the grass better and sticks to everything.  Looks a lot nicer. 

[AtlanticWx]

5 minutes ago, 300 square feet said:

Serious question here from someone wanting to learn. 
 

You all remember last winter, I think it was near the end of winter, there was a strong cold front moving through and all the models were calling for anafrontal snow? It went from a prediction of nothing to several inches even in the metros shortly before the event, and we ended up getting nothing.

Is there something about this setup that’s different? Growing up in this area, I know how difficult it is for us to get anafrontal snow, and I’m trying not to get my hopes up. 

i was wondering this too but after looking into it further, that event was just synoptically different as a whole. we had a GL low that brought a cold front down here followed by some gusty flurries. I think that event was farfetched to begin with and we were j desperate because there was no trailing low or trough digging in the south.

this event, meanwhile, is caused by a trough digging in the south and turning negative rapidly bringing cold for the last few hours of precipitation. definitely a more promising event where we see a coastal low spawn and bring back moisture into our area for a few hours of flakes or even accumulating snow. def a more promising setup compared to most anafrontals.

[TJ3]

54 minutes ago, Eskimo Joe said:

Dec 5, 2009

Good one. Snowed to beat the band that afternoon 

[stormy]

29 minutes ago, TJ3 said:

Good one. Snowed to beat the band that afternoon 

I received 6 inches of the white stuff.

[yoda]

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
156 PM EST Sat Dec 9 2023

MDZ001-WVZ501-505-100300-
/O.NEW.KLWX.WW.Y.0024.231211T0000Z-231211T1500Z/
Garrett-Western Grant-Western Pendleton-
156 PM EST Sat Dec 9 2023

...WINTER WEATHER ADVISORY IN EFFECT FROM 7 PM SUNDAY TO 10 AM
EST MONDAY...

* WHAT...Snow expected. Total snow accumulations of 2 to 4 inches
  with localized amounts upwards of 5 inches on the higher ridges.
  Winds gusting as high as 45 mph.

* WHERE...In Maryland, Garrett County. In West Virginia, Western
  Grant and Western Pendleton Counties.

* WHEN...From 7 PM Sunday to 10 AM EST Monday.

* IMPACTS...Plan on slippery road conditions. The hazardous
  conditions could impact the morning commute. Gusty winds could
  bring down tree branches.

* ADDITIONAL DETAILS...Rain will change to snow Sunday evening
  with temperatures rapidly falling below freezing. Snow showers
  will continue overnight into Monday morning.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling.

When venturing outside, watch your first few steps taken on
steps, sidewalks, and driveways, which could be icy and slippery,
increasing your risk of a fall and injury.

[yoda]

Um, I know it's the BR... but I wasn't expecting a WSWatch...

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
156 PM EST Sat Dec 9 2023

VAZ507-100300-
/O.NEW.KLWX.WS.A.0002.231211T0000Z-231211T1200Z/
Northern Virginia Blue Ridge-
156 PM EST Sat Dec 9 2023

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

* WHAT...Heavy snow possible. Total snow accumulations in excess
  of 5 inches are possible. Winds could gust as high as 45 mph.

* WHERE...Northern Virginia Blue Ridge.

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

* IMPACTS...Travel could be very difficult. The hazardous
  conditions could impact the morning commute. Gusty winds could
  bring down tree branches.

* ADDITIONAL DETAILS...Rain will change to snow Sunday evening and
  continue through the overnight.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the latest forecasts for updates on this situation.

&&

$$

BELAK

[AtlanticWx]

hrrr looks a lot better so far, more - tilt and more held back. looks similar to nam3k at h32

[yoda]

Excellent afternoon AFD from LWX about all the hazards (225pm issuance)

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
A potent upper-level trough with northern and southern stream
energy will continue to push east from the Great Lakes and
Tennessee River Valley Sunday. At the surface, a strong cold
front will slowly approach from the west Sunday morning into
Sunday afternoon before working east of the area early Monday
morning. 12z guidance continues to illustrate a fairly
progressive system with limited phasing between the northern and
southern stream. Even with that said, a strong meridional
component remains to the upper level trough axis with ample
warm/moist advection ahead of the cold frontal boundary. 12z
upper level guidance from the CAMS and global solutions even
show a negative tilt to the trough as the low level jet
strengthen overhead.

The strong thermal gradient combined with ample moisture advection
will lead to widespread heavy rain and gusty winds across the
region. Thunderstorms are also a possibility as the region resides
in the warm sector with some elevated instability (i.e MLCAPE values
less than 150 j/kg) Sunday morning into Sunday evening. A line of
heavier showers and perhaps a thunderstorm will also accompany the
frontal passage Sunday afternoon/evening given the latest 12z CAM
guidance. Given the strong winds aloft (0-6km shear 60-80kts), this
has the potential to mix down leading to a locally damaging wind
threat. One mitigating factor for the thunderstorm threat will be
the lack of instability that is progged to be rooted within the
boundary layer. Therefore, certainty for damaging wind gusts is low
at this time (with the best chance for strong to damaging wind gusts
across south-central MD and the central VA Piedmont).

Any thunderstorm activity that we do see will enhance the heavy
rainfall threat across the region given the anomalously high PWATS
and given dynamic. Rainfall amounts will range between 1-2 inches
west of I-81 with 2-3 inches further east. Much of this rain may
fall within a 3 to 6 hour period Sunday afternoon into late Sunday
evening. This will lead to instances of urban flooding  where
relatively low FFG guidance overlaps. For that reason, a Flood Watch
has been hoisted for the Baltimore/Washington DC metros as well as
portions of northern VA.

Now for winter - this is a complex anafrontal system with
multiple waves of low pressure progged to move along the front.
The colder air will first move into the Allegheny front Sunday
evening, and spread southeast through the area overnight Sunday.
Given the anafrontal nature of the cold front, moderate precipitation
is likely to persist behind the front before cooler & drier air
works into the region. Guidance continues to bring in more cold
air which does result in more snow across the region. The best
chance for accumulating snow is in areas of higher terrain
(generally above 1750`). Have issued a Winter Weather Advisory
for portions of the Allegheny Front given the strong signal for
advisory level snow on the backside of the system coupled with
the potential for snow squalls and showers lingering into Monday
morning. Model soundings have a favorable overlap in moisture
and lift through the DGZ through mid-morning Monday. Now the
second area of winter headline is the northern Virginia Blue
Ridge zone. Have issued a Winter Storm Watch for this area given
the overwhelming signal for several inches of snow. There is
uncertainty with respect to how quickly the dry air moves in and
snow ends, but given some of the more robust scenarios, felt a
watch was prudent for this area. There is a non-zero chance for
accumulating snow further east, even near the DC and Baltimore
metros. If the precipitation rates on the cold side of the
boundary can be heavy enough well into the overnight this would
take place. However, the most likely scenario is for the
boundary layer to remain above freezing while precipitation
rates decrease as low-level drier air moves in toward morning.
Will continue to monitor.

The cold front will move off to the east Monday and a northwest
flow will usher chilly conditions. There will be a snow showers
to start along/west of the Allegheny Front (flurries may spill
east) before drier air works its way into the area during the
afternoon.

The main story for Monday will be the blustery and gusty
northwest winds due to low pressure rapidly intensifying to our
northeast (system phases during this time). Frequent gusts
around 30 to 45 mph are possible for most areas. Even stronger
winds are possible over the ridges and an a Wind Advisory may be
warranted. High pressure will build toward the area Monday
night. Winds will gradually diminish, but it will be cold with
lows in the 20s for most areas (teens in the mountains and
portions of the Shenandoah Valley).

[stormy]

Sunday night will mostly depend on how far the trough axis lingers behind the front, how long precipitation lingers behind the front and if any wrap around banding occurs.

This should be an elevation event even more so than normally expected. 

[AtlanticWx]

yea this is ab to puke snow for those NW of DC

[yoda]

Looks like DC metro changes over to snow around 07z MON on 18z HRRR 

[NorthArlington101]

1 minute ago, yoda said:

Looks like DC metro changes over to snow around 07z MON on 18z HRRR 

Would love a little more juice - around D.C. (now MBY ) the change seems to be a bit rate dependent. 

Could always spend the night across the river at least...

[AtlanticWx]

[AtlanticWx]

still puking at hr 41.

[NorthArlington101]

Just now, AtlanticWx said:

Regardless of whether it would actually pan out like that - super cool how it has it as rain up the Potomac to D.C. then following the Anacostia. 

[yoda]

2 minutes ago, NorthArlington101 said:

Would love a little more juice - around D.C. (now MBY ) the change seems to be a bit rate dependent. 

Could always spend the night across the river at least...

18z HRRR would suggest around 5 hours of snow in DC metro 

[AtlanticWx]

Just now, NorthArlington101 said:

Regardless of whether it would actually pan out like that - super cool how it has it as rain up the Potomac to D.C. then following the Anacostia. 

yeah it's really elevation dependent this run, it rains IMBY at hr 37 while 5 miles north of me gets puking snow. and that makes sense given im like 50' lower. super cool to see

[NorthArlington101]

2 minutes ago, yoda said:

18z HRRR would suggest around 5 hours of snow in DC metro 

Can't tell what is high-res nonsense vs. what's real. Will be an interesting test.

Massive differences on the 10:1/Kuchera/snow depth maps, which makes sense. Snow depth maps would verify the WSW you pointed out for the BR, but are pretty stingy almost everywhere else. 

[Terpeast]

HRRR soundings suggest temps at 33-35 F west of I-95 towards route 15

[AtlanticWx]

1 minute ago, NorthArlington101 said:

Can't tell what is high-res nonsense vs. what's real. Will be an interesting test.

Massive differences on the 10:1/Kuchera/snow depth maps, which makes sense. Snow depth maps would verify the WSW you pointed out for the BR, but are pretty stingy almost everywhere else. 

honestly gonna be fun to see these rates tho, haven't seen these type of rates modeled in a while

[Solution Man]

Anything that falls will trump last year tenfold in the PWC

Go Army Beat Navy!

[Stormchaserchuck1]

7 minutes ago, NorthArlington101 said:

Can't tell what is high-res nonsense vs. what's real. Will be an interesting test.

Massive differences on the 10:1/Kuchera/snow depth maps, which makes sense. Snow depth maps would verify the WSW you pointed out for the BR, but are pretty stingy almost everywhere else. 

snow depth maps always verify the best

[WesternFringe]

2 minutes ago, Stormchaserchuck1 said:

snow depth maps always verify the best

Any way to zoom out that map a little more?  Lol

I think it says 2-4” for Augusta County, but not really sure!