Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 012157
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
457 PM EST SUN MAR 1 2015

.SYNOPSIS...
A FAST MOVING LOW PRESSURE SYSTEM WILL BRING ACCUMULATING SNOW
THIS EVENING AND TONIGHT WITH THE HIGHEST AMOUNTS EXPECTED SOUTH
OF THE MASSACHUSETTS TURNPIKE. HIGH PRESSURE BRINGS DRY COLD AIR
FOR THE EARLY WEEK. LOW PRESSURE FROM NORTHERN CANADA AND
ASSOCIATED LOW FORMING OVER THE PLAINS MONDAY WILL MERGE...THEN
PASS WEST AND NORTH OF NEW ENGLAND. THIS WILL SWING A COLD FRONT
ACROSS THE REGION ON WEDNESDAY. DRY AND COLD WEATHER RETURNS FOR
THE END OF THE WEEK. ANOTHER COLD FRONT MOVES THROUGH ON SATURDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
445 PM UPDATE...

LOW PRESSURE EMERGING FROM THE MID ATLANTIC COASTLINE IS EXPECTED
TO PASS SOUTHEAST OF NANTUCKET TONIGHT...BRINGING A WIDESPREAD
SNOW TO SOUTHERN NEW ENGLAND. SURFACE OBS AS OF 21Z INDICATE THAT
SNOW HAS OVERSPREAD THE ENTIRE AREA. THE STRONGEST RADAR
RETURNS AT 21Z WERE NEAR THE SOUTH COAST OF CT INTO RI...AND TO
THE SOUTHWEST. THE BETTER FORCING FROM THIS EVENT IS EXPECTED TO OCCUR
TO THE SOUTH OF THE MA TURNPIKE. 12Z MODELS WERE IN DECENT
AGREEMENT ON PLACING THE HIGHEST QPF IN THAT AREA.

BECAUSE OF THE QUICK HITTING NATURE OF THIS SYSTEM WITH A SHORT
LIVED WINDOW FOR VERY STRONG LIFT/FORCING...CONTINUE TO THINK THAT
FOR MOST OF THE REGION WINTER WEATHER ADVISORY/S FOR 3 TO 6 INCHES
OF SNOW WILL COVER THIS EVENT. HOWEVER...GIVEN THERE IS NICE
OMEGA IN THE SNOW GROWTH REGION...WE MIGHT BE LOOKING AT SOME
DECENT RATIOS. SO WE STILL CAN NOT RULE OUT THE LOW RISK OF
REACHING WARNING AMOUNTS...ESPECIALLY ACROSS NORTHERN CT AND
NORTHWEST RI.

WE DID UPGRADED BLOCK ISLAND TO A WINTER STORM WARNING FOR THE
LATE AFTERNOON FORECAST PACKAGE. THERE MAY BE SOME MIXING WITH
RAIN IN THIS AREA AT TIMES.

EXPECT THIS TO BE A SNOW EVENT FOR THE VAST MAJORITY OF SOUTHERN
NEW ENGLAND. IT DOES BECOME A VERY CLOSE CALL NEAR THE SOUTH
COAST...BUT WERE LEANING TOWARDS IT STAYING MAINLY WET SNOW.
CONTINUED THE HIGH END WINTER WEATHER ADVISORY FOR THE CAPE
BECAUSE THEY MAY CHANGE TO RAIN FOR A TIME...ESPECIALLY EAST OF
HYANNIS. IF THE CHANGE OVER DOES NOT OCCUR...SNOWFALL TOTALS MAY
BE SOMEWHAT HIGHER. THE PRECIPITATION IS EXPECTED TO COME TO AN
END ACROSS THE MAJORITY OF THE AREA BY DAYBREAK MONDAY.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...

MONDAY...
PRECIPITATION WILL HAVE LARGELY COME TO AN END FOR DAYBREAK MONDAY
...WITH THE LOW PRESSURE RAPIDLY PULLING AWAY INTO THE CANADIAN
MARITIMES AND DRIER AIR/HIGH PRESSRUE MOVING IN FROM THE WEST.
INCREASING SUNSHINE EXPECTEED DURING THE DAY...WITH TEMPS TOPPING
OUT IN THE UPPER 20S TO MID 30S. HOWEVER AS WE GET TOWARDS
MIDDAY/AFTERNOON TIGHTENING GRADIENT WILL ALLOW NORTHWEST FLOW TO
BECOME BLUSTERY...WITH GUSTS OF 25 TO 30 MPH...25 TO 35 MPH ON THE
CAPE AND ISLANDS.

MONDAY NIGHT...
HIGH PRESSURE SETTLES OVER THE AREA WITH CLEAR SKIES EXPECTED.
GIVEN OUR SNOWPACK IN PLACE AND LIGHT WINDS...SHOULD BE ANOTHER
NIGHT FOR EXCELLENT RADIATIONAL COOLING. BECAUSE OF THIS DID
GENERALLY GO BELOW MODEL GUIDANCE FOR MIN TEMPS...LOOKING TO
ANTICIPATED SURFACE DEWPOINTS FOR A GUIDELINE ON HOW LOW WE CAN
GO. MAY SEE SOME SPOTS IN THE INTERIOR DROP BELOW ZERO.

.LONG TERM /TUESDAY THROUGH SUNDAY/...
BIG PICTURE... THE BROAD UPPER FLOW CONTINUES TO FEATURE A TROUGH
TRANSITING EAST ACROSS THE COUNTRY...REACHING THE EASTERN USA DURING
THE LATE WEEK AND LINGERING THROUGH THE WEEKEND. MEANWHILE AN UPPER
RIDGE SHIFTS FROM THE PACIFIC OCEAN BACK ASHORE ONTO THE WEST COAST.
CONTOUR HEIGHTS IN THE TROUGH ARE LOWEST THURSDAY-FRIDAY AND NEAR
NORMAL OVER THE WEEKEND. THIS MEANS A TREND TO COLDER TEMPS THURSDAY-
FRIDAY FOLLOWED BY A TREND CLOSER TO NORMAL OVER THE WEEKEND.

DAILIES...

TUESDAY... HIGH PRESSURE OVER THE REGION MOVES OFFSHORE BY AFTERNOON
WITH AIRFLOW SWINGING FROM NORTHWEST TO SOUTHWEST. THE SURFACE
AIRMASS STARTS OUT QUITE DRY WITH DEW POINTS IN THE SINGLE NUMBERS
BELOW ZERO TO START...CLIMBING TO 5-10 ABOVE BY EVENING. MODEL CROSS
SECTIONS SHOW INCREASING MOISTURE MORNING AND AFTERNOON ABOVE 700
MB. THIS SUGGESTS INCREASING MID AND HIGH CLOUDS WHILE DRY BENEATH.
LOW LEVEL JETS FROM THE CAROLINAS AND MIDWEST AND THE SURFACE
PRESSURE GRADIENT ALL SUGGEST THE INFLOW AND ISENTROPIC LIFT WILL
REMAIN TO OUR WEST THROUGH THE DAY...POSSIBLY ENTERING WESTERN MA/CT
AT OR AFTER 21Z. SO WE EXPECT INCREASING CLOUDS TUESDAY BUT
OTHERWISE DRY WEATHER THROUGH THE DAY. POSSIBLE LIGHT SNOW AROUND
THE EVENING RUSH HOUR IN THE CT RIVER VALLEY. TEMPS SHOULD REACH THE
MID 20S TO AROUND 30.

TUESDAY NIGHT-WEDNESDAY... NORTHERN AND SOUTHERN STREAM SHORTWAVES
MERGE OVER THE GREAT LAKES AND TRACK INTO CANADA. THIS BRINGS A MILD
FLOW OF AIR UP OVER NEW ENGLAND. THE LEADING EDGE OF THIS AIR
REACHES WESTERN SECTIONS TUESDAY EVENING AND EASTERN SECTIONS
TUESDAY NIGHT. TEMPERATURE PROFILES SUPPORT AN INITIAL PERIOD OF
SNOW CHANGING TO RAIN OR FREEZING RAIN OVERNIGHT. ACTUALLY...THE
MODELS MAY NOT BE HANDLING WELL THE CHILLING MASS OF SNOW AND COLD
GROUND /A.K.A. THE GIANT ICECUBE/ WHICH WOULD MEAN THE ACTUAL MAX
SFC TEMPS WILL BE COOLER THAN MODEL FORECASTS. TEMPERATURES AT 925
AND 950 MB WILL BE IN THE 30S...SO EXPECT SURFACE TEMPS NO HIGHER
THAN THE LOWER 40S.

THE SURFACE LOW PRESSURE AREA PASSES WELL NORTH OF NEW ENGLAND
WEDNESDAY AND SWINGS A COLD FRONT THROUGH THE REGION DURING THE
AFTERNOON OR EVENING. MOISTURE CROSS SECTIONS SHOW DECREASING RH IN
THE LIFT AND NUCLEATION ZONES ALOFT WEDNESDAY MORNING...SO THE TREND
THROUGH THE DAY SHOULD BE TO DIMINISHING POPS.

THURSDAY-FRIDAY... THE WEDNESDAY COLD FRONT WILL ALIGN WITH THE
UPPER FLOW AS IT MOVES SOUTH OF NEW ENGLAND...SLOWING ITS OFFSHORE
PROGRESS TO A CRAWL. MEANWHILE WE WILL BE UNDER THE RIGHT ENTRANCE
REGION OF THE SUPPORTING UPPER JET...A SOURCE OF UPPER VENTING. THIS
SHOULD SUPPORT LINGERING CLOUDS AND A CHANCE OF PCPN...WITH TEMPS
SUPPORTIVE OF SNOW. BEST CHANCE SOUTH COAST...LESSER CHANCE FARTHER
NORTH. THE JET AND SURFACE FRONT SWEEP OFFSHORE THURSDAY NIGHT. HIGH
PRESSURE THEN MOVES OVER THE EASTERN USA FOR FRIDAY. TEMPS ALOFT
SUPPORT MAX SFC TEMPS IN THE 20S.

SATURDAY-SUNDAY... ANOTHER NORTHERN STREAM SHORTWAVE AND COLD FRONT
SWINGS THROUGH THE FLOW SATURDAY. CROSS SECTIONS SHOW SOME MOISTURE
ALOFT BUT MOST OF IT IS CONCENTRATED TO OUR NORTH.  ALSO JUST
LIMITED LIFT TO WORK ON THAT MOISTURE. WE WILL HAVE 25-50 PCT SKY
COVER AND NIL POPS. HIGH PRESSURE THEN BUILDS FOR SUNDAY.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /TODAY AND TONIGHT/...

2130Z UPDATE...

TONIGHT...MODERATE CONFIDENCE. MVFR CIGS DETERIORATING TO
IFR/LIFR IN SNOW. THE BULK OF THE MODERATE TO EVEN BRIEFLY HEAVY
SNOW WILL OCCUR THIS EVENING. THE LOWEST CONDITIONS WILL MOST
LIKELY BE SOUTH OF THE MA TURNPIKE. PTYPE PRETTY MUCH ALL
SNOW...EXCEPT FOR THE VERY IMMEDIATE SOUTH COAST/CAPE WHERE SNOW
MAY MIX WITH OR CHANGE TO RAIN FOR A TIME. WHETHER OR NOT THAT
HAPPENS IS UNCERTAIN...BUT WE DO THINK THAT AT LEAST THE ISLANDS
WILL MIX OR CHANGE TO RAIN.

BULK OF SNOW ENDS BY 8Z TO 9Z TONIGHT AND MUCH OF THE THE REGION
SHOULD IMPROVE TO VFR CONDITIONS BY 12-13Z MONDAY.

KBOS TAF...CONFIDENT IN OVERALL TRENDS BUT THERE IS UNCERTAINTY ON
TIMING. THE BULK OF ACCUMULATING SNOW WITH IFR TO LIFR CONDITIONS
EXPECTED MAINLY THIS EVENING.

KBDL TAF...CONFIDENT IN OVERALL TRENDS BUT THERE IS UNCERTAINTY ON
TIMING. BULK OF ACCUMULATING SNOW WITH IFR TO LIFR CONDITIONS
EXPECTED MAINLY THIS EVENING.

MONDAY AND MONDAY NIGHT...HIGH CONFIDENCE VFR. NORTHWEST WINDS
GUSTING TO 25 TO 30 MPH ACROSS MUCH OF THE AREA DURING MONDAY
AFTERNOON...25 TO 35 MPH GUSTS CAPE/ISLANDS. WINDS DIMINISHING
TOWARDS SUNSET.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY...MODERATE CONFIDENCE. VFR DURING THE DAY WITH INCREASING
SKY COVER. MVFR CIGS/VSBYS POSSIBLE LATE IN THE DAY CT RIVER VALLEY.

TUESDAY NIGHT-WEDNESDAY...MODERATE CONFIDENCE. CONDITIONS LOWERING
TO IFR/LIFR. INITIALLY SNOW BUT CHANGING TO SLEET/FREEZING RAIN
DURING THE NIGHT AND RAIN IN THE COASTAL PLAIN OVERNIGHT. PCPN
CHANGES TO RAIN ALL AREAS WEDNESDAY...BUT COLD SURFACES COULD
MAINTAIN A FREEZING RAIN ELEMENT WEDNESDAY MORNING. COLDER AIR MOVES
IN WEDNESDAY NIGHT CHANGING ANY RAIN TO SNOW.

THURSDAY...LOW CONFIDENCE. VFR NORTH OF A HFD-BOS LINE. MVFR CIGS
AND AREAS OF MVFR/IFR VSBYS IN SNOW...DIMINISHING BY EVENING.
NORTHWEST WINDS GUSTING TO 20 KNOTS.

FRIDAY...MODERATE CONFIDENCE. VFR.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...HIGH CONFIDENCE.

A WEAK WAVE OF LOW PRESSURE MOVES ACROSS THE WATERS TONIGHT.
THIS SYSTEM REALLY INTENSIFIES AS IT MOVES INTO THE CANADIAN
MARITIMES NEAR DAYBREAK MONDAY...SO WESTERLY WIND GUSTS MAY REACH
20 TO 25 KNOTS NEAR 12Z MONDAY. OTHERWISE...RAIN AND SNOW THIS
EVENING AND TONIGHT WILL REDUCE VISIBILITIES AT TIMES FOR
MARINERS.

MONDAY...AS THE LOW PRESSURE GOING INTO THE CANADIAN MARITIMES
INTENSFIES...INCREASING NORTHWEST WINDS ARE EXPECTED OVER THE
SOUTHERN NEW ENGLAND COASTAL WATERS...WITH GALE FORCE GUSTS
EXPECTED. GALE WARNINGS HAVE BEEN HOISTED FOR ALL COASTAL WATERS
FROM MIDDAY MONDAY INTO MONDAY NIGHT.

OUTLOOK...TUESDAY THROUGH FRIDAY..MODERATE CONFIDENCE.

TUESDAY... LINGERING 5 FOOT SEAS SOUTH AND EAST OF NANTUCKET IN THE
MORNING BUT DIMINISHING. NORTHWEST WINDS DIMINISHING FROM 20 KNOTS.
ANY SMALL CRAFT ADVISORY SHOULD END IN THE MORNING.

TUESDAY NIGHT-WEDNESDAY...SOUTH TO SOUTHWEST WINDS WILL INCREASE TO
20-25 KNOTS. SEAS WILL BUILD 6 TO 10 FEET ON THE OUTER WATERS AND ON
RI SOUND. REDUCED VSBYS...INITIALLY SNOW BUT CHANGING TO RAIN. A
SMALL CRAFT ADVISORY MAY BE NEEDED.

THURSDAY...NORTHWEST WIND GUSTING TO 25 KNOTS. SEAS 5 TO 8 FEET
MAINLY ON THE OUTER WATERS...DIMINISHING LATE. A SMALL CRAFT
ADVISORY MAY BE NEEDED.

FRIDAY... SHIFTING WINDS LESS THAN 20 KNOTS. SEAS LESS THAN 5 FEET.
QUIET WEATHER.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR CTZ002>004.
MA...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR MAZ017>021.
     WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR MAZ002>016-
     022>024-026.
RI...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR RIZ002>008.
     WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR RIZ001.
MARINE...GALE WARNING FROM 11 AM MONDAY TO 4 AM EST TUESDAY FOR ANZ231-
     232-250-251-254-255.
     GALE WARNING FROM 11 AM TO 11 PM EST MONDAY FOR ANZ233>235-237-
     256.
     GALE WARNING FROM 11 AM TO 8 PM EST MONDAY FOR ANZ230-236.

&&

$$
SYNOPSIS...WTB/NMB
NEAR TERM...FRANK/DOODY/NMB
SHORT TERM...NMB
LONG TERM...WTB
AVIATION...WTB/NMB
MARINE...WTB/NMB



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