Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 221424
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1024 AM EDT TUE JUL 22 2014

.SYNOPSIS...
SOUTHWEST FLOW WILL BRING AN INCREASE IN HEAT AND HUMIDITY
TODAY...WHICH WILL PERSIST INTO WEDNESDAY. SHOWERS AND
THUNDERSTORMS WILL LIKELY MOVE ACROSS THE REGION LATE WEDNESDAY
AFTERNOON AND EVENING AHEAD OF A COLD FRONT. A FEW STRONG TO
SEVERE THUNDERSTORMS WILL BE POSSIBLE. COLD FRONT SLOWLY MOVES OFFSHORE
THURSDAY WITH A TREND TO IMPROVING WEATHER. HIGH PRESSURE BUILDS
OVER THE REGION FRIDAY AND SATURDAY...THEN MAKES WAY FOR UNSETTLED
WEATHER APPROACHING FROM THE SOUTHWEST SUNDAY AND MONDAY.

&&

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

1030 AM UPDATE...

OVERALL TREND IN THE FORECAST REMAINS ON TRACK FOR TODAY. HAVE
BUMPED TEMPS UP JUST A DEGREE OR TWO TO ACCOUNT FOR THE MIXING AND
FULL SUNSHINE. OTHERWISE BIGGEST CHANGE IS TO ADD IN THE POTENTIAL
FOR THE SEABREEZE LATE THIS MORNING. NOTICED A FEW MESONET SITES
ARE ALREADY SWITCHING MORE IN A EASTERLY TRAJECTORY. THIS MAY DROP
BOSTONS TEMPS A TAD BUT THIS SEABREEZE SHOULD MIX OUT BY THE
AFTERNOON.

PREVIOUS DISCUSSION...
THE TWO MAIN ISSUES TODAY INVOLVE BURNING OFF OF LOW CLOUDS AND
FOG AND RISK OF ANY LATE AFTERNOON CONVECTION IN THE WEST.

WITH REGARD TO LOW CLOUDS AND FOG...EXPECT GRADUAL IMPROVEMENT THROUGH
MID/LATE MORNING. HAVE A STRONG SUN ANGLE AT THIS TIME OF
YEAR...BUT DEVELOPING SW FLOW AND GRADUALLY INCREASING DEWPOINTS
WILL LIKELY SLOW THE PACE AT WHICH THE LOW CLOUDS AND FOG BURN OFF
OVER THE CAPE AND NANTUCKET.

CONVECTION CHANCES APPEAR TO BE VERY LIMITED THIS AFTERNOON AS
MODELS DEPICT MID LEVEL CAP BECOMING ESTABLISHED.
NEVERTHELESS...WILL RETAIN A SLIGHT CHANCE OVER THE EAST SLOPES OF
THE BERKSHIRES WHERE SHOWALTER INDEX DROPS TO NEAR ZERO AND THE K
INDEX RISES TO NEAR 30 FOR A PERIOD. ALSO...ISOLATED SHOWERS/TSTMS
DEVELOPED MON AFTERNOON ACROSS NEW YORK STATE IN AN AIR MASS THAT
IS SLIDING IN OUR DIRECTION.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
TONIGHT...EXPECTING TEMPERATURES TO BE 2 OR 3 DEGREES MILDER
TONIGHT IN MOST LOCATIONS WITH DEWPOINTS RISING FROM THE LOW TO
MID 60S. ALSO EXPECTING AREAS OF LOW CLOUDS AND FOG ALONG S
COASTAL AREAS AND POSSIBLY IN A FEW INTERIOR VALLEYS.

WEDNESDAY...WEATHER BECOMES MORE INTERESTING AS A COLD FRONT
APPROACHES FROM THE WEST. INITIALLY A MID LEVEL CAP IS EXPECTED TO
INHIBIT CONVECTION BUT THAT CAP SHOULD ERODE AS THE FRONT
APPROACHES IN THE LATE AFTERNOON. SBCAPE PROJECTED TO BE 1200 TO
2000 J/KG AND MID LEVEL LAPSE RATES 6.0 TO 6.5 C/KM. A FAIRLY
NOTABLE BUMP OF THE K INDICES INTO THE MID TO UPPER 30S TAKES
PLACE LATE WED AFTERNOON/EVENING WHILE THE SHOWALTER INDICES DROP
TO AROUND -2 TO -3. THE 0 TO 6 KM WIND SHEAR IS FAIRLY MARGINAL AT
AROUND OR JUST STRONGER THAN 30 KT WITH STRONGER WIND SHEAR
INDICATED NORTH OF THE FORECAST AREA PER THE 00Z GFS AND ECMWF.
THE 00Z NAM RUN PROJECTED CLOSER TO 40 KT SHEAR ACROSS THE
NORTHERN ZONES BUT NOT QUITE READY TO BUY THAT. AT ANY
RATE...SHEAR STILL LOOKS STRONG ENOUGH COMBINED WITH THE
INSTABILITY TO SUPPORT SOME STRONG TO SEVERE TSTMS TO PERHAPS AS
FAR EAST AS AN ASH-LWM-BED-IJD LINE. PWATS ARE EXPECTED TO RISE TO
BETWEEN 1.7 AND 2 INCHES AND SO THE RISK FOR LOCALIZED FLASH
FLOODING NEEDS TO BE CONSIDERED AS WELL. HAVE PUT IN MILD ENHANCED
WORDING FOR GUSTY WINDS AND HEAVY RAINFALL. WILL MENTION THE RISK
OF STRONG TO SEVERE TSTMS AND LOCALIZED FLASH FLOOD RISK IN THE
HWO.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
BIG PICTURE... BIG RIDGE BUILDS OVER THE ROCKIES AND PLAINS WHILE
TROUGHS DIG INTO THE NORTHEAST AND THE PACIFIC NORTHWEST.  UPPER
RIDGE LINGERS OVER THE WESTERN ATLANTIC. FOR US...THIS WILL BRING
FALLING HEIGHTS/COOLING TEMPS ALOFT THURSDAY AND FRIDAY...THEN
RISING HEIGHTS/WARMING TEMPS OVER THE WEEKEND. THE PAC NORTHWEST
TROUGH EJECTS OVER THE TOP OF THE ROCKIES RIDGE AND MOVES EAST.
OVER THE WEEKEND IT WILL MERGE WITH THE NORTHEAST TROUGH AND PULL
THE TROUGH AXIS BACK TO OUR WEST. THE ATLANTIC RIDGE REMAINS IN
PLACE TO OUR EAST. THIS WILL BRING A MOIST SOUTHWEST FLOW UP OVER
NEW ENGLAND SUNDAY-MONDAY.

GOOD AGREEMENT AMONG MOST OF THE LONG RANGE MODELS...ALLOWING US TO
USE A CONSENSUS.

THE DAILIES...

WEDNESDAY NIGHT-THURSDAY... THE COLD FRONT CROSSES MUCH OF OUR
REGION WHILE THE RIGHT ENTRANCE REGION OF THE UPPER JET MOVES INTO
POSITION OVERHEAD. WINDS AT 500 MB WILL BE 35-40 KNOTS. TOTALS NEAR
50/LI -4 AND LOWER DURING THE EARLY PART OF THE NIGHT. THE
COMBINATION OF DYNAMICS AND INSTABILITY AND SHEAR SUGGEST A
POTENTIAL FOR STRONG WIND GUSTS. PRECIPITABLE WATER VALUES WILL BE
NEAR 2 INCHES...SO HEAVY DOWNPOURS ALSO POSSIBLE.

THE COLD FRONT WILL BE JUST OFF THE SOUTH COAST AT 12Z. THE RIGHT
ENTRANCE OF THE UPPER JET WILL STILL BE IN POSITION OVERHEAD. THIS
MAY CAUSE A WAVE TO FORM ON THE FRONT AND KEEP SHOWERS OVER
SOUTHERN/EASTERN PARTS OF SOUTHERN NEW ENGLAND THROUGH THE MORNING.
BUT THE TREND DURING THE DAY WILL BE FOR IMPROVEMENT FROM NORTHWEST
TO SOUTHEAST WITH AT LEAST PARTIAL CLEARING IN SOUTHERN NH AND THE
CT VALLEY.  TEMPS IN THE MIXED LAYER WILL SUPPORT MAX SFC TEMPS
IN THE MID 70S TO AROUND 80.

FRIDAY-SATURDAY... HIGH PRESSURE BUILDS OVERHEAD. SOME CONCERN THAT
FRIDAY WOULD FEATURE MORE CLOUDS DURING THE DAY.  THE UPPER TROUGH
AXIS AND COOLER TEMPS ALOFT WILL MOVE OVERHEAD AT THIS TIME WITH
SOME INCREASE IN CLOUD LEVEL MOISTURE. WITH THIS IN MIND WE HAVE
INCREASE FRIDAY SKY COVER. THEN ON SATURDAY THE UPPER FLOW STARTS TO
SHIFT TO SOUTHWEST WITH AN INCREASING IN HIGH CLOUDS. OVERALL A
COUPLE OF FAIR DAYS WITH TEMPS AT SEASONABLE LEVELS OR A LITTLE
BELOW.

SUNDAY-MONDAY... AS THE UPPER FLOW RE-ESTABLISHES AS SOUTHWEST AND
AIMED UP THE COAST...A SHORTWAVE MOVES INTO THE FLOW. THIS HAS THE
POTENTIAL TO DEVELOP A COASTAL LOW THAT MOVES OUR WAY AND SPREADS
CLOUDS AND RAIN OUR WAY ESPECIALLY FOR SUNDAY NIGHT/MONDAY. GIVEN
HOW FAR OUT THIS IS...DAY 6/DAY 7...WE WILL SHOW CHANCE POPS
DEVELOPING SUNDAY AND CONTINUING MONDAY.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH WEDNESDAY NIGHT/...

GENERALLY MODERATE CONFIDENCE ON FORECAST.

AREAS OF IFR CIGS/VSBYS CAPE AND NANTUCKET AND PATCHY IFR VSBYS
IN FOG ACROSS THE INTERIOR. THE LOW CLOUDS AND FOG SHOULD
GRADUALLY BURN OFF THIS MORNING AND THEN REAPPEAR ALONG THE SOUTH
COAST AGAIN TONIGHT. OTHERWISE...VFR CONDITIONS ARE EXPECTED
THROUGH WED MID AFTERNOON.

DURING LATE WED AFTERNOON...MVFR CIGS AND VSBYS IN VICINITY OF SCT
TSTMS AHEAD OF A COLD FRONT. A FEW TSTMS MAY BRIEFLY LOWER
CIGS/VSBYS TO IFR LEVELS. ALSO...A FEW TSTMS MAY PRODUCE STRONG
WIND GUSTS...ESPECIALLY NW OF AN ASH-LWM-BED-IJD LINE.

KBOS TAF...HIGH CONFIDENCE. MODERATE CONFIDENCE IN SEABREEZE
DEVELOPMENT. T-STORMS POSSIBLE BY WED LATE AFTERNOON.

KBDL TAF...HIGH CONFIDENCE IN TAF. LOW PROB ON FOG POTENTIAL
TONIGHT. T-STORMS POSSIBLE BY WED AFTERNOON.

OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...MODERATE CONFIDENCE

WEDNESDAY NIGHT-THURSDAY... MAINLY VFR. COLD FRONT CROSSES THE
REGION WITH PERIOD OF MVFR CIGS/VSBYS IN SHOWERS/TSTMS. PATCHY IFR
IN FOG...MAINLY SOUTH COAST AND ISLANDS.

FRIDAY-SATURDAY...VFR.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH WEDNESDAY/...MODERATE CONFIDENCE.

WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY
LEVELS THROUGH TONIGHT. THE SW FLOW WILL STRENGTHEN AHEAD OF A
COLD FRONT ON WED WITH A RISK OF GUSTS APPROACHING 25 KT. AREAS OF
FOG WILL GRADUALLY BURN OFF THIS MORNING BUT MAY REDEVELOP ALONG
THE SOUTH COASTAL WATERS TONIGHT.

OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...MODERATE CONFIDENCE.

WEDNESDAY NIGHT-THURSDAY... A COLD FRONT CROSSES THE WATERS LATE AT
NIGHT AND DURING THURSDAY.  GUSTY SOUTHWEST WINDS LEADING THE FRONT
MAY APPROACH 25 KNOTS AT TIMES WEDNESDAY NIGHT. WINDS SHIFT TO NORTH
AND NORTHEAST ON THURSDAY. SHOWERS AND SCATTERED THUNDERSTORMS WITH
STRONG WIND GUSTS AND BRIEFLY HEAVY RAIN.  SEAS REMAIN BELOW 5
FEET...BUT BRIEFLY HIGHER SEAS POSSIBLE IN ANY THUNDERSTORMS.

FRIDAY-SATURDAY... NORTH WINDS SHIFT TO SOUTHWEST WITH SPEEDS 15
KNOTS OR LESS. SEAS REMAIN LESS THAN 5 FEET.

&&

.EQUIPMENT...
KBOX RADAR IS IN STANDBY MODE TODAY WHILE CONSTRUCTION TAKES
PLACE NEARBY. THE RADAR WILL RETURN TO SERVICE WHEN CONSTRUCTION
ENDS FOR THE DAY.

&&

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

&&

$$
SYNOPSIS...WTB/THOMPSON
NEAR TERM...DUNTEN/THOMPSON
SHORT TERM...THOMPSON
LONG TERM...WTB
AVIATION...WTB/THOMPSON
MARINE...WTB/THOMPSON
EQUIPMENT...STAFF



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