MESO: Mesoscale Discussion 0124

ACUS11 KWNS 082152
SWOMCD
SPC MCD 082151
MAZ000-NHZ000-RIZ000-CTZ000-NYZ000-VTZ000-NJZ000-090145-

MESOSCALE DISCUSSION 0124
NWS STORM PREDICTION CENTER NORMAN OK
0351 PM CST FRI FEB 08 2013

AREAS AFFECTED...SRN NEW ENGLAND...LONG ISLAND AND SRN NY...FAR NERN
NJ

CONCERNING...HEAVY SNOW

VALID 082151Z - 090145Z

SUMMARY...SNOWFALL RATES ARE EXPECTED TO INCREASE MARKEDLY THIS
EVENING ...WITH RATES OF 1-2 INCHES PER HR OVER SRN NY/NERN NJ...TO
2-3 INCHES ACROSS SRN NEW ENGLAND. ADDITIONALLY...STRENGTHENING
WINDS MAY RESULT IN LOCALIZED BLIZZARD CONDITIONS...ESPECIALLY NEAR
THE COAST.

DISCUSSION...SFC OBS FROM 21Z CONTINUE TO REFLECT A RAPIDLY
DEEPENING OFFSHORE CYCLONE...WITH PRESSURE FALLS OF 3-4 MB/HR
OBSERVED. RADAR REFLECTIVITY MOSAIC SHOWS HIGHER PRECIPITATION RATES
ARE BEGINNING TO SPREAD INLAND ACROSS LONG ISLAND AND TOWARDS RI/SRN
MA/SRN CT. HOWEVER...SOME BRIGHT-BAND ENHANCEMENT MAY BE OCCURRING
AS MIXED P-TYPE OF RAIN AND/OR SNOW IS PREDOMINANT ACROSS LONG
ISLAND...WHERE SFC TEMPERATURES ARE CURRENTLY RANGING FROM 33-35 F.
INITIALLY...NEAR- OR ABOVE-FREEZING TEMPERATURES MAY SUPPRESS RATES
IMMEDIATELY ALONG THE COAST...BUT WITH LOW-LEVEL COLD ADVECTION
INCREASING AS THE CYCLONE TRACKS N-NE...A CHANGEOVER TO
PREDOMINANTLY SNOW IS EXPECTED WITHIN THE NEXT 2-3 HRS ACROSS MOST
OF THE HIGHLIGHTED AREA.

SNOWFALL RATES WILL BE INCREASING IN CONCERT WITH INTENSE ISENTROPIC
LIFT AND LOW-LEVEL FRONTOGENESIS WITHIN A DEFORMATION ZONE.
ADDITIONALLY...AN UPSTREAM SHORTWAVE UPPER TROUGH /LOCATED OVER THE
UPPER OH VALLEY PER 2130Z WATER VAPOR IMAGERY/ IS FORECAST TO PHASE
WITH THE OFFSHORE DEEP-LAYER CYCLONE. AS THIS OCCURS...THE
COMBINATION OF STRONG MIDLEVEL HEIGHT FALLS AND UPPER DIVERGENCE
WITHIN A COUPLED UPPER JET STRUCTURE WILL CONTRIBUTE TO INCREASING
DEEP-LAYER ASCENT. FORECAST MODEL SOUNDINGS SHOW A NEARLY SATURATED
COLUMN WITH A DEEP ISOTHERMAL LAYER LOCATED BENEATH THE DENDRITIC
GROWTH ZONE. THESE FACTORS WILL BE FAVORABLE FOR EXTREMELY HIGH
SNOWFALL RATES...ESPECIALLY FROM ERN LONG ISLAND INTO SRN NEW
ENGLAND...INCLUDING THE BOSTON METRO AREA...AS SUPPORTED BY THE
RECENT SUITE OF HIGH-RESOLUTION NUMERICAL GUIDANCE.

..ROGERS.. 02/08/2013

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

ATTN...WFO...GYX...BOX...OKX...ALY...PHI...

LAT...LON 41487041 41157173 40917237 40527347 40487426 40887445
41967427 42867373 43097258 43197147 43017087 42627073
42117042 41487041

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.