Thursday, October 30, 2014

SPC: 2-3″ per hour snowfall rates tonight

The Storm Prediction Center has issued a mesoscale discussion highlighting the possibility of 2-3″ per hour snowfall rates in Southern New England Friday evening. This is a historic storm capable of producing near all-time record snow totals in RI and SE MA. Thunder snow may occur Friday evening. It’s a remarkably dynamic situation as the storm rapidly develops over the Atlantic Ocean.

I-95 at Exit 1 at 5pm Friday - Heavy snow has arrived

I-95 at Exit 1 in SW RI at 5pm Friday – Heavy snow has arrived

mcd0124

The technical discussion is below.

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

About Fred Campagna

President and Chief Meteorologist - Right Weather LLC AMS Certified Broadcast Meteorologist

4 comments

  1. A few shots of snow lightning in Cranston! :-) And some lights flickering too :-(

  2. Fred, we just got the thunder snow at 6:30PM here in Westerly, It is crazy, the lights are flickering, the wind howling and the snow…..hope we get a break soon.

  3. Do you think the snowfall rates being seen in central CT will shift east overnight?