MD 2112 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF VT…NH…MAINE…MA…RI…CT
MESOSCALE DISCUSSION 2112
NWS STORM PREDICTION CENTER NORMAN OK
0242 AM CST TUE DEC 29 2015
AREAS AFFECTED...PORTIONS OF VT...NH...MAINE...MA...RI...CT
CONCERNING...WINTER MIXED PRECIPITATION
VALID 290842Z - 291445Z
SUMMARY...AREAS OF WINTER PRECIPITATION WILL CONTINUE TO SPREAD
ACROSS MUCH OF SRN AND CNTRL NEW ENGLAND DURING THE PRE-DAWN
HOURS...AND CONTINUE INTO THE MORNING. THIS INCLUDES AREAS OF
MODERATE TO HEAVY SNOW AND SLEET...ALONG WITH PATCHY FREEZING RAIN.
AREAS OF LIQUID RAIN MAY BECOME INCREASINGLY ESTABLISHED ACROSS SRN
NEW ENGLAND DURING THE MORNING...ALTHOUGH THERE IS UNCERTAINTY
REGARDING PROSPECTS FOR A CHANGEOVER TO LIQUID RAIN IN THE MORNING.
DISCUSSION...WIDESPREAD SFC PRESSURE FALLS ON THE ORDER OF 2-3 MB
PER 2 HOURS ARE ANALYZED ACROSS PARTS OF THE MID-ATLANTIC INTO SRN
NEW ENGLAND AND JUST OFF THE ATLANTIC COAST...AS AMPLE WARM
ADVECTION CONTINUES TO OVERSPREAD THE AREA WELL E OF A STRONG
MID-LEVEL PV MAX CROSSING THE GREAT LAKES REGION. AS SUCH...AREA VWP
DATA SAMPLE STRONGLY VEERING WINDS WITH HEIGHT. MOSAIC RADAR LOOPS
INDICATE A SHIELD OF WIDESPREAD PRECIPITATION COINCIDING WITH THE
WARM-ADVECTION/CONVEYOR PATTERN...WHICH IS FORECAST TO CONTINUE
SPREADING ACROSS THE DISCUSSION AREA THROUGH THE MORNING HOURS.
LOW-LEVEL SATURATION IN ASSOCIATION WITH WET-BULB EFFECTS WILL
ENCOURAGE INCREASING PRECIPITATION INTENSITY THROUGH THE PRE-DAWN
HOURS...WITH WINTER MIXED PRECIPITATION LIKELY ENSUING OWING TO
SUB-FREEZING SFC TEMPERATURES.
AREAS OF SNOW -- MODERATE TO HEAVY AT TIMES -- WILL CONTINUE
SPREADING NWD/NEWD ACROSS PARTS OF NH...VT...AND FAR SRN MAINE
THROUGH THE MORNING. SNOWFALL RATES TO 1.0-1.5 INCHES PER HOUR WILL
BE LIKELY AS STRONG UPWARD MOTION COINCIDES WITH DEEP DENDRITIC
GROWTH ZONES PER FORECAST SOUNDINGS. THE 00Z CHATHAM MA RAOB SAMPLED
A WELL DEFINED WARM NOSE AROUND THE 750-MB LEVEL -- WHICH WILL BE
MAINTAINED BY ELEVATED WARM ADVECTION -- ABOVE A WELL MIXED PBL
EXTENDING TO AROUND H85. THIS PROFILE AND RELATED MODIFICATIONS
THEREOF SUGGEST PARTIAL TO COMPLETE MELTING OF DESCENDING
HYDROMETEORS WILL BE LIKELY ACROSS PARTS OF SRN NEW ENGLAND
INCLUDING PORTIONS OF MA/RI/CT...WITH RE-FREEZING LIKELY IN THE PBL.
AS SUCH...SLEET WILL BE LIKELY...OWING TO ICE NUCLEATION AT THE TOP
OF THE PBL WHERE MINIMUM COLD-LAYER TEMPERATURES AROUND -10C TO -6C
WILL BE PRESENT. SLEET-ACCUMULATION RATES AROUND ONE-TENTH TO
ONE-QUARTER INCH PER HOUR -- LOCALLY HIGHER -- WILL BE POSSIBLE.
PATCHY FREEZING RAIN COULD ALSO OCCUR...WITH ASSOCIATED RATES OF
0.05 TO LOCALLY 0.10 INCH PER HOUR POSSIBLE. SLEET/FREEZING RAIN IS
ALREADY BEING OBSERVED ACROSS PARTS OF ERN NY INTO SRN NEW ENGLAND.
THIS TRANSITION-ZONE PRECIPITATION WILL HAVE A TENDENCY OF SPREADING
NWD/NEWD INTO OTHER PARTS OF NEW ENGLAND INCLUDING PORTIONS OF
VT/NH/FAR SRN MAINE THROUGH THE MORNING HOURS...IN ASSOCIATION WITH
WARMING ALOFT IN THESE AREAS.
INCREASING NEAR-SFC WARM ADVECTION ASSOCIATED WITH INLAND FLUXES OF
OCEAN-MODIFIED AIR ON THE N SIDE OF AN EVOLVING COASTAL LOW WILL
OCCUR THIS MORNING...ESPECIALLY AROUND/AFTER 12Z-15Z. IT IS POSSIBLE
THAT SOME AREAS MAY EXPERIENCE SFC TEMPERATURES RISING ABOVE
FREEZING -- PARTICULARLY IN PROXIMITY TO THE COAST OF SRN NEW
ENGLAND -- RESULTING IN RAIN POSSIBLY MIXED WITH SLEET.
HOWEVER...WITH ABUNDANT COLD AIR IN PLACE WITHIN A COLD-AIR-DAMMING
PATTERN...CONFIDENCE IN THE EROSION OF SUB-FREEZING PBL AIR IS
LIMITED...AND FROZEN PRECIPITATION MAY BE PERVASIVE ACROSS MOST OF
THE AREA THROUGH THE MORNING HOURS.
..COHEN.. 12/29/2015
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...GYX...BOX...BTV...ALY...
LAT...LON 45207104 44087098 43327066 42437120 41757120 41897265
43317288 44267267 44907245 45077159 45207104
from SPC Mesoscale Discussions http://1.usa.gov/1Ow5cYz
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