Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 281050
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
650 AM EDT MON JUL 28 2014

.SYNOPSIS...
A RATHER STRONG LOW PRESSURE SYSTEM BY JULY STANDARDS WILL
MOVE ACROSS UPSTATE NEW YORK TODAY BEFORE HEADING INTO NORTHERN
NEW ENGLAND TONIGHT. IT WILL BRING SHOWERS AND STORMS THIS
MORNING...FOLLOWED BY POSSIBLE STRONG STORMS THIS AFTERNOON. A
COLD FRONT WILL CROSS THE REGION TONIGHT AND TUESDAY...BRINGING
DRIER AND LESS HUMID WEATHER...AS THE FRONT REMAINS STALLED OVER
THE MARITIMES AND NEW ENGLAND OFFSHORE WATERS THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
*** HEAVY RAINFALL/STORMS THIS MORNING ***
*** FEW STRONG/SEVERE STORMS THIS AFTERNOON ***

7 AM UPDATE...
NO CHANGES MADE TO THE FORECAST.

PREVIOUS DISCUSSION...
BAND OF SHOWERS/STORMS FROM WESTERN AND CENTRAL NY INTO NYC AND
NJ IS ASSOCIATED WITH STRONG MID LEVEL Q-VECTOR CONVERGENCE AS
UPPER LOW CLOSES OFF OVER EASTERN GREAT LAKES. MODELS IN GOOD
AGREEMENT THAT THIS ACTIVITY WILL LIFT THROUGH SOUTHERN NEW
ENGLAND THROUGH THIS MORNING...BEFORE SHIFTING FARTHER N THIS
AFTERNOON. MOST OF THIS MAY END UP AFFECTING LOCATIONS NEAR S
COAST AS OPPOSED TO INTERIOR PER RADAR TRENDS.

MAIN THREAT THIS MORNING IS LOCALIZED FLASH FLOODING FROM HEAVY
RAINFALL...IN ADDITION TO FREQUENT LIGHTNING. ALSO CANNOT RULE OUT
STRONG WIND GUSTS GIVEN ENVIRONMENT OF RATHER HIGH 0-6KM SHEAR AND
DECENT MID LEVEL LAPSE RATES...THOUGH GIVEN TIME OF DAY CONFIDENCE
IS LOW THAT STRONG WINDS WILL BE REALIZED.

ONCE THIS INITIAL ROUND OF SHOWERS/STORMS LIFTS N BY EARLY
AFTERNOON...ATTENTION THEN TURNS TO POSSIBLE REDEVELOPMENT OF
SCATTERED SHOWERS/STORMS.

MODELS INSISTENT THAT DRY SLOT WILL WORK ITS WAY UP COAST INTO SE
NEW ENGLAND...AND DEEPER MOISTURE SHOULD RESIDE ACROSS INTERIOR AS
SEEN IN K-INDEX FIELDS. INSTABILITY IS IN QUESTION AS WE ARE NOT
CONFIDENT ON HOW MUCH CLEARING WILL OCCUR...IF AT ALL. BUT
CONTINUED PRESENCE OF HIGH 0-6KM SHEAR /OVER 35KT/ AND GOOD LOW
LEVEL TURNING IN FORECAST HODOGRAPHS SUGGESTS POTENTIAL FOR AT
LEAST FEW STRONG OR SEVERE STORMS THIS AFTERNOON. DAMAGING WINDS
AND HAIL ARE MAIN THREATS...BUT WE CANNOT RULE OUT AN ISOLATED
WEAK TORNADO GIVEN HIGHLY SHEARED ENVIRONMENT...LOW LCL/S AND
PRESENCE OF CLOSED UPPER LOW. SYSTEM ALSO HAS HISTORY OF PRODUCING
A FEW WEAK TORNADOES THUS FAR AS WELL.

GIVEN UNCERTAINTY IN AMOUNT OF HEATING...STAYED CLOSE TO MODEL
BLEND FOR HIGHS TODAY /70S TO AROUND 80/ WHICH ALSO MATCHES MIXING
TO 850 MB /10-11C/.

&&

.SHORT TERM /TUESDAY/...
COLD FRONT PUSHES THROUGH REGION TONIGHT BRINGING MUCH LESS HUMID
AIR BY DAYBREAK AS SKIES CLEAR. LIGHT WINDS WITH LEFTOVER MOISTURE
MAY LEAD TO PATCHY FOG ACROSS INTERIOR.

RIDGE OF HIGH PRESSURE BUILDS OVER NEW ENGLAND TUE...RESULTING IN
PLENTY OF SUNSHINE. NOT MUCH OF AIRMASS CHANGE SO HIGHS ONCE AGAIN
SHOULD TOP OFF IN 70S TO AROUND 80 BUT WITH LOW HUMIDITY. WEAK
GRADIENT SUPPORTS AFTERNOON SEA BREEZES ALONG BOTH COASTS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
BIG PICTURE...

MODELS CONTINUE TO ADVERTISE A MERIDIONAL TYPE FLOW THROUGH THE
WEEK. THE FOUR LOBES OF THIS FLOW ARE THE GULF OF ALASKA
TROUGH...WESTERN NORTH AMERICA RIDGE...EASTERN NORTH AMERICA
TROUGH...AND WEST ATLANTIC RIDGE.

MODELS CONTINUE TO SHOW A WEAK COLD POOL IN EASTERN NO-AM
TROUGH...SUFFICIENT TO GENERATE DAILY INSTABILITY SHOWERS. ALSO
SHOWERS ALONG THE STALLED FRONT OFFSHORE.  THE CORE OF THE EASTERN
NO-AM TROUGH EJECTS NORTH THROUGH QUEBEC FRIDAY AND SATURDAY. BUT A
WEAKER TROUGH LINGERS OVER THE GREAT LAKES/MISS RIVER VALLEY OVER
THE WEEKEND.

THE SIMILARITY IN MODEL FIELDS FAVORS A BLEND OF AVAILABLE DATA.

THE DAILIES...

TUESDAY NIGHT THROUGH FRIDAY... WITH THE UPPER TROUGH TO OUR WEST
AND UPPER RIDGE TO OUR EAST...EXPECT THE DEPARTED COLD FRONT TO
ALIGN WITH THE UPPER FLOW AND STALL.  UPPER FLOW OVER NEW ENGLAND
WILL REMAIN FROM THE SOUTHWEST. MEANWHILE COLD POOL INSTABILITY
UNDER THE UPPER TROUGH WILL BE OVER NY AND ONTARIO WHILE NEW ENGLAND
IS UNDER THE LEFT ENTRANCE REGION OF THE UPPER JET...A SUBSIDENT
ZONE.  SURFACE HIGH PRESSURE WILL BUILD OVER SOUTHERN NEW ENGLAND.
FOR THE MOST PART THIS LOOKS LIKE A DRY WEATHER PERIOD WITH
DEWPOINTS IN THE 50S...TRENDING TO THE LOWER 60S FRIDAY.

THIS WILL MEAN A CHANCE OF SHOWERS WELL OFFSHORE AND OVER
NY/ONTARIO. MAIN CONCERN FOR PRECIPITATION IN SOUTHERN NEW ENGLAND
WOULD BE IF SCATTERED DIURNAL SHOWERS/TSTMS FROM THE UPPER TROUGH
WHICH COULD SLIDE ACROSS THE BERKSHIRES INTO THE CT VALLEY.  SURFACE
HIGH PRESSURE AND THE LEFT ENTRANCE REGION OF THE UPPER JET WILL
FAVOR SUBSIDENCE AND DRY WEATHER.  WE WILL HAVE SLIGHT CHANCE POPS
IN THE BERKS WEDNESDAY AND WEST OF MHT-ORH-IJD THURSDAY-FRIDAY...AND
CHANCE POPS ALONG/WEST OF THE CT VALLEY THURSDAY-FRIDAY. PATCHY FOG
POSSIBLE EACH NIGHT.

SATURDAY-SUNDAY... AS THE CORE OF THE UPPER TROUGH LIFTS
NORTH...EXPECT THE ATLANTIC HIGH TO SHIFT A LITTLE TO THE WEST. THIS
WOULD PUSH THE OFFSHORE FRONT WEST CLOSER TO THE COAST AND BRING AN
INCREASE IN THE CHANCE OF SHOWERS...WITH THE BEST CHANCE ON THE CAPE
AND ISLANDS.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...

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

MODERATE CONFIDENCE ON TRENDS TODAY. HIGH CONFIDENCE TONIGHT AND
MONDAY.

IFR/LIFR IN SHOWERS/TSTMS THIS MORNING. ALSO LIFR IN FOG AREAS
ALONG THE SOUTH COAST AND CENTRAL HILLS. EXPECT THESE INITIAL
TSTMS TO MOVE NORTH OF OUR AREA THIS MORNING WITH CONDITIONS
IMPROVING TO VFR BY MIDDAY. FOG ALONG THE SOUTH COAST MAY BE
SLOWER TO IMPROVE IN THE HUMID AIRMASS.

SCATTERED SHOWERS/TSTMS SHOW REDEVELOP ACROSS THE INTERIOR AFTER
18Z. EXPECT MVFR CIGS/VSBYS IN ANY TSTMS. BEST CHANCE FOR TSTMS
WILL BE IN AREAS ALONG/WEST/NORTH OF I-495. THERE WILL BE POTENTIAL
FOR SOME OF THE STORMS IN THIS AREA TO PRODUCE STRONG OR DAMAGING
WIND GUSTS.

IMPROVING CONDITIONS TO VFR AFTER 00Z TUE...ALTHOUGH PATCHY
MVFR/IFR POSSIBLE IN FOG. VFR TUE WITH AFTERNOON SEA BREEZES.

KBOS TAF...MODERATE CONFIDENCE. IFR CIGS/VSBYS...FAIRLY CONFIDENT
ON IMPROVING CONDITIONS AFTER 15Z. TS SHOULD REMAIN W OF AIRPORT
18Z-22Z.

KBDL TAF...MODERATE CONFIDENCE. LIFR CIGS/VSBYS...FAIRLY
CONFIDENT IN IMPROVING CONDITIONS AFTER 13Z. TS MOST LIKELY 18Z-
22Z.

OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE.

VFR. AREAS OF IFR IN EARLY MORNING FOG EACH DAY.  MVFR CIGS/VSBYS IN
WIDELY SCATTERED AFTERNOON TSTMS MAINLY WEST OF MHT AND ORH.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

MODERATE CONFIDENCE THROUGH TUE. MAIN CONCERN IS FOR ROUGH SEAS ON
S COASTAL WATERS WHERE SCA HAS BEEN EXTENDED INTO TUE.

S/SW FLOW PREVAILS TODAY WHICH WILL LEAD TO BUILDING SEAS ON S
COASTAL WATERS...REACHING AS HIGH AS 5 OR 6 FT OFFSHORE THIS
AFTERNOON. THIS WILL ALSO MAINTAIN PATCHY DENSE FOG THIS MORNING
ON S COASTAL WATERS.

SHOWERS/STORMS WILL MOVE ACROSS WATERS THIS MORNING FROM LONG
ISLAND. SO FAR THESE STORMS HAVE PRODUCED FREQUENT LIGHTNING AND
MAY PRODUCE STRONG WIND GUSTS TO 35KT. POSSIBILITY OF A FEW MORE
STORMS THIS AFTERNOON...ESPECIALLY ON E MA WATERS.

COLD FRONT APPROACHES WATERS TONIGHT BUT EXPECT ANOTHER ROUND OF
PATCHY DENSE FOG...AT LEAST EARLY TONIGHT BEFORE DRIER AIR ARRIVES
OVERNIGHT. HIGH PRESSURE BUILDS OVERHEAD TUE WITH LIGHT WINDS AND
AFTERNOON SEA BREEZES. SEAS SLOWLY SUBSIDE OFFSHORE.

OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE.

SEAS GENERALLY LESS THAN 5 FEET THROUGH THE PERIOD...BUT MAY
APPROACH 5 FEET ON THE OUTER WATERS WEDNESDAY NIGHT AND THURSDAY.
LIGHT WINDS THROUGH THE PERIOD...SOUTHWEST MIDWEEK SHIFTING TO
SOUTHEAST FRIDAY.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 PM EDT TUESDAY
     FOR ANZ235-237-250-254>256.

&&

$$
SYNOPSIS...WTB/JWD
NEAR TERM...WTB/JWD
SHORT TERM...JWD
LONG TERM...WTB
AVIATION...WTB/JWD
MARINE...WTB/JWD


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