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Area Forecast Discussion
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000
FXUS61 KBOX 240820
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
420 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/...
4 AM UPDATE...

WATER VAPOR IMAGERY SHOWS A WEAK SHORT WAVE MOVING THROUGH CENTRAL
MA AT 4 AM. AHEAD OF IT THERE WAS A BATCH OF SHOWERS RACING
NORTHEAST THROUGH SOUTHERN NH. THESE SHOWERS WILL BE LONG GONE BY
DAYBREAK. FOG AND LOW CLOUDINESS HAS NOT BEEN AS WIDESPREAD AS THE
MODELS INDICATED. SO FAR...ONLY NANTUCKET HAS VISIBILITY OF 1/2
MILE IN FOG. IN FACT...MOST OTHER PORTIONS OF SOUTHERN NEW ENGLAND
HAD ONLY PARTIAL CLOUD COVER...SO MANY AREAS MAY START OUT PARTLY
SUNNY AT DAYBREAK.

AT THE SURFACE...THE COLD FRONT IS ALREADY ALONG THE COAST. THE
UPPER TROUGH AXIS IS STILL TO OUR WEST AND AN UPPER LEVEL JET
MAXIMUM IS FORECAST TO STRENGTHEN AS IT MOVES ACROSS OUR REGION
THIS AFTERNOON. THIS IS LIKELY TO KEEP IT ON THE CLOUDY SIDE
THROUGH THE MORNING AND EARLY AFTERNOON ESPECIALLY IN RI AND
SOUTHEAST MA. THE FRONT WILL BE SLOW TO EXIT THE COASTAL WATERS
SINCE A WEAK WAVE OF LOW PRESSURE WILL BE MOVING ALONG IT. WE ARE
WATCHING A BATCH OF SHOWERS IN EASTERN PA BUT WITH DRIER DEWPOINTS
FILTERING IN FROM THE NORTHWEST...ALREADY DOWN TO 57 AT KEENE...THINKING
THAT THESE WILL ERODE. ALL MODELS RESTRICT ANY CHANCE OF SHOWERS
TO MAINLY THE CAPE AND ISLANDS INTO THE EARLY AFTERNOON HOURS...SO
HAVE CUT BACK ON POPS FOR TODAY. THE NORTHWEST TWO-THIRDS OF THE
REGION SHOULD BECOME MOSTLY SUNNY AND PLEASANT IN THE AFTERNOON.
HIGHS TODAY MAINLY UPPER 70S TO LOWER 80S.

&&

.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 /08Z 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.

MVFR CIGS WERE SCATTERED THROUGHOUT SOUTHERN NEW ENGLAND SHORTLY
BEFORE DAYBREAK EXCEPT LOW IFR ON NANTUCKET WITH LOCALLY DENSE
FOG. EXPECT SKIES TO DAWN PARTLY SUNNY. THERE IS A SLIGHT CHANCE
OF SHOWERS TODAY IN SOUTHEASTERNMOST MA INCLUDING CAPE COD AND THE
ISLANDS. SKIES SHOULD BECOME VFR ACROSS THE NORTHWEST TWO-THIRDS
OF THE REGION BY MID AFTERNOON.

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 KNOTSD 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...GAF/WTB
NEAR TERM...GAF 
SHORT TERM...GAF 
LONG TERM...WTB 
AVIATION...GAF/WTB
MARINE...GAF/WTB
EQUIPMENT...GAF



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