Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 260153
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
953 PM EDT SAT APR 25 2015

.SYNOPSIS...
UNSEASONABLY COOL WEATHER CONTINUES THROUGH THIS WEEKEND WITH
SPOTTY SHOWERS OR SPRINKLES. PERIODS OF UNSETTLED WEATHER AND
BELOW NORMAL TEMPERATURES WILL CONTINUE THROUGH MOST OF NEXT
WEEK AS WELL.

&&

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

AS HAS BEEN THE CASE THE PAST FEW NIGHT...CLOUDS WERE PLAYING A
SIGNIFICANT ROLE IN THE FORECAST FOR THIS TIME OF NIGHT. LATEST
SATELLITE IMAGERY CONTINUES TO SHOW ABUNDANT LOW LEVEL CLOUDS OVER
SOUTHERN NEW ENGLAND. THIS HAS BROUGHT INTO QUESTION THE
POSSIBILITY FOR FROST FORMATION...AND THE NEED FOR THE FROST
ADVISORY ACROSS NORTHERN CT...AS WELL AS PORTIONS OF NORTHERN RI
AND SOUTHEAST MA.

SATELLITE DATA ALSO SHOWED SOME CLEARING OVER SOUTHERN NH. OF ALL
THE NEAR-TERM GUIDANCE...THE LAV GUIDANCE WAS HANDLING THE SKY
COVER THE BEST. LEANED HEAVILY UPON IT WHEN MAKING ADJUSTMENTS
THIS EVENING. THE LAV ALSO CLEARED THE CLOUDS AWAY FROM SOUTHERN
NEW ENGLAND IN THE 04-06Z TIME FRAME. WITH LIGHT WINDS ALREADY...
RADIATIONAL COOLING WILL BE EFFECTIVE WITH THE CLEAR SKIES. IN
CONSIDERATION OF ALL THE FACTORS...AND COLLABORATION WITH A
NEIGHBORING OFFICE...DECIDED TO LEAVE THE ADVISORY INTACT AT THIS
TIME.

MADE QUITE A FEW CHANGES TO TEMPERATURES THIS EVENING DUE TO THE
CLOUDS AS WELL.

PREVIOUS DISCUSSION...

TONIGHT...LIGHT WINDS AND MOSTLY CLEAR SKIES WILL RESULT IN
EXCELLENT RADIATIONAL COOLING OVERNIGHT.  THIS WILL DROP MANY
LOCATIONS INTO BELOW FREEZING ACROSS THE INTERIOR.  TEMPERATURES
WILL FALL INTO THE LOW TO MID 30S ACROSS NORTHERN CONNECTICUT...RHODE
ISLAND...AND SOUTHEASTERN MASSACHUSETTS. BECAUSE THE GROWING
SEASON HAS BEGUN ACROSS THESE AREAS...WILL ISSUE A FROST ADVISORY
FOR THIS REGION. THERE IS ALSO A LOW PROBABILITY OF FROST
OCCURRING ALONG THE EAST COAST OF MASSACHUSETTS.
HOWEVER...CONFIDENCE IS LOWER THERE SO HAVE HELD OFF ON ISSUING AN
ADVISORY.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
SUNDAY...THE UPPER LOW IS EXPECTED TO MOVE SLIGHTLY CLOSER TO OUR
REGION. THUS WE WILL BE IN A MORE FAVORABLE POSITION FOR DIURNAL
CLOUDS AND SHOWERS. SKIES SHOULD START OFF PARTLY TO MOSTLY SUNNY
THEN CLOUDS DEVELOP ALONG WITH A FEW SPOTTY SHOWERS.  THESE SHOWERS
ARE MORE LIKELY TO OCCUR NORTH OF THE MASS PIKE.  HIGH TEMPERATURES
SHOULD BE IN THE 50S ONCE AGAIN...THOUGH IF ENOUGH SUN PEEKS THROUGH
THE CLOUDS...COULD SEE TEMPS NEAR 60 THROUGH THE CONNECTICUT VALLEY
AND IN PARTS OF RHODE ISLAND AND SOUTHEASTERN MASSACHUSETTS.

SUNDAY NIGHT...SCATTERED SHOWERS WILL CONTINUE TO AFFECT SOUTHERN
NEW ENGLAND WITH THE UPPER LOW JUST EAST OF THE AREA.  WITH CLOUDY
SKIES AND RAIN SHOWERS...EXPECT TEMPERATURES TO BE A BIT WARMER THAN
EITHER OF THE PREVIOUS TWO NIGHTS WITH LOWS IN THE UPPER 30S TO THE
LOWER 40S.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
HIGHLIGHTS...

* RISK FOR SHOWERS AT TIMES BUT DRY MOST OF PERIOD
* LOW CONFIDENCE AFTER WEDNESDAY

OVERVIEW...PERSISTENT UPPER TROF OVER MARITIMES RETROGRADES EARLY
IN THE WEEK BEFORE MOVING BACK OFFSHORE. SOUTHERN STREAM ENERGY
WHICH CAME ASHORE LAST NIGHT IN CA MAY PHASE WITH NORTHERN STREAM
ENERGY LATE IN THE WEEK. OPERATIONAL GFS DOES NOT SHOW PHASING.
THE 12Z ECMWF DOES SHOW PHASING LIKE ITS PREDECESSOR...BUT ALSO
LIKE ITS PRIOR RUN...STILL TAKES THE SURFACE LOW WELL SOUTH OF NEW
ENGLAND. THE ECMWF HAS SHOWN BETTER RUN TO RUN CONTINUITY AND ITS
12Z OPERATIONAL RUN SEEMS FAIRLY CONSISTENT WITH ITS 00Z ENSEMBLE
MEAN. THE OPERATIONAL GFS RUNS SHOW LITTLE RUN TO RUN
CONTINUITY...AND ITS ENSEMBLES ARE WIDELY DISPERSED WITH MANY
MEMBERS SHOWING NO SURFACE LOW OFF THE MID ATLC COAST AND A FEW
OTHERS DEPICTING AN INTENSE COASTAL LOW JUST SE OF NEW ENGLAND.
ALTHOUGH OVERALL CONFIDENCE IS LOW AFTER WEDNESDAY...TEND TO HAVE
A LITTLE MORE CONFIDENCE IN THE ECMWF SOLUTION AT THIS TIME GIVEN
ITS BETTER INTERNAL CONSISTENCY.

DETAILS...

MONDAY...UPPER LOW RETROGRADES TO THE WEST AND INDUCES SOME LOW
LEVEL MOISTURE CONVERGENCE AND A COLD POOL ALOFT THAT SUPPORTS
SHOWERS. HAVE POPS GENERALLY AROUND 40 PERCENT BUT THINKING THAT
FUTURE SHIFTS MAY WISH TO INCREASE THOSE IF FUTURE MODEL RUNS REMAIN
CONSISTENT. NOTED THAT TOTAL TOTALS WERE NEAR 50...REFLECTIVE OF THE
COLD POOL ALOFT.

MONDAY NIGHT...MAY SEE SHOWERS LINGER INTO THE EVENING HOURS BEFORE
GRADUALLY DISSIPATING AND UPPER TROF STARTS TO SHIFT SE IN ADDITION
TO LOSS OF DAYTIME HEATING.

TUESDAY...HAVE KEPT SLIGHT CHANCE OF SHOWERS FOR THE AFTERNOON IN
THE EAST GIVEN SOME LINGERING MOISTURE...CYCLONIC FLOW AND PROXIMITY
OF COLD POOL ALOFT.

WEDNESDAY AND THURSDAY...WEDNESDAY IS LOOKING DRY FOR NOW. GFS
BRINGS UPPER SHORT WAVE TOWARD NEW ENGLAND LATE IN DAY/EVENING BUT
ECMWF HOLDS IT BACK. ENOUGH UNCERTAINTY THAT HAVE JUST LOW END
SLIGHT CHANCE POPS FOR THURSDAY.

THURSDAY NIGHT THROUGH SATURDAY...A LOT OF UNCERTAINTY FOR THIS
PERIOD DEPENDENT UPON EVOLUTION OF PROBABLE LOW DEVELOPMENT OFF THE
MID ATLC COAST. THE ECMWF SHOWS BEST CONSISTENCY RUN TO RUN AND WITH
ITS ENSEMBLES SO LEANING IN THAT DIRECTION FOR THE MOMENT. THIS
WOULD SUGGEST THE POTENTIAL OF A SIGNIFICANT SURFACE LOW FORMING
NEAR THE MID ATLC COAST BUT PROBABLY REMAINING SE OF NEW ENGLAND.

IT IS POSSIBLE THAT BY SATURDAY WILL SEE BUILDING HEIGHTS ALOFT AND
INCREASING THICKNESSES AS A RIDGE AMPLIFIES OVER THE OH VALLEY AND
ATTEMPTS TO BUILD TOWARD NEW ENGLAND. THIS MAY SIGNAL THE START OF A
WARMER PERIOD FOR THE AREA.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
FORECASTER CONFIDENCE LEVELS...

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

TONIGHT...HIGH CONFIDENCE. CONTINUE TO EXPECT VFR WITH LIGHT
WINDS.

SUNDAY...HIGH CONFIDENCE. VFR WITH LIGHT WINDS. SEA BREEZES
LIKELY. POSSIBLE BRIEF MVFR IN SPOTTY SHOWERS.

SUNDAY NIGHT...HIGH CONFIDENCE. VFR WITH LIGHT WINDS. POSSIBLE
BRIEF MVFR IN SPOTTY SHOWERS.

KBOS TAF...GENERALLY HIGH CONFIDENCE. SEA BREEZE DEVELOPED LATE
THIS AFTERNOON. ANTICIPATE LIGHT OFFSHORE FLOW TO REDEVELOP AROUND
OR VERY SHORTLY AFTER 01Z. OTHERWISE...VFR CONDITIONS EXPECTED
THROUGHOUT THE FORECAST PERIOD.

KBDL TAF...HIGH CONFIDENCE IN OVERALL TAF.

OUTLOOK...MONDAY THOUGH THURSDAY...

MONDAY INTO MONDAY NIGHT...VFR MOST OF THE TIME BUT AREAS OF MVFR
CIGS/VSBYS IN SCATTERED SHOWERS.

TUESDAY THROUGH THURSDAY...VFR CONDITIONS APPEAR LIKELY AT THIS
TIME.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

HIGH CONFIDENCE. ADJUSTED SEAS SLIGHTLY UP ACROSS THE OUTER SOUTH
COASTAL WATERS AS WELL AS MASS BAY PER LATEST OBSERVATIONS BUT NOT
A CONCERN AS SEAS REVERTING BACK TO LARGELY A GENTLE SWELL
OVERNIGHT. QUIET BOATING WEATHER EXPECTED THROUGHOUT THE PERIOD
WITH WINDS AND SEAS REMAINING BELOW SMALL CRAFT ADVISORY CRITERIA.
WINDS WILL SHIFT FROM TIME TO TIME THROUGH SUNDAY NIGHT BUT SHOULD
BE OUT OF THE NORTHWEST FOR MUCH OF THE TIME.

OUTLOOK...MONDAY THOUGHT THURSDAY...

MODERATE TO HIGH CONFIDENCE.

ENOUGH NORTHERLY GRADIENT ANTICIPATED MON NIGHT INTO TUE MORNING
THAT SMALL CRAFT ADVISORY CONDITIONS MIGHT BE MET...ESPECIALLY
COASTAL WATERS TO THE EAST. MAY TAKE UNTIL TUE EVENING BEFORE SEAS
SUBSIDE BACK BELOW 5 FEET.

OFFSHORE LOW MAY BRING INCREASING WINDS AND SEAS...PERHAPS NEAR OR
ABOVE SMALL CRAFT ADVISORY THRESHOLDS...TO THE OUTER SOUTH COASTAL
WATERS LATE THU OR THU NIGHT...BUT CONFIDENCE IS LOW ON THE
EVOLUTION OF THE WIND FIELD FOR THAT TIME FRAME GIVEN HIGHER THAN
AVERAGE NUMERICAL WEATHER PREDICTION MODEL UNCERTAINTIES.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR CTZ002>004.
MA...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR MAZ017-018.
RI...FROST ADVISORY FROM 2 AM TO 8 AM EDT SUNDAY FOR RIZ001-003.
MARINE...NONE.

&&

$$
SYNOPSIS...RLG/THOMPSON
NEAR TERM...BELK/RLG/THOMPSON
SHORT TERM...RLG
LONG TERM...THOMPSON
AVIATION...RLG/THOMPSON
MARINE...RLG/THOMPSON



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