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Storm obs snow/ice/rain/wind 12/26/12


Allsnow

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For folks out to our west.

MESOSCALE DISCUSSION 2234

NWS STORM PREDICTION CENTER NORMAN OK

1040 AM CST WED DEC 26 2012

AREAS AFFECTED...NERN OH...PARTS OF CNTRL/WRN/NRN PA...SWRN NY

CONCERNING...HEAVY SNOW

VALID 261640Z - 262245Z

SUMMARY...HEAVY SNOW WITH RATES OF 1-2 IN/HR IS EXPECTED TO DEVELOP

NEWD THROUGH THE AFTERNOON.

DISCUSSION...A BAND OF STRONG/DEEP ISENTROPIC ASCENT WITHIN THE WARM

CONVEYOR BELT OF THE LARGE EXTRATROPICAL CYCLONE OVER THE ERN CONUS

WILL SHIFT NEWD THROUGH THE DAY IN TANDEM WITH THE MOTION OF THE

CYCLONE CENTER. AS THE ASCENT MOVES OVER PROGRESSIVELY COLDER/DEEPER

SUBFREEZING LAYER PER REGIONAL 12Z RAOBS...INCREASED CHANCES FOR

HEAVY SNOW WILL OCCUR INTO THE AFTERNOON FROM N-CNTRL OH EWD ACROSS

CNTRL PA AND NWD INTO SWRN NY.

THE HEAVY SNOW WILL BE MOST LIKELY AFTER 18Z OVER N-CNTRL OH INTO

NWRN PA AND GRADUALLY SHIFT NEWD TOWARD SWRN NY AND CNTRL/N-CNTRL PA

LATER THIS AFTERNOON INTO THE EARLY EVENING. FORECAST SOUNDINGS

SUGGEST THAT THE ASCENT WILL ALIGN WITH DENDRITIC GROWTH ZONES

ENCOMPASSING DEPTHS OF AROUND 50 MB CENTERED BETWEEN THE 600- AND

500-MB LEVELS...WHICH WILL OVERLIE ISOTHERMAL LAYERS ABOVE THE

900-MB LEVEL. THESE FACTORS WILL SUPPORT EFFICIENT SNOW GROWTH AND

SNOWFALL RATES OF 1-2 IN/HR. ALSO...NARROW ELEVATED CAPE LAYERS

FEATURING MEAGER BUOYANCY COULD SUPPORT A MODEST CONVECTIVE

ENHANCEMENT TO PRECIPITATION RATES. A LIGHTNING STRIKE OR TWO CANNOT

BE RULED OUT WITH THE HIGHEST SNOWFALL RATES.

..COHEN.. 12/26/2012

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Intellicast is not very accurate for determining a R/S line..

this shows the same as intellicast - you are wrong plus we are up to 32.6 here by the time the precip reaches the ground will be in the 34 - 38 degree range

http://www.meteo.psu...E/loop25ne.html

precip still hours away moving north very slowly

http://www.wunderground.com/radar/radblast.asp?zoommode=pan&prevzoom=zoom&num=6&frame=0&delay=15&scale=1.000&noclutter=0&ID=PHL&type=TR0&showstorms=0&lat=0&lon=0&label=you&map.x=400&map.y=240&scale=1.000&centerx=400&centery=240&showlabels=1&rainsnow=0&lightning=0&lerror=20&num_stns_min=2&num_stns_max=9999&avg_off=9999&smooth=0

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this shows the same as intellicast - you are wrong plus we are up to 32.6 here by the time the precip reaches the ground will be in the 34 - 38 degree range

http://www.meteo.psu...E/loop25ne.html

I think the point is that while winter mosaic loops are fun to look at on account of their wide range of colors, the precip type display is formed solely by whether the surface is below, at, or above freezing. Especially considering that most of the precip in NJ is still probably not making it to the ground, I wouldn't worry about what p-type radar shows right now.

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Watch for the temps to wetbulb down to around freezing (if not there already) once the precip starts.

http://i1219.photobu...85012-26-12.gif

Warm air not advancing north as fast as first thought it would. Core cooling.

Their dew point is 25 with a wet bulb still below freezing. They'd easily be snow if it was precipitating right now.

This. Beat me to the submit button lol.

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mcd2235.gif

MESOSCALE DISCUSSION 2235

NWS STORM PREDICTION CENTER NORMAN OK

1148 AM CST WED DEC 26 2012

AREAS AFFECTED...PARTS OF ERN/SRN PA...NRN NJ...WRN/CNTRL

MD...WRN/NRN VA...ERN WV

CONCERNING...WINTER MIXED PRECIPITATION

VALID 261748Z - 262345Z

SUMMARY...WINTER MIXED PRECIPITATION WILL CONTINUE ALONG AND E OF

THE CNTRL APPALACHIANS AND ACROSS PARTS OF THE MID ATLANTIC THROUGH

THIS AFTERNOON AND INTO THE EARLY EVENING.

DISCUSSION...WIDESPREAD PRECIPITATION CONTINUES IN ASSOCIATION WITH

ISENTROPIC ASCENT ACCOMPANYING THE WARM CONVEYOR BELT OF A LARGE

EXTRATROPICAL CYCLONE ACROSS THE ERN CONUS. SNOW WITH RATES TO 1

IN/HR...SLEET...AND FREEZING RAIN WITH RATES OF 0.05 TO 0.10 IN/HR

WILL ALL REMAIN POSSIBLE DURING THE NEXT SEVERAL HOURS ACROSS THE

DISCUSSION AREA. SNOW WILL BE RELATIVELY MORE LIKELY ACROSS NERN PA

AND NRN NJ WHERE DEEPER LAYERS OF SUBFREEZING TEMPERATURES WILL

EXIST. FARTHER SOUTH...AN ELEVATED WARM LAYER WILL SUPPORT

PARTIAL/COMPLETE MELTING OF FALLING HYDROMETEORS ATOP SUBFREEZING

SFC TEMPERATURES SUPPORTING FREEZING RAIN/SLEET...THOUGH AREAS OF

SNOW WILL ALSO BE POSSIBLE.

WITH TIME...ESPECIALLY AFTER 20Z...THE PRECIPITATION-TYPE TRANSITION

ZONE WILL GRADUALLY ADVANCE NWD. THIS WILL OCCUR AS A SECONDARY SFC

CYCLONE -- CURRENTLY DEEPENING OVER CNTRL NC IN ASSOCIATION WITH SFC

PRESSURE FALLS OF AROUND 5.5 MB PER 2 HOURS -- MOVES NNEWD/NWD. AS

THIS OCCURS...WARMER LOW-LEVEL TRAJECTORIES EMANATING OVER THE WRN

ATLANTIC WATERS WILL ADVANCE NWD...PROMOTING MORE EFFICIENT

HYDROMETEOR MELTING. PRECIPITATION MAY CHANGE TO RAIN ACROSS PARTS

OF SERN PA...CNTRL MD...AND ADJACENT NRN VA. HOWEVER...COLD AIR

DAMMING PROCESSES E OF THE APPALACHIANS SHOULD MAINTAIN SHALLOW SFC

LAYERS OF SUB-FREEZING AIR ACROSS PARTS OF ERN WV...WRN VA...WRN

MD...AND S-CNTRL PA TO MAINTAIN A SLEET/FREEZING RAIN THREAT.

NEWD MID-LEVEL CYCLONE TRANSLATION WILL SUPPORT THE NEWD-MOTION OF A

MID-LEVEL DRY SLOT ACROSS THE AREA LATER THIS AFTERNOON INTO THE

EVENING...RESULTING IN A DECREASE IN PRECIPITATION

COVERAGE/INTENSITY FROM SW TO NE AFTER 21Z. HOWEVER...WINTER MIXED

PRECIPITATION WILL REMAIN POSSIBLE...ESPECIALLY OVER E-FACING SLOPES

OF THE CNTRL APPALACHIANS WHERE UPSLOPE FLOW WILL LOCALLY ENHANCE

ASCENT.

..COHEN.. 12/26/2012

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