NWS accumulation forecast for Friday: 1" - 3"
BOX AFD
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TAUNTON MA
450 AM EST THU FEB 1 2007
.SHORT TERM /TODAY THROUGH FRIDAY/...
...ACCUMULATING SNOW REMAINS POSSIBLE FRI NORTH AND WEST OF THE I95
CORRIDOR IN RI AND MA...INCLUDING MUCH OF INTERIOR CT...
TODAY...
WARM AIR ADVECTION ALOFT IN THE FORM OF MID AND HIGH CLOUDS ARE
OVERSPREADING THE REGION THIS MORNING. WIND FIELDS ALOFT INDICATE
MID LEVEL JET CROSSING THE AREA THIS AFTERNOON AND EVENING. MODEST
THERMAL AND MOISTURE ADVECTION ASSOCIATED WITH THIS JET.
HOWEVER...BOUNDARY LAYER REMAINS SOMEWHAT DRY. THE EXCEPTION WILL BE
ACROSS THE SOUTH COAST...INCLUDING CAPE COD AND ISLANDS...WHERE
SOUTHWEST WINDS OFF THE OCEAN MAY SUFFICIENTLY SATURATE THE BOUNDARY
LAYER FOR PRECIPITATION ALOFT TO REACH THE SURFACE. ELSEWHERE...
EXPECTING JUST CLOUDY CONDITIONS WITH POSSIBLY A FEW FLURRIES.
AS FOR PTYPE...COLD ALOFT TO SUPPORT SNOW...HOWEVER SOUTHWEST WINDS
BLOWING ACROSS WATER TEMPS IN THE UPPER 30S AND LOWER 40S WILL
LIKELY WARM BOUNDARY LAYER FOR A MIX OF LIGHT SNOW AND RAIN. NOT
EXPECTING MUCH QPF AS FORCING IS WEAK AND GIVEN RAIN MAY MIX
IN...ANY SNOW ACCUMULATIONS WOULD LIKELY BE CONFINED TO A COATING AT
MOST.
TONIGHT AND FRIDAY...
O.K. NOW FOR THE REAL DRAMA. 00Z MODEL GUIDANCE CONTINUES TO OFFER
DIFFERENT SOLUTIONS REGARDING AMPLITUDE OF MID LEVEL SHORT WAVE AND
ITS SURFACE RESPONSE...IN THE FORM OF A COASTAL LOW. NAM CONTINUES
TO OFFER THE FLATTEST AND MOST SUPPRESSED SOLUTION WITH SURFACE LOW
OUTSIDE THE 40N/70W BENCHMARK. EVEN THE DUSTY 00Z NGM IS FARTHER
NORTHWEST THAN THE NAM. THE GFS AT FIRST GLANCE APPEARED TOO ROBUST
WITH DEVELOPING A MID LEVEL CIRCULATION SOUTH OF NANTUCKET ALONG
WITH MODEST CYCLOGENESIS NEAR THE BENCHMARK 18Z FRI. HOWEVER...00Z
GFS ENSEMBLE MEAN AND 00Z UKMET SUPPORT THE 00Z GFS. ALOFT THE
ENSEMBLE MEAN AND THE UKMET ARE A BIT WEAKER WITH THE MID LEVEL
CIRCULATION...HOWEVER THE UKMET IS ABOUT 2 MBS DEEPER /989 MB/ WITH
THE COASTAL LOW AT 18Z FRI. THE 00Z GGEM JUST ARRIVED AND ITS IN
BETWEEN THE GFS AND THE NAM.
MAIN PLAYER HERE APPEARS TO BE BUNDLE OF JET ENERGY ACROSS BAJA AND
APPROACHING NEW MEXICO THIS MORNING. THIS FEATURE IS IMPRESSIVE ON
WATER VAPOR IMAGERY AND THE KEY HERE WILL BE HOW MODELS HANDLE THIS
JET ENERGY AND ITS ASSOCIATED DEEP CONVECTION AS IT INTERACTS WITH
DEEP LAYER MOISTURE FROM THE GULF OF MEXICO TODAY AND TONIGHT. GIVEN
THIS JET FEATURE ALREADY APPEARS IMPRESSIVE ON SATELLITE ALONG WITH
THE 00Z GFS ENSEMBLE MEAN AND THE 00Z UKMET SUPPORTING THE 00Z
GFS...PREFERENCE HERE IS TO GO WITH A MODIFIED VERSION OF THE GFS -
SLIGHTLY WEAKER...LESS QPF AND NOT AS WARM.
NOW FOR PTYPE...EXPECTING PRECIPITATION TO OVERSPREAD THE REGION
EARLY FRIDAY MORNING FROM SOUTH TO NORTH. ATMOSPHERE AT THIS TIME IS
ONLY MARGINALLY COLD ENOUGH TO SUPPORT SNOW ACROSS MOST OF THE
REGION. BOUNDARY LAYER ABOVE FREEZING ACROSS THE COASTAL PLAIN IN
RESPONSE TO EAST-NORTHEAST FLOW AND OCEAN TEMPERATURES STILL IN THE
UPPER 30S AND LOWER 40S. HOWEVER...PRESSURE FALLS SOUTH OF NEW
ENGLAND AHEAD OF COASTAL LOW MAY BE SUFFICIENT TO BACK SURFACE WIND
TO NORTH-NORTHEAST...LIMITING THE NORTHWEST PROGRESSION OF THE MILD
MARINE LAYER.
TEMPERATURES ALOFT...GFS ENSEMBLE MEAN AND UKMET 850 MB TEMPS ARE
ABOUT 2C COOLER THAN THE OPERATIONAL GFS...LIKELY DUE TO LESS
THERMAL ADVECTION GIVEN THESE SOLUTIONS ARE SLIGHTLY WEAKER THAN THE
GFS. ENSEMBLE MEAN AND UKMET HAVE 0C 850 MB ISOTHERM LIFTING AS FAR
NORTH AS GON-PVD-PYM BY 18Z FRI. THIS WOULD SUGGEST RAIN/SNOW LINE
SOMEWHERE VICINITY OF I84 TO I90 AND NORTHEAST TO LWM. WHAT ADDS TO
COMPLEXITY OF THE FORECAST...IS THAT QPF BEGINS TO DIMINISH THIS FAR
NORTHWEST. THIS SEEMS REASONABLE WITH SURFACE LOW EXPECTED TO TRACK
NEAR THE BENCHMARK AND THE MID LEVEL CIRCULATION SOUTHEAST OF
NANTUCKET. THUS...A SMALL AREA WHERE APPRECIABLE QPF AND COLD
ATMOSPHERE OVERLAP EACH OTHER. RIGHT NOW IT APPEARS THE GREATEST
RISK FOR ACCUMULATING SNOWS WOULD BE FROM NORTHEAST CT /INCLUDING
HFD/ INTO NORTHERN RI TO THE NORTHWEST SUBURBS OF BOSTON...AND
EXTENDING WEST INTO CENTRAL MA /WORCESTER HILLS/. FARTHER TO THE
NORTHWEST ACROSS WESTERN MA AND SOUTHERN NH QPF DIMINISHES...THUS
LESS OF A SNOW THREAT.
GIVEN MODEL SPREAD...MARGINAL COLD AIR IN PLACE AND TIGHT QPF
GRADIENT...FORECAST CONFIDENCE IS NOT HIGH ENOUGH TO ISSUE AN
ADVISORY AT THE MOMENT. WE WILL CONTINUE TO HIGHLIGHT THE DETAILS
VIA OUR SPECIAL WEATHER STATEMENT.
...and there is more to the AFD which elaborates on arctic outbreak coming up, but want to focus on Friday's storm first.
Special Weather Statement
Special Weather Statement
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TAUNTON MA
514 AM EST THU FEB 1 2007
CTZ002>004-MAZ002>018-026-NHZ011-012-015-RIZ001-012145-
HARTFORD CT-TOLLAND CT-WINDHAM CT-WESTERN FRANKLIN MA-
EASTERN FRANKLIN MA-NORTHERN WORCESTER MA-CENTRAL MIDDLESEX MA-
WESTERN ESSEX MA-EASTERN ESSEX MA-WESTERN HAMPSHIRE MA-
WESTERN HAMPDEN MA-EASTERN HAMPSHIRE MA-EASTERN HAMPDEN MA-
SOUTHERN WORCESTER MA-WESTERN NORFOLK MA-SOUTHEAST MIDDLESEX MA-
SUFFOLK MA-EASTERN NORFOLK MA-NORTHERN BRISTOL MA-
WESTERN PLYMOUTH MA-NORTHERN MIDDLESEX MA-CHESHIRE NH-
EASTERN HILLSBOROUGH NH-WESTERN AND CENTRAL HILLSBOROUGH NH-
NORTHWEST PROVIDENCE RI-
INCLUDING THE CITIES OF...HARTFORD...WINDSOR LOCKS...UNION...
VERNON...PUTNAM...WILLIMANTIC...CHARLEMONT...GREENFIELD...
ORANGE...BARRE...FITCHBURG...FRAMINGHAM...LOWELL...LAWRENCE...
GLOUCESTER...CHESTERFIELD...BLANDFORD...AMHERST...NORTHAMPTON...
SPRINGFIELD...MILFORD...WORCESTER...FOXBORO...NORWOOD...
CAMBRIDGE...BOSTON...QUINCY...TAUNTON...BROCKTON...AYER...
JAFFREY...KEENE...MANCHESTER...NASHUA...PETERBOROUGH...WEARE...
FOSTER...SMITHFIELD
514 AM EST THU FEB 1 2007
...ACCUMULATING SNOW IS STILL POSSIBLE FRIDAY FOR PORTIONS OF
SOUTHERN NEW ENGLAND...
A LOW PRESSURE CENTER WILL MOVE OFF THE MID ATLANTIC COAST TONIGHT...
AND THEN BEGIN TO INTENSIFY AS IT PASSES ABOUT 125 MILES OR SO
SOUTHEAST OF NANTUCKET FRIDAY AFTERNOON. PRECIPITATION WILL
BEGIN TO OVERSPREAD THE REGION EARLY FRIDAY MORNING FROM SOUTH TO
NORTH. THERE WILL BE A LACK OF VERY COLD AIR IN PLACE...AND THUS THE
SNOW IS EXPECTED TO MIX WITH AND CHANGE TO RAIN ALONG THE COAST FROM
BOSTON SOUTH. RAIN WILL LIKELY MIX WITH THE SNOW AS FAR INLAND AS THE
BOSTON TO PROVIDENCE INTERSTATE 95 CORRIDOR.
ACROSS INTERIOR NORTHEAST MASSACHUSETTS...THIS INCLUDES THE 128 AND
495 CORRIDORS...CENTRAL MASSACHUSETTS INCLUDING WORCESTER AND
EXTENDING INTO INTERIOR CONNECTICUT INCLUDING THE CITY OF HARTFORD...A
LIGHT TO MODERATE SNOWFALL IS POSSIBLE FRIDAY...BUT BY NO MEANS
CERTAIN. DEPENDING ON THE EXACT TRACK OF THE COASTAL LOW AND ITS
INTENSITY...ACCUMULATING SNOWS MAY EXTEND SOUTHEAST INTO NORTHWEST RHODE
ISLAND. FARTHER INLAND ACROSS WESTERN MASSACHUSETTS AND SOUTHWEST NEW
HAMPSHIRE...LESS SNOWFALL IS POSSIBLE GIVEN THE DISTANCE OF THE STORM
TRACK OFFSHORE. JUST HOW MUCH SNOW FALLS WILL DEPEND UPON THE EXACT
TRACK AND INTENSITY OF THIS STORM...WHICH STILL REMAINS UNCERTAIN.
ANY SNOW SHOULD END OR TAPER OFF TO JUST FLURRIES AS THE LOW MOVES
OFF THE NOVA SCOTIA COAST LATE FRIDAY.
LOOKING AHEAD...AN ARCTIC BLAST OF COLD AIR REMAINS SCHEDULED TO
ARRIVE INTO SOUTHERN NEW ENGLAND THE MIDDLE PART OF NEXT WEEK. MANY
INTERIOR AREAS MAY ENCOUNTER LOW TEMPERATURES BELOW ZERO AND WIND
CHILL VALUES OF 10 BELOW OR COLDER.
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