December 15-16 Mixed Bag of Precip

[WxUSAF]

^even that snow depth map seems sketchy here, but clearly a trend to colder initial conditions in the last 24hrs. 2 rules of thumb to keep in mind in this sort of scenario:

1. Surface temps will stay cold longer with CAD

2. Low/mid levels will get eroded faster than expected. 

[Scraff]

Just now, WxUSAF said:

^even that snow depth map seems sketchy here, but clearly a trend to colder initial conditions in the last 24hrs. 2 rules of thumb to keep in mind in this sort of scenario:

1. Surface temps will stay cold longer with CAD

2. Low/mid levels will get eroded faster than expected. 

Howard County Schools  (as well as others) with a good likelihood of Thursday delays. My wife will be jumping for joy! 

[WxUSAF]

Just now, Scraff said:

Howard County Schools  (as well as others) with a good likelihood of Thursday delays. My wife will be jumping for joy! 

My wife will go nuts if they have a day off school for a little ice in the trees…

[WinterWxLuvr]

3 minutes ago, WxUSAF said:

^even that snow depth map seems sketchy here, but clearly a trend to colder initial conditions in the last 24hrs. 2 rules of thumb to keep in mind in this sort of scenario:

1. Surface temps will stay cold longer with CAD

2. Low/mid levels will get eroded faster than expected. 

On number 1, absolutely 100%.

I have not looked at this until this morning but my goodness that looks like a lot of precip on the Euro

[H2O]

10 minutes ago, WxUSAF said:

^even that snow depth map seems sketchy here, but clearly a trend to colder initial conditions in the last 24hrs. 2 rules of thumb to keep in mind in this sort of scenario:

1. Surface temps will stay cold longer with CAD

2. Low/mid levels will get eroded faster than expected. 

If model soundings show a warm nose then believe it.  Those verify a ton for I-95 E

[mattie g]

19 minutes ago, WxUSAF said:

My wife will go nuts if they have a day off school for a little ice in the trees…

Fairfax County gets five actual snow days. Any days beyond that will be synchronous virtual learning days (two-hour delays). It would be suck if the kids were to get a day off for some mixed bullshit, but I honestly don't see that happening. maybe a delay, but definitely not a day off.

[SnowenOutThere]

1 minute ago, mattie g said:

Fairfax County gets five actual snow days. Any days beyond that will be synchronous virtual learning days (two-hour delays). It would be suck if the kids were to get a day off for some mixed bullshit, but I honestly don't see that happening. maybe a delay, but definitely not a day off.

I need a day off, though a two hour delay would still work. If anything I need some mental health days built into the calendar 

[Deck Pic]

1 minute ago, mattie g said:

Fairfax County gets five actual snow days. Any days beyond that will be synchronous virtual learning days (two-hour delays). It would be suck if the kids were to get a day off for some mixed bullshit, but I honestly don't see that happening. maybe a delay, but definitely not a day off.

I miss the old days. @H2O and I had a 2 Hour delay for one flake. 
 

I wonder how far west one would have to go to get decent snow. 

[TSSN+]

Anyone have the zoomed in GEFS snow map? Looks pretty snowy for NW zones 

[TSSN+]

Code orange 

[H2O]

18 minutes ago, Deck Pic said:

I miss the old days. @H2O and I had a 2 Hour delay for one flake. 
 

I wonder how far west one would have to go to get decent snow. 

Ah the days before the knew what brining was.  And then hoping the teacher couldn't make it in.  

We didn't get a ton of ice events IIRC.  Less concrete and asphalt jungle.  

 

This one could be sneaky where western burbs ice some and all those E of the beltway go "yay cold rain"

[Paleocene]

1 minute ago, H2O said:

Ah the days before the knew what brining was.  And then hoping the teacher couldn't make it in.  

We didn't get a ton of ice events IIRC.  Less concrete and asphalt jungle.  

 

This one could be sneaky where western burbs ice some and all those E of the beltway go "yay cold rain"

Yes, for MBY, this one has "hey a bit of sleet on the grass, my trees look kind of icy! but the roads are wet, and those look like raindrops, and its 34 degrees... oh moco schools are cancelled? cool i guess" written all over it. But i'll hold out for a pleasant crunchy icey surprise

[high risk]

58 minutes ago, WxUSAF said:

^even that snow depth map seems sketchy here, but clearly a trend to colder initial conditions in the last 24hrs. 2 rules of thumb to keep in mind in this sort of scenario:

1. Surface temps will stay cold longer with CAD

2. Low/mid levels will get eroded faster than expected. 

     3.   See rule 1, and the GFS always erodes the surface cold air too quickly.

[Terpeast]

42 minutes ago, TSSN+ said:

Code orange 

 

Even southern MD is under code yellow? Bullish much? 

[mappy]

1 hour ago, TSSN+ said:

Thursday morning going to be a mess. Sleet covered roads excellent 

yeah, I think it's going to be a messy Thursday morning for those of us in the northern tier. You probably more so than me, I tend to warm at the mid-levels faster than Westminster. 

[DDweatherman]

7 minutes ago, Terpeast said:

 

Even southern MD is under code yellow? Bullish much? 

The non-retired meteorologists must see something they like. 

[Chase]

15 minutes ago, Terpeast said:

 

Even southern MD is under code yellow? Bullish much? 

They only have three zones (the heavier black outlines), not county-by-county. Don't read too much into that.

Western ridges, Shenandoah Valley/north and west suburbs, and I-95/Southern Maryland.

[Ji]

euro dosent seem too interested

[WesternFringe]

Euro doesn't think too much of snow chances, even at my elevation and location in the valley.  Anyone have freezing rain and sleet accumulation from the Euro?

[mappy]

@WesternFringe

[Eskimo Joe]

LWX 3pm AFD. See red highlighted section.

Quote

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
TEMPERATURES ON WEDNESDAY SHOULD SOMEWHAT REBOUND TO THE UPPER
30S TO LOW 40S, THOUGH THERE IS UNCERTAINTY IN THAT ASPECT AS 
CLOUD COVER WILL OVERSPREAD THE AREA FROM WEST TO EAST, 
POTENTIALLY KEEPING THOSE WEST OF THE BLUE RIDGE COLDER THAN 
CURRENTLY FORECAST. AS A STRONG AREA OF LOW PRESSURE TRACKS 
FROM THE CENTRAL PLAINS TOWARD THE GREAT LAKES A WARM ADVECTION 
PRECIPITATION STARTS TO REACH AREAS ALONG I-64 AND BACK TOWARD 
AUGUSTA AND HIGHLAND COUNTIES BY THE AFTERNOON HOURS. 

AFTER SUNSET WEDNESDAY EVENING THE TRANSITION FROM PLAIN RAIN TO
A WINTRY MIX SHOULD BEGIN FOR THE HIGHER ELEVATIONS AT AND
BETWEEN THE BLUE RIDGE AND ALLEGHENY FRONT. THIS WINTRY MIX WILL
STEADILY TAKE HOLD ACROSS THE SHENANDOAH VALLEY THROUGH THE 
NIGHT AS THE LOWEST LEVELS COOL DUE TO EVAPORATIVE COOLING, AND 
ADDITIONAL WARM AIR MOVES IN ABOVE THAT. SIGNIFICANT ICING IS 
POSSIBLE ACROSS THE SHENANDOAH VALLEY, ALLEGHENIES, BLUE RIDGE, 
AND THEIR MOUNTAIN VALLEYS. HOWEVER, A GREAT DEAL OF 
UNCERTAINTY PLAGUES THE FORECAST WHICH WILL HELP DICTATE THE 
TIMING AND PRECIPITATION TYPES/OVERALL INTENSITY.

FOR AREAS EAST OF THE BLUE RIDGE THERE'S STILL A LOT OF 
UNCERTAINTY AS TO WHAT THE INITIAL P-TYPE AND TOTAL DURATION
WILL BE. IT COULD START OFF AS RAIN OR A SHORT BURST OF 
SNOW/SLEET, ESPECIALLY NORTH OF I-66. THEN, FOR MOST OF THE 
MORNING A PERIOD OF RAIN WITH SLEET AND FREEZING RAIN POSSIBLY 
MIXED IN MOVES FROM SOUTH TO NORTH ACROSS THE METRO AREAS. BY 
THE EARLY AFTERNOON, MOST OF THE I-95 CORRIDOR SHOULD TRANSITION
OVER TO RAIN.

THE AREAS MOST LIKELY TO SEE ACCUMULATING SNOW AT THIS TIME ARE
IN WESTERN MD AND THE EASTERN WV PANHANDLE WHERE MODEL SOUNDINGS
SHOW THE THERMAL PROFILE COULD DROP BELOW FREEZING THROUGHOUT, 
AND ALLOW FOR A PERIOD OF SNOW. SOMETHING TO NOTE IN THE 
MODELS THIS AFTERNOON IS THAT THE WARM LAYER ALOFT IS SHALLOWER 
THAN WHAT WAS DEPICTED YESTERDAY. WITH THIS KIND OF SETUP, THIS 
COULD BE ONE OF THE FACTORS THAT PUSH FINAL SNOW, ICE, SLEET, 
AND FREEZING RAIN AMOUNTS UP OR DOWN. 

GIVEN CURRENT TRENDS, IT'S POSSIBLE WINTER STORM WATCHES ARE 
ISSUED FOR SOME ZONES LATER TONIGHT OR BY TUESDAY AFTERNOON.
ALL IN ALL, STILL A LOT TO DETERMINE IN THE COMING DAYS. STAY 
TUNED!

 

[batmanbrad]

5 hours ago, Weather Will said:

WB 12Z NAM.  Temps go above freezing NW between 10 am and 1pm.

So from this map, instead of the DC Snow Hole, we have the FairfaxCo/MoCo/HoCo/Baltimore ZR Hole!

[Paleocene]

4 minutes ago, batmanbrad said:

So from this map, instead of the DC Snow Hole, we have the FairfaxCo/MoCo/HoCo/Baltimore ZR Hole!

The day when I get accumulating ZR inside the beltway and you don't in Gaithersburg will be an interesting day.

[SnowenOutThere]

32 minutes ago, batmanbrad said:

So from this map, instead of the DC Snow Hole, we have the FairfaxCo/MoCo/HoCo/Baltimore ZR Hole!

But we get the sleet 

[MillvilleWx]

This storm is a classic case of CAD with the fall line and west the primary beneficiary of any winter precip. Judging by initial thermals off guidance, the storm will start as some snow out by I-81 and MAYBE a short period in the beginning for places along and west of the fall line. 925/850mb winds increase out of the SE during the 12-15z time frame, likely when we see the advection of warm air within the boundary layer that's pivotal to ptype. At the surface, the wedge of cold air will be tough to erode west of the BR with 30-35F likely to hold through a majority of Thursday. NBM 25th percentile shows places like Winchester/MBG/Cumberland hanging tight around 31-33F for an extended period of time with a textbook ZR signature on soundings from deterministic models. A light icing event is probably best suited for places east of US15 with more ice located west of the US15 divide, especially in valleys where cold air will take longest to scour out. 

Currently looks like a high-end Advisory event for I-81 and west with some WSW potential if the CAD signature shows more staying power. The 925-700mb is getting torched no matter what, so don't feel disgruntled if you see the snow chances eroded with mainly ZR/IP as the primary ptypes during the event. The metros should see very little icing, but a light glaze prior to 9am is possible before we see temps mix efficiently above 32F as SE flow ramps up the second half of the morning, through the rest of the day. 

Obviously if cold trends point to a colder start, then everyone could see Advisory level icing with warnings out by I-81 and the eastern WV hill country. We've seen that before, but as @WxUSAF mentioned, cold air within the BL gets eroded faster than normal. Especially early season where local water temps are hovering in the 50s.  

[H2O]

I’ll wait for the NAMing to show colder until Wednesday 12z run that will warm nose and  wash the beet juice brine away

[mappy]

Thanks for stopping in and offering your thoughts @MillvilleWx!

I know how these usually are IMBY -- I will maybe see snow, but sleet/zr for a little bit before the mid-levels get warm. Despite being north and west of 95, I'm still just close enough to the bay that those mid-levels warm quickly. 

edit to add: I anticipate a 2hr delay for school

[Buddy1987]

18Z NAM really laying the smackdown from about HR 60 to HR 72 up and down 81. Waiting for Pivotal to update Freezing Rain map totals, as there seems to be a glitch... Here is HR 66 when it's already been happening:

[Buddy1987]

Does the RDPS normally run colder than most models? The Freezing Rain totals are prolific, even if you cut them in half here..

[osfan24]

3 minutes ago, Buddy1987 said:

Does the RDPS normally run colder than most models? The Freezing Rain totals are prolific, even if you cut them in half here..

Yeah that's a weenie model.