February 12-13 Storm, Part III: Trilogy ends and then Obs thread soon!

[NattyBo]

I'm sorry if this has been covered, but is there at least consensus on an onset time?   I have to work until after 7PM tomorrow, and am wondering just how risky the drive from Columbia --->Rockville will be, if at all.  Apologies for the IMBYish question, but I'd like to be prepared.

[NorthArlington101]

Weather Channel now showing 1-2 inches of wintery mix for Arlington

You are misunderstanding the forecast, we are due for 5-8 the previous night.

 

Wintry mix throughout the day seems likely though.

[Ian]

I actually don't hate the NAM as much as most here. The 0z run is prime time for it IMO. If it holds, it's a definite factor IMO

I like the nam but I certainly don't favor it here at least for now

[yoda]

That is a weird QPF field at 48 on the GEFS

[Ji]

Whenever you start seeing weird thing on models ...It's a bad sign of sloppy. The great storms don't show weird things

[ThePhotoGuy]

Looks like a pretty good forecast...

[MN Transplant]

We suck at dendrite making

 

We live in the south.  We generally get big storms through massive amounts of precipitation, not great snowmaking conditions.

[smokeybandit]

State of emergency already declared for maryland

[ravensrule]

Looks like a pretty good forecast...

Mark is usually very good, good sign he is bullish. Has me in the 8-12"

[HM]

The euro had this too and is honestly my biggest concern. Do you think it has some merit or do you think the models are overdoing the W Atl convection

I think the convection is legit. Its effects on the Mid Atlantic snow...I have no idea. I think the bigger synoptic players/circulations will be the main thing here, despite the GFS QPF.

The positive frontogenesis overnight / early Thu is VERY strong. This period should rock.

[cng885]

2m temps on 18z rgem approaching 40 at 48 hours

 

Edit: In central va that is

[Deck Pic]

This is what I posted on facebook to the general public

 

Latest Thoughts for DC Proper - Low Confidence - All subject to change

Percentage chance of at least (these will change)

1" - 90%
3" - 75%
6" - 45%
8" - 33%
12" - 15%
18" - 5%

I have medium confidence that for the late evening and overnight period, we will start as snow and see accumulating snow with temperatures below freezing.

I have medium confidence that we will mix with and perhaps flip to sleet and then perhaps rain sometime toward dawn on Thursday.

I have low confidence on what happens after 7 am on Thursday. 

Options for Thursday day/evening include, but are not limited to - 

- mostly snow with significant additional accumulations - 30%
- light/steady rain/mixed precipitation/snow throughout day/evening and little additional accumulation - 35%
- Rain/mix flipping back to snow, with some additional accumulation - amounts dependent on rates, duration, surface temps. - 35%

[NorthArlington101]

This is what I posted on facebook to the general public

 

Latest Thoughts for DC Proper - Low Confidence - All subject to change

Percentage chance of at least (these will change)

1" - 90%

3" - 75%

6" - 45%

8" - 33%

12" - 15%

18" - 5%

I have medium confidence that for the late evening and overnight period, we will start as snow and see accumulating snow with temperatures below freezing.

I have medium confidence that we will mix with and perhaps flip to sleet and then perhaps rain sometime toward dawn on Thursday.

I have low confidence on what happens after 7 am on Thursday. 

Options for Thursday day/evening include, but are not limited to - 

- mostly snow with significant additional accumulations - 30%

- light/steady rain/mixed precipitation/snow throughout day/evening and little additional accumulation - 35%

- Rain/mix flipping back to snow, with some additional accumulation - amounts dependent on rates, duration, surface temps. - 35%

That seems very fair, but at this point I have to think 1" is a 100% lock. A total miss seems near impossible. other then that small bit, this is the best forecast for the beltway today.

[weathercoins]

Zwyts, you're more optimistic on there than here

[yoda]

VAZ048-049-060>064-067>069-121200-

/O.CON.KAKQ.WS.W.0003.140212T1800Z-140214T0000Z/

FLUVANNA-LOUISA-PRINCE EDWARD-CUMBERLAND-GOOCHLAND-HANOVER-

CAROLINE-NOTTOWAY-AMELIA-POWHATAN-

INCLUDING THE CITIES OF...LOUISA...FARMVILLE...GOOCHLAND...

ASHLAND...CREWE

551 PM EST TUE FEB 11 2014

...WINTER STORM WARNING REMAINS IN EFFECT FROM 1 PM WEDNESDAY TO

7 PM EST THURSDAY...

A WINTER STORM WARNING REMAINS IN EFFECT FROM 1 PM WEDNESDAY TO

7 PM EST THURSDAY.

* LOCATIONS...PORTIONS OF CENTRAL VIRGINIA.

* TIMING...WEDNESDAY AFTERNOON THROUGH THURSDAY EVENING.

* HAZARDS...HEAVY SNOW...POSSIBLY MIXED WITH SLEET AT TIMES.

* ACCUMULATIONS...HEAVY SNOW ACCUMULATIONS OF 8 TO 12 INCHES ARE

EXPECTED...WITH LOCALLY UP TO 14 INCHES ACROSS FLUVANNA COUNTY

AND WESTERN PORTIONS OF LOUISA COUNTY.

[astarck]

NWS "maximum" (90th percentile) has dropped to 13.2" for DC. It begins...

[cgillesp]

NWS "maximum" (90th percentile) has dropped to 13.2" for DC. It begins...

But the hourly forecast looks up to me. Seems like they're just honing, not actually attacking the substance of the storm.

 

Also: that's from 3:44/20:44z. Quite old in the scale we're talking about.

[NCWX]

Doesn't this always happen 48 hours out? Models kill the storm, then bam it's big and bad again? 

[weathercoins]

And it makes sense that the maximum and minimums get closer together as the storm starts to develop. Anyone that thought 20+" was realistic in this setup with our climo should not really be predicting weather tbh.

There will absolutely be warnings tonight for "5 to 10 inches with locally higher amounts"

[PDIII]

Doesn't this always happen 48 hours out? Models kill the storm, then bam it's big and bad again? 

Usually the models get better as the event gets closer.   So when you see trends at this stage they probably mean something.  

[yoda]

And it makes sense that the maximum and minimums get closer together as the storm starts to develop. Anyone that thought 20+" was realistic in this setup with our climo should not really be predicting weather tbh.

There will absolutely be warnings tonight for "5 to 10 inches with locally higher amounts"

 

Yup... prob 6-10 with locally higher amounts away from I-95

[yoda]

New in 630pm ZPF's from LWX for Wed Night:

 

Snow amounts of 4-6 PG to DC to Montgomery and west toward Frederick County... 4-8 Wed night in N VA out toward I-81 corridor and down to EZF and into VA Piedmont (includes Charles Cty MD)... 6-10 in Green/Augusta/Albermarle... 8-12 in Nelson

[nj2va]

Yup... prob 6-10 with locally higher amounts away from I-95

 

Very reasonable.  

[ohleary]

bad news on WSR...aircraft had fuel leak had to abort...got about 5 drops

[yoda]

bad news on WSR...aircraft had fuel leak had to abort...got about 5 drops

 

Dang that sucks... when is the next one due to go out then?

[WEATHER53]

In the midst of concerns that have already been shared is that fact that the system remains unconsolidated right now.

I think "low confidence....medium confidence" are unnecessary elements of good forecasting. What I would choose to say instead is that as of right now, and subject to revision as more data and observation becomes available, my forecast is:

DCA:4"

Right around Beltway especially n&w:5-6"

15 miles north and west of Beltway: 6-8"

[cgillesp]

For what it's worth, the NWS keeps pushing the rain forward (sooner) without significant decline in snow totals. I know rain/sleet sucks, but a day off will certainly sweeten it. (this is NW DC) [Edited for clarity]

[Deck Pic]

In the midst of concerns that have already been shared is that fact that the system remains unconsolidated right now. I think "low confidence....medium confidence" are unnecessary elements of good forecasting. What I would choose to say instead is that as of right now, and subject to revision as more data and observation becomes available, my forecast is: DCA:4" Right around Beltway especially n&w:5-6" 15 miles north and west of Beltway: 6-8"

 

It's the exact same thing as saying you aren't confident...just more circuitously..anyway...I like your forecast

[Bob Chill]

There is still a fair amount of spread in handling the orientation of the trough and when (or if in the nam's case) the upper level low closes off. I don't feel like wasting time pulling snips together. It's easy to just look at the panels. Pull up 18z Thursday h5 vorticity panels. Each model handles it different. 

 

Euro op is the most aggressive still with closing it off and then going negative. This pulls the low into the chesapeake. It's easy to see why if goes from the nc sounds - jogs due nnw into the mouth of the bay (and stalls for a bit) and then continues its trek.

 

GFS is sloppy with the close but still has a good track. Deform never gets going strong for various reasons.

 

Nam remains open and neutral and has the best track and solution.

 

GEM is euro'ish but not as negative

 

RGEM is overdoing it imo. It's closed 3-4 contours and goes negative. That's probably the least likely.  

 

 

The spread in solutions isn't huge. Except for the rgem, i think they are all viable or anything in between. We'll see if the euro holds onto tucking the low into the bay @ 0z. I doubt it does. 

 

Front end is going to be juiced up and depending on the phasing of the energy prior to the precip getting here will determine how heavy we can get. I think it will be a pretty solid period. 

 

Like Matt said, after that, all bets are off. 

[dallen7908]

"For what it's worth, the NWS keeps pushing the rain forward without significant decline in totals. I know rain/sleet sucks, but a day off will certainly sweeten it. (this is NW DC)"

 

cgillesp,

 

What do you mean by forward?

What do you mean by "without significant declines in totals"? Declines in snow or rain? 

 

Also, what model is this based off of?