976
FXUS61 KBOX 130604
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
200 AM EDT TUE AUG 13 2013
.SYNOPSIS...
MUGGY CONDITIONS INCREASE INTO TUESDAY AHEAD OF AN
APPROACHING COLD FRONT...WHICH WILL BRING SCATTERED SHOWERS AND
THUNDERSTORMS TUE INTO TUE EVENING. DRY AND SEASONABLE WEATHER
RETURNS WED FOR THE REST OF THE WEEK AND INTO NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 7 AM THIS MORNING/...
200 AM UPDATE...
DRY WEATHER CONTINUED ACROSS SOUTHERN NEW ENGLAND VERY EARLY THIS
MORNING. THE MAIN CLUSTER OF SHOWERS AND THUNDERSTORMS WERE STILL
ACROSS WESTERN NEW YORK...SO EXPECT MAINLY DRY WEATHER TO CONTINUE
THROUGH DAYBREAK. A FEW SHOWERS AND PERHAPS AN EMBEDDED
THUNDERSTORM OR TWO MAY WORK INTO INTERIOR SOUTHERN NEW ENGLAND
TOWARDS 12Z...BUT MUCH OF THE REGION MAY REMAIN DRY THROUGH THIS
TIME. MID LEVEL CLOUDINESS WILL CONTINUE TO INCREASE ACROSS THE
REGION...AS LOW TEMPS BOTTOM OUT MAINLY IN THE 60S.
&&
.SHORT TERM /7 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
IT IS A TRICKY FORECAST FOR TUESDAY. LOTS OF SYNOPTIC INGREDIENTS
IN PLACE TO SUPPORT CONVECTION...INCLUDING A STRONG UPPER-LEVEL
JET...MODEST MID-LEVEL VORTICITY ADVECTION...LOW-LEVEL ORGANIZING
WIND SHEAR...AS WELL AS THE EVENTUAL PASSAGE OF A COLD FRONT. THE
KEY MISSING INGREDIENT WILL BE INSTABILITY. AT THIS POINT AM
THINKING THAT STRONGER CONVECTION ACROSS THE MID-ATLANTIC STATES
WILL ROB MOST OF THE INSTABILITY. MOST UNSTABLE CAPE VALUES SHOULD
BE LESS THAN 1000 J/KG. LOW AND MID-LEVEL LAPSE RATES ARE
MARGINAL AT BEST TO SUPPORT CONVECTION. SHOULD THERE BE MORE
SUNSHINE THAN EXPECTED...OR THE MID-LEVEL COLD POOL ARRIVES A
LITTLE QUICKER...STRONGER STORMS WOULD BE POSSIBLE. WILL NEED TO
CONTINUE TO MONITOR.
AS NOTED ABOVE...WE FAVORED THE SLOWER ECMWF SOLUTION. THE GGEM
ALSO TRENDED IN THIS DIRECTION...SO WE BLENDED THE TWO. THIS
BRINGS THE SURFACE COLD FRONT TO THE BERKSHIRES/CT VALLEY AROUND
00Z AND TO THE COASTAL PLAIN AROUND 06Z. FAVORABLE UPPER JET
SUPPORT AND INSTABILITY AS WELL AS PRECIPITABLE WATER VALUES AT OR
ABOVE 1.5 INCHES...SO WE HAVE LIKELY POPS THROUGH THE PRE-FRONTAL
PERIOD IN THE EARLY NIGHT WITH HIGHEST POPS CONTOURED ALONG THE
925-700 MB THETA-E AXIS. WITH PW/S AT THOSE LEVELS WE COULD EXPECT
SOME LOCALLY HEAVY DOWNPOURS. SUPPORT DIMINISHES AFTER THE COLD
FRONT MOVES THROUGH...SO DIMINISHING POPS FROM WEST TO EAST
THROUGH THE PERIOD.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
HIGHLIGHTS...
* QUIET...SEASONABLE WEATHER WED THRU THE WEEKEND
* POSSIBILITY OF SOME RAIN NEXT MON
MODELS ARE IN VERY GOOD AGREEMENT THROUGHOUT MUCH OF THE VERY QUIET
LONG TERM PERIOD. THERE ARE SOME DISCREPANCIES OUT AROUND DAY 7
WHERE THERE IS POTENTIAL FOR A SHORTWAVE TROUGH TO MOVE THROUGH NEXT
TUESDAY WITH INCREASING CLOUDS ON MONDAY /PER THE GFS/. THE ECMWF
KEEPS MID LEVEL RIDGING IN PLACE FOR ANOTHER 24 HOURS WITH A SURFACE
HIGH PRESSURE OVER SOUTHERN NEW ENGLAND. FOR THE REMAINDER OF THE
LONG TERM PORTION OF THE FORECAST IT LOOKS DRY AND SEASONABLE WITH
THE DOMINANT FEATURE OVER THE REGION HIGH PRESSURE.
WEDNESDAY AND THURSDAY...TEMPERATURES WILL BE SLIGHTLY COOLER THESE
TWO DAYS FOLLOWING THE COLD FRONT THAT MOVES THROUGH LATE TUESDAY
NIGHT. OTHERWISE CLEARING SKIES AND QUIET WEATHER.
FRIDAY THROUGH SUNDAY...HIGH PRESSURE DOMINANT. TEMPERATURES
MODERATE BACK TOWARDS SEASONABLE LEVELS.
MONDAY...AS STATED ABOVE...SOME QUESTION HERE IN THE MODELS WHETHER
HIGH PRESSURE HOLDS /ECMWF/ OR A SHORTWAVE TROUGH MOVES THROUGH
PUSHING THE RIDGE OFFSHORE /GFS/.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
OVERVIEW...MODERATE CONFIDENCE TODAY AND TONIGHT. HIGH CONFIDENCE
ON WEDNESDAY.
BEFORE 12Z TODAY...LOW CLOUDS AND FOG PATCHES RESULTING IN SOME MVFR-
IFR CONDITIONS WILL BE MAINLY CONFINED TO THE SOUTH COAST/CAPE AND
ISLANDS EARLY THIS MORNING. THE REST OF THE REGION SHOULD MAINLY BE
VFR.
AFTER 12Z TODAY...WILL PROBABLY SEE A WIDE VARIETY OF CONDITIONS
ACROSS THE REGION. PERIODS OF VFR CONDITIONS WILL BE MIXED IN WITH
MVFR TO IFR CONDITIONS IN ROUNDS OF SHOWERS AND EMBEDDED
THUNDERSTORMS. EXACT TIMING IS HIGHLY UNCERTAIN.
TONIGHT...LEFT OVER SHOWERS/ISOLATED THUNDERSTORMS
THIS EVENING. OTHERWISE...MAY SEE SOME LINGERING LOW CLOUDS AND FOG
PATCHES PERSIST AT SOME TERMINALS INTO THE OVERNIGHT HOURS.
AREAL COVERAGE OF LOW CLOUDS AND FOG PATCHES ARE UNCERTAIN.
WEDNESDAY...ANY LEFT OVER MVFR-IFR CONDITIONS IN SCATTERED LOW
CLOUDS/FOG PATCHES WILL IMPROVE TO VFR BY MID TO LATE MORNING.
OTHERWISE...VFR CONDITIONS.
KBOS TERMINAL...MODERATE CONFIDENCE IN TRENDS. LOW CONFIDENCE IN
TIMING.
KBDL TERMINAL...MODERATE CONFIDENCE IN TRENDS. LOW CONFIDENCE IN
TIMING.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
HIGH CONFIDENCE. VFR.
&&
.MARINE...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
OVERVIEW THROUGH TUESDAY NIGHT...HIGH CONFIDENCE.
WINDS EXPECTED TO REMAIN BELOW 20 KT...EVEN IN GUSTS...THROUGH
TUESDAY NIGHT. GUSTS COULD BE STRONGER SHOULD THUNDERSTORMS
DEVELOP OVER THE WATERS. SEAS SHOULD BE HIGHEST ACROSS THE
SOUTHERN OUTER COASTAL WATERS...BUT STILL 4 FEET OR LESS.
PATCHY FOG ACROSS THE COASTAL WATER LATE TONIGHT...WITH LESS FOG
LIKELY TUESDAY NIGHT.
OUTLOOK...WEDNESDAY THROUGH SATURDAY...
HIGH CONFIDENCE. QUIET BOATING WEATHER EXPECTED. WINDS WILL SHIFT
DIRECTION AS HIGH PRESSURE BUILDS OVER SOUTHERN NEW ENGLAND AND THE
WATERS BUT WILL REMAIN BELOW 25 KTS.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...BELK/RLG
NEAR TERM...FRANK
SHORT TERM...BELK
LONG TERM...RLG
AVIATION...FRANK/RLG
MARINE...BELK/RLG