Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 230858
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
358 AM EST TUE DEC 23 2014

.SYNOPSIS...
WEAK LOW PRESSURE MOVING UP THE COAST WILL BRING PERIODS OF RAIN
TODAY AND EARLY TONIGHT. A MUCH STRONGER STORM TRACKING ACROSS THE
GREAT LAKES WILL BRING HEAVY RAIN...GUSTY WINDS AND MINOR COASTAL
FLOODING WEDNESDAY 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
THEN A STORM MAY AFFECT THE REGION SUN NIGHT INTO MON...BUT IT
COULD ALSO PASS WELL TO THE SOUTH.

&&

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

RAIN LIFTING NE LOOKS MUCH MORE FRAGMENTED THAN WHAT MOST OF 00Z
MODELS INDICATED...IN FACT HIGH-RES MODELS MAY HAVE RIGHT IDEA
THAT WE WILL SEE MORE IN WAY OF PERIODS OF RAIN TODAY RATHER THAN
ALL-DAY SOAKING. TEMPERATURES ACROSS INTERIOR HAVE ALREADY RISEN
ABOVE FREEZING SO WE ARE NO LONGER CONCERNED ABOUT POTENTIAL OF
ANY ICING.

OTHERWISE CLOUDY DAY IN STORE WITH INCREASING E WINDS NEAR
COAST...GUSTING TO 25 MPH AT TIMES. SHOULD SEE PATCHES OF RAIN
DIMINISH LATER THIS AFTERNOON AS LOW PRESSURE APPROACHES S COAST
BUT EXPECT AREAS OF FOG AND PATCHY DRIZZLE TO PERSIST.

HIGHS TODAY WILL RANGE FROM AROUND 40 IN NW MA TO MID/UPPER 40S
ELSEWHERE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
WEAK LOW PRESSURE TRACKS THROUGH SE NEW ENGLAND TONIGHT. MODELS
SHOW MOST OF LIFT REMAINING TO OUR N AND W BUT WITH CONTINUED
ONSHORE FLOW AND DEEP MOISTURE...EXPECT AREAS OF FOG/DRIZZLE
THROUGH MOST OF NIGHT.

TEMPERATURES SHOULD ONLY FALL BACK FEW DEGREES...INTO UPPER 30S NW
TO MID 40S SE.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
HIGHLIGHTS...

* RAIN...HEAVY AT TIMES AND UNSEASONABLY MILD WEDNESDAY INTO
  CHRISTMAS MORNING WITH GUSTY SOUTH WINDS IN THE COASTAL PLAIN WED
  NIGHT
* DRY AND WINDY CHRISTMAS AFTERNOON WITH GUSTS TO 45 MPH POSSIBLE
* CONTINUED DRY WITH ABOVE NORMAL TEMPS FRI AND SAT
* A STORM MAY AFFECT THE REGION SUN NIGHT INTO MON...BUT CONFIDENCE
  IS LOW

OVERVIEW...
HIGH AMPLITUDE TROF OVER THE MS VALLEY ON WED LIFTS NE THROUGH THE
GT LAKES AND INTO CANADA BY CHRISTMAS DAY.  DEEP SOUTHERLY FLOW AND
ANOMALOUS PWAT AIRMASS AHEAD OF THE TROF WILL BRING A PERIOD OF
HEAVY RAINFALL TO THE REGION WED AND WED NIGHT BEFORE DRYING OUT
CHRISTMAS AFTERNOON. BEYOND CHRISTMAS...MODELS IN AGREEMENT ON
ANOMALOUSLY STRONG MID LEVEL RIDGE OVER THE SE US FRI THROUGH THE
WEEKEND WHICH WILL RESULT IN CONTINUED MILD CONDITIONS.  BY
SUNDAY...NORTHERN STREAM SHORTWAVE DELIVERS A COLD FRONT...THEN
THERE IS QUITE A BIT OF UNCERTAINTY REGARDING A SOUTHERN STREAM
SHORTWAVE EJECTING NE FROM SOUTHERN PLAINS TROF WITH POSSIBLE
FRONTAL WAVE SUN NIGHT INTO MON. PREVIOUS RUNS OF THE ECMWF SHOWED A
MORE AMPLIFIED SHORTWAVE AND FRONTAL WAVE...BUT LATEST RUN OF THE
ECMWF HAS TRENDED FLATTER AND MORE SUPPRESSED ALTHOUGH IT STILL
BRINGS SOME SNOW SUN NIGHT INTO MON.  GFS CONTINUES TO BE WELL
SUPPRESSED WITH THE WAVE WITH HIGH PRES DOMINATING. DUE TO
UNCERTAINTY...WE USED A BLEND OF ECMWF/GFS

WEDNESDAY INTO WEDNESDAY NIGHT...
DEEP SOUTHERLY FLOW WILL BRING ANOMALOUS HIGH PWAT AIRMASS INTO SNE
BY WED NIGHT WITH PWATS NEARING 1.75" AND 850 MB DEWPOINTS NEAR 12C
WHICH IS PRETTY REMARKABLE FOR LATE DECEMBER. PWATS ARE 4-5 SD ABOVE
NORMAL WHICH IS QUITE IMPRESSIVE AND SIGNALS THREAT FOR HEAVY
RAINFALL.  HOWEVER...850 MB WIND ANOMALIES ARE NOT AS
IMPRESSIVE...NEAR 2 SD ABOVE NORMAL WHICH WILL LIKELY BE A
LIMITATION TO EXCESSIVE RAINFALL THREAT.  IN ADDITION INDIVIDUAL
GEFS MEMBERS ARE ALL BELOW 2" QPF.  WE ARE EXPECTING ADDITIONAL
RAINFALL WED INTO CHRISTMAS MORNING OF 1-2" WHICH IS LINE WITH
GFS/ECMWF/NAM QPF...BUT CANT RULE OUT ISOLD AMOUNTS OF 3 INCHES
GIVEN ANOMALOUS PWAT AIRMASS AND POTENTIAL FOR SOME ELEVATED
CONVECTION. THIS WILL CAUSE TYPICAL URBAN AND POOR DRAINAGE FLOOD
PROBLEMS BUT RIVER FLOODING IS NOT ANTICIPATED.

THERE WILL LIKELY BE MULTIPLE PULSES OF HEAVY RAIN WED AFTERNOON
INTO WED NIGHT AS SW LOW LEVEL JET MOVES INTO THE REGION. ELEVATED
INSTABILITY INDICES ARE MARGINAL BUT CANT RULE OUT AN ISOLD TSTM WED
AFTERNOON AND NIGHT...PARTICULARLY AS THE LOW LEVEL JET STRENGTHENS
ACROSS THE REGION.

WIND THREAT...LOW LEVEL JET AT 925 MB PEAKS AROUND 70 KT LATE WED
NIGHT ACROSS THE COASTAL PLAIN.  HOWEVER...SOUNDINGS INDICATE A
RATHER STRONG INVERSION WHICH WILL LIKELY LIMIT STRONGER WINDS FROM
MIXING TO SURFACE.  GIVEN WARM TEMPS ALOFT...PROBABLY NEED SFC TEMPS
TO REACH MID 60S TO MIX SOME OF THIS WIND DOWN TO THE SURFACE. WHILE
WE DO EXPECT TEMPS TO REACH 60+ IN THE COASTAL PLAIN WED
NIGHT...THERE IS JUST A LOW PROB OF MID 60S SO THINK MOST OF THE
GUSTS WILL FALL SHORT OF WIND ADVISORY CRITERIA.  IF A FINE LINE OF
CONVECTION CAN DEVELOP AHEAD OF THE FRONT... THIS COULD HELP TO
BRING DOWN STRONGER GUSTS WITH THE TIMING OF THIS BEING 06-12Z.

MAX TEMPS WED WILL BE MOSTLY IN THE 40S INTERIOR AND 50S COASTAL
PLAIN...RISING THROUGH THE 50S WED NIGHT AND LIKELY LOWER 60S ACROSS
PORTIONS OF RI AND SE MA.  DEWPOINTS MAT APPROACH 60 WED NIGHT IN
THE COASTAL PLAIN.

CHRISTMAS...
HEAVY RAIN WILL LIKELY BE ONGOING CHRISTMAS MORNING IN THE COASTAL
PLAIN...THEN RAIN MOVES OUT BY MIDDAY WITH SKIES BECOMING PTSUNNY IN
THE AFTERNOON.  GUSTY SW WINDS IN THE MORNING NEAR THE COAST ASSOCD
WITH THE LLJ...THEN ALL AREAS WILL SEE STRONG WEST WIND GUSTS IN THE
AFTERNOON AS COLD ADVECTION DEVELOPS WITH STEEPENING LOW LEVEL LAPSE
RATES.  WIND GUSTS TO 45 MPH WILL BE POSSIBLE AND WIND ADVISORIES
MAY BE NEEDED.  MAX TEMPS IN THE 50S TO NEAR 60 DEGREES WILL OCCUR
IN THE MORNING...WITH TEMPS FALLING IN THE AFTERNOON.

FRIDAY INTO SAT...
HIGH PRES BRINGS DRY WEATHER WITH ABOVE NORMAL TEMPS. THE MILDER DAY
WILL BE SATURDAY WITH TEMPS REACHING INTO THE 50S AS THE HIGH SLIDES
TO SE WITH SW FLOW DEVELOPING.

SUNDAY INTO MONDAY...
LOW CONFIDENCE FORECAST.  A COLD FRONT MAY BRING A FEW RAIN/SNOW
SHOWERS SUNDAY...THEN WILL HAVE TO WATCH FOR POSSIBLE FRONTAL WAVE
SUN NIGHT INTO MON.  THIS WAVE MAY END UP TOO FAR SOUTH BUT WILL
KEEP LOW POPS IN THE FORECAST.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
FORECASTER CONFIDENCE LEVELS...

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

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

MVFR/IFR CIGS BECOME MORE WIDESPREAD THROUGH DAYBREAK AS PATCHES
OF RAIN LIFT NE ACROSS REGION. MOST OF RAIN WILL FALL FROM EARLY
THIS MORNING INTO AFTERNOON BEFORE TAPERING OFF TO SPOTTY DRIZZLE
LATER IN DAY. INCREASING E WINDS NEAR COAST WHERE 25KT GUSTS
EXPECTED.

WINDS DIMINISH THIS EVENING BUT WIDESPREAD IFR/LIFR EXPECTED IN
FOG AND SPOTTY DRIZZLE.

KBOS TERMINAL...MODERATE CONFIDENCE. ONSET OF LOWER CEILINGS THIS
MORNING MAY BE 2-3 HOURS TOO FAST...BUT FAIRLY CONFIDENT IN IFR BY
12Z.

KBDL TERMINAL...MODERATE CONFIDENCE.

OUTLOOK...WEDNESDAY THROUGH SATURDAY...

WEDNESDAY AND WED NIGHT...HIGH CONFIDENCE.  IFR CONDITIONS IN
WIDESPREAD RAIN. LLWS IS LIKELY PARTICULARLY WEDNESDAY AFTERNOON AND
NIGHT AS S/SW LOW LEVEL JET STRENGTHENS ACROSS THE REGION.

CHRISTMAS...MODERATE CONFIDENCE.  IFR IN RAIN TO START...THEN
CONDITIONS IMPROVE TO VFR IN THE AFTERNOON. WEST WIND GUSTS TO 35-40
KT POSSIBLE IN THE AFTERNOON.

FRIDAY AND SATURDAY...HIGH CONFIDENCE. VFR.

&&

.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.

SCA REMAINS POSTED FOR INCREASING E WINDS AND BUILDING SEAS
THROUGH THIS EVENING...AS LOW PRESSURE HEADS UP THE COAST FROM MID
ATLANTIC AND BRINGS PERIODS OF RAIN AND PATCHY FOG.

WINDS DIMINISH QUICKLY THIS EVENING AS LOW PRESSURE REACHES S
COAST OF NEW ENGLAND...BUT FOG SHOULD BECOME MORE WIDESPREAD WITH
VSBYS 1-3 NM AND SPOTTY DRIZZLE. SEAS WILL REMAIN AOA 5 FT ON
OUTER WATERS.

OUTLOOK...WEDNESDAY THROUGH SATURDAY...MODERATE CONFIDENCE

WED AND WED NIGHT...SOUTHERLY LOW LEVEL JET MOVES INTO THE WATERS
LATE WED AND WED NIGHT BUT STRONG LOW LEVEL INVERSION WILL LIKELY
PREVENT THESE WINDS FROM MIXING DOWN TO THE SURFACE. EXPECT GUSTS TO
25-30 KT WED NIGHT. VSBYS REDUCED IN RAIN AND FOG.

CHRISTMAS...WINDS SHIFT TO SW/W WITH GALE FORCE GUSTS POSSIBLE.
IMPROVING VSBYS IN THE AFTERNOON AS RAIN MOVES OUT.

FRI AND SAT...EXPECT WEST WINDS BELOW SCA FRI...THEN INCREASING SW
WINDS SAT WITH GUSTS TO 25 KT.

&&

.TIDES/COASTAL FLOODING...

EASTERN MASSACHUSETTS COAST:

HIGH TIDE AT BOSTON WILL BE 11.6 FT AT MIDDAY TODAY AND 11.7 FT
AT MIDDAY WED WITH A SURGE OF 1.0 TO 1.5 FT. SHOULD SEE SOME MINOR
COASTAL FLOODING AT MORE VULNERABLE LOCATIONS ON BOTH HIGH TIDE
CYCLES...BUT CERTAINLY NOTHING SIGNIFICANT AS WINDS AND SEAS ARE
NOT FAVORABLE. COASTAL FLOOD ADVISORY REMAINS POSTED FOR TODAY AND
WILL PROBABLY NEED TO BE ISSUED LATER FOR WED HIGH TIDE.

SOUTH COAST:

WE DO NOT EXPECT MUCH IF ANY COASTAL FLOODING ALONG THE SOUTH COAST.
NOT ENOUGH WIND OR SURGE FOR THE WED EVENING HIGH TIDE.  HIGHEST
SURGE OF 1-2 FEET LIKELY TO OCCUR DURING LOW TIDE LATE WED NIGHT
WITH THE SURGE AND SEAS DECREASING DURING THE CHRISTMAS MORNING HIGH
TIDE. WORST CASE IS MINOR SPLASHOVER FOR THE CHRISTMAS MORNING HIGH
TIDE BUT EVEN THIS IS NOT LOOKING FAVORABLE.

&&

.CLIMATE...
RECORD HIGHS FOR DEC 24 / DEC 25...

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...NONE.
MA...COASTAL FLOOD ADVISORY FROM 9 AM THIS MORNING TO 3 PM EST THIS
     AFTERNOON FOR MAZ007-015-016-019-022.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ231-
     232.
     SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR ANZ233-
     234.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ235-237-
     250-251-254>256.

&&

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


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