Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 040813
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
413 AM EDT SAT JUL 4 2015

.SYNOPSIS...
A LOW PRESSURE RACES SOUTH OF NEW ENGLAND TODAY AND MAY BRINGING
SOME LIGHT RAIN TO SOUTH COASTAL AREAS. HIGH PRESSURE RETURNS
SUNDAY AND LINGERS THROUGH MONDAY. A TRANSITION PERIOD IS LIKELY
MID NEXT WEEK...WITH A CHANCE FOR SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LOW PRESSURE ALONG THE MID ATLANTIC COAST RACES SOUTH OF OUR AREA
ON SATURDAY. THE LOW WILL BE SUPPORTED BY AN UPPER SHORTWAVE

LATEST GUIDANCE IS SPLIT INTO TWO CAMPS. THE MORE GLOBAL MODELS
ARE MOSTLY DRY ACROSS SOUTHERN NEW ENGLAND. WHILE THE HI-
RESOLUTION GUIDANCE IS MORE AGGRESSIVE IN BRINGING RAINFALL TO
WESTERN MA...AS WELL AS CAPE COD AND THE ISLANDS.

BASED ON THE OVERALL PATTERN...AM THINKING SCATTERED SHOWERS WILL
MOVE INTO WESTERN MA AS A MID LEVEL SHORTWAVE CROSSES OUR REGION.
THE HIGHEST RAINFALL CHANCES WILL BE SOUTH OF THE MASS PIKE...AND
ESPECIALLY ACROSS CAPE COD AND THE ISLANDS. THE MAIN ISSUE WILL
BE THE AMOUNT OF LOW LEVEL DRY AIR TO OVERCOME. GIVEN THE TIMING...
AM THINKING THE DRIEST CONDITIONS WILL BE TOWARD NORTHEAST MA...
WHICH IS THE FARTHEST AWAY FROM THE LOW TO THE SOUTH.

THIS SOLUTION IS A COMPROMISE BETWEEN THE TWO AFOREMENTIONED
CAMPS. THERE IS NOT A LOT OF INSTABILITY...SO NOT THINKING
THUNDERSTORMS WILL BE AN ISSUE TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
THE COASTAL LOW MOVES FARTHER OFFSHORE THIS EVENING...MOVING SOUTH
OF NOVA SCOTIA LATE TONIGHT. THIS SHOULD BRING ANY RAINFALL TO AN
END LATE THIS EVENING. THE SUPPORTING UPPER TROUGH MOVES EAST OF
US BY MORNING. THIS SHOULD BRING A CLEARING TREND AFTER MIDNIGHT
WITH WINDS TURNING NORTHWEST.

WEAK HIGH PRESSURE MOVES INTO SOUTHERN NEW ENGLAND FROM THE SOUTH
SUNDAY. THIS SHOULD MEAN DRY WEATHER WITH HIGHER TEMPERATURES.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
HIGHLIGHTS...

 * HIGH PRESSURE AND WARMING CONDITIONS INTO EARLY NEXT WEEK.
 * UNSETTLED CONDITIONS RETURN MID-LATE NEXT WEEK.

OVERVIEW AND MODEL PREFERENCES...WITH 04.00Z MODEL GUIDANCE
COMING IN...THERE IS BETTER AGREEMENT WITH THE MID AND LONG TERM
THAN PREVIOUS RUNS...ALTHOUGH TYPICAL UNCERTAINTY REMAINS IN THE
LONG TERM. STRONG RIDGING EARLY IN THE WEEK WILL GIVE WAY TO
MAINLY ZONAL FLOW ON THE SW QUADRANT OF A STRONG NRN STREAM VORTEX
DEVELOPING ACROSS N CENTRAL CANADA. THE FLATTENING WAVE WILL
ARRIVE MID WEEK...WITH HIGH PWATS AND INSTABILITY IN TOW WHICH MAY
NEED TO BE WATCHED. THERE ARE TIMING ISSUES...ESPECIALLY REGARDING
THE INFLUENCE OF THE RIDGE OF HIGH PRES FOR TUE...BUT WITH BETTER
AGREEMENT IN THIS ROUND OF GUIDANCE A BLEND OF OPERATIONAL MODELS
WILL WORK WELL AS A BASELINE.

DETAILS...

SUN NIGHT INTO MON NIGHT...WARM RIDGING BUILDS ACROSS SRN NEW
ENGLAND WITH HIGH PRES AT THE SFC. MAINLY DRY WX PREVAILS WITH
MODERATING HIGHS/LOWS AS H85 TEMPS INCREASE TO BETWEEN +12C AND
+14C BY LATE MON. THIS SUGGESTS HIGHS MAINLY IN 80S ACROSS THE
REGION.

TUE...UPPER LVL WAVE WILL BE APPROACHING FROM THE W. MODELS
INDICATE INCREASING MOISTURE AS PWATS APPROACH 2 STD DEVIATIONS
ABOVE NORMAL WITH K-VALUES OVER 30. A WARM FRONT WILL BE THE
INITIAL SFC REFLECTION OF THIS WAVE. HOWEVER...SOUNDINGS SUPPORT
THE POSSIBILITY OF HIGH PRES REMAINING IN CONTROL THROUGH MUCH OF
TUE. THEREFORE...CHANCE FOR AFTERNOON SHRA/T-STORM WITH THE WARM
FRONTAL APPROACH MAY BE QUITE LOW TO NEAR ZERO THE FURTHER E ONE
GOES. IN FACT...THE BEST AXIS OF SFC CAPE/THETA-E RIDGE IS MAINLY
W OF THE MA/NY BORDER. THEREFORE...CHANCE POPS W WILL BE LOWERED
TO SLIGHT CHANCE TO NIL POPS FURTHER E. WILL INCLUDE THUNDER WITH
THIS FORECAST GIVEN THE FAVORABLE PARAMETERS.

WED...AS PREVIOUS FORECASTER NOTED...THIS IS WHERE THE MODEL
SOLUTION DIVERGENCE BEGINS TO SHOW MORE SIGNIFICANTLY. MAINLY WITH
THE TIMING OF A COLD FRONTAL PASSAGE. GFS REMAINS PROGRESSIVE
WHILE ECMWF/CMC CONTINUES TO LINGER AS THE FRONT BEGINS TO
PARALLEL THE ZONAL FLOW DEVELOPING ALOFT. WILL CONTINUE WITH THE
CHANCE AND SLIGHT CHANCE POPS FROM THE THE PREVIOUS FORECAST SINCE
THE CONVERGENT BOUNDARY REMAINS IN PLACE. SOUNDINGS DO SUPPORT
SOME SFC BASED CAPE EXCEEDING 1000J/KG AND HIGH K-VALUES...SO WILL
CONTINUE TO INCLUDE TS...BUT GIVEN THE LACKING SHEAR...REMAIN
SOMEWHAT DUBIOUS OF SEVERE CHANCES AT THIS TIME.

THU...THE UNCERTAINTY REMAINS AS THE COLD FRONT CONTINUES TO PUSH
FURTHER SOUTHEAST...ALBEIT SLOWLY. WILL GRADUALLY REDUCE POPS FROM
N-S DURING THE DAY...BUT WILL HAVE TO WAIT BEFORE WE CAN NAIL DOWN
TIMING FOR THE LATE WEEK.

FRI AND SAT...UNCERTAINTY REMAINS BUT WITH ZONAL FLOW...A SERIES
OF RIDGE/TROUGH COUPLETS IS LIKELY TO YIELD PERIODS OF
DRY/POTENTIALLY WET PERIODS ARE LIKELY. INTERESTINGLY...WITH SRN
NEW ENGLAND ON THE RIDGE PERIPHERY MAY NEED TO MONITOR FOR MCS
STEERING FLOW AS WELL. STILL WAY TOO MANY VARIABLES TO NAIL
ANYTHING DOWN...BUT SEASONABLE TEMPS AND LOW TO NIL POPS SHOULD
COVER THE SPREAD.

&&

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

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

SHORT-TERM /THROUGH FRIDAY NIGHT/...

TODAY...MODERATE CONFIDENCE. VFR TO START. MVFR POSSIBLE IN
SCATTERED AREAS OF LIGHT SHOWERS,,,MAINLY THIS AFTERNOON AND
EVENING. GREATEST RISK FOR MVFR IS AT TERMINALS ALONG THE SOUTH
COAST. LOW CONFIDENCE EAST TO NORTHEAST FLOW WILL BRING IFR
CONDITIONS AT BOSTON TOWARD EVENING.

TONIGHT...HIGH CONFIDENCE. RAIN OVER SOUTHEAST MASS/RI SHOULD
TAPER OFF DURING THE FIRST PART OF THE NIGHT. MVFR CONDITIONS
POSSIBLE IN ANY AREAS OF RAIN/FOG...OTHERWISE VFR WITH CLOUD BASES
LIFTING/CLEARING.

SUNDAY...HIGH CONFIDENCE. VFR.

KBOS TERMINAL...HIGH CONFIDENCE IN TAF. EXPECTING VFR THROUGH THE
PERIOD. LOW CONFIDENCE LOWER CONDITIONS COULD DEVELOP IN ONSHORE
FLOW LATER TODAY.

KBDL TERMINAL...HIGH CONFIDENCE IN TAF WITH VFR THROUGH THE
PERIOD...EVEN IF A FEW SPRINKLES LATE THIS AFTERNOON.

OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...

SUN NIGHT INTO MON...HIGH CONFIDENCE. VFR WITH HIGH PRES.  SEA
BREEZES LIKELY MON.

TUE AND WED...MODERATE CONFIDENCE. FIRST A WARM FRONT TUE...THEN A
COLD FRONT WED MAY PROVIDE A FOCUS FOR OCCASIONAL SHOWERS AND
THUNDERSTORMS EACH DAY WITH PERIODIC MVFR OR LOWER CONDITIONS.
OTHERWISE VFR. SOME FOG POSSIBLE DURING THE OVERNIGHTS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

MODERATE CONFIDENCE TODAY AND TONIGHT...HIGH CONFIDENCE SUNDAY.

LOW PRESSURE DEVELOPING ALONG THE MID ATLANTIC COAST WILL PASS
OVER OR SOUTH OF THE SOUTHERN OUTER WATERS THIS AFTERNOON AND
EVENING. THIS WILL BRING LOWER VSBYS IN RAIN TO THE SOUTHERN
WATERS WITH EAST WINDS INCREASING TO 15-20 KNOTS. FARTHER NORTH
THE WINDS WILL BECOME EAST...BUT WITH LIGHTER SPEEDS. AS THIS LOW
PRESSURE MOVES OFF TO THE EAST...WINDS WILL DIMINISH AND TURN
NORTH OVERNIGHT. WEAK HIGH PRESSURE BUILDS OVER THE WATERS
SUNDAY.

PERSISTENT WINDS WILL BUILD SEAS ACROSS THE OUTER SOUTHERN COASTAL
WATERS. THERE HAS BEEN A PERSISTENT SIGNAL THE PAST FEW DAYS FOR 5
FT SEAS. WHILE MARGINAL...DECIDED TO ISSUE A SMALL CRAFT ADVISORY
DUE TO THIS PERSISTENT SIGNAL.

OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...

SUN NIGHT INTO MON...HIGH CONFIDENCE. ANY LINGERING SWELL RECEDES
BELOW 5 FT SUN NIGHT.  HIGH PRES THEN BRINGS QUIET BOATING WEATHER
TO THE WATERS THROUGH MON.

TUE AND WED...MODERATE CONFIDENCE. A WARM FRONT ON TUE...THEN A COLD
FRONT ON WED WILL BE APPROACHING FROM THE W. WHILE WINDS SHOULD
GENERALLY REMAIN OUT OF THE S-SE...WIND SPEEDS SHOULD REMAIN BELOW
SMALL CRAFT ADVISORY THRESHOLDS. SEAS IS ALSO LIKELY TO REMAIN
BELOW SMALL CRAFT THRESHOLDS. SOME SHOWERS/THUNDERSTORMS AND/OR
FOG ARE POSSIBLE OVER THE WATERS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 AM TO 5 PM EDT
     SUNDAY FOR ANZ254.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 8 PM THIS EVENING
     TO 5 PM EDT SUNDAY FOR ANZ255.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM THIS
     AFTERNOON TO 5 PM EDT SUNDAY FOR ANZ256.

&&

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



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