Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 191423
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1023 AM EDT SAT JUL 19 2014

.SYNOPSIS...

HIGH PRESSURE OVER THE NORTHEAST WILL SLOWLY MOVE OFFSHORE THROUGH
SUNDAY. LOW PRESSURE DEVELOPING OFF THE CAROLINAS WILL PASS
SOUTHEAST OF NANTUCKET DURING THE DAY ON SUNDAY. ANOTHER ROUND OF
HIGH PRESSURE WILL BRING ABOUT DRY...BUT WARMER AND HUMID
CONDITIONS THROUGH MID WEEK. A COLD FRONT FROM CANADA MOVES OVER
NEW ENGLAND LATE IN THE WEEK.

&&

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

1030 AM UPDATE...

WEAK OPEN-WAVE DISTURBANCE PRESENTLY TRANSLATING THROUGH THE
EASTERN GREAT LAKES REGION ALONG WITH ACCOMPANYING ISENTROPIC LIFT
AND WEAK ASCENT IS LENDING TO SHOWERS OVER THE OHIO RIVER VALLEY
WITH BROKEN-OVERCAST CONDITIONS ELSEWHERE ENCOMPASSING A MAJORITY
OF THE NORTHEASTERN CONUS. COMBINED WITH A SLIGHTLY COOLER AIRMASS
IN PLACE ALOFT /H85 TEMPERATURES +10-12C WITH H925 AROUND +16C/
NETS HIGHS AROUND THE UPPER-70S...ROUGHLY 5-DEGREES BELOW NORMAL
WITH RESPECT TO HIGHS FOR THIS TIME OF YEAR.

ANY RADAR RETURNS OVER NEW ENGLAND ARE MAINLY WITHIN THE MID- TO
UPPER-LEVELS. ABUNDANCE OF DRY AIR REMNANT TO THE DEPARTING HIGH
PRESSURE WILL SQUASH ANY WET WEATHER FROM REACHING THE GROUND.
SHOULD REMAIN A DRY DAY.

OTHERWISE...AS NOTED BY THE PREVIOUS FORECASTER...CONTINUE TO
MONITOR A WEAK MID-ATLANTIC IMPULSE LIFTING NORTHEAST ALONG A
STALLED FRONTAL BOUNDARY WELL OFFSHORE OF NEW ENGLAND. INVOKING A
WAVE LOW ALONG THE FRONT...THIS WILL BECOME AN AREA OF INTEREST
TONIGHT INTO SUNDAY WITH SOME LIGHT SHOWERY WEATHER FOR S/SE
COASTAL REGIONS. BUT ACTIVITY SOUTH OF THE FRONT WITHIN THE MORE
TROPICAL AND SOUPY AIRMASS MAY LIMIT ACTIVITY NORTH.

NO MAJOR CHANGES MADE TO THE FORECAST OTHER THAN MINOR TWEAKS TO
ACCOUNT FORE PRESENT TRENDS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...

TONIGHT...AN OFFSHORE HIGH PRESSURE WILL KEEP THE WEATHER DRY
MOST PLACES...AS A SURFACE RIDGE EXTENDS WEST ACROSS SOUTHERN NEW
ENGLAND. WE CONTINUE TO WATCH A SOUTHERN STREAM SHORTWAVE THAT IS
EXPECTED TO GENERATE A COASTAL LOW OFF THE CAROLINAS BY THIS
EVENING. WITH SOUTHWEST FLOW ALOFT...WE EXPECT THIS WEAK LOW
PRESSURE WILL MOVE TOWARD OUR REGION TONIGHT. THE QUESTION WHICH
REMAINS IS HOW CLOSE THIS LOW PRESSURE WILL GET.

JUST ABOUT ALL OF THE 19/00Z GUIDANCE BRINGS SOME PRECIPITATION
INTO CAPE COD AND THE ISLANDS. SOME GUIDANCE SOURCES BRING SOME
RAINFALL EVEN FARTHER NORTHWEST. THINKING THE SURFACE RIDGE WILL
HOLD STRONG...SO HAVE KEPT THE BRUNT OF THE RAINFALL OFFSHORE.
THIS IS SIMILAR TO PREVIOUS FORECAST THINKING.

SUNDAY...BEST CHANCE OF SHOWERS WILL BE ACROSS THE CAPE/ISLANDS
WITH A MOIST ONSHORE FLOW...WHILE A RIDGE OF HIGH PRESSURE SHOULD
CURTAIL THE RAINFALL FROM MAKING FURTHER NORTH/WEST. HOWEVER...
THIS WILL HAVE TO BE CLOSELY MONITORED. THERE WILL BE CONSIDERABLE
CLOUDINESS...WITH A GRADUAL CLEARING TREND GETTING UNDERWAY...
ESPECIALLY LATER IN THE DAY. AN ONSHORE FLOW WILL KEEP COASTAL
AREAS IN PARTICULAR COOLER.

&&

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

HIGHLIGHTS...

* INCREASING HUMIDITY MON.
* WARMER AND MORE HUMID THROUGH MID WEEK.
* BEST CHANCE OF SHOWERS AND THUNDERSTORMS IN THE WEDNESDAY AND
  THURSDAY TIMEFRAME WITH THE APPROACH OF A COLD FRONT.

OVERVIEW AND MODEL PREFERENCES...
WHILE THERE IS DECENT AGREEMENT THROUGH THE MID TERM BETWEEN BOTH
OPERATIONAL AND ENSEMBLE MODELS...TYPICAL LATE LONG TERM ISSUES
ARE EVIDENT IN THE FLOW. THE ISSUE AT HAND IS A DEEPENING AND
DIGGING WAVE FROM CENTRAL CANADA AND INTO THE MIDWEST. IT IS
ATTEMPTING TO SPLIT BUILDING MID AND UPPER LVL RIDGING BOTH ACROSS
THE SW CONUS AND THE SUBTROPICAL RIDGE ASSOCIATED WITH THE BERMUDA
HIGH. THESE FEATURES WILL DEFINE THE EARLY PART OF THE WEEK...BUT
IT/S THIS LATE WEEK TROF...WHERE MOST OF THE UNCERTAINTY
LIES...WHICH WILL DEFINE THE END OF THE WEEK. THE CAMPS ARE SPLIT
BETWEEN THE MORE PROGRESSIVE GFS...WHICH PUSHES A COLD FRONT
THROUGH BY THU WITH THIS TROF...WHILE THE DEEPER AND SLOWER ECMWF
LEAVES THE FRONT TO LINGER ACROSS THE REGION INTO THE WEEKEND. FOR
NOW...A CONSENSUS BLEND WILL BE USED UNTIL THE TROF/RIDGE
BREAKDOWN IS BETTER RESOLVED.

DETAILS...

SUN NIGHT INTO MON...
HIGH PRES SLOWLY REGAINS CONTROL ACROSS THE REGION AS A WEAK
FRONTAL WAVE MOVES NE INTO THE MARITIMES...AND BOTH SW CONUS
RIDGING AND THE BERMUDA HIGH BUILDS. THIS WILL BRING AN END TO ANY
SHOWER THREAT FROM THE FRONTAL WAVE...HOWEVER LINGERING CLOUDS AND
ONSHORE FLOW WILL KEEP MIN TEMPS MILD SUN NIGHT AND HIGHS ON THE
COOL SIDE DURING THE DAY MON. WILL CARRY LOWS ABOVE NORMAL AND
HIGHS BELOW. FRONTAL WAVE APPROACH WILL INCREASE THE THREAT FOR
EVENING STRATUS/FOG.

TUE INTO WED...
WITH BUILDING SE RIDGE AND BERMUDA HIGH...INCREASING TEMPS AND
HUMIDITY THROUGH THE COLUMN ARE EXPECTED. A WEAK WARM FRONT WILL
MOVE NW OF THE AREA ON TUE...AND MAY YIELD AN ISOLATED THREAT FOR
AFTERNOON CONVECTION BUT TO THE W...WHERE A WEAK SLACKENING IN THE
PRES GRADIENT SUGGESTS A POTENTIAL WEAK TROF. FLOW IS WEAK SO WILL
MAINLY HOLD POPS TO NIL EXCEPT FOR THE EXTREME W PERIPHERY OF
MA/CT. BY WED WITH A COLD FRONT APPROACHING FROM CANADA/GREAT
LAKES...SHOULD A TRUE PRE FRONTAL TROF DEVELOP MAY HAVE A BETTER
SHOT AT AFTERNOON CONVECTION. AS PREVIOUS SHIFT NOTED...COLUMN IS
CERTAINLY DESTABILIZED...BUT THE QUESTIONS ARE THE LACK OF
SHEAR...A FOCUS FOR LIFT...OR CAP WITH H7 TEMPS NEAR +10C. SO ONLY
LOW CHANCE OF SLIGHT CHANCE POPS WILL BE USED AT THIS TIME. H85
TEMPS APPROACH +18C EACH DAY...SO WITH ENOUGH SUNSHINE AND MIXING
TEMPS ARE LIKELY TO REACH NEAR 90F IN SPOTS...WITH DWPTS IN THE
60S SUGGESTING HIGHER HUMIDITY.

THU INTO FRI...
A SLOWING COLD FRONT WILL CROSS THE REGION AT SOME POINT DURING
THIS PERIOD. ALTHOUGH THE AMPLIFYING PATTERN FAVORS THE SLOWER
SOLUTIONS. IN FACT...MODELS DO INDICATE A WAVE OF LOW PRES MAY
DEVELOP ALONG THE FRONT AS IT SLOWS IN THE VICINITY OF SRN NEW
ENGLAND. IN ANY CASE...THE PERIPHERY OF THE RIDGE STILL FEATURES
MODESTLY UNSTABLE AIRMASS WITH MUCAPES APPROACHING 1000-1500J/KG
AND A MORE SHEAR AS THE JET DEVELOPS TO THE W. THEREFORE...WILL
CARRY CHANCE POPS HIGHEST DURING PEAK HEATING EACH DAY FOR
SHOWERS AND THUNDERSTORMS. HEAVY RAIN IS POSSIBLE GIVEN PWATS
1.75-2.00 INCHES.

NEXT WEEKEND...
DEPENDENT ON FRONTAL TIMING. HOWEVER...THE PROJECTED AIRMASS
SUGGESTS LOWER HUMIDITY AND SEASONABLE TEMPERATURES.
HOWEVER...SHOULD THE FRONT STALL IN THE VICINITY...UNSETTLED WX
MAY CONTINUE.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...

FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH THURSDAY NIGHT/...

TODAY...HIGH CONFIDENCE.
VFR AFTER SOME PATCHY EARLY MORNING GROUND FOG BURNS OFF. SEA
BREEZES LIKELY DEVELOP A BIT EARLIER THAN NORMAL...MAINLY BY MID
MORNING THANKS TO WEAK EASTERLY COMPONENT TO THE WIND.

TONIGHT...HIGH CONFIDENCE. VFR. SHOWERS MAY BRING BRIEF MVFR
VSBYS TO THE ISLANDS LATE AT NIGHT.

SUNDAY...MODERATE CONFIDENCE. MVFR/IFR POSSIBLE IN LOW CEILINGS
AND SHRA MAINLY CONFINED TO CAPE COD AND THE ISLANDS. VFR
EXPECTED ELSEWHERE.

KBOS TAF...HIGH CONFIDENCE IN TAF. SEA BREEZE DEVELOPS AROUND
14-15Z TODAY.

KBDL TAF...HIGH CONFIDENCE IN TAF.

OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...

MONDAY THROUGH WEDNESDAY...MODERATE CONFIDENCE.
WHILE VFR WILL LIKELY DOMINATE MOST DAYS...SOME OVERNIGHT
FOG/STRATUS MAY LEAD TO MVFR/IFR CONDITIONS ESPECIALLY ALONG S
COASTAL LOCATIONS MON NIGHT AND TUE NIGHT. CHANCE FOR LOCALIZED
MVFR/IFR CONDITIONS IN SHOWERS AND THUNDERSTORMS ESPECIALLY WED.

&&

.MARINE...

FORECASTER CONFIDENCE LEVELS...

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

THROUGH SUNDAY...HIGH CONFIDENCE.

WAVE MODELS CONTINUE TO OVER-FORECAST WAVE HEIGHTS OFF OUR COAST
BY ABOUT A FOOT. LOWERED THE WAVE HEIGHT GUIDANCE BY 20 PERCENT
THROUGH THE FORECAST PERIOD.

TRANQUIL BOATING WEATHER EXPECTED WITH HIGH PRESSURE OVERHEAD.
LIGHT WINDS TREND TO SOUTHEAST TODAY AS THE HIGH MOVES OFFSHORE...
THEN TO EAST TONIGHT. WINDS AND SEAS WILL REMAIN BELOW SMALL
CRAFT THRESHOLDS THROUGH SUNDAY.

COASTAL LOW PRESSURE DEVELOPING OFF THE CAROLINAS TODAY WILL MOVE
UP THE COAST TONIGHT. CURRENT FORECAST TRACK WOULD KEEP MOST OF
THIS STORM WELL OFFSHORE. BUT FORECAST MODELS AGREE ON LIGHT
SHOWERS INTO OUR SOUTHERN WATERS AFTER MIDNIGHT TONIGHT...
ESPECIALLY SOUTH AND EAST OF NANTUCKET.

OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...

AFTER LOW PRESSURE EXITS TO THE EAST LATE SUNDAY NIGHT...HIGH
PRESSURE WILL ONCE AGAIN REGAIN CONTROL ACROSS THE WATERS. HAVE
MODERATE CONFIDENCE THAT WINDS AND SEAS WILL REMAIN BELOW SMALL
CRAFT ADVISORY THRESHOLDS THROUGH THE PERIOD. BUT A FEW WIND GUSTS
AND HIGHER SEAS ARE POSSIBLE ESPECIALLY BY WED AS THE SW WINDS
INCREASE.

SOME SHOWERS OR THUNDERSTORMS ARE POSSIBLE OVER THE SOUTHEAST
WATERS SUN NIGHT WITH A THREAT FOR SHOWERS AND THUNDERSTORMS
POSSIBLE ACROSS ALL WATERS ON WED. SOME FOG MAY LEAD TO VSBY
RESTRICTIONS ON ESPECIALLY MON AND TUE NIGHTS.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...

CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.

&&

$$

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



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