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Chill Storm Discussion and Obs


WinterWxLuvr

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With surface low pressure over Alabama right now in turn having the storm more south and east than modeled will this allow HP to funnel in more cooler air down to Southern VA or if storm goes more south and east will it be harder to scour out low level air? Just curious

Yes, you would continue have a N to NNE wind keeping in the cold air locked in at the surface.

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Common sense tells me mostly rain here....yesterday's storm kinda made my common sense waver....euro and gfs say we start frozen here...even nam says a little...don't think I'm buying it...my call is a bit of freezing rain turning to rain by 9am...very pessimistic on this one since yesterday over performed.

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Common sense tells me mostly rain here....yesterday's storm kinda made my common sense waver....euro and gfs say we start frozen here...even nam says a little...don't think I'm buying it...my call is a bit of freezing rain turning to rain by 9am...very pessimistic on this one since yesterday over performed.

we have been watching this so long I will be happy to see it come and go...the thing I am most interested in seeing is how far north it gets before moving east....even a 50 mile difference may mean holding the cold longer...I remember a few days ago when it was thought this would plow deep into Ohio as a 992

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Common sense tells me mostly rain here....yesterday's storm kinda made my common sense waver....euro and gfs say we start frozen here...even nam says a little...don't think I'm buying it...my call is a bit of freezing rain turning to rain by 9am...very pessimistic on this one since yesterday over performed.

I sense 2" of snow and sleet then a flip to ZR till around noon or so then to plain ole rain. Snowpack in the yard is still holding on nicely. Down to 34* now on my PWS

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the rainfall totals are going to be in record breaking territory (for the day, that is) so it (snow) will all be gone by 12Z Thursday for anyone in our area <2K' asl

12/26 record precip for the day is 1.31" and 12/27 is 1.21"

the only thing that may prevent breaking one of those records is that half, more or less, will fall before/after midnight on the 27th

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I sense 2" of snow and sleet then a flip to ZR till around noon or so then to plain ole rain. Snowpack in the yard is still holding on nicely. Down to 34* now on my PWS

The RAP agrees, the NAM says "Yeah, right, straight to sleet for you!, the HRRR agrees with the RAP. Interesting short-term model battle unfolding. My bet is slightly towards the HRRR/RAP idea.

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The nam is really way off from all other guidance now. Not saying its wrong. Perhaps with its higher res it can see something the others are missing but it blasts the warm layer way north of all other models early tomorrow. It doesn't matter as much here but in east central pa for instance it's the difference between 6-12" and almost nothing. Amazing. I remember one similar scenario with the v-day storm in 2007 and the nam was right with the warm layer getting way further north in pa then other guidance. We will see this time.

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I sense 2" of snow and sleet then a flip to ZR till around noon or so then to plain ole rain. Snowpack in the yard is still holding on nicely. Down to 34* now on my PWS

Big difference a few miles east of leesburg where nothing is left as of this morning. Only got a 1/2 inch here. Might be as close a difference tomorrow.

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Before bed thoughts on tomorrow:

Timing on the precip is everything tomorrow morning because by 1 pm we're all rain except for the Shenandoah Valley /I-81 corridor. I think even SE-DC/PG and Annapolis (and N) could start as a bit of sleet or snow before going to all rain by 10AM. Areas NW of I95 should start as snow before going to sleet and then rain. Areas S and E of IAD or MD200 should be all rain by 11:30AM. Leesburg/Fredrick/Westminster by 12:30 and everyone else outside of the Shenandoah by 1. I'm thinking .15 to .3" of QPF across the entire area by 1 PM.

Windy and Rainy the rest of the day.

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MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

1121 PM EST TUE DEC 25 2012

VALID DEC 26/0000 UTC THRU DEC 29/1200 UTC

STORM MOVING ACROSS THE SOUTH AND EAST

======================================

PREFERENCE: NON-NAM COMPROMISE WITH AVERAGE CONFIDENCE

INITIALLY, THE 00Z NAM APPEARS TO BE 2-3C TOO WARM WITH ITS 850

HPA FREEZING LINE ACROSS VIRGINIA/MARYLAND AND THE UPPER OHIO

VALLEY. THE 00Z GFS PROBLEMS ARE CONSTRAINED TO A 2-3C ERROR IN

THE UPPER OHIO VALLEY. THESE 850 HPA TEMPERATURE ERRORS HAVE

POSSIBLE IMPLICATIONS FOR THEIR FORECAST WINTER WEATHER

PRECIPITATION TYPES EARLY ON. SEE WINTER WEATHER

GRAPHICS/PRODUCTS FROM HPC AND LOCAL FORECAST OFFICES FOR MORE ON

SNOW/SLEET/FREEZING RAIN EXPECTATIONS WITH THIS CYCLONE.

DURING THE SHORT RANGE PERIOD, THE 00Z NAM BECOMES A SLOWER THAN

THE REMAINDER OF THE GUIDANCE WITH THE SYSTEM MOVING THROUGH THE

NORTHEAST FROM LATE THURSDAY ONWARD, AND LIES NEAR THE SOUTHWEST

CORNER OF THE 12Z GLOBAL ENSEMBLE SPREAD WITH ITS ASSOCIATED

SURFACE LOW POSITION FRIDAY MORNING. TREND-WISE, THE GUIDANCE HAS

STRENGTHENED THIS SYSTEM OVER THEIR PAST DAY OF RUNS, BUT THE NAM

HAS STOPPED TRENDING QUICKER/NORTHEAST. WITH THE 21Z SREF/18Z

GEFS/12Z ECMWF ENSEMBLE MEANS SUPPORTING THE QUICKER NON-NAM

CONSENSUS, THE PREFERENCE IS FOR A NON-NAM COMPROMISE HERE WITH

AVERAGE CONFIDENCE CONSIDERING ITS PROGRESSIVE NATURE.

...MODEL TREND GRAPHICS AT www.hpc.ncep.noaa.gov/html/model2.shtml

...500 MB FORECASTS AT www.hpc.ncep.noaa.gov/h5pref/h5pref.shtml

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OMG I haven't been in these threads here for so long I've forgotten what a crackhead jebman is.

Anyways, DCA is 37/28 and IAD is 35/25 as of 3AM. Virga beginning to overspread the area, although the time between virga & storm onset should be short.

Composite radar is your best friend for hallucinations. Base actually isn't much worse, but it's clear there is minor dry air the precipitation will have to work through.

http://radar.weather.gov/radar.php?rid=LWX&product=NCR&overlay=11101111&loop=yes

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Well the NAM is either going to score the coup or it is going down with the ship. Its even warmer at 6z. It doesn't matter as much for our area, the difference between an inch or two of frozen and nothing...but its even more pronounced just north of us where all other guidance shows 6" or more and the NAM would imply just a quick change to rain. major difference right to the end, very interesting to see who wins.

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GFS is colder :lol: even has .5 QPF in NW VA with 850s below 0c at 12 hrs. IAD N and W is 32 per 2m at 12 hrs while DCA is 34ish and rising. DCA is 32 at 9 hrs wth over .25 QPF already and is or about to change to rain from sleet I would think. Someone is busting badly... NAM or GFS. By 21z everyone should be rain except way NW corner

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