December 29-30 storm.

[TUweathermanDD]

The GFS look a little drier than 12Z to me? Through 0Z Sunday. Looks like .1 to .25 area wide.

West of DC yes towards you, .35 for Baltimore folks Phin and co.

[PhineasC]

The GFS look a little drier than 12Z to me? Through 0Z Sunday. Looks like .1 to .25 area wide.

No doubt the 18Z suite was drier for Leesburg west. I am sure now that there will be both a precip screw and a temp screw. The area south of 40N that gets decent snow will be rather small, I think.

[TUweathermanDD]

Holy crap my newly gifted Kestrel via easternuswx worth 100 dollars just plummeted the temp to 35 here. Woah. Probably wrong, except they're not. Olympics baby.

[WinterWxLuvr]

We had clear skies all darn day long here and the clouds rolled in exactly at 4:30 as the sun was starting to set. Absolute horrible timing. Our high was 37. 36 now and the local wxbug says the dp is 23F. Winchester reports 29F dp, so I don't know what is accurate. Hopefully, the dp is lower than 29 and we may get some help from evaporational cooling later on tonight.

I doubt your worry is p-type. It's the p.

[mitchnick]

No doubt the 18Z suite was drier for Leesburg west. I am sure now that there will be both a precip screw and a temp screw. The area south of 40N that gets decent snow will be rather small, I think.

the NAM was more pronounced with its precip hole probably because GFS is a global model, which suggests the GFS is seeing the same thing the NAM is seeing but w/o the NAM's resolution

time to review the 84 hr NAM I guess

[Kmlwx]

Holy crap my newly gifted Kestrel via easternuswx worth 100 dollars just plummeted the temp to 35 here. Woah. Probably wrong, except they're not. Olympics baby.

It sounds like you are advertising the product

"But order now and get TWO!!!"

Anyway, even if we lose a few more degrees it is going to be a close call.

[mitchnick]

Holy crap my newly gifted Kestrel via easternuswx worth 100 dollars just plummeted the temp to 35 here. Woah. Probably wrong, except they're not. Olympics baby.

yeah, but the warmer air has got to go somewhere, and it is up

you're only getting an inversion a few hundred meters above you and that air will have to be cooled too by the precip

you'll see in in the soundings at iad when they come out around 9pm

[TUweathermanDD]

the NAM was more pronounced with its precip hole probably because GFS is a global model, which suggests the GFS is seeing the same thing the NAM is seeing but w/o the NAM's resolution

time to review the 84 hr NAM I guess

Or the NAM sucks, but the GFS dies out the so-called primary that goes up into W PA earlier than the NAM, so the moisture transport is completed quicker on the model, therefore the further SW cutoff.

[TUweathermanDD]

yeah, but the warmer air has got to go somewhere, and it is up

you're only getting an inversion a few hundred meters above you

you'll see in in the soundings at iad when they come out around 9pm

Maybe so, but I'll take my chances if the temp keeps falling, better than going for it at 35. My suburb here seems to randomly be chillier. Thinking about driving NW.

[mitchnick]

Or the NAM sucks, but the GFS dies out the so-called primary that goes up into W PA earlier than the NAM, so the moisture transport is completed quicker on the model, therefore the further SW cutoff.

I guess I ain't feelin' this one bro

hope I'm wrong

[Deck Pic]

there should be no concern with surface temps...they are fine..even DCA is 38/25 last hour

[TUweathermanDD]

there should be no concern with surface temps...they are fine..even DCA is 38/25 last hour

I'd be a lot more concerned about the precip Matt, for sure.

[EastCoast NPZ]

Twisterdata.com is pretty good for forecast soundings. Easy click to location. I

Great site, thank you. Here is a 18z GFS sounding +15 hr. Everything looks good temp wise, but what about the rel humidities? At 500 - 700 mb the air is close to saturated, but at 850 it is not. As someone trying to learn, could someone weigh in with this sounding wrt to ideal humidities for snow at these layers?

GFS Text Sounding | 09 UTC Sat 29 Dec 2012 | Latitude: 39.0000 | Longitude: -78.0000 PRES HGHT TEMP DWPT RELH MIXR DRCT SKNT TWTB TVRT THTA THTE THTV 987.5 210 -0.4 -1.0 95 3.6 141 4 -0.7 0.1 273.7 283.6 274.3 975.0 312 -0.5 -1.5 93 3.5 150 8 -0.9 0.0 274.6 284.3 275.2 950.0 519 -1.1 -2.4 91 3.4 162 16 -1.6 -0.6 276.0 285.5 276.6 925.0 732 -1.9 -3.1 92 3.3 171 20 -2.4 -1.4 277.3 286.6 277.9 900.0 949 -2.9 -4.2 91 3.1 180 23 -3.4 -2.4 278.4 287.3 279.0 850.0 1402 -3.1 -5.5 84 3.0 193 31 -4.0 -2.7 282.8 291.5 283.3 800.0 1881 -3.6 -5.2 89 3.3 191 30 -4.2 -3.1 287.2 296.8 287.8 750.0 2392 -3.6 -4.3 95 3.7 197 32 -3.9 -3.0 292.6 303.7 293.2 700.0 2937 -4.0 -4.3 98 4.0 210 38 -4.2 -3.4 297.9 310.1 298.7 650.0 3520 -5.8 -5.9 99 3.8 222 43 -5.8 -5.1 302.4 314.2 303.1 600.0 4145 -8.5 -8.7 99 3.3 230 46 -8.6 -8.0 306.1 316.7 306.7 550.0 4815 -12.0 -12.3 98 2.7 233 51 -12.2 -11.6 309.7 318.5 310.2 500.0 5540 -15.9 -16.3 97 2.1 235 58 -16.1 -15.6 313.5 320.7 313.9 450.0 6326 -20.8 -21.0 99 1.6 238 67 -20.9 -20.6 316.9 322.4 317.2 400.0 7185 -27.8 -28.3 96 0.9 239 78 -28.0 -27.7 318.6 322.0 318.8 350.0 8128 -35.9 -38.7 76 0.4 237 86 -36.4 -35.9 320.1 321.5 320.1 300.0 9178 -44.8 -55.8 28 0.1 238 96 -45.6 -44.8 321.9 322.2 321.9 250.0 10374 -52.3 -65.4 19 0.0 242 112 -52.9 -52.3 328.0 328.1 328.0 200.0 11801 -56.1 -70.4 15 0.0 245 119 -56.7 -56.1 343.5 343.6 343.5 150.0 13619 -59.1 -72.1 17 0.0 259 99 -59.7 -59.1 367.8 367.8 367.8 100.0 16157 -60.6 -80.0 6 0.0 260 48 -61.3 -60.6 410.0 410.0 410

well, that did not work. let me figure a way to post this info.

[mitchnick]

Great site, thank you. Here is a 18z GFS sounding +15 hr. Everything looks good temp wise, but what about the rel humidities? At 500 - 700 mb the air is close to saturated, but at 850 it is not. As someone trying to learn, could someone weigh in with this sounding wrt to ideal humidities for snow at these layers?

GFS Text Sounding | 09 UTC Sat 29 Dec 2012 | Latitude: 39.0000 | Longitude: -78.0000 PRES HGHT TEMP DWPT RELH MIXR DRCT SKNT TWTB TVRT THTA THTE THTV 987.5 210 -0.4 -1.0 95 3.6 141 4 -0.7 0.1 273.7 283.6 274.3 975.0 312 -0.5 -1.5 93 3.5 150 8 -0.9 0.0 274.6 284.3 275.2 950.0 519 -1.1 -2.4 91 3.4 162 16 -1.6 -0.6 276.0 285.5 276.6 925.0 732 -1.9 -3.1 92 3.3 171 20 -2.4 -1.4 277.3 286.6 277.9 900.0 949 -2.9 -4.2 91 3.1 180 23 -3.4 -2.4 278.4 287.3 279.0 850.0 1402 -3.1 -5.5 84 3.0 193 31 -4.0 -2.7 282.8 291.5 283.3 800.0 1881 -3.6 -5.2 89 3.3 191 30 -4.2 -3.1 287.2 296.8 287.8 750.0 2392 -3.6 -4.3 95 3.7 197 32 -3.9 -3.0 292.6 303.7 293.2 700.0 2937 -4.0 -4.3 98 4.0 210 38 -4.2 -3.4 297.9 310.1 298.7 650.0 3520 -5.8 -5.9 99 3.8 222 43 -5.8 -5.1 302.4 314.2 303.1 600.0 4145 -8.5 -8.7 99 3.3 230 46 -8.6 -8.0 306.1 316.7 306.7 550.0 4815 -12.0 -12.3 98 2.7 233 51 -12.2 -11.6 309.7 318.5 310.2 500.0 5540 -15.9 -16.3 97 2.1 235 58 -16.1 -15.6 313.5 320.7 313.9 450.0 6326 -20.8 -21.0 99 1.6 238 67 -20.9 -20.6 316.9 322.4 317.2 400.0 7185 -27.8 -28.3 96 0.9 239 78 -28.0 -27.7 318.6 322.0 318.8 350.0 8128 -35.9 -38.7 76 0.4 237 86 -36.4 -35.9 320.1 321.5 320.1 300.0 9178 -44.8 -55.8 28 0.1 238 96 -45.6 -44.8 321.9 322.2 321.9 250.0 10374 -52.3 -65.4 19 0.0 242 112 -52.9 -52.3 328.0 328.1 328.0 200.0 11801 -56.1 -70.4 15 0.0 245 119 -56.7 -56.1 343.5 343.6 343.5 150.0 13619 -59.1 -72.1 17 0.0 259 99 -59.7 -59.1 367.8 367.8 367.8 100.0 16157 -60.6 -80.0 6 0.0 260 48 -61.3 -60.6 410.0 410.0 410

now that made me laugh

[swimmatte]

Weatherbug dropped to 33.2 with a 27 dp while my WS dropped all the way from 39 to 32.5 in a matter of 2 hours here.

[PhineasC]

Still clear and temp dropping still. Agree that surface temps DC north should be fine.

[NOVAForecaster]

33 degrees here, not bad!

[Swiscaster]

I accidentally just watched local news weather. "Erica Grow" on Channel 9 just called for T-1" in the immediate metro area, 1-2" N+W of the Loudoun/Fairfax line, and 2-4" in BFE. But she also just called the Kennedy Center the "Lincoln Center....." uhboy

[EastCoast NPZ]

I doubt your worry is p-type. It's the p.

Yeah, these latest model runs are not trending in our favor.

[swimmatte]

Yeah, these latest model runs are not trending in our favor.

Looks pretty good to me?

http://www.goes.noaa.gov/GSSLOOPS/ecwv.html

[Kmlwx]

The 4-5 nearest Weatherbug stations to me are running 33-35ish. One random one is at 37. It FEELS pretty cold out there but I'd almost believe the 37 more than the 33

[EastCoast NPZ]

Looks pretty good to me?

http://www.goes.noaa...LOOPS/ecwv.html

I'm not nearly knowledgeable enough to make assumptions based on the WV imagery. The radar looks decent to my eyes, but the 18z models don't look very good for my area wrt precip.

[Deck Pic]

I'd be a lot more concerned about the precip Matt, for sure.

I'm not concerned about precip either....I am concerned about precip type...that is 90% of my concern

[Kmlwx]

Just for fun I took my cheap infrared thermometer and tested a couple spots in the yard. Walkway is reading like 30-32 while the grass and dirt along the walkway is in the upper 20s. Driveway and street (not heavily traveled) was around 30 as well. Should bode well for accumulation. I might be inclined to believe the 33ish Weatherbug readings around me.

[87storms]

still have a light N/NE wind. temps are in a good shape. i'm wondering how much of that energy is left as it crosses over the mountains and how soon the coastal takes over. this does look like at least a relatively decent event for dc and vicinity.

[WVclimo]

32/22. Snow cover really helping out with cooling.

[aldie 22]

32.8 dp 26

[NOVAForecaster]

[swimmatte]

I'm not nearly knowledgeable enough to make assumptions based on the WV imagery. The radar looks decent to my eyes, but the 18z models don't look very good for my area wrt precip.

Honestly, less than 12 hours from the storm, I'm really not worried what 18z models say. It's all about where the players actually are. It's almost like having NFL coaches watching old game film during halftime, instead of discussing the first half of the game.

[Ian]

Doug K going for the DC screw job