Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 062250
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
550 PM EST SAT FEB 6 2016

.SYNOPSIS...
HIGH PRESSURE BRINGS DRY WEATHER ALONG WITH MODERATING TEMPERATURES
TONIGHT AND SUNDAY. AN OCEAN STORM MAY BRING A PLOWABLE SNOWFALL
TO SOUTHEAST MASSACHUSETTS INCLUDING CAPE COD AND THE ISLANDS
MONDAY AND MONDAY NIGHT. PERIODS OF LIGHT SNOW ARE LIKELY FOR THE
REMAINDER OF THE REGION MONDAY THROUGH WEDNESDAY...AND POSSIBLY
LINGERING INTO THURSDAY. AN ARCTIC COLD FRONT BRINGS BITTERLY COLD
CONDITIONS THE END OF THE WEEK INTO NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
4 PM UPDATE...

TONIGHT...

CONFLUENT FLOW ALOFT PROVIDES DRY WEATHER TONIGHT ALONG WITH HIGH
PRES AT THE SURFACE JUST SOUTH OF NEW ENGLAND. THIS WILL RESULT IN
SW PRES GRADIENT/SURFACE WINDS AND YIELDING TEMPS NOT AS COLD AS
LAST NIGHT AS DEW PTS CLIMB INTO THE 20S.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
SUNDAY ...

NOT MUCH CHANGE WITH CONFLUENT FLOW ALOFT AND HIGH PRES AT THE
SURFACE. THUS EXPECTING A DRY COLUMN SUPPORTING LOTS OF SUNSHINE
AND LIGHT WINDS...WHICH WILL MAKE TEMPS IN THE L40S FEEL EVEN
MILDER.

SUNDAY NIGHT ...

1035 QUEBEC SURFACE HIGH ADVECTS SHALLOW ARCTIC AIR SOUTHWARD
INTO SOUTHERN NEW ENGLAND. MEANWHILE MID LEVEL SOUTHERN STREAM
TROUGH OVER THE GULF STATES THIS AFTERNOON INDUCES CYCLOGENESIS
OFF THE EAST COAST OF FL THIS EVENING AND THEN RAPIDLY
INTENSIFYING INTO A SUB 980 MB LOW/GALE CENTER WELL EAST OF THE
NC COAST SUN NIGHT. TYPICALLY THIS TRACK IS TOO FAR OFFSHORE TO
YIELD ACCUMULATING SNOW TO SOUTHEAST MA. HOWEVER THIS CYCLONE HAS
A VERY LARGE CIRCULATION/WCB/FIREHOSE IN ADDITION TO 1035 MB
SURFACE HIGH OVER QUEBEC. THUS SNOW COMES ONSHORE 06Z-12 MON AND
WILL LIKELY HAVE SOME OCEAN EFFECT SNOW /OES/ COMPONENT GIVEN NE
WINDS AND SHALLOW ARCTIC AIR BLEEDING IN FROM THE NORTH. BIG
DIFFERENCES WITH MODEL QPF WITH NAM/ARW/NMM MOST ROBUST. EC/GFS
AND RGEM MORE MODEST SO FOLLOWED A MODEL BLEND GIVEN UNCERTAINTY.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...

DISCUSSION...
AMPLIFIED LONG WAVE UPPER LEVEL PATTERN REMAINS IN PLACE FOR MUCH
IF NOT ALL OF THE LONG TERM PERIOD...THOUGH SIGNS CONTINUE TO SHOW
SOME DEAMPLIFICATION OF THE LONG WAVE TROUGH LATER THIS WEEK
ACROSS THE EAST. MODELS AND ENSEMBLES CONTINUE TO SIGNAL UNSETTLED
CONDITIONS THROUGH WED AND POSSIBLY INTO THU...THEN WILL START TO
SETTLE DOWN. HOWEVER...LOOKS LIKE WINTER TEMPERATURES WILL PUSH
IN WITH THE DRIER CONDITIONS LATE NEXT WEEK INTO THE WEEKEND.

STILL PROBLEMS WITH SEPARATION BETWEEN SHORT WAVES IN THE OVERALL
CUTOFF LOW PRES/LONG WAVE TROUGH MON-WED...THOUGH DOES LOOK LIKE
SOME SETTLING IN WITH SOME OF THE DETAILS. HOWEVER...WITH UPPER
LEVEL CYCLONIC FLOW IN PLACE...WILL STILL SEE PERIODS OF PRECIP
CONTINUE THROUGH AT LEAST MID WEEK.

USED A BLEND OF MOST OF THE AVAILABLE GUIDANCE ALONG WITH
ENSEMBLES WHICH GAVE REASONABLE CONTINUITY WITH PREVIOUS
FORECAST.

DETAILS...

MONDAY-TUESDAY...MODELS SETTLING IN WITH CONTINUE NE FLOW IN
PLACE. FIRST LOW PRES PASSES WELL SE OF NANTUCKET...BUT
COMBINATION OF THIS STRONG STORM /CENTRAL PRES FROM 970-978 HPA AS
IT PASSES MON AFTERNOON/ AND HIGH PRES RIDGING EXTENDING S OUT OF
QUEBEC ACROSS W NEW ENGLAND...VERY TIGHT PRES GRADIENT IN PLACE.
THIS WILL PRODUCE STRONG NE WINDS ACROSS E COASTAL
AREAS...GENERALLY S OF BOSTON. GUSTS MAY REACH UP TO 35-45 MPH
ALONG E COASTAL AREAS THROUGH MONDAY AFTERNOON...THEN WILL SLOWLY
DIMINISH.

MODELS DO KEEP PUSHING NW FRINGE OF PRECIP INTO EASTERN AND
POSSIBLY CENTRAL AREAS...PLUS WILL LIKELY SEE COMBINATION OF OCEAN
EFFECT SNOW. NOTING AT LEAST CONDITIONAL CONDITIONS FOR LAKE
EFFECT ON BOTH GFS AND 4 KM BUFKIT SOUNDINGS LATE MON/MON NIGHT.

DID HAVE ISSUES WITH QPF FORECAST...THOUGH WITH STRONG ONSHORE
WINDS SHOULD SEE SOME ENHANCEMENT THERE. USED A BLEND OF WPC
GUIDANCE... 12Z GFS AND A TOUCH OF THE 15Z SREF...WITH HIGHEST
AMOUNTS ON THE CAPE AND ISLANDS BETWEEN 12Z AND 18Z MONDAY WITH
INITIAL SURGE OF LOW LEVEL MOISTURE AS LOW PASSES.

WITH THE COMBINATION OF INITIAL LOW LEVEL MOISTURE AND STRONG
ONSHORE WINDS ENHANCING THE PRECIPITATION...EXPECT TO SEE BEST
CHANCE FOR SNOW ACROSS CAPE COD AND THE ISLANDS INTO PLYMOUTH
COUNTY. PARTIAL THICKNESSES SUPPORT MAINLY SNOW...THOUGH COULD SEE
SOME MIX WITH RAIN DURING TUESDAY WITH LIGHTER PRECIP. BASED ON
THIS...HAVE ISSUED WINTER STORM WATCH FOR THOSE AREAS MONDAY
THROUGH TUESDAY MORNING.

PRECIP SHOULD TAPER OFF BUT NOT TOTALLY END DURING TUESDAY AS
UPPER LEVEL COLD POOL SITS CLOSE TO THE REGION. THIS WILL KEEP
CYCLONIC FLOW IN PLACE AND KEEPING LIGHT SNOWFALL IN PLACE. WILL
LIKELY ALSO SEE A MIX WITH RAIN ALONG THE S COAST. BEST SHOT FOR
PRECIP WILL REMAIN ACROSS S COASTAL AREAS...THOUGH LOOKS TO BECOME
A BIT MORE SPOTTY TUE NIGHT.

WEDNESDAY-THURSDAY...WILL REMAIN UNSETTLED FOR MOST OF THIS
PERIOD. WILL SEE CLOUDINESS AND SCATTERED SNOW SHOWERS. NOT A LOT
OF QPF TO DEAL WITH...MORE NUISANCE SNOW BUT COULD STILL SEE LIGHT
SNOW ACCUMULATIONS THROUGH MIDDAY WED. AS UPPER LEVEL LONG WAVE
TROUGHING STARTS TO FLATTEN...NOTING AN ARCTIC FRONT IN THE NW
FLOW. EXPECT TO CROSS THE REGION LATE WED NIGHT OR EARLY
THU...WHICH WILL BE A DRY PASSAGE. EXPECT NW WINDS TO PICK UP ON
THU ALONG AS ARCTIC AIRMASS SHIFTS SE. HIGHS THU WILL ONLY BE IN
THE 20S TO LOWER 30S.

FRIDAY-SATURDAY...EXPECT DRY TO VERY COLD CONDITIONS IN PLACE.
ANOTHER REINFORCING ARCTIC FRONT CROSSES FRI NIGHT...WITH EVEN
COLDER AIR MOVING IN. CURRENT FORECAST SUGGESTS HIGHS ON SATURDAY
RUNNING AROUND 15 DEGREES BELOW SEASONAL NORMALS FOR MID FEBRUARY.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH SUNDAY NIGHT/...

THRU TONIGHT ... HIGH FORECAST CONFIDENCE FOR VFR/DRY AND LIGHT
SW WIND. WINDS MAY GUSTS UP TO 15-20 KT CAPE COD AND ISLANDS THIS
EVENING.

SUNDAY ... HIGH CONFIDENCE FOR VFR. LIGHT AND VARIABLE WINDS
BECOMING NE TOWARD SUNSET.

SUNDAY NIGHT ... VFR AND DRY THRU ABOUT MIDNIGHT. THEN LOWERING TO
MVFR WITH INCREASING CHANCES OF SNOW OR MIX RAIN/SNOW TOWARD
DAYBREAK MON. NE WINDS GUSTING UP TO 35 KT CAPE COD AND ISLANDS
TOWARD 12Z MON.

KBOS TERMINAL...HIGH CONFIDENCE THRU SUN EVENING THEN LOWERING
LATE SUN NIGHT REGARDING ARRIVAL OF LOWER CIGS/VSBYS IN SNOW/RAIN.

KBDL TERMINAL...HIGH CONFIDENCE IN TRENDS.

OUTLOOK /MONDAY THROUGH THURSDAY/...

MONDAY-TUESDAY...LOW TO MODERATE CONFIDENCE.
AREAS OF MVFR CIGS/IFR VSBYS IN -SN ACROSS MOST OF THE REGION.
LOWEST CONDITIONS EXPECTED ACROSS E MA/RI...WHERE THEY MAY SEE
PERIODS OF MODERATE SNOW IN OCEAN EFFECT ESPECIALLY SE COASTAL MA
/PLYMOUTH COUNTY/...CAPE COD AND THE ISLANDS LATE MON AND MON
NIGHT. MAY SEE MIXED -RN-SN ALONG E COAST TUE AFTERNOON. NE WIND
GUSTS UP TO 35 KT MON INTO MON NIGHT ALONG IMMEDIATE E COASTAL
MA...DIMINISHING TO AROUND 25 KT TUE.

WEDNESDAY-THURSDAY...LOW CONFIDENCE.
EXPECT -SHSN TO LINGER ACROSS THE REGION AS UPPER LEVEL SYSTEM
REMAINS ACROSS THE NORTHEAST. MAY SEE MIX WITH -RA ALONG S COAST
WED AFTERNOON. COULD SEE PERIODS OF MVFR TO LOCALLY IFR
CIGS/VSBYS... MAINLY WED-WED NIGHT. CONDITIONS SHOULD SLOWLY
IMPROVE TO VFR FROM WEST TO EAST DURING THU. N-NE WIND GUSTS
AROUND 25 KT EARLY WED WILL DIMINISH BY AROUND MIDDAY.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

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

TONIGHT AND SUNDAY ... TRANQUIL WIND AND SEAS ALONG WITH DRY
WEATHER AND GOOD VSBY.

SUNDAY NIGHT ... NE WINDS LIKELY INCREASE TO GALE FORCE ACROSS THE
RI AND SOUTHERN MA WATERS. THUS GALE WARNINGS POSTED. LOW
PROBABILITY NORTH OF CAPE COD SO GALE WATCHES POSTED THERE. VSBY
LOWERING IN SNOW LATE. SEAS WILL BUILD RAPIDLY WITH POWERFUL LOW
PRES OFF THE NC COAST COMBINING WITH 1035 MB SURFACE HIGH OVER
QUEBEC.

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

MONDAY...GALE CENTER WILL PASS WELL SE OF NANTUCKET...BUT GALE
FORCE GUSTS WILL CONTINUE TO EXTEND WELL NW OF THE CENTER. NE
WINDS GUSTING TO 35-45 KT...HIGHEST E AND S OF CAPE COD AND
NANTUCKET... WILL CONTINUE THROUGH LATE MORNING THEN WILL SLOWLY
DIMINISH DURING THE AFTERNOON AND MON NIGHT. SEAS UP TO 14-18 FT
ON THE EASTERN OUTER WATERS WILL SLOWLY SUBSIDE MON AFTERNOON.
VSBY RESTRICTIONS FOR AREAS OF LIGHT RAIN AND/OR SNOW MON-MON
NIGHT.

TUESDAY-WEDNESDAY...SMALL CRAFT CONDITIONS WILL CONTINUE DURING
THIS TIMEFRAME. NE WINDS IN PLACE TUE AND TUE NIGHT...GUSTING UP
TO 25-30 KT...WITH SEAS UP TO 8-11 FT. EXPECT WINDS TO BACK TO
N-NW WITH GUSTS CONTINUING AT AROUND 25 KT. SEAS WILL BUILD AGAIN
ON TUESDAY...HIGHEST E AND S OF NANTUCKET...UP TO 9-14 KT AS
ANOTHER LOW PASSES SE OF NANTUCKET. VSBY RESTRICTIONS CONTINUE FOR
LIGHT RAIN AND/OR SNOW.

THURSDAY...NW WINDS CONTINUE TO GUST UP TO 25-30 KT. LOW RISK OF
GUSTS UP TO 35 KT THU NIGHT E AND S OF CAPE COD AND NANTUCKET.
SEAS UP TO 7-11 FT ON THE SE OUTER WATERS. LOCAL VSBY RESTRICTIONS
IN SCT RAIN AND/OR SNOW SHOWERS...BUT SHOULD IMPROVE THU
AFTERNOON/EVENING.

&&

.TIDES/COASTAL FLOODING...
ASTRO TIDES LATE MON MORNING ARE HIGH WITH 11.2 FT AT BOSTON.
STRONG NE WINDS UP TO 40 KT WILL YIELD A STORM SURGE OF 1.5 FT TO
2.0 FT AT THE TIME OF HIGH TIDE. THIS COMBINED WITH STRONG WAVE
ACTION OF 12-18 FT JUST OFFSHORE WILL YIELD A RISK OF MODERATE
COASTAL FLOODING.

ETSS WAS A BIT HIGHER THAN ESTOFS AND SEEMS REASONABLE. WIND
FIELD DECREASES SUBSTANTIALLY NORTH OF PLYMOUTH COUNTY. THUS
THREAT OF COASTAL FLOODING IS LOWER FROM BOSTON NORTHWARD.
THEREFORE HAVE CONFINED THE COASTAL FLOOD WATCH SOUTH OF BOSTON
THRU PLYMOUTH TO CAPE COD AND NANTUCKET.

OTHER CONCERN IS BEACH EROSION GIVEN THE HIGH WATER LEVELS...STRONG
WAVE ACTION OVER MULTIPLE TIDE CYCLES. AGAIN APPEARS HIGHEST RISK
WILL BE SOUTH OF BOSTON. HOWEVER WILL HAVE TO MONITOR LATER MODEL
RUNS FOR POSSIBLE EXPANSION OF THE WATCH NORTHWARD.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...COASTAL FLOOD WATCH FROM MONDAY MORNING THROUGH MONDAY
     AFTERNOON FOR MAZ019-022-024.
     WINTER STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING
     FOR MAZ018-019-021>024.
RI...NONE.
MARINE...GALE WARNING FROM MIDNIGHT SUNDAY NIGHT TO 6 PM EST MONDAY FOR
     ANZ231>235-237-254>256.
     GALE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY AFTERNOON FOR
     ANZ230-250-251.

&&

$$
SYNOPSIS...NOCERA/EVT
NEAR TERM...NOCERA
SHORT TERM...NOCERA
LONG TERM...EVT
AVIATION...NOCERA/EVT
MARINE...NOCERA/EVT
TIDES/COASTAL FLOODING...NOCERA


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