Mesoscale Discussion 2235

Issued

Dec 26, 2012, 12:48 PM EST (17:48 UTC)

Expired

Dec 26, 2012, 6:45 PM EST

In force

6 hr

Issued by

the Storm Prediction Center

The State College radar (KCCX), 107 km from the middle of the area, began a volume at 17:48 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

066 
ACUS11 KWNS 261749
SWOMCD
SPC MCD 261748
NJZ000-PAZ000-MDZ000-VAZ000-WVZ000-262345-

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

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...OKX...PHI...BGM...CTP...LWX...RNK...PBZ...RLX...

LAT...LON   41957615 41527518 40967410 40517450 39747626 39117736
            37447885 37668002 39577984 40297915 40567781 40887681
            41807674 41957615

Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in West Virginia, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.