Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 170611
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
111 AM EST WED DEC 17 2014

.SYNOPSIS...
A WAVE OF LOW PRESSURE WILL BRING A PERIOD OF RAIN TONIGHT INTO
EARLY WEDNESDAY BEFORE TAPERING TO A FEW SHOWERS. ANOTHER ROUND OF
SNOW OR RAIN SHOWERS POSSIBLE WEDNESDAY NIGHT INTO THURSDAY...
ESPECIALLY NORTH OF THE MASS PIKE. HIGH PRESSURE BRINGS DRY AND
NEAR SEASONABLE CONDITIONS LATE THIS WEEK. STRENGTHENING LOW
PRESSURE IS FORECAST TO PASS SOUTHEAST OF NEW ENGLAND SOMETIME
THIS WEEKEND INTO EARLY NEXT WEEK.

&&

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

110 AM UPDATE...

NUMEROUS SHOWERS WORKING ACROSS SOUTHERN NEW ENGLAND EARLY THIS
MORNING.  SECONDARY LOW PRESSURE DEVELOPING ALONG THE SOUTH COAST
WILL LIKELY ENHANCE THE AREA OF RAIN ACROSS EASTERN MA/RHODE ISLAND
TOWARD DAYBREAK.  THIS A RESULT OF FAIRLY STRONG SYNOPTIC FORCING
AND DEEP MOISTURE IN PLACE FOR MID DECEMBER.  BURST OF INSTABILITY
MAY RESULT IN BRIEF HEAVY RAIN BETWEEN 4 AND 7 AM ACROSS EASTERN NEW
ENGLAND.  ACTIVITY SHOULD RAPIDLY COME TO AN END BETWEEN 7 AND 9 AM
ACROSS MOST OF THE EASTERN MA COAST...AS LOW PRESSURE LIFTS TO THE
NORTHEAST OF THE REGION.  THE OTHER CONCERN WILL BE FOR AREAS OF FOG
EARLY THIS MORNING...PARTICULARLY IN CENTRAL AND NORTHEAST MA.  WILL
CONTINUE TO COVER THIS WITH A SPECIAL WEATHER STATEMENT AND THINK
RAIN WILL PRECLUDE THE NEED FOR A DENSE FOG ADVISORY.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...

WEDNESDAY...
MAIN FOCUS FOR SHOWERS EARLY WED MORNING WILL BE ACROSS CENTRAL
AND NE MA BEFORE DEEPER MOISTURE AND MID LEVEL OMEGA MOVES TO THE
N. OTHERWISE...MUCH OF THE DAY WILL LIKELY BE DRY OTHER THAN A FEW
PASSING SHOWERS. BEST CHANCE FOR AFTERNOON SHOWERS LATER IN THE
DAY WILL BE ACROSS W MA AS MID LEVEL LOW AND SHORTWAVE APPROACH
FROM THE WEST. IT WILL BE A MILD DAY WITH TEMPS REACHING INTO THE
MID/UPPER 40S ACROSS MUCH OF THE REGION AND AROUND 50 DEGREES
NEAR THE COAST WHERE A FEW BREAKS OF SUNSHINE POSSIBLE.
OTHERWISE...MAINLY CLOUDY SKIES WILL PREVAIL.

WEDNESDAY NIGHT...
MID LEVEL LOW FORECAST TO TRACK ACROSS CENTRAL/NORTHERN NEW ENG
WED NIGHT AS THE COLUMN COOLS FROM TOP DOWN. BEST FORCING AND
MOISTURE WILL BE ALONG AND ESPECIALLY TO THE NORTH OF THE MID
LEVEL CENTER SO BEST CHANCE OF SNOW SHOWERS WILL BE ACROSS N NEW
ENG. HOWEVER...WILL LIKELY SEE A FEW RAIN/SNOW SHOWERS SPILLING
INTO SNE...ESPECIALLY N MA WHICH WILL BE ON SOUTHERN EDGE OF
DEEPER MOISTURE AND QG FORCING. ANY ACCUM WILL BE LIGHT...AN INCH
OR LESS AND CONFINED TO HIGHER TERRAIN. GUSTY WEST WINDS
DEVELOPING OVERNIGHT AS LOW PRES DEEPENS IN THE GULF OF MAINE.
GUSTS TO 30 MPH POSSIBLE.

&&

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

*  SNOW SHOWERS ACROSS THE INTERIOR THROUGH MIDDAY THURSDAY
*  DRY WEATHER WITH NEAR OR SLIGHTLY BELOW TEMPS FRIDAY AND SAT
*  POSSIBLE COASTAL SYSTEM SAT NIGHT THROUGH SUN NIGHT

OVERVIEW AND MODEL PREFERENCES...

12Z OP MODEL RUNS APPEAR IN FAIRLY GOOD AGREEMENT EARLY IN THE
MEDIUM RANGE PERIOD...BUT UPPER LEVEL SPLIT FLOW ACROSS THE LOWER 48
LEADS TO TIMING DIFFERENCES INTO THIS WEEKEND AND BEYOND. THE BIG
ISSUE APPEARS TO BE IN PHASING SOUTHERN STREAM ENERGY INTO POSSIBLE
COASTAL CYCLOGENESIS LATE THIS WEEKEND INTO EARLY NEXT WEEK. OVERALL
H5 PATTERN APPEARS FLAT UNTIL THE SOUTHERN STREAM SHORT WAVE WORKS
OUT OF THE 4 CORNERS REGION AND STARTS DIGGING...WHILE THE NORTHERN
STREAM REMAINS RATHER FAST. THE 12Z ECMWF/GFS APPEAR TO KEEP THIS
SYSTEM RATHER WEAK AND WELL S OF THE REGION WHILE THE GGEM IS
STRONGER AND EVEN FURTHER OFFSHORE. DID NOTE SOLUTION DIFFERENCES
BETWEEN THE 00Z AND 12Z EC OP RUN...WITH THE 12Z RUN MOVING THE
LATE WEEKEND LOW PRES FASTER THAN ITS 00Z COUNTERPART.

WITH THE 00Z AND 12Z OP CANADIAN GGEM BEING FAST OUTLIERS...LEANED
TOWARD A BLEND OF THE EC ENSEMBLE MEANS WITH A BIT OF THE GFS OP RUN
AS THIS SHOWED DECENT RUN TO RUN CONSISTENCY VS. THE EC OP RUN...
ALONG WITH PREVIOUS FORECAST FOR CONTINUITY. THIS WAS NOT TOO FAR
FROM THE PREVIOUS FORECAST...THOUGH STILL QUITE A BIT OF
UNCERTAINTY ESPECIALLY WITH THE TRACK AND INTENSITY OF THE LATE
WEEKEND SYSTEM.

DETAILS...

THURSDAY...HIGH CONFIDENCE.
AS H5 CUTOFF LOW ELONGATES ACROSS THE NORTHEAST U.S. ON THU...
SURFACE LOW EXITS TO THE MARITIMES. WILL STILL SEE A BIT OF
LEFTOVER MOISTURE AS CYCLONIC FLOW LINGERS MAINLY THROUGH MIDDAY.
SOME DRYING DOES FILTER INTO S COASTAL AREAS ON GUSTY W-NW WINDS.
MAY SEE SOME LIGHT SNOW ACCUMULATIONS ACROSS THE HIGHER TERRAIN OF
NW MA...GENERALLY LESS THAN AN INCH. CORE OF COLDEST AIR REMAINS W
OF THE REGION INTO THU NIGHT...SO EXPECT HIGHS MAINLY AROUND
SEASONAL NORMS.

FRIDAY AND SATURDAY...MODERATE TO HIGH CONFIDENCE.
SURFACE HIGH PRES WILL REMAIN ACROSS THE REGION WHILE UPPER LEVEL
CUTOFF LOW EXITS TO THE MARITIMES. DRY CONDITIONS WILL BE IN PLACE
THROUGH MOST OF THIS PERIOD WITH TEMPS RUNNING CLOSE TO OR
SLIGHTLY BELOW SEASONAL NORMALS.

HIGH PRES CENTER WILL PASS ACROSS SOUTHERN QUEBEC BY SATURDAY
WHICH WILL ALLOW WINDS TO VEER TO NE-E OVER TIME THOUGH REMAIN
RATHER LIGHT. BIG QUESTION AT THIS POINT WILL BE HOW QUICKLY THE
LOW THAT DEVELOPS OVER THE EASTERN GULF OF MEXICO MOVES TO THE SE
U.S. COAST AND BRING ITS LEADING EDGE OF MOISTURE NORTHWARD. FOR
NOW...HAVE KEPT WITH PREVIOUS FORECAST TRENDS AND BROUGHT
INCREASING CLOUDS FROM S-N DURING THE DAY. KEPT A DRY FORECAST
GOING ALONG WITH SEASONAL TEMPS.

SATURDAY NIGHT THROUGH SUNDAY NIGHT...LOW CONFIDENCE.
OP MODEL TIMING IS STILL SUSPECT WITH THE PHASING OF THE SPLIT
FLOW AS LOW PRES WORKS NE. ONE CONSISTENT THING HAS BEEN THE
FLATNESS OF THE WAVE ALONG WITH SECOND SHORT WAVE TRYING TO WORK
INTO THIS SYSTEM. ANOTHER QUESTION IS HOW MUCH QPF TO EXPECT WITH
THIS FEATURE. BLENDING OF PREVIOUS FORECAST WITH ENSEMBLES AND WPC
GUIDANCE GAVE SOME CONSISTENCY ON THIS FORECAST PACKAGE.

KEPT ONLY CHANCE POPS GOING FOR NOW...BUT HAVE SOME CONFIDENCE
THAT PRECIP WILL OCCUR SOMETIME DURING THIS TIMEFRAME BUT ONSET
AND EXIT ARE STILL VERY MUCH IN QUESTION. AT THIS POINT...LOOKS
LIKE BEST SHOT OF PRECIP WILL OCCUR LATE SAT NIGHT INTO EARLY
SUNDAY NIGHT. NEXT QUESTION IS PTYPE. LOOKS LIKE GENERAL EASTERLY
WINDS WILL BRING SOMEWHAT MILDER AIR ACROSS EASTERN AREAS...WITH
SOME MIXED RAIN/SNOW A BIT FURTHER INLAND. QPF FORECASTED AMOUNTS
VARIED WIDELY. LEANED TOWARD LIGHTER AMOUNTS WITH THE WEAKNESS OF
THIS SYSTEM /FOR NOW/.

ANOTHER QUESTION IS THE WIND...WHICH IS ALL DEPENDENT UPON STORM
TRACK AND STRENGTH. WHILE THIS LOOKS LIKE AN OPEN WAVE VS. A
DEEPENING STORM /FOR NOW/...SHOULD NOT HAVE TOO MANY WIND ISSUES.
HOWEVER...IF STORM DOES TREND STRONGER HENCE HIGHER ONSHORE
WINDS...MAY NEED TO CONTEND WITH COASTAL CONCERNS AS ASTRO TIDES
ARE HIGH DURING SUN AND MON. WILL CONTINUE TO MONITOR MODEL RUNS
AND ENSEMBLES CLOSELY.

MONDAY AND TUESDAY...LOW CONFIDENCE.
TIMING ISSUES VERY MUCH IN PLACE DURING THIS TIMEFRAME. AT THIS
POINT...HAVE PUSHED PRECIP OFFSHORE AS ANOTHER HIGH BUILDS E.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
FORECASTER CONFIDENCE LEVELS...

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

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

TODAY...IFR TO LIFR CONDITIONS IN SHOWERS AND FOG EXPECTED THROUGH
EARLY TO MID MORNING.  NORTHWEST FLOW BEHIND DEPARTING LOW PRESSURE
SHOULD ALLOW MOST AREAS TO IMPROVE TO MVFR CONDITIONS BY
AFTERNOON...BUT THE CAPE/ISLANDS MAY REMAIN IFR.  BULK OF THE RAIN
OVER BY MID MORNING...OTHERWISE DRY WEATHER DOMINATES
TODAY BESIDES A PASSING SHOWER OR TWO.

TONIGHT...MARGINAL VFR TO MVFR CEILING EXPECTED TONIGHT.  IN
ADDITION...A FEW RAIN/SNOW SHOWERS EXPECTED PARTICULARLY NORTH OF
THE MA TURNPIKE.  THIS MAY RESULT IN BRIEF IFR CONDITIONS...MAINLY
ACROSS OUR NORTHERN ZONES.  WEST TO NORTHWEST WIND GUSTS OF 20 TO 25
KNOTS DEVELOP ACROSS THE COASTAL PLAIN.

THURSDAY...MARGINAL VFR TO MVFR CEILINGS EXPECTED.  A LEFT OVER
RAIN/SNOW SHOWER POSSIBLE MAINLY IN THE MORNING...BUT DRY WEATHER
DOMINATES.  NORTHWEST WIND GUSTS OF 20 TO 30 KNOTS EXPECTED.

KBOS TERMINAL...MODERATE CONFIDENCE.  IFR TO LIFR CIGS/VSBYS SHOULD
IMPROVE TO MVFR THIS AFTERNOON AS SURFACE WINDS TURN NORTHWEST.

KBDL TERMINAL...MODERATE CONFIDENCE.  IFR TO LIFR CONDITIONS SHOULD
IMPROVE TO MVFR BY AFTERNOON AS SURFACE WINDS TURN NORTHWEST.

OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY...

THURSDAY NIGHT THROUGH SATURDAY...MODERATE TO HIGH CONFIDENCE.
VFR. MID AND HIGH CLOUDS MOVE IN FROM S-N DURING SAT.

SATURDAY NIGHT-SUNDAY...LOW CONFIDENCE...MAINLY FOR TIMING. VFR TO
START...THEN AREAS OF MVFR-IFR CIGS/VSBYS FROM S-N. MAINLY RAIN
ACROSS E MA/MOST OF RI...WITH MIXED RAIN/SNOW INLAND.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH WEDNESDAY NIGHT/...HIGH CONFIDENCE.

SE WINDS LESS THAN 20 KT TONIGHT...THEN SHIFTING TO WEST
WEDNESDAY WITH GUSTS INCREASING TO 25 KT DURING THE AFTERNOON OVER
THE SOUTHERN WATERS. EXPECT GUSTS TO 30 KT WED NIGHT AS LOW PRES
INTENSIFIES IN THE GULF OF MAINE. A FEW GALE FORCE GUSTS TO 35 KT
POSSIBLE OVER WATERS SOUTH AND EAST OF CAPE COD. BUILDING SEAS WED
AFTERNOON AND ESPECIALLY WED NIGHT...8 TO 10 FT OVER THE OUTER
WATERS.

OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE TO HIGH CONFIDENCE.

THURSDAY...SMALL CRAFT CONDITIONS CONTINUE ON W-NW WINDS. LOW
PROB OF GALE FORCE GUSTS OVER THE OUTER WATERS DURING THU. WINDS
SLOWLY DIMINISH LATE THU NIGHT. SEAS UP TO 7-10 FT MAINLY OVER THE
SOUTHERN OUTER WATERS...SLOWLY SUBSIDING THU NIGHT.

FRIDAY-SATURDAY...NW WINDS DIMINISH BELOW SMALL CRAFT DURING FRI
AND REMAIN BELOW SMALL CRAFT THROUGH SAT. SEAS LINGER AOA 5 FT
INTO EARLY FRI NIGHT THEN WILL SUBSIDE.

SATURDAY NIGHT-SUNDAY...WINDS VEER TO NE-E SAT NIGHT...THEN
INCREASE DURING SUNDAY. MAY SEE GUSTS TO 25 KT LATE SUN/SUN NIGHT.
SEAS SLOWLY BUILD SUN NIGHT.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST
     THURSDAY FOR ANZ232>235-237.
     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 6 PM EST
     THURSDAY FOR ANZ230-236.
     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM EST
     THURSDAY FOR ANZ231-251.
     SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 6 PM EST
     THURSDAY FOR ANZ250-254>256.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...FRANK
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...FRANK/EVT
MARINE...KJC/EVT


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