Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 241543
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1143 AM EDT THU JUL 24 2014

.SYNOPSIS...
A COLD FRONT SLOWLY EXITS THE COASTAL WATERS TODAY. HIGH PRESSURE
CENTERED OVER THE OHIO VALLEY WILL BUILD EASTWARD AND PROVIDE
SUNNY SKIES FRIDAY. THE HIGH SHIFTS OFFSHORE SATURDAY. THEN
UNSETTLED CONDITIONS LATE IN THE WEEKEND AND INTO NEXT WEEK. A WARM
FRONT APPROACHES SUNDAY BRINGING WARM HUMID AIR. A COLD FRONT THEN
SWINGS ACROSS THE REGION MONDAY AND TUESDAY...AND LINGERS OFF THE
EAST COAST THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1140 AM UPDATE...

THE SURFACE COLD FRONT HAS CLEARED THE SOUTHEAST NEW ENGLAND COAST
AS OF LATE MORNING.  HOWEVER...UPPER TROUGH WAS STILL TO THE WEST OF
THE REGION.  ITS ASSOCIATED COLD POOL ALOFT HAS ALLOWED ISOLATED
SHOWERS TO POP UP ACROSS EASTERN NEW ENGLAND.  THESE ISOLATED
SHOWERS MAY CONTINUE THROUGH THE AFTERNOON...GENERALLY ACROSS
EASTERN SECTIONS BUT STILL FAR FROM A WASHOUT.  INSTABILITY VERY
MARGINAL...BUT WITH APPROXIMATELY 500 J/KG OF CAPE NEAR THE SOUTH
COAST CAN/T RULE OUT AN ISOLATED THUNDERSTORM IN THAT REGION THIS
AFTERNOON.

A MIXTURE OF CLOUDS AND SUN EXPECTED ACROSS THE INTERIOR...WITH
CLOUDS DOMINATING IN THE EASTERN SECTIONS.  HIGH TEMPS TOP OUT WELL
INTO THE 70S TO THE LOWER 80S...BUT A BIG RELIEF FROM THE HEAT AND
HUMIDITY OF YESTERDAY!

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
A MOSTLY CLEAR NIGHT IS EXPECTED TONIGHT. THE ONLY EXCEPTION MAY
BE ON THE ISLANDS WHERE MODELS ARE QUITE EMPHATIC ABOUT THE RETURN
OF LOW CLOUDINESS AND FOG WITH LIGHT NORTHEASTERLY WIND FLOW AND
DEWPOINT TEMPERATURES HANGING IN THE LOWER 60S. THE POSSIBILITY
EXISTS FOR LOW VISIBILITIES ON NANTUCKET. LOWS WILL BE MUCH MORE
COMFORTABLE...IN THE MID 50S TO LOWER 60S EXCEPT LOWER TO MID 60S
ON THE ISLANDS.

HIGH PRESSURE CENTERED OVER THE OHIO VALLEY WILL BUILD EASTWARD ON
FRIDAY AND PROVIDE SUNNY SKIES TO SOUTHERN NEW ENGLAND WITH HIGHS
REACHING INTO THE LOWER 80S...COOLER ON THE ISLANDS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
BIG PICTURE...

MUCH OF THE UPPER FLOW REMAINS UNCHANGED THROUGH THE FORECAST
PERIOD. DEEP RIDGES WILL EXTEND ACROSS WESTERN NORTH AMERICA AND THE
WESTERN ATLANTIC. CLOSED LOW OVER NORTHERN QUEBEC ANCHORS A TROUGH
OVER EASTERN NORTH AMERICA. SHORTWAVE EJECTING FROM THE PACIFIC
NORTHWEST WILL PLOW OVER THE TOP OF THE WESTERN RIDGE...THEN MERGE
WITH THE EASTERN NORTH AMERICA TROUGH OVER THE WEEKEND. THIS WILL
DEEPEN THE TROUGH AND PULL ITS FEATURES FARTHER SOUTH. THE DEPTH OF
THE TROUGH AND THE EXTENT OF THE RIDGES ON EITHER SIDE WILL MAKE
STRAIGHT WEST-TO-EAST MOVEMENT DIFFICULT NEXT WEEK.

THE MASS FIELDS AND THERMAL FIELDS OF THE GFS AND ECMWF LOOK SIMILAR
IN OVERVIEW. SOME DIFFERENCES IN DETAILS EMERGE DURING THE FIRST
HALF OF NEXT WEEK.  THE SIMILARITY BUILDS CONFIDENCE IN THE OVERALL
FLOW OF THE FORECAST. THE LONGER RANGE DIFFERENCES IN DETAIL SUPPORT
USING A BLEND OF THE FORECAST DATA.

THE DAILIES...

FRIDAY NIGHT AND SATURDAY...

THIS SHOULD BE A FAIR PERIOD BUT WITH SIGNS OF CHANGES TO COME. HIGH
PRESSURE SHIFTS OFFSHORE AND THE SURFACE FLOW TURNS SOUTHWEST. ALSO
INCREASING SOUTHWEST FLOW ALOFT WITH INCREASING MOISTURE AT THE
CIRRUS LEVEL. CROSS SECTIONS DO SHOW SOME INCREASING MOISTURE TOWARD
SATURDAY EVENING AROUND 5000 FEET AS WELL.  EXPECT MOSTLY CLEAR
SKIES AND LIGHT WINDS FRIDAY NIGHT.  SKY COVER INCREASES SATURDAY
BUT MOSTLY HIGH THIN CLOUDS UNTIL LATE IN THE DAY. TEMPS IN THE
MIXED LAYER WILL BE 12-14C WHICH SUPPORTS MAX SFC TEMPS LOW TO MID
80S.

SATURDAY NIGHT-SUNDAY... AS THE SHORTWAVE PHASES WITH THE EASTERN
UPPER TROUGH...THE SUPPORTING UPPER JET EXTENDS EAST TOWARD NEW
ENGLAND. MEANWHILE WEST TO SOUTHWEST LOW LEVEL WINDS WILL BRING
INCREASING HUMIDITY. THIS WILL MEAN INCREASING CLOUDS AND AN
INCREASING CHANCE OF SHOWERS/THUNDER OVERNIGHT INTO SUNDAY AS THE
RESULTING WARM FRONT APPROACHES. EXPECT DEWPOINTS TO INCREASING
DURING THIS TIME AND REACH 65-70.

MONDAY-TUESDAY-WEDNESDAY... SURFACE LOW ASSOCIATED WITH THE
SHORTWAVE PIVOTS OVER THE GREAT LAKES SUNDAY NIGHT/MONDAY AND SWINGS
A COLD FRONT TOWARD THE EAST COAST. AT THIS SAME TIME...THE UPPER
TROUGH DEEPENS AND TURNS THE UPPER FLOW OVER THE EAST COAST MORE
SOUTH-SOUTHWEST. AS A RESULT OF THIS...THE COLD FRONT WILL SLOW ITS
EASTWARD PROGRESS MONDAY AS IT BECOMES PARALLEL TO THE UPPER FLOW.
WE WILL BE IN THE WARM SECTOR LEADING THE COLD FRONT MONDAY AND
PROBABLY TUESDAY. THIS SHOULD SUPPORT A CHANCE OF SHOWERS/TSTMS EACH
DAY...ALTHOUGH LESS CONFIDENCE IN THE AREAL COVERAGE OF CHANCE POPS
TUESDAY.  LONG RANGE GUIDENCE SUGGESTS DRY WEATHER WEDNESDAY EVEN
WITH THE UPPER LOW OVER THE LAKES AND BROAD CYCLONIC FLOW OVER NEW
ENGLAND. WE WENT ALONG WITH THIS IDEA FOR NOW...BUT WITH LOW
CONFIDENCE.

&&

.AVIATION /16Z THURSDAY THROUGH MONDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH FRIDAY/...MODERATE CONFIDENCE.

VFR FOR MANY SITES ESPECIALLY OUT WEST WHERE MORE DRY AIR IS
FILTERING INTO THE REGION. AREA OF MVFR ACROSS THE GULF OF MAINE
WILL FILTER SOUTHWARD AND MOVE ACROSS THE MASS EASTERN SEABOARD.
HAVE ADJUSTED TAFS TO ACCOUNT FOR THESE LOWER CLOUDS. SHOULD MIX
OUT TO ALL VFR BY 18Z.

VFR WITH MOSTLY CLEAR SKIES EXPECTED MOST AREAS TONIGHT. THE ONLY
EXCEPTION MAY BE ON THE ISLANDS WHERE MODELS ARE QUITE EMPHATIC
ABOUT THE RETURN OF LOW CLOUDINESS AND FOG WITH LIGHT NORTHEASTERLY
WIND FLOW AND DEWPOINT TEMPERATURES HANGING IN THE LOWER 60S. THE
POSSIBILITY EXISTS FOR LOW VISIBILITIES ON NANTUCKET.

VFR WITH ABUNDANT SUNSHINE EXPECTED REGION-WIDE ON FRI. LOCAL SEA
BREEZES IN THE AFTERNOON.

KBOS TAF...MODERATE CONFIDENCE.

KBDL TAF...MODERATE CONFIDENCE.

OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...MODERATE CONFIDENCE.

FRIDAY NIGHT THROUGH SATURDAY...VFR. LOCAL IFR POSSIBLE IN EARLY
MORNING FOG/LOW CLOUDS.

SATURDAY NIGHT-SUNDAY-MONDAY... VFR BUT WITH AREAS OF MVFR IN
SHOWERS/TSTMS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH FRIDAY/...MODERATE CONFIDENCE.

WINDS AND SEAS ARE FORECAST TO BE BELOW SMALL CRAFT ADVISORY
THRESHOLDS THROUGH FRIDAY. NORTHWEST TO NORTHEAST WINDS ARE
FORECAST FOR TODAY...GRADUALLY SHIFTING TO THE SOUTHWEST BY FRIDAY
AFTERNOON. LOCAL SEA BREEZES ARE EXPECTED ON FRIDAY. LOCALLY DENSE
FOG AT TIMES TODAY AND TONIGHT...ESPECIALLY OVER THE WATERS
SOUTHEAST OF MA WITH VISIBILITIES 1 MILE OR LESS AT TIMES.

OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...MODERATE CONFIDENCE.

FRIDAY NIGHT-SATURDAY... LIGHT SOUTHWEST WINDS FRIDAY NIGHT INCREASE
ON SATURDAY BUT SHOULD REMAIN BELOW 25 KNOTS. SEAS ALSO BUILD BUT
SHOULD REMAIN BELOW 5 FEET.

SATURDAY NIGHT-SUNDAY...A WARM FRONT APPROACHES THE WATERS WITH
WARMER MORE HUMID AIR AND WITH CLOUDS/SHOWERS/TSTMS. INCREASING
SOUTHWEST WINDS WITH GUSTS NEAR 25 KNOTS SUNDAY AFTERNOON AND
SEAS BUILD TO 5-6 FEET ON THE EXPOSED WATERS. A SMALL CRAFT
ADVISORY MAY BE NEEDED.

MONDAY...WARM HUMID AIR OVER THE WATERS WITH SOUTHWEST WINDS GUSTING
20-22 KNOTS. THIS SHOULD KEEP SEAS AT 5-7 FEET ON THE EXPOSED
WATERS. THE POTENTIAL FOR SMALL CRAFT ADVISORY WILL CONTINUE.

&&

.EQUIPMENT...
THE BLUE HILL NOAA WEATHER RADIO TRANSMITTER IS TEMPORARILY OUT OF
SERVICE DUE TO A PHONE COMPANY ISSUE. THIS IS BEING WORKED ON AND
IS EXPECTED TO BE RESOLVED TODAY.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...WTB/GAF
NEAR TERM...FRANK
SHORT TERM...GAF
LONG TERM...WTB
AVIATION...WTB/DUNTEN/GAF
MARINE...WTB/GAF
EQUIPMENT...



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