Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 040320
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1020 PM EST WED FEB 3 2016

.SYNOPSIS...
A SLOW MOVING COLD FRONT WILL MOVE ACROSS THE REGION TONIGHT.
AHEAD OF THE FRONT...EXPECT WIDESPREAD RAIN WITH POSSIBLY A
RUMBLE OF THUNDER. THE COLD FRONT WILL STALL JUST OFF THE COAST
THURSDAY...THEN LOW PRESSURE WILL DEVELOP ALONG THE MID ATLC COAST
THU NIGHT AND TRACK ALONG THE FRONT PASSING SOUTH AND EAST OF
NANTUCKET FRIDAY. THIS STORM WILL LIKELY BRING ACCUMULATING SNOW TO
SOUTHEAST NEW ENG LATE THU NIGHT INTO FRIDAY. HIGH PRESSURE
BRINGS DRY WEATHER OVER THE WEEKEND. A COASTAL STORM SHOULD AFFECT
THE REGION LATER MONDAY INTO TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

1030 PM UPDATE...

SEVERAL UPDATES TO THIS FORECAST AS WAA/HIGHER THETA-E VALUE RAIN
CONTINUES TO PUSH EASTWARD OVER THE NEXT FEW HOURS. BULK OF THE
RAIN IS NOT AT A BOS TO PVD LINE AND POINTS EASTWARD. SHOULD MOVE
OFFSHORE AFTER MIDNIGHT. HOWEVER LOOKING UPSTREAM...A FEW SHOWERS
CONTINUE TO DEVELOP ACROSS UPSTATE NY WHERE SURFACE COLD FRONT IS
LOCATED. CANNOT RULE OUT A FEW ISOLATED SHOWERS TO DEVELOP
OVERNIGHT BEHIND THE RAIN AS WEAK SHORTWAVE MOVES THROUGH THE
FLOW.

GUSTY WINDS WILL CONTINUE OVERNIGHT AS POTENT LLJ CONTINUES TO
STRENGTHEN OVER SOUTHERN NEW ENGLAND. THIS JET SEAMS TO STALL OVER
THE CAPE AND ISLANDS KEEPING GUSTS UP DURING THE OVERNIGHT HOURS.
HAVE RECEIVED A LOT OF DAMAGE REPORTS EVEN THOUGH GUSTS ARE IN
30-40 MPH RANGE. A FEW LOCATIONS HAVE GUSTED TO 45 MPH BUT THAT
HAS BEEN FOCUSED ACROSS THE HIGHER TERRAIN AND ACROSS NORTHEAST
MASS...WHICH IS NEAR THE CORE OF THE JET. GUSTY WINDS SHOULD BEGIN
TO SUBSIDE AFTER MIDNIGHT FROM WEST TO EAST.

LASTLY ONE THING TO KEEP A CLOSE EYE ON IS THE FOG POTENTIAL. HAVE
NOTICED DOWN STREAM THAT SEVERAL SITES HAVE DROPPED DOWN TO DENSE
FOG...ESP ACROSS EASTERN PA. WILL NEED TO CONTINUE TO MONITOR AS
THE REGION IS IN A VERY MOIST AIRMASS AND IF SKIES END UP CLEARING
A BIT...THEN VSBYS WILL GO DOWN.

PREVIOUS DISCUSSION...

WIDESPREAD SHOWERS ACROSS SNE THIS EVENING ASSOCD WITH STRONG
WARM ADVECTION AND ENHANCED BY LOW LEVEL CONVERGENCE ALONG THE
NOSE OF THE LOW LEVEL JET. MODELS INDICATING SOME DRYING ALOFT
MOVING INTO WESTERN NEW ENG THIS EVENING WHICH WILL RESULT IN RAIN
DECREASING WHILE ACTIVITY BECOMES FOCUSED ACROSS SE NEW ENG ALONG
THE AXIS OF THE SLOW MOVING LOW LEVEL JET. ADJUSTED POPS TO
REFLECT THIS THINKING. WARM FRONT HAS LIFTED TO THE N OF THE
REGION AS TEMPS HAVE SOARED INTO AND THROUGH THE 50S. WILL LIKELY
SEE TEMPS REACH 60 DEGREES IN THE COASTAL PLAIN OVERNIGHT. COLD
FRONT MOVES INTO W NEW ENG LATE TONIGHT WITH TEMPS COOLING INTO
THE 40S HERE TOWARD DAYBREAK...BUT REMAINING IN THE 50S ELSEWHERE.

AXIS OF LOW LEVEL JET WILL MOVE TO E NEW ENG THIS EVENING THEN
ACROSS SE NEW ENG COAST OVERNIGHT. STRONG LOW LEVEL INVERSION IN
PLACE WHICH WILL LIMIT STRONGER GUSTS FROM REACHING THE SURFACE.
FOR THE MOST PART...EXPECTING WINDS TO GUST UP TO 30-40 MPH WITH
THE STRONGEST WINDS SHIFTING TO THE CAPE/ISLANDS OVERNIGHT. IF
ANY HEAVIER RAIN OR ISOLATED THUNDERSTORMS ARE ABLE TO TAP INTO
THE STRONGER WINDS ALOFT...WE MAY SEE A FEW HIGHER GUSTS IN AND
AROUND THOSE STORMS TONIGHT.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
THE COLD FRONT STALLS OFF THE SOUTH COAST OF SOUTHERN NEW ENGLAND
THURSDAY MORNING. THIS WILL KEEP SOME SHOWERS ON THE SOUTH COAST
THROUGH MUCH OF THE DAY.  THE BIG STORY FOR THURSDAY WILL BE THE
TEMPERATURES.  AFTER STARTING OUT WITH MINS WARMER THAN OUR NORMAL
MAXES...TEMPS WILL CLIMB QUICKLY THROUGH THE MORNING INTO THE 50S TO
EVEN AROUND 60 ON THE COASTAL PLAIN.  AS WINDS SHIFT TO THE
NORTHWEST DURING THE AFTERNOON...EXPECT TEMPERATURES TO COOL BACK
INTO THE 40S.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
HIGHLIGHTS...

* RAIN CHANGING TO ACCUMULATING SNOW LATE THU NIGHT INTO FRIDAY
  ACROSS SE NEW ENG
* DRY WEATHER THIS WEEKEND
* ANOTHER COASTAL STORM MAY AFFECT THE REGION SOMETIME MONDAY OR
  TUESDAY

THURSDAY NIGHT INTO FRIDAY...
** WINTER STORM WATCH ISSUED FOR FAR SE MA AND CAPE COD AND MARTHAS
  VINEYARD ***

DIFFICULT FORECAST WITH RESPECT TO TIMING OF CHANGEOVER FROM RAIN TO
SNOW AND POTENTIAL SNOW ACCUMULATIONS NEAR THE COAST LATE THU NIGHT
INTO FRIDAY. MODELS ALL SHOW A SHARP MID LEVEL TROF AXIS BACK TO THE
WEST WITH RATHER POTENT MID LEVEL SHORTWAVE ROUNDING THE BASE OF THE
TROF AND LIFTING NE OFF THE MID ATLC COAST. THIS WILL INDUCE A
FRONTAL WAVE DEVELOPING ALONG THE EXISTING BAROCLINIC ZONE OFF THE
COAST AND TRACKING SE OF THE BENCHMARK FRIDAY. THE DIFFICULTY WITH
THE FORECAST INVOLVES THE WESTWARD EXTENT OF SIGNIFICANT QPF MOVING
INTO SNE AND TIMING OF CHANGEOVER FROM RAIN TO SNOW AS THE COLUMN
COOLS FROM WEST TO EAST WITH THE APPROACH OF THE MID LEVEL TROF.
ALSO THERE IS A SHARP QPF GRADIENT ON THE NW FRINGE OF THE PRECIP
FIELD WHICH ADDS TO THE UNCERTAINTY.

TIMING OF CHANGEOVER...
PRECIP COMES IN AS RAIN ALONG THE COAST THU EVENING. MODELS ARE IN
REASONABLE GOOD AGREEMENT ON TIMING OF CHANGEOVER WITHIN A FEW HOURS
WITH ECMWF LATER THAN NAM/GFS BUT IT IS ALSO HEAVIER WITH QPF. WE
USED A BLEND OF PARTIAL THICKNESS DATA WHICH SUGGESTS CHANGEOVER 06-
09Z SE MA/RI AND 09-12Z CAPE/ISLANDS.

QPF...
UKMET IS ON THE WESTERN EDGE OF THE MODEL ENVELOPE AND BRINGS
SIGNIFICANT QPF INTO SNE WITH AMOUNTS 1-2 INCHES ACROSS E NEW ENG
BUT IS A WARMER SOLUTION. ECMWF ALSO QUITE ROBUST WITH 0.50 INCHES
TO WEST OF I95 CORRIDOR AND 1 INCH TO WEST OF THE CAPE COD CANAL AND
A GOOD CHUNK OF THIS FALLS AFTER THE CHANGEOVER WHICH WOULD RESULT
IN A LARGE SWATH OF GREATER THAN 6 INCHES SNOW ACCUM FOR MUCH OF HE
COASTAL PLAIN. 12Z GFS AND NAM ARE ON THE EASTERN
ENVELOPE...CONFINING HEAVY QPF TO CAPE/ISLANDS WITH LIGHT AMOUNTS
BACK TO THE I95 CORRIDOR...BUT 18Z NAM HAS TRENDED EAST AND IS A
SHUTOUT FOR BOS/PVD WITH ONLY LIGHT QPF AFTER CHANGEOVER FOR
CAPE/ISLANDS. VERY DIFFICULT FORECAST SO WE ARE LEANING TOWARD A
BLEND OF AVAILABLE GUIDANCE AS WELL AS ECMWF EPS MEAN. GIVEN
SHARPNESS OF THE UPPER TROF AND STRENGTH OF THE SHORTWAVE EXPECT
THIS TO BACK FLOW ENOUGH TO PUSH HEAVIER QPF ACROSS CAPE/ISLANDS AND
POSSIBLY FAR SE MA NEAR THE CANAL BUT MUCH LESS CONFIDENCE
GETTING FURTHER NW.

SNOWFALL...
HIGHEST CONFIDENCE OF 6 INCHES ACCUM IS THE AREA NEAR THE CAPE COD
CANAL SO WE ISSUED A WATCH FOR FAR SE MA AND CAPE COD...INCLUDING
MARTHAS VINEYARD. SNOW COULD BE HEAVY AT TIMES VERY LATE THU NIGHT
INTO FRI MORNING WHICH MAY AFFECT THE MORNING COMMUTE. DESPITE MORE
QPF FOR NANTUCKET...WE EXPECT LESS SNOWFALL THERE DUE TO LATER
TIMING OF CHANGEOVER AND MARGINAL BOUNDARY LAYER WHICH WILL LEAD TO
SOME MELTING. OBVIOUSLY WITH SHARP MOISTURE/QPF GRADIENT ON THE NW
FRINGE OF THE PRECIP SHIELD THERE IS BIG BUST POTENTIAL. FURTHER
EAST AND ITS JUST MINOR ACCUM FOR CAPE COD...BUT FURTHER WEST AND
HEAVY SNOW COULD EXTEND BACK ACROSS BOS/PVD WITH MORE RAIN FOR THE
CAPE/ISLANDS. OUR PROBABILISTIC SNOWFALL MAPS AND BEST/WORST CASE
SCENARIOS TRY TO COMMUNICATE THE EXPECTED RANGE OF EXPECTATIONS.
WATCH WAS BASED ON A 50 PERCENT PROBABILITY OF 6 INCHES WITH
LIKELIHOOD OF AT LEAST ADVISORY LEVEL SNOW FOR THIS AREA.
INTERESTING TO NOTE THAT THERE ARE MANY ECMWF EPS MEMBERS WITH
SIGNIFICANT SNOWFALL BACK ACROSS COASTAL PLAIN. THIS MAY BE TOO
AGGRESSIVE...BUT 51 MEMBER ECMWF EPS HAS 50 PERCENT PROBS FOR 6
INCHES SE MA AND 90 PERCENT FOR 3 INCHES.

IMPACTS...
THIS WILL BE A WET SNOW AND IF HEAVY SNOW MATERIALIZES THERE WILL BE
POTENTIAL FOR POWER OUTAGES DUE TO ACCUMULATION ON TREES AND POWER
LINES.

SATURDAY INTO SUNDAY...MODERATE CONFIDENCE.
HIGH PRESSURE BUILDS OVER REGION SAT WITH DRY WEATHER EXPECTED.
CLIPPER LOW TRACKING ACROSS EASTERN CANADA WILL SWING A COLD FRONT
THROUGH SOUTHERN NEW ENGLAND SUN...BUT BEST DYNAMICS/MOISTURE REMAIN
FAR ENOUGH TO OUR N THAT WE SHOULD REMAIN DRY. HOWEVER FRONT WILL
BRING COLDER AIRMASS INTO REGION BY SUN NIGHT WHICH SETS STAGE FOR
POTENTIALLY STORMY WEATHER EARLY NEXT WEEK.

MONDAY INTO TUESDAY...LOW CONFIDENCE.
MODELS CONTINUE TO STRUGGLE WITH HANDLING OF TWO SHORTWAVES
CURRENTLY OVER PACIFIC...WHICH IS TO BE EXPECTED UNTIL THU OR FRI
WHEN THESE FEATURES BECOME BETTER SAMPLED. SO EXPECT TO SEE WOBBLES
OR EVEN WILD SWINGS IN THESE DETERMINISTIC SOLUTIONS UNTIL THEN.

12Z ECMWF NOW PUTS MORE EMPHASIS ON FIRST SHORT WAVE...WHICH RESULTS
IN COASTAL LOW AFFECTING SOUTHERN NEW ENGLAND MON BUT IS MORE OF A
GLANCING BLOW DUE TO A MORE OFFSHORE TRACK. 12Z GFS PUTS MORE FOCUS
ON SECOND SHORT WAVE AND AS A RESULT ITS COASTAL LOW HAS MORE OF AN
IMPACT ON SOUTHERN NEW ENGLAND TUE. DUE TO WIDE VARIATIONS IN THESE
DETERMINISTIC SOLUTIONS...WE ARE BASING FORECAST MORE ON ENSEMBLES
AND WILL UTILIZE CONSENSUS BLEND TO WORK OUT DETAILS FOR NOW.

THIS RESULTS IN SNOW MOVING INTO REGION LATER MON INTO TUE...BUT
DESPITE COLD TEMPERATURES ALOFT WE WILL PROBABLY BE DEALING WITH
WARMTH IN BOUNDARY LAYER WHICH WILL GIVE US ISSUES WITH RAIN/SNOW
MIX OR EVEN RAIN...PRIMARILY FROM PROVIDENCE AND BOSTON TO CAPE COD
AND ISLANDS. SETUP RIGHT NOW FAVORS HIGHER SNOWFALL AMOUNTS ACROSS
INTERIOR...BUT AGAIN...CONFIDENCE IS LOW AND THERE COULD BE
SIGNIFICANT ADJUSTMENTS TO FORECAST IN COMING DAYS.

FOR NOW...THE POTENTIAL IS THERE BUT WE NEED TO SEE HOW THESE TWO
SHORT WAVES EVOLVE AS THEY ENTER WEST COAST AND WORK THEIR WAY
ACROSS COUNTRY.

WEDNESDAY...LOW CONFIDENCE.
AGAIN MODEL SPREAD IS HIGH AT THIS TIME RANGE GIVEN UNCERTAINTIES IN
HOW MON/TUE EVOLVES. BUT WE DO EXPECT TO SEE DRYING IN WAKE OF
SYSTEM WITH SEASONABLE TEMPERATURES.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH THURSDAY/...MODERATE CONFIDENCE.

TONIGHT...MVFR/IFR CONDITIONS CONTINUE WITH RAIN SLOWLY
DIMINISHING FROM NORTHWEST TO SOUTHEAST. RAIN WILL LIKELY
CONTINUE THROUGH THE NIGHT ALONG THE SOUTH COAST...CAPE...AND
ISLANDS. WILL SEE SOME IMPROVEMENT TO VFR ACROSS THE NORTHWESTERN
TERMINALS TOWARDS 12Z. POTENTIAL FOR ISOLD TSRA ALONG THE SOUTH
COASTS OF RI/MA CONTINUES. AREAS OF LLWS ACROSS SNE THIS
EVENING...SHIFTING TO SE NEW ENG OVERNIGHT.

THURSDAY...QUICK IMPROVEMENT TO VFR ACROSS THE REMAINDER OF THE
AREA THROUGH 15Z THOUGH CLOUDS WILL LINGER THROUGH MUCH OF THE
DAY.

KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN
TIMING OF WINDS/PRECIP.

KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN
TIMING OF WINDS/PRECIP.

OUTLOOK /THURSDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE

THU NIGHT INTO FRIDAY...HIGH CONFIDENCE IN IFR/LIFR DEVELOPING SE
NEW ENG AND CAPE/ISLANDS WITH RAIN CHANGING TO ACCUMULATING SNOW
LATE THU NIGHT INTO FRI MORNING...IMPROVING FRI AFTERNOON. MAINLY
VFR FURTHER INTO THE INTERIOR. LOW CONFIDENCE ON WHERE TRANSITION
FROM IFR TO VFR OCCURS.

SATURDAY AND SUNDAY...VFR.
MONDAY...MVFR POSSIBLE IN RAIN OR SNOW...ESPECIALLY LATE.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE.

TONIGHT...MODERATE CONFIDENCE.  STRONG SOUTHERLY WINDS WILL CONTINUE
TO BUILD THROUGH THE EVENING AND INTO TONIGHT.  HAVE UPGRADED THE
SOUTHERN INNER WATERS TO GALE WARNINGS FOR THIS AFTERNOON AND INTO
TONIGHT.  SEAS INCREASE TO 6 TO 10 FEET ON THE OUTER WATERS AS A
COLD FRONT MOVES ACROSS THE WATERS LATE TONIGHT INTO EARLY THURSDAY
MORNING.

THURSDAY...MODERATE CONFIDENCE. SEAS DIMINISH SLOWLY...ESPECIALLY ON
THE EASTERN WATERS WHERE THE FRONT WILL MOVE THROUGH EARLIER.  THE
COLD FRONT STALLS ACROSS THE SOUTHERN WATERS WHICH WILL SLOW THE
DIMINISHING OF THE SEAS.  SMALL CRAFT ADVISORIES WILL NEED TO
CONTINUE FOR SEAS ON MOST OF THE OUTER WATERS.  SOUTHERLY WINDS WILL
SLOWLY SHIFT TO THE NORTHWEST DURING THE AFTERNOON...REMAINING BELOW
SMALL CRAFT CRITERIA.

OUTLOOK /THURSDAY NIGHT THROUGH MONDAY/...MODERATE CONFIDENCE...

THU NIGHT INTO FRIDAY...INCREASING N WINDS LATE THU NIGHT INTO FRI
WITH GUSTS TO 25 KT POSSIBLE OVER S WATERS. VSBYS REDUCED IN
RAIN...WHICH WILL CHANGE TO SNOW LATE THU NIGHT AND FRI MORNING.

SAT INTO SUN...WINDS AND SEAS REMAIN BELOW SCA.

MON...CONFIDENCE IS LOW BUT EXPECT INCREASING N/NE WINDS AHEAD OF
COASTAL LOW. SCA CONDITIONS POSSIBLE WITH 25-30KT GUSTS AND SEAS
BUILDING TO 5 FT OR HIGHER ON OUTER WATERS.

&&

.CLIMATE...
RECORD HIGHS FOR FEB 4TH...

BOS...64/1991
BDL...64/1991
PVD...66/1991
ORH...61/1991

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
     AFTERNOON FOR MAZ018>023.
RI...NONE.
MARINE...GALE WARNING UNTIL 4 AM EST THURSDAY FOR ANZ231-232-255-256.
     GALE WARNING UNTIL 1 AM EST THURSDAY FOR ANZ233>237.
     SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR ANZ230.
     GALE WARNING UNTIL 7 AM EST THURSDAY FOR ANZ250-254.
     SMALL CRAFT ADVISORY UNTIL 1 PM EST THURSDAY FOR ANZ251.

&&

$$
SYNOPSIS...KJC/RLG
NEAR TERM...KJC/DUNTEN
SHORT TERM...RLG
LONG TERM...KJC/JWD
AVIATION...KJC/RLG
MARINE...KJC/RLG
CLIMATE...


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