Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 280630
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
230 AM EDT THU AUG 28 2014

.SYNOPSIS...
A COLD FRONT MOVES OFFSHORE THIS MORNING. HIGH PRESSURE BUILDS IN
WITH DRIER WEATHER AND LESS HUMIDITY FOR TODAY AND FRIDAY.
HURRICANE CRISTOBAL WILL PASS WELL OFFSHORE TODAY BRINGING
DANGEROUS SURF AND RIP CURRENTS TO SOUTH FACING OCEAN BEACHES OF
RI AND MA. PLEASANT WEATHER LINGERS INTO SATURDAY...THEN A FRONT
WILL SWEEP ACROSS NEW ENGLAND LATE SUNDAY INTO MONDAY BRINGING
UNSETTLED CONDITIONS.

&&

.NEAR TERM /THROUGH TODAY/...

THROUGH 8 AM...
AT 1 AM THE COLD FRONT WAS OVER SOUTHEAST MASS AND MOVING
OFFSHORE. WIDELY SCATTERED SHOWERS LED THE FRONT. THESE WILL MOVE
OFFSHORE BY SUNRISE. CLEARING SKIES MOVING INTO WESTERN NEW
ENGLAND WILL TREND EAST TO THE COAST BY MORNING. PATCHY FOG
LINGERS NEAR NANTUCKET...AND SHOULD LINGER UNTIL FROPA. THE WIND
SHIFT SHOULD THEN START MOVING THE FOG OUT TO SEA.

TODAY...
DRIER AIR AT THE SURFACE BUT A LAYER OF 80 PCT RH LINGERS BETWEEN
800 AND 850 MB. UPPER TROUGH AND COLD POOL MOVE ACROSS NEW
ENGLAND...ALTHOUGH MOST OF THIS IS FOCUSSED ON NORTHERN NEW
ENGLAND.

DAYTIME HEATING IN THE MOSTLY CLEAR SKIES SHOULD
REACH 850 MB OR A LITTLE HIGHER...TAPPING THIS MOISTURE AND
FORMING DIURNAL CLOUDS LATE MORNING AND AFTERNOON...ESPECIALLY
ALONG AND NORTH OF THE MASS PIKE. THE MIXING WILL ALSO TAP A DEEP
LAYER OF 20 KNOT NORTHWEST WINDS CREATING GUSTS TO THAT SPEED
DURING THE MIDDAY AND AFTERNOON.

TEMPS AT THE TOP OF THE MIXED LAYER WILL BE EQUIV TO
10-12C...SUPPORTING MAX SFC TEMPS IN THE MID 70S TO LOWER 80S.
WITH DEWPOINTS FALLING INTO THE 50S...THIS WILL MEAN A PLEASANT
BREEZY DAY.

HURRICANE CRISTOBAL WILL PASS ABOUT 375 MILES SOUTHEAST OF
NANTUCKET TODAY. TROPICAL STORM FORCE WINDS ONLY EXTEND ABOUT 205
MILES OUT FROM THE STORM. SWELL ALREADY TRANSMITTED NORTH THROUGH
THE OCEAN HAS REACHED OUR WATERS WITH A 13-15 SECOND PERIOD
OBSERVED ON BOTH THE SOUTHERN AND EASTERN WATERS...AND A 7 FOOT
HEIGHT HAS BEEN OBSERVED AT THE BUOY SOUTHEAST OF BLOCK ISLAND.
WAVE MODEL DATA SHOWS A 7-8 FOOT SWELL LINGERING ON OUR SOUTHERN
EXPOSED WATERS THROUGH THE DAY AND THEN DIMINISHING TONIGHT.
CALCULATIONS SUGGEST BREAKERS OF 6-12 FEET ON SOUTH-FACING OCEAN
BEACHES. WE WILL CONTINUE THE HIGH SURF ADVISORY AND EXTEND IT
THROUGH EARLY FRIDAY.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...

TONIGHT...HIGH PRESSURE BUILDS OVER THE REGION AND SHOULD BRING
DIMINISHING WIND WITH DECOUPLING IN THE INTERIOR. DEWPOINTS WILL
FALL TO 45-55 MOST AREAS. THIS WILL ALLOW TEMPERATURES INLAND TO
FALL TO THE UPPER 40S AND 50S. OCEAN INFLUENCE WILL KEEP COASTAL
AREAS AROUND 60 OR LOW 60S.

FRIDAY...
HIGH PRESSURE SURFACE AND ALOFT BUILDS OVERHEAD. THIS WILL MEAN
FAIR SKIES AND LIGHT WINDS...AS WELL AS SEABREEZES ALONG THE
COASTS. TEMPS ALOFT 8-10C SHOULD SUPPORT MAX TEMPS IN THE 70S.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
*/ HIGHLIGHTS...

 - HOT AND HUMID CONDITIONS THROUGH THE WEEKEND
 - THUNDERSTORMS POSSIBLE ACROSS N/W NEW ENGLAND SUNDAY
 - WET WEATHER ANTICIPATED SUNDAY NIGHT INTO MONDAY NIGHT
 - COULD REMAIN WARMER THAN AVERAGE INTO NEXT WEEK

*/ OVERVIEW AND MODEL PREFERENCE...

BETTER AGREEMENT AMONG ENSEMBLE MEMBERS WOULD SUGGEST A ZONAL FLOW
REGIME WITH SOME WEAK RIDGING AS BOTH THE NAO/PNA REMAIN NEGATIVE TO
NEAR-NEUTRAL. EXPECTING AN ABOVE AVERAGE TEMPERATURE PATTERN AS THE
ECENS/GEFS/NAEFS/CPC WOULD SUGGEST INTO EARLY SEPTEMBER...ANOMALOUS
ON THE ORDER OF +2-3 STANDARD DEVIATIONS. WITH ANTICIPATED WARMER
CONDITIONS SUBSEQUENT OF RIDGING...EXPECTING PROLONGED S-FLOW TO
ADVECT MUGGY CONDITIONS N. LOOKING TO BE A WARM AND HUMID TIMEFRAME.

FOR THE FORECAST PERIOD OVER THE NEXT WEEK BEGINNING FRIDAY...EXPECT
THE W-ATLANTIC RIDGE TO BE THE DOMINANT INFLUENCE OVER THE REGIONS
WEATHER. FAVOR THE ECMWF WITH THE CONFLUENT FLOW SETUP AND ATTENDANT
SURFACE FRONTAL POSITION BETWEEN THE NE-CANADA TROUGH AND W-ATLANTIC
RIDGE REMAINING N OF THE REGION PARENT WITH BETTER JET-DYNAMICS AND
SHEARED MID-LEVEL ENERGY. ONLY AS A C-CONUS DISTURBANCE INVOKES A
WEAK-WAVE LOW ALONG THE FRONT WILL WET-WEATHER SHIFT INTO OUR AREA
AROUND MONDAY BASED ON A CONSENSUS OF MODEL DATA.

DESPITE MODEL VARIANCE...A BROAD SIGNAL IS DISCERNIBLE OF A BRIEF
PERIOD OF DRY WEATHER AFTER PASSAGE OF THE WEAK-WAVE
LOW...FOLLOWED BY A SHARP COLD FRONT AND PERHAPS THE RETURN OF
MORE SEASONABLE CONDITIONS. LOW CONFIDENCE AT THIS TIME AS
ENSEMBLE MEANS WOULD SUGGEST THE PROPENSITY FOR ZONAL-FLOW WITH
WEAK RIDGING. FAVOR THE DETERMINISTIC ECMWF WITH POSSIBLE
OUTCOMES.

HIGHLIGHTS/CONFIDENCE ARE BROKEN DOWN IN THE DAILY DISCUSSION BELOW.

*/ DAY-TO-DAY DETAILS...

SATURDAY...

SURFACE WARM FRONT LIFTING NE ACROSS NEW ENGLAND LATE...JOINING WITH
A TRAILING COLD FRONT FROM A LOW DISTURBANCE OVER NE-CANADA. AS THE
RIDGE SUBSEQUENTLY ENHANCES AHEAD OF THE FRONTAL DISTURBANCE AND A
WEAKER DISTURBANCE OVER THE C-CONUS...BELIEVE WET-WEATHER ACTIVITY
WILL BE PUSHED WELL N OF THE REGION BY THE INFLUENCE OF THE RIDGE.
THUS WILL GO WITH A DRY-WEATHER FORECAST.

EXPECT PREVAILING S-FLOW TO BEGIN USHERING WARMER / HUMID CONDITIONS
ACROSS THE REGION. WILL SEE HIGHS WARM INTO THE LOW-80S AS A WELL-
MIXED BOUNDARY LAYER ALLOWS FOR SCATTERED CUMULUS ALONG WITH THE MIX-
DOWN OF BREEZY S/SW FLOW. FEEL THIS WILL RESTRICT SEA-BREEZES...SO
EXPECT INTERIOR WINDS TO PUSH THE WARM / HUMID CONDITIONS ALL THE
WAY TO THE E-SHORES.

MILD AND DRY OVERNIGHT. WITH A LINGERING DRY-SUBSIDENCE INVERSION...
HIGHER DEWPOINT AIR ADVECTING N COULD LEND TO LOW CLOUDS / FOG ALONG
THE S-SHORE. EXPECTING LOWS AROUND THE LOW- TO MID-60S.

SUNDAY...

WARM-FRONT WELL-DEFINED TO THE N. PUSH OF H85 +16-18C AIR ACROSS THE
REGION. EXPECT S NEW ENGLAND TO BE WITHIN THE WARM-SECTOR OF A HOT
AND HUMID AIRMASS. COLLOCATED WITHIN A WELL-MIXED BOUNDARY LAYER...
BREEZY S/SW-FLOW DURING THE DAY SHOULD ALLOW FOR INTERIOR WINDS ONCE
AGAIN TO RESTRICT SEA-BREEZES AND PUSH FORECAST HIGH TEMPERATURES
AROUND THE UPPER-80S TO THE E-SHORES.

HEIGHTS FALL AS THE C-CONUS DISTURBANCE SHIFTS E WITHIN THE QUASI-
ZONAL FLOW REGIME. SHOWERS / THUNDERSTORMS ARE CERTAINLY PLAUSIBLE N
AND W WITHIN MODEST INSTABILITY AND SHEAR...CLOSER TO REGIONS OF
FAVORABLE DYNAMICS / ASCENT AS WELL AS THE CONVERGENT NOSE OF HIGHER
THETA-E AIR AHEAD OF THE FRONT. LIKELY THE MAJORITY OF ACTIVITY IS
ACROSS THE E GREAT LAKES INTO NY/PA...BUT ITS POSSIBLE THAT ACTIVITY
DEVELOPS INTO N/W NEW ENGLAND LATE. THIS WOULD POSSIBLY BE THE CASE
AS THE CONVECTIVE TEMPERATURE IS MET SUCH THAT ANY INVERSION WOULD
ERODE AND BOTH SURFACE-BASED INSTABILITY AND EFFECTIVE SHEAR COULD
BE UTILIZED. CAN NOT RULE OUT STRONG STORMS...ESPECIALLY ACROSS S/W
FACING SLOPES OF HIGH TERRAIN OVER NW CT / W MA / S NH AS OROGRAPHIC
PROCESSES AID IN LIFTING THE WARM / JUICY AIRMASS ALOFT. BUT IT IS
POSSIBLE THAT THE RIDGE WINS OUT. STILL A FORECAST WAY OUT IN TIME
AND AS WE HAVE SEEN JUST IN THE PAST SEVERAL MODEL RUNS THERE HAS
BEEN A FAIR AMOUNT OF VARIABILITY. HAVE MODERATE CONFIDENCE WITH
THIS FORECAST TIMEFRAME.

RIDGE AND SUBSIDENCE INVERSION LINGERS FOR THE S/E SO WILL KEEP WITH
A DRY-FORECAST FOR THOSE AREAS.

SUNDAY NIGHT THROUGH MONDAY NIGHT...

WEAK-WAVE LOW ALONG THE FRONT THROUGH THE QUASI-ZONAL FLOW PUSHES E
AND ACROSS THE REGION. THOUGH APPEARING AS A NOCTURNAL PASSAGE...THE
COLLOCATION OF DEEP-LAYER MOISTURE...MINOR INSTABILITY AND SHEAR...
AND FORCING ALONG THE FRONTAL BOUNDARY WILL LIKELY YIELD WIDESPREAD
SHOWERS WITH THE POSSIBILITY OF HEAVY RAIN AND THUNDERSTORMS. THOUGH
IT APPEARS THE BETTER FORCING DYNAMICS SHIFT N/E...SHUNTED BY THE
RIDGING PATTERN AND BERMUDA HIGH REMAINING DOMINANT.

LOW CONFIDENCE FORECAST AS THE CONSENSUS OF MODEL SOLUTIONS CONTAINS
A FAIR AMOUNT OF VARIABILITY. WILL PREVAIL WITH SLIGHTLY ABOVE-
AVERAGE CONDITIONS.

TUESDAY ONWARD...

A LULL IN ACTIVITY IS POSSIBLE BEHIND THE WEAK-WAVE DISTURBANCE. A
SHARPER COLD FRONT INTO MIDWEEK FOLLOWED BY HIGH PRESSURE. NOT ALL
ENTIRELY CONVINCED ON SUCH OUTCOMES BASED ON ENSEMBLE TRENDS. WOULD
ANTICIPATE RIDGING TO REMAIN DOMINANT WITH TEMPERATURES BEING ABOVE-
AVERAGE FOR THE TIMEFRAME.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT-TERM /TODAY THROUGH FRIDAY/...HIGH CONFIDENCE.

VFR THROUGH THE PERIOD. NORTHWEST WINDS WILL BECOME GUSTY NEAR 20
KNOTS LATE THIS MORNING AND AFTERNOON...THEN DIMINISH TOWARD
EVENING. LIGHT WINDS FRIDAY WILL ALLOW SEA BREEZES TO DEVELOP
ALONG THE COAST LATE MORNING AND AFTERNOON.

KBOS TERMINAL...HIGH CONFIDENCE IN TAF. NORTHWEST WINDS GUST TO 20
KNOTS MIDDAY AND AFTERNOON.

KBDL TERMINAL...HIGH CONFIDENCE IN TAF.

OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...

SATURDAY INTO SUNDAY...MODERATE CONFIDENCE.

VFR. BREEZY S/SW WINDS. SCT CIGS 4-6 KFT SATURDAY. MVFR-IFR CIGS /
VSBYS POSSIBLE ALONG THE S-COAST SATURDAY NIGHT. SHRA/TSRA POSSIBLE
FOR N/W NEW ENGLAND LATE SUNDAY.

SUNDAY NIGHT INTO MONDAY...LOW CONFIDENCE.

MIX OF LOW-END VFR TO MVFR. WIDESPREAD SHRA ACROSS THE TERMINALS.
POSSIBLE TSRA. CONTINUED S/SW WINDS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT-TERM /TONIGHT THROUGH THURSDAY/...HIGH CONFIDENCE.

TONIGHT...

SOUTH SWELLS FROM CRISTOBAL CONTINUE TO INCREASE. A FEW SHOWERS
POSSIBLE OVERNIGHT. SSW WINDS BECOME NW TOWARD SUNRISE AS COLD
FRONT APPROACHES FROM THE WEST.

THURSDAY...

SWELLS PEAK AT 5 TO 11 FT TOMORROW ACROSS THE SOUTH COAST WATERS.
ADDING TO THE ROUGH SEAS WILL BE A DEVELOPING NW WIND WAVE BEHIND
THE FRONTAL PASSAGE. OTHERWISE DRY WEATHER WITH GOOD VSBY. HOWEVER
A FEW SHOWERS MAY LINGER EARLY IN THE MORNING ACROSS THE SOUTH
COASTAL WATERS.

THURSDAY NIGHT...

NW WINDS BECOME N-NE LATE. GOOD VSBY AND DRY WEATHER.

OUTLOOK...FRIDAY THROUGH MONDAY...

FRIDAY...HIGH CONFIDENCE.

HIGH PRESSURE IN CONTROL. LIGHT WINDS. DIMINISHING SEAS WITH ONLY
THE S/SE OUTER WATERS EXPERIENCING WAVE HEIGHTS IN EXCESS OF 5-FEET
BY MORNING. GOOD BOATING WEATHER.

SATURDAY INTO SUNDAY...MODERATE CONFIDENCE.

INCREASING S-WINDS. PROLONGED S-FETCH LENDING TO WAVE HEIGHTS IN
EXCESS OF 5-FEET ACROSS THE S/SE WATERS. FOG POSSIBLE DURING THE
OVERNIGHT HOURS...ESPECIALLY ALONG THE S-COAST.

MONDAY...MODERATE CONFIDENCE.

CONTINUED S-WINDS. WET-WEATHER MOVING ACROSS THE WATERS. FOG MAY
REMAIN AN ISSUE OVER THE WATERS...ESPECIALLY DURING OVERNIGHT
PERIODS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...HIGH SURF ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MAZ020-
     022>024.
NH...NONE.
RI...HIGH SURF ADVISORY UNTIL 8 PM EDT THIS EVENING FOR RIZ006>008.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY
     FOR ANZ235-237-254>256.

&&

$$
SYNOPSIS...WTB/SIPPRELL
NEAR TERM...WTB/SIPPRELL
SHORT TERM...WTB
LONG TERM...SIPPRELL
AVIATION...WTB/SIPPRELL
MARINE...NOCERA/SIPPRELL


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