Area Forecast Discussion
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000
FXUS61 KBOX 210830
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
430 AM EDT TUE OCT 21 2014

.SYNOPSIS...
A LONG DURATION COASTAL STORM WILL BRING PERIODS OF RAIN THROUGH
THURSDAY WITH LINGERING SHOWERS FRIDAY AS THE STORM SLOWLY PULLS
AWAY FROM NEW ENGLAND. MAINLY DRY WEATHER EXPECTED THIS WEEKEND
WITH SEASONABLE TEMPERATURES.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
TODAY...

PER LATEST WATER VAPOR IMAGERY TROUGH AMPLIFICATION TAKING PLACE
OVER THE OH VLY INTO PA AND NY STATE. IN RESPONSE TO THIS
AMPLIFICATION WARM CONVEYOR BELT AND ASSOCIATED RAINS DEVELOPING
OVER THE NORTHEAST INTO WESTERN MA INTO SOUTHWEST NH...ALONG WITH
ANOTHER AREA RI...SOUTHEAST MA AND ADJACENT WATERS. THIS SECOND AREA
SHOULD BECOME THE FOCUS FOR POTENTIALLY HEAVIER RAINFALL LATER THIS
MORNING INTO THIS AFTERNOON...AS LOW LEVEL JET DEVELOPS AND
INCREASES IN MAGNITUDE ACROSS THIS AREA. THIS DIFFERENTIAL WARM AIR
ADVECTION WILL YIELD ELEVATED INSTABILITY INCREASING THE RISK OF
EMBEDDED CONVECTION WITHIN THE WARM CONVEYOR BELT RAINS ACROSS CAPE
COD AND THE ISLANDS LATER THIS MORNING INTO THIS AFTERNOON.

THE 00Z GUID INCLUDING THE LATEST RAP13/W-ARW/HRRR AND THE 03Z SREF
ARE ALL IN GOOD AGREEMENT ON ANY HEAVIER RAINBANDS AND EMBEDDED
CONVECTION TO TRACK OVER THE CAPE AND ISLANDS...AND POSSIBLY
OFFSHORE. THUS HAVE CONFINED CHANCE OF HEAVY RAIN AND THUNDER TO THE
REGION. RISK OF HEAVY RAIN WILL BE FROM ABOUT 15Z TO 21Z TODAY AND
CONFINED TO CAPE COD AND THE ISLANDS.

ELSEWHERE NOT MUCH APPRECIABLE RAINFALL TODAY. MAINLY PERIODS OF
RAIN AND FOR THE MOST PART ON THE LIGHT SIDE.

AS FOR TEMPS...ON THE MILD SIDE WITH HIGHS IN THE LOW TO MID 60S
ACROSS MUCH OF RI AND SOUTHEAST MA AS WARM SECTOR OVERSPREADS THIS
REGION. FARTHER INLAND COOLER WITH HIGHS IN THE 50S.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
TONIGHT...

DRY SLOT OVERSPREADS THE REGION. THIS WILL RESULT IN PERIODS OF
DRIZZLE AS LOW LEVEL MOISTURE BECOMES TRAPPED BENEATH DRY AIR ALOFT.
FARTHER INLAND ACROSS SOUTHERN NH AND WESTERN MA A STEADIER RAIN IS
POSSIBLE AS COMMA HEAD RAINS MAY CLIP THIS REGION WHILE BULK OF RAIN
IS CONFINED TO CENTRAL AND NORTHERN NEW ENGLAND.

AS FOR TEMPS...NOT MUCH OF A DROP OFF GIVEN ONSHORE FLOW/CLOUDS AND
LIGHT PRECIP.

WEDNESDAY...

TRAILING SHORT WAVE ENERGY ROUNDS THE BASE OF THE TROUGH AND THEN
TAKES AIM AT SOUTHERN NEW ENGLAND LATER IN THE DAY. STRONG SYNOPTIC
SCALE FORCING WITH THIS FEATURE AND RESULTS IN COASTAL LOW OFF NJ
COAST TO INTENSIFY. THUS SLUG OF HEAVY RAIN LIKELY TO MOVE ONSHORE
INTO SOUTHERN NEW ENGLAND LATE IN THE DAY. IN ADDITION AS DRY SLOT
APPROACHES THETA-E LAPSE RATES BEGIN TO DECREASE. THUS EMBEDDED
CONVECTION POSSIBLE AND WOULD ENHANCE HEAVY RAINFALL POTENTIAL. THIS
WILL INCREASE THE RISK URBAN/POOR DRAINAGE FLOODING AND MAY IMPACT
THE EVENING COMMUTE.

TEMPS SIMILAR AS TODAY WITH HIGHS IN THE L60S OVER SOUTHEAST MA AND
COOLING INTO THE 50S ELSEWHERE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
OVERVIEW AND MODEL PREFERENCES...

WITH FAIRLY GOOD MODEL AGREEMENT THROUGH THE MID TERM REGARDING A
SLOW MEANDERING AND STACKED LOW PRES SYSTEM MOVING JUST TO THE S
OF SRN NEW ENGLAND...A GENERAL CONSENSUS BLEND WILL BE USED AS A
BASELINE FOR THIS FORECAST. FOR THE REMAINDER...TOWARD THE END OF
THE WEEK...THE OPERATIONAL ECMWF CONTINUES TO EXHIBIT A BIT OF A
HIGHER AMPLIFICATION BIAS /SOMEWHAT TYPICAL OF THIS MODEL/. WHILE
OTHER OPERATIONAL MODELS AND SEVERAL OF IT/S OWN ENSEMBLES ARE
MORE PROGRESSIVE WITH A SECONDARY KICKER WAVE AND HIGH PRES.
THEREFORE...WILL ADD LESS WEIGHT TO THE ECMWF BY THE LATE WEEK AND
WEEKEND-EARLY NEXT WEEK TIME FRAME.

AS MENTIONED ABOVE THE KEY FEATURE INITIALLY IS A SLOW MOVING
CUTOFF LOW PRES WITH ATTENDANT OCCLUDING SFC LOW THROUGH LATE IN
THE WEEK. IT/S NOT UNTIL A KICKER WAVE /DEEPENING WAVE EJECTING
OUT OF THE CANADIAN W/ MOVES IN ON SAT THAT THE LOW PRES MOVES
FULLY INTO THE MARITIMES AND ALLOWS DRIER AIR TO FULLY BUILD IN.
THEREFORE...EXPECT THE WET/GRAY CONDITIONS TO CONTINUE THROUGH FRI
WITH GRADUAL IMPROVEMENT FROM THEN INTO EARLY NEXT WEEK.

DETAILS...

WED NIGHT INTO THU...
AT THIS POINT ALL FEATURES LINE UP FOR THE POTENTIALLY WETTEST
PERIOD OF THE FORECAST. IN ESSENCE A REINFORCING LLJ /ABOUT 40+ KT
MAINLY N OF THE BOX CWA/ MOVES IN COMBINED WITH UPPER LVL DRY SLOT
AND NEAR 6.0+ C/KM LAPSE RATES. THEREFORE...LOOKS LIKE A DECENT
SETUP FOR CONVECTIVE ELEMENTS WITH THIS LLJ PARTICULARLY BETWEEN
00Z AND 12Z ON THU. WITH MODEST PWATS UP TO 1.5 INCHES /ABOUT 2+
STD DEVIATIONS ABOVE NORMAL/. COULD SEE POCKETS OF HEAVIER RAIN
THROUGH THE PERIOD...GRADUALLY DIMINISHING INTO THE DAYLIGHT HOURS
ON THU AS THE LLJ AND DRY SLOT SHIFT N. RIGHT NOW THE PRIMARY
THREAT WOULD BE THE TYPICAL URBAN AREAS WHERE DRAINAGE IS POOR FOR
ANY NUISANCE FLOODING...BUT WILL NEED TO KEEP AN EYE ON THIS OVER
THE NEXT 24-36 HOURS. OTHERWISE...THE GRAY/DAMP CONDITIONS
CONTINUE WITH ONSHORE FLOW AND PLENTY OF MOISTURE/CLOUD COVER. DUE
TO THIS CLOUD COVER...SUSPECT THAT LOWS REMAIN MAINLY IN THE 50S
AND HIGHS ONLY RISE INTO THE MID 50S AND LOW 60S.

FRI...
GRADUAL IMPROVEMENT AS THE UPPER LVL SHORTWAVE EJECTING OUT OF
CANADA BEGINS TO FORCE THE UPPER LVL CUTOFF TO THE E AND WEAKENS
IT. STILL ENOUGH UPPER LVL COOL AIR AND MOISTURE TO SUPPORT A FEW
MORE SHOWERS. SO THE GRAY/WET CONDITIONS CONTINUE...BUT WITH A
MORE N COMPONENT TO THE FLOW...THESE SHOWERS ARE LIKELY TO BE
FEWER AND FARTHER BETWEEN. TEMPS A BIT WARMER...MAINLY UPPER 50S
TO MID 60S.

SAT AND SUN...
SFC COLD FRONT ASSOCIATED WITH THE SHORTWAVE WILL BE MOVING
THROUGH THE REGION...WHICH SHOULD FINALLY RELEASE THE REGION FROM
THE GRIPS OF THE CUTOFF. AT THIS POINT WITH DRIER AIR MOVING
IN...MAY ONLY SEE CLOUD COVER WITH THIS FRONTAL PASSAGE...BUT AN
ISOLATED SHOWER IS NOT OUT OF THE QUESTION MAINLY SAT NIGHT INTO
EARLY SUN. THE DIFFERENCES IN AMPLIFICATION BETWEEN MODELS MAKE
IT DIFFICULT TO TELL EXACTLY HOW DEEP THE COLD AIR GETS SAT NIGHT
INTO SUN...BUT WITH FULL MIXING HIGHS OF LOW-MID 60S ARE NOT OUT
OF THE QUESTION WITH LOWS FALLING BACK INTO THE 40S.

MON AND TUE...
HIGH PRES BUILDS IN ACROSS THE AREA WITH DRIER AIR AND MOSTLY
CLEAR CONDITIONS. TEMPS MAY BE NEAR SEASONAL NORMALS...IF NOT
SLIGHTLY ABOVE DEPENDING ON HOW DEEP THE COOL AIR BECOMES AT THIS
POINT.

&&

.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 WEDNESDAY/...

AVERAGE FORECAST CONFIDENCE. BAND OF HEAVIER RAIN SHOULD DEVELOP
OVER CAPE COD AND THE ISLANDS AROUND OR AFTER 15Z TODAY...THEN
LIFT NORTH AND PIVOT NORTHWEST INTO CENTRAL NEW ENGLAND TONIGHT.
CONFIDENCE IS LOWER ON EXACT LOCATION AND TIMING OF THIS FEATURE.

THRU 12Z...

VFR WITH LOW RISK OF AREAS OF LIGHT RAIN DEVELOPING ACROSS WESTERN
NEW ENGLAND AND ALSO OVER CAPE COD AND THE ISLANDS. OTHERWISE
MAINLY DRY WEATHER PREVAILS.

AFTER 12Z...

VFR WITH LIGHT SPOTTY RAIN POSSIBLE WESTERN NEW ENGLAND AND OVER
CAPE COD AND THE ISLANDS. THEN RAIN SHOULD BECOME FOCUSED OVER THE
CAPE AND ISLANDS AFTER 15Z WITH AREAS OF LIGHT/SPOTTY RAIN
ELSEWHERE. VFR WILL LOWER TO MVFR AFTER 15Z ACROSS EASTERN MA AND
POSSIBLE WESTWARD INTO RI. VERY LOW RISK OF ISOLATED THUNDER OVER
THIS AREA.

TONIGHT...

MAIN AREA OF RAIN LIFTS NORTHWARD INTO CENTRAL NEW ENGLAND.
SPOTTY LIGHT RAIN AND DRIZZLE WILL BE COMMON ACROSS SOUTHERN NEW
ENGLAND TERMINALS WITH VFR/MVFR TRENDING TOWARD IFR LATE TONIGHT.

WEDNESDAY...

IFR/MVFR WITH MOST OF THE RAIN CONFINED TO THE INTERIOR. HOWEVER
A NEW AREA OF RAIN SHOULD MOVE ONSHORE TO THE SOUTH COAST LATE IN
THE DAY. E-NE WINDS WILL INCREASE LATE IN THE DAY AS WELL.

KBOS...HIGH CONFIDENCE IN TAF ON TRENDS BUT LOWER CONFIDENCE ON
EXACT TIMING AND DETAILS.

KBDL...HIGH CONFIDENCE IN TAF ON TRENDS BUT LOWER CONFIDENCE ON
EXACT TIMING AND DETAILS.

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

WEDNESDAY NIGHT THROUGH THURSDAY...
MAINLY IFR/MVFR WITH PERIODS OF HEAVY RAIN POSSIBLE. LOW CIGS AND
VSBYS IN HEAVIER RAIN AND FOG. SLIGHT CHANCE OF THUNDER THROUGH
THE PERIOD. CHANCE FOR LLWS ESPECIALLY OVERNIGHT INTO EARLY THU
MORNING WITH UP TO 40 KT POSSIBLE AT AROUND 2KFT ESPECIALLY
TERMINALS N OF THE MASS PIKE.

FRIDAY AND SATURDAY...
IMPROVING TO VFR. AREAS OF MVFR CIGS/VSBYS IN SHOWERS ON
FRIDAY...WITH THE BEST CHANCE IN SOUTHERN NH AND EASTERN MASS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /TODAY THROUGH WED/...

TODAY...

STRONGEST SOUTHEAST WINDS WILL OCCUR OVER THE EASTERN MA
WATERS...WITH GUSTS UP TO 25 KT. THUS SCA POSTED FOR THAT AREA.
HEAVY RAIN WITH LOW RISK OF T-STORMS ACROSS THIS AREA. ELSEWHERE
LIGHTER WINDS AND SHOWERS.

TONIGHT...

EAST TO NORTHEAST WINDS. LOW RISK OF 25 KT OVER CAPE ANN WATERS.
VSBY REDUCED IN AREAS OF FOG AND DRIZZLE.

WEDNESDAY...

HEAVY RAIN AND POSSIBLE EMBEDDED THUNDER MOVES SOUTHEAST TO
NORTHWEST ACROSS THE WATERS AND THEN ONSHORE LATE IN THE DAY.
NORTHEAST WINDS 15-20 KT. VSBY REDUCED IN AREAS OF FOG AND HEAVY
RAIN LATE IN THE DAY.

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

WED NIGHT INTO THU...
MAINLY E-NE FLOW ALONG THE WATERS WED NIGHT INTO EARLY THU. THEN
SHIFTING TO NW DURING THE AFTERNOON AND EVENING THU. A FEW WIND
GUSTS MAY APPROACH GALE FORCE WED NIGHT MAINLY ACROSS THE N
WATERS...WITH SMALL CRAFT ADVISORY LEVEL WINDS ELSEWHERE. THE
WINDS DROP OFF AS THEY SHIFT THU...BUT THEN GUST AGAIN TO SMALL
CRAFT ADVISORY LEVELS LATE DAY THU. OTHERWISE...SEAS BUILD WED
NIGHT INTO THU MORNING WITH AT LEAST 5-9 FT SEAS POSSIBLE. SOME
HEAVY RAIN POSSIBLE WED NIGHT INTO EARLY THU MORNING.

FRI...
LOW PRES MOVES FURTHER OFFSHORE...WINDS AND SEAS MAY STILL REACH
SMALL CRAFT ADVISORY LEVELS DURING THE DAY FRI AND INTO FRI
NIGHT...BUT EXPECT GRADUAL IMPROVEMENT.

SATURDAY...WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT LEVELS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 8 AM EDT WEDNESDAY FOR
     ANZ250-254.
     SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 8 AM EDT
     WEDNESDAY FOR ANZ251.

&&

$$
SYNOPSIS...NOCERA/DOODY
NEAR TERM...NOCERA
SHORT TERM...NOCERA
LONG TERM...DOODY
AVIATION...NOCERA/DOODY
MARINE...NOCERA/DOODY



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