MESOSCALE DISCUSSION 0034
NWS STORM PREDICTION CENTER NORMAN OK
0657 PM CST SUN JAN 07 2007

AREAS AFFECTED...PORTIONS OF NRN NY AND NRN/CENTRAL VT ABOVE 1000 FT

CONCERNING...WINTER MIXED PRECIPITATION

VALID 080057Z - 080700Z

MODERATE SNOW WILL DEVELOP NWD ACROSS HIGHER ELEVATIONS OF THE AREA
BETWEEN 04-06Z...BEFORE CHANGING OVER TO FREEZING RAIN AROUND OR
SHORTLY AFTER 06Z. HRLY SNOWFALL RATES UP TO 1 INCH AND FREEZING
RAIN RATES UP TO 0.10 INCH WILL BE POSSIBLE FOR A 2-3 HR PERIOD INTO
THE EARLY MORNING HOURS.

A DEEP LAYER OF STRONG VERTICAL MOTION ASSOCIATED WITH THE NOSE OF A
STRONG /60 KT/ LOW LEVEL JET AND AHEAD OF A 150 KT UPPER LEVEL JET
HAS SUPPORTED MODERATE TO HVY PRECIPITATION DEVELOPMENT OVER
PORTIONS OF PA EARLY THIS EVENING. THIS FORCING WILL CONTINUE TO
DEVELOP NNEWD IN ADVANCE OF THE UPPER AND LOW LEVEL JETS ACROSS NRN
NEW ENGLAND DURING THE NEXT 3-6 HRS. INSPECTION OF 00Z ALBANY
SOUNDING INDICATED A FAIRLY DEEP DRY LAYER BELOW 700 MB.
HOWEVER...THE STRENGTH OF THE LOW LEVEL MOIST ADVECTION SHOULD
SUPPORT SATURATION TO AT LEAST 850 MB WITHIN THE NEXT 3-4 HRS ACROSS
NRN NY/NRN VT. OBS OVER NRN PA/SRN NY INDICATED LIGHT PRECIPITATION
WAS FALLING FROM CIGS AROUND 6 KFT THAT DEVELOPED A MERE 1-2 HRS
AFTER CIGS HAD BEEN ABOVE 10 KFT. HEAVIER PRECIPITATION WAS FALLING
OVER CENTRAL/ERN PA WITH CIGS AROUND 5 KFT /850 MB/. GIVEN THE SPEED
OF THE 850 MB FLOW AND STRENGTH OF THE WARM ADVECTION...AT LEAST
MODERATE PRECIPITATION RATES ARE EXPECTED TO BEGIN OCCURRING BETWEEN
04-06Z OVER THE NRN NY AND NRN/CENTRAL VT. AN EXTRAPOLATION OF THE
00Z ALBANY/BUFFALO AND GREY MAINE SOUNDINGS ALONG WITH 00Z OBS
INDICATE A WET BULB FREEZING LEVEL BETWEEN 1500-2000 FT OVER NRN NY
AND NRN VT. THIS LEVEL IS LIKELY TO FALL SOMEWHAT TO BETWEEN
1000-1500 FT OVER THE NEXT FEW HOURS DUE TO RADIATIONAL COOLING.
INITIAL PTYPE IS EXPECTED TO BE IN THE FORM OF SNOW GIVEN THE SUDDEN
ONSET OF PRECIP AND ASSOCIATED WET-BULB COOLING AFFECTS.
HOWEVER...GIVEN THE STRENGTH OF THE WARM ADVECTION...PTYPE IS
EXPECTED TO CHANGE OVER TO FREEZING RAIN WITHIN 1-2 HRS OF SNOW
DEVELOPMENT.

..CROSBIE.. 01/08/2007