Mesoscale Discussion 2239

Issued

Dec 26, 2012, 4:39 PM EST (21:39 UTC)

Expired

Dec 26, 2012, 9:45 PM EST

In force

5 hr

Issued by

the Storm Prediction Center

Counties Berkshire County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Worcester County, MA, Cheshire County, NH, Hillsborough County, NH, Sullivan County, NH, Rensselaer County, NY, Washington County, NY, Kent County, RI, Providence County, RI, Bennington County, VT, Windham County, VT, Windsor County, VT

The Albany radar (KENX), 126 km from the middle of the area, began a volume at 21:41 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.

073 
ACUS11 KWNS 262140
SWOMCD
SPC MCD 262139
NHZ000-MAZ000-RIZ000-CTZ000-VTZ000-NYZ000-270245-

MESOSCALE DISCUSSION 2239
NWS STORM PREDICTION CENTER NORMAN OK
0339 PM CST WED DEC 26 2012

AREAS AFFECTED...SRN VT...SRN NH...CNTRL/WRN MA...MUCH OF
CT/RI...PARTS OF FAR ERN NY

CONCERNING...WINTER MIXED PRECIPITATION

VALID 262139Z - 270245Z

SUMMARY...SNOW WITH RATES OF 1-2 IN/HR WILL OVERSPREAD THE AREA
AFTER 00Z. A TRANSITION TO WINTER MIXED PRECIPITATION IS EXPECTED TO
OCCUR FROM S TO N AFTER 03Z.

DISCUSSION...INTENSIFYING SFC LOW PRESSURE WILL TRACK NNEWD ALONG
THE ATLANTIC COAST FROM THE MID ATLANTIC TO NEW ENGLAND THROUGH
TONIGHT. STRONG ISENTROPIC ASCENT PRECEDING THE CYCLONE CENTER WILL
ALLOW PRECIPITATION TO SPREAD ACROSS THE AREA LATE THIS AFTERNOON
INTO THIS EVENING. CURRENT OBSERVATIONAL TRENDS AND THE BULK OF
HIGH-RESOLUTION WRF GUIDANCE SUGGEST THAT HEAVY SNOW WILL OVERSPREAD
PARTS OF SRN/WRN NEW ENGLAND AND ADJACENT FAR ERN NY FROM SW TO NE
AFTER 00Z.

THE AFOREMENTIONED ASCENT...AUGMENTED BY THE ASCENDING BRANCHES OF
FRONTOGENETIC CIRCULATIONS...WILL INTERSECT DENDRITIC GROWTH ZONES
BETWEEN THE 560- AND 500-MB LEVELS AS EVIDENT IN FORECAST SOUNDINGS.
THIS WILL SUPPORT EFFICIENT SNOW GROWTH. FORECAST SOUNDINGS ALSO
DEPICT ISOTHERMAL LAYERS FEATURING TEMPERATURES AROUND/JUST BELOW 0C
BETWEEN THE 900- AND 700-MB LEVELS...WHICH WILL SUPPORT SNOW
AGGREGATION. AS SUCH...SNOWFALL RATES OF 1-2 IN/HR WILL BE
POSSIBLE...WITH THE HIGHEST RATES ACCOMPANYING ANY CONVECTIVELY
ENHANCED PRECIPITATION OWING TO THE PRESENCE OF NARROW ELEVATED CAPE
LAYERS. AN ISOLATED LIGHTNING STRIKE OR TWO MAY OCCUR WITH THE
HEAVIEST SNOW.

AFTER 03Z...STRONG WARM ADVECTION ACCOMPANYING A NWD-MOVING
LOW-LEVEL JET MAX WILL RESULT IN A PRECIPITATION-TYPE TRANSITION
FROM S TO N. THIS WILL OCCUR AS WARMER TRAJECTORIES EXTEND INLAND
FROM THE MARINE LAYER OVER THE ATLANTIC WATERS. SLEET/FREEZING RAIN
WILL BE POSSIBLE AS PARTIAL/COMPLETE MELTING OF FALLING HYDROMETEORS
OCCURS ATOP SUB-FREEZING SFC TEMPERATURES. A PHASE CHANGE TO RAIN
MAY OCCUR WHERE SFC TEMPERATURES RISE ABOVE FREEZING. WINTER MIXED
PRECIPITATION COULD CONTINUE INTO THE NIGHT.

..COHEN.. 12/26/2012

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

ATTN...WFO...GYX...BOX...BTV...OKX...ALY...

LAT...LON   43167145 42137125 41497157 41397277 41237353 42277337
            43147368 43507355 43687265 43167145

Mesoscale Discussions in Connecticut, 2012Mesoscale Discussions in Massachusetts, 2012Mesoscale Discussions in New Hampshire, 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.