Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 241128
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
628 AM EST WED DEC 24 2014

.SYNOPSIS...
STRONG LOW PRESSURE TRACKING ACROSS THE GREAT LAKES WILL BRING
HEAVY RAIN...GUSTY WINDS AND MINOR COASTAL FLOODING TODAY INTO
CHRISTMAS MORNING. DRY WEATHER WITH ABOVE NORMAL TEMPERATURES WILL
FOLLOW FROM CHRISTMAS AFTERNOON INTO SAT. A COLD FRONT MAY BRING A
FEW RAIN OR SNOW SHOWERS SUNDAY. ANOTHER STORM MAY AFFECT US
LATE MONDAY INTO TUESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
630 AM UPDATE...

FORECAST IN GOOD SHAPE. AREAS OF FOG/DRIZZLE WILL PERSIST UNTIL
STEADIER RAIN APPROACHING NYC AREA ARRIVES IN SOUTHERN NEW ENGLAND
DURING MORNING. HIGH-RES MODELS MAINTAIN PERIODS OF RAIN THRU MID
AFTERNOON AHEAD OF WARM FRONT.

PREVIOUS DISCUSSION... HIGH AMPLITUDE TROF OVER MS VALLEY LIFTS NE
TO THE GT LAKES TODAY WITH DEEP SOUTHERLY FLOW ADVECTING
ANOMALOUSLY HIGH PWATS EXCEEDING 1.5" INTO SNE BY EVENING. THIS IS
4-5 SD ABOVE NORMAL WHICH IS QUITE IMPRESSIVE. DEVELOPING LOW
LEVEL JET 50-60 KT MOVES INTO SNE THIS AFTERNOON WHICH WILL RESULT
IN AREAS OF DRIZZLE AND LIGHT RAIN THIS MORNING TRANSITIONING TO
HEAVIER RAINFALL DURING THE AFTERNOON AS LOW LEVEL MOISTURE
TRANSPORT/CONVERGENCE INCREASES. DESPITE THE LOW LEVEL
JET...STRONG LOW LEVEL INVERSION N OF THE WARM FRONT WILL PREVENT
STRONGER WINDS FROM MIXING DOWN WITH LIGHT NE WINDS IN THE
INTERIOR. WINDS WILL GRADUALLY SHIFT TO SOUTH AFT 18Z ALONG THE S
COAST AND COASTAL PLAIN AS THE WARM FRONT LIFTS NWD AND MAY SEE
SOME GUSTY WINDS DEVELOP LATE IN THE DAY OVER THE ISLANDS AND
IMMEDIATE S COAST. TEMPS WILL RISE THROUGH THE 50S ALONG THE S
COAST AND COASTAL PLAIN THROUGH LATE AFTERNOON...BUT REMAIN IN THE
40S ACROSS THE DISTANT INTERIOR.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
*** LOCALLY HEAVY RAINFALL...ISOLATED TSTMS AND STRONG GUSTY
 WINDS IN THE COASTAL PLAIN ***

PERIODS OF RAIN...LOCALLY HEAVY AT TIMES WILL CONTINUE TONIGHT BUT
OF MORE CONCERN IS THE POTENTIAL FOR A FINE LINE OF CONVECTION
ALONG THE COLD FRONT TO MOVE ACROSS SNE LATE TONIGHT TOWARD
DAYBREAK CHRISTMAS MORNING WHICH WOULD BRING LOCALLY HEAVY
RAINFALL RATES...STRONG WINDS AND ISOLATED TSTMS. MODELS SHOW A
SECONDARY STRONGER LOW LEVEL JET MOVING UP FROM THE SOUTH LATE
TONIGHT AHEAD OF THE COLD FRONT WHILE FORCING FROM UPPER LEVEL JET
MOVES IN FROM THE WEST. INSTABILITY IS MARGINAL BUT NAM IS SHOWING
SWI DROPPING NEAR OR SLIGHTLY BELOW ZERO AND THIS COMBINED WITH
FRONTAL FORCING AND A LOW LEVEL JET SUGGESTS A POSSIBLE FINE LINE
OF CONVECTION. SOME OF THE HI-RES MODELS ALSO SIGNALING A FINE
LINE.

RAINFALL...
EXPECT 1-2 INCHES OF RAIN ACROSS THE REGION THROUGH CHRISTMAS
MORNING. BUT GIVEN HIGH PWAT AIRMASS AND THE POTENTIAL FOR A FINE
LINE WITH LOCALLY HEAVY CONVECTIVE ELEMENTS...COULD SEE LOCALIZED
3 INCH RAINFALL AMOUNTS. WE WILL CONTINUE THE FLOOD WATCH WITH
MAIN THREAT BEING URBAN AND POOR DRAINAGE FLOODING. WE DO NOT
ANTICIPATE ANY RIVER FLOODING.

WIND THREAT...
SECONDARY LOW LEVEL JET MOVES ACROSS MAINLY SE NEW ENGLAND
06-12Z. NAM IS STRONGEST WITH 65-70 KT DOWN TO 925 MB BUT
GFS/ECMWF OVER 60 KT. NAM IS A BIT SLOWER WITH THE TIMING OF THE
LLJ EXITING CAPE/ISLANDS THU MORNING. SOUNDINGS SHOW PRONOUNCED
LOW LEVEL INVERSION OVER THE WATERS WHICH WILL LIKELY PREVENT
STRONGER WINDS FROM MIXING DOWN NEAR THE IMMEDIATE S COAST AND
ISLANDS. HOWEVER...LATER TONIGHT INVERSION WEAKENS WITH NEAR
ISOTHERMAL PROFILE IN THE LOW LEVELS JUST INLAND FROM THE COAST.
BEST CHANCE FOR SEEING GUSTS TO 40-50 MPH WILL BE ACROSS SE MA
AND PORTIONS OF RI WHERE TEMPS WILL LIKELY RISE INTO LOWER 60S
OVERNIGHT ENHANCING MIXING POTENTIAL. IN ADDITION...ANY FINE
LINE LATE TONIGHT WOULD HELP TO BRING DOWN STRONGER WIND GUSTS.
WE ISSUED A WIND ADVISORY FOR LATER TONIGHT FOR SE RI AND SE MA
INCLUDING THE CAPE/ISLANDS.

TEMPS RISE THROUGH THE 50S TONIGHT AND INTO THE LOWER 60S FOR
PORTIONS OF RI AND SE MA. MAY EVEN SEE DEWPOINTS NEAR 60 DEGREES
IN SE MA OVERNIGHT WHICH IS PRETTY REMARKABLE FOR LATE DECEMBER.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
* CLEARING...WINDY AND MILD CHRISTMAS DAY.
* REMAINING DRY WITH ABOVE NORMAL TEMPERATURES FRI AND SAT.
* POTENTIAL FOR SOME RAIN OR SNOW EARLY NEXT WEEK.

CHRISTMAS DAY...HIGH CONFIDENCE.

COLD FRONT WILL BE PUSHING OFFSHORE FIRST THING IN MORNING AND
TAKING ANY LEFTOVER SHOWERS WITH IT. EXPECT RAPID DRYING ON
INCREASING W/SW WINDS BY AFTERNOON WHICH WILL BRING CLEARING
SKIES...BUT STEEPENING LAPSE RATES WILL ALSO BRING ROUND OF GUSTY
WINDS. FORECAST SOUNDINGS FROM NAM AND GFS SHOW POTENTIAL 35-40 MPH
GUSTS WHICH IS SHORT OF WIND ADVISORY CRITERIA. BEST MIXING OCCURS
THU AFTERNOON. AIRMASS BEHIND FRONT IS FROM PACIFIC SO WE WILL NOT
SEE ANY KIND OF COOL DOWN...AND IN FACT DOWNSLOPE W FLOW SHOULD LEAD
TO SOME ADDITIONAL WARMING NEAR COAST WHICH WOULD OFFSET ANY COOL
ADVECTION. NONETHELESS HIGHS SHOULD OCCUR IN MORNING BEFORE
TEMPERATURES DROP OFF A BIT IN AFTERNOON.

FRIDAY AND SATURDAY...MODERATE CONFIDENCE.

HIGH PRESSURE BUILDS TO MID ATLANTIC COAST. DRY WEATHER WILL PREVAIL
WITH LIGHTER WINDS. TEMPERATURES WILL REMAIN ABOVE AVERAGE WITH
HIGHS IN 40S BOTH DAYS AND LOWS MAINLY IN 30S.

SUNDAY THROUGH TUESDAY...LOW CONFIDENCE.

MODELS DROP A WEAK COLD FRONT THROUGH SOUTHERN NEW ENGLAND SUN.
MOISTURE APPEARS TO BE LIMITED AND CONVERGENCE RATHER WEAK...SO ONLY
EXPECTING WIDELY SCATTERED RAIN SHOWERS AS IT MOVES THROUGH.
TEMPERATURE PROFILES MAY BE COLD ENOUGH FOR SOME WET SNOW TO MIX IN
ACROSS HIGHER TERRAIN IN W MA.

FROM THERE...MODELS STRUGGLE WITH STRENGTH AND POSITION OF UPPER
TROUGH HEADING E FROM SOUTHERN PLAINS. RIDGE OFF SE COAST HOLDS ITS
OWN AND LEADS TO DIFFICULTIES IN HOW NORTHERN AND SOUTHERN STREAMS
INTERACT ACROSS CENTER OF COUNTRY. 00Z ECMWF MAINTAINS MORE SOUTHERN
STREAM ENERGY AND MAINTAINS MORE SEPARATION THAN GFS WHICH HAS
BROADER TROUGH BY MIDDLE OF NEXT WEEK. THIS HAS IMPACT ON
DEVELOPMENT OF LOW PRESSURE ALONG FRONT TO OUR S...NAMELY HOW FAR N
IT BRINGS ITS PRECIPITATION SHIELD. MODELS HAVE CERTAINLY SHOWN
SIGNIFICANT RUN-TO-RUN VARIATION OVER PAST DAY OR TWO EITHER
COMPLETELY SUPPRESSING SYSTEM TO OUR S OR BRINGING IT DIRECTLY OVER
SOUTHERN NEW ENGLAND. THERE HAVE ALSO BEEN VARIATIONS IN HAVING ONE
LOW PRESSURE SYSTEM OR A SERIES OF TWO WEAKER LOWS.

LEANED TOWARD MODEL BLEND TO HELP IRON OUT THESE DIFFERENCES FOR NOW
WHICH BRINGS CHANCE POPS TO MOST OF AREA...ESPECIALLY S OF MASS
PIKE. THERMAL PROFILES SUGGEST AT LEAST SOME LIGHT SNOW IN MON/TUE
TIMEFRAME WITH RAIN MORE LIKELY CLOSER TO S COAST.

ALTHOUGH THIS IS SEVERAL DAYS AWAY AND CONFIDENCE IS LOW IN
DETAILS...LOW LEVEL TEMPERATURES LOOK A BIT WARM FOR ANY SIGNIFICANT
ACCUMULATIONS...ESPECIALLY FROM MASS PIKE TO S COAST. BUT WE NEED TO
SEE HOW LARGER SCALE FEATURES WILL BE RESOLVED OVER NEXT FEW DAYS.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH TONIGHT/...MODERATE CONFIDENCE.

WIDESPREAD IFR/LIFR THIS MORNING AS STEADIER RAIN OVERSPREADS
REGION FROM SW TO NE. LOOKS LIKE PERSISTENCE IS BEST FORECAST AS
CIGS/VSBYS ONLY LIFT SLIGHTLY AS RAIN ARRIVES AND CONTINUES
THROUGH TONIGHT.

A BAND OF LOCALLY HEAVY SHOWERS AND ISOLATED THUNDERSTORMS WITH
POTENTIALLY STRONG WINDS MAY MOVE ACROSS THE REGION 09-12Z. LOW
LEVEL WIND SHEAR WILL DEVELOP LATE TODAY AND THIS EVENING AS 2000
FT WINDS INCREASE TO 40-50 KT. THE LLWS WILL SHIFT TO SE NEW
ENGLAND LATE TONIGHT WITH 2000 FT WINDS INCREASING TO 60 KT.

KBOS TERMINAL...HIGH CONFIDENCE IN TAF.

KBDL TERMINAL...HIGH CONFIDENCE IN TAF.

OUTLOOK...THURSDAY THROUGH SUNDAY.

THURSDAY...MODERATE CONFIDENCE. CONDITIONS IMPROVE TO VFR BY
AFTERNOON. W WINDS GUST TO 35KT THU AFTERNOON.

FRIDAY AND SATURDAY...HIGH CONFIDENCE. VFR.

SUNDAY...MODERATE CONFIDENCE. MVFR POSSIBLE IN ISOLATED RAIN
SHOWERS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

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

TODAY...SOUTH WINDS GRADUALLY INCREASE LATER THIS AFTERNOON WITH
GUSTS POSSIBLY REACHING 25-30 KT BY LATE IN THE DAY...MAINLY FOR
S COASTAL WATERS. POOR VSBYS IN RAIN AND FOG.

TONIGHT...LOW LEVEL JET STRENGTHENS OVERNIGHT BUT VERY STRONG LOW
LEVEL INVERSION WILL LIKELY PREVENT THESE WINDS FROM MIXING DOWN
TO THE OCEAN SURFACE. IN FACT...WINDS WILL LIKELY REMAIN BELOW
GALE FORCE ACROSS THE WATERS WITH GUSTS TO 30 KT. HOWEVER...WE DO
EXPECT GALE FORCE GUSTS IN NARRAGANSETT BAY WHERE MIXING WILL BE
BETTER SO WE ISSUED A GALE WARNING HERE. POOR VSBYS IN RAIN AND
FOG WITH ISOLATED TSTMS POSSIBLE OVERNIGHT.

OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE.

COLD FRONT PUSHES OFFSHORE THU MORNING FOLLOWED BY INCREASING W/SW
WINDS...WHICH SHOULD PEAK AT GALE FORCE /35KT/ FROM LATE MORNING
INTO THU EVENING. GALE WATCHES HAVE BEEN POSTED FOR ALL WATERS.

WINDS GRADUALLY DIMINISH THU NIGHT AND FRI WITH SEAS ALSO SUBSIDING
DURING THAT TIME AS HIGH PRESSURE BUILDS OVER MID ATLANTIC STATES.
WEAKENING COLD FRONT MAY BRING AN ISOLATED SHOWER AS IT DROPS
THROUGH NEW ENGLAND SUN...BUT WINDS AND SEAS SHOULD REMAIN BELOW SCA.

&&

.TIDES/COASTAL FLOODING...
EASTERN MASSACHUSETTS COAST...

HIGH TIDE AT BOSTON WILL BE 11.7 FT AROUND MIDDAY WITH A SURGE OF
AROUND 1.0 FT WHICH WILL LIKELY RESULT IN MINOR SPLASHOVER. A
COASTAL FLOOD ADVISORY REMAINS IN EFFECT FOR THE MIDDAY HIGH
TIDE.

SOUTH COAST:

WE DO NOT EXPECT MUCH IF ANY COASTAL FLOODING ALONG THE SOUTH
COAST. SURGE OF 1 TO 1.5 FT EXPECTED FOR THIS EVENINGS HIGH TIDE
WHICH FALLS SHORT OF WHAT IS NEEDED TO BEGIN COASTAL FLOODING. FOR
THE CHRISTMAS MORNING HIGH TIDE...WINDS ARE SHIFTING TO SW/W AND
SURGE IS DECREASING SO THREAT IS MINIMAL.

&&

.CLIMATE...
RECORD HIGHS FOR TODAY / CHRISTMAS DAY

BOS...61 IN 1996 / 65 IN 1889
PVD...60 IN 1990 / 63 IN 1964
BDL...59 IN 1996 / 64 IN 1964
ORH...57 IN 1996 / 60 IN 1964

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...FLOOD WATCH FROM 4 PM EST THIS AFTERNOON THROUGH THURSDAY
     MORNING FOR CTZ002>004.
MA...FLOOD WATCH FROM 4 PM EST THIS AFTERNOON THROUGH THURSDAY
     MORNING FOR MAZ002>022-026.
     WIND ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR
     MAZ013-016>021.
     COASTAL FLOOD ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
     MAZ007-014>016-019-022.
     WIND ADVISORY FROM 1 AM TO 9 AM EST THURSDAY FOR MAZ022>024.
RI...FLOOD WATCH FROM 4 PM EST THIS AFTERNOON THROUGH THURSDAY
     MORNING FOR RIZ001>007.
     WIND ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR
     RIZ002-004-005-007.
MARINE...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR
     ANZ232>235-237-254>256.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 10 AM EST
     THURSDAY FOR ANZ230>234.
     GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR
     ANZ230-231-250-251.
     GALE WARNING FROM 10 PM THIS EVENING TO 7 AM EST THURSDAY FOR
     ANZ236.
     SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 10 AM EST
     THURSDAY FOR ANZ235-237.
     SMALL CRAFT ADVISORY UNTIL 10 AM EST THURSDAY FOR ANZ250-251-
     254>256.

&&

$$
SYNOPSIS...KJC/JWD
NEAR TERM...KJC/JWD
SHORT TERM...KJC
LONG TERM...JWD
AVIATION...KJC/JWD
MARINE...KJC/JWD
TIDES/COASTAL FLOODING...KJC
CLIMATE...STAFF


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