Special Weather Statement, NWS Boston/Norton, MA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
ISSUED BY NATIONAL WEATHER SERVICE UPTON NY
404 PM EDT FRI MAY 20 2011

.SYNOPSIS...
LOW PRESSURE OVER THE REGION WILL CONTINUE TO BRING SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH SATURDAY...MAINLY DURING THE
AFTERNOON/EVENING HOURS. A WARM FRONT WILL MOVE THROUGH THE REGION
ON MONDAY WITH PERHAPS A PERIOD OF SCATTERED RAIN SHOWERS. THIS WILL
SET THE STAGE FOR MILDER TEMPERATURES FOR EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
UPPER LOW OVER NYC AREA EXPECTED TO SLOWLY DRIFT SE...SOUTH OF LI
TONIGHT...WITH BROAD SURFACE REFLECTION CENTERED OVER THE HUDSON
RIVER VALLEY SLOWLY SLIDING EAST. MAIN FOCUS AREAS FOR SCATTERED
SHOWERS AND ISOLATED TSTMS THROUGH THIS EVENING WILL BE ACROSS
INTERIOR SOUTHERN SECTIONS OVER THE AREA ALONG SEA BREEZE
BOUNDARY...AND THEN LIKELY SPREADING N/NW IN COVERAGE WITH
SHORTWAVE ROTATING NORTHWARD...MARGINAL SURFACE INSTABILITY DUE TO
PARTIAL CLEARING...AND WEAK CONVERGENCE ALONG OUTFLOW AND
DIFFERENTIAL HEATING BOUNDARIES. ISOLD STRONG/SEVERE WITH GUSTY
WINDS AND SMALL HAIL POSSIBLE IN STRONGEST TSTMS WITH DEEP COLD
POOL ALOFT. CONTINUED MENTION IN THE HWO. MORE ISOLATED ACTIVITY
ALONG THE COAST WITH STABLE MARINE AIRMASS IN PLACE.

WOULD EXPECT COVERAGE OF SHOWERS AND TSTMS TO DIMINISH THIS EVENING
AS DAYTIME INSTABILITY WANES.

WIDESPREAD FOG/STRATUS DEVELOPMENT EXPECTED AGAIN TONIGHT WITH MOIST
LOW-LEVELS AND LIGHT FLOW...LOCALLY DENSE PARTICULARLY ALONG COAST
AND IN VALLEY LOCATIONS. OVERNIGHT LOWS WILL FALL TO THE LOWER-MID
50S.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
MODELS IN GOOD AGREEMENT WITH UPPER LOW CONTINUING TO DRIFT SE OF
CAPE COD...WITH WEAK SURFACE LOW REFLECTION GIVING WAY TO BACKDOOR
COLD FRONT NOSING INTO NORTHERN AND EASTERN SECTIONS OF THE REGION
LATE IN THE AFTERNOON AS HIGH BUILDS OVER SE CANADA. WITH
MODERATING COLD POOL INSTABILITY...MARGINAL DAYTIME SURFACE
INSTABILITY...AND VORT ENERGY SLIDING DOWN BACKSIDE OF UPPER
LOW...ANOTHER ROUND OF SCATTERED DIURNAL SHRA/TSRA EXPECTED. THIS
WILL AGAIN MAINLY BE ACROSS THE INTERIOR TO THE INTERIOR OF SEA BREEZE
AND S/SW OF BACKDOOR COLD FRONT.

WIDESPREAD FOG AND STRATUS ALONG THE COAST IN THE MORNING WILL
LIKELY BE SLOW TO SCOUR THROUGH THE MORNING INTO EARLY
AFTERNOON...WITH CONSIDERABLE INSTABILITY CU ACROSS INTERIOR ONCE
AGAIN. WITH MORE OF A NW FLOW REGIME...EXPECTING A BIT MORE
SUNSHINE THAN TODAY. ALSO WITH A SLIGHTLY MODERATED COLD POOL
WOULD EXPECT TEMPS TO WARM A FEW DEGREES HIGHER THAN TODAY...LOWER
TO MID 70S INTERIOR...MID TO UPPER 60S COAST.

DIURNAL SHRA/TSRA ACTIVITY EXPECTED TO DISSIPATE QUICKLY IN THE
EVENING IN DEEP NW FLOW. BACKDOOR COLD FRONT SINKS SOUTH THROUGH
THE ENTIRE REGION SAT NIGHT. DRIER LOW-LEVEL AIRMASS IN SHOULD
SIGNIFICANTLY IMPROVE VSBY...BUT STRATUS DEVELOPMENT POSSIBLE WITH
STRENGTHENING SUBSIDENCE INVERSION. OVERNIGHT LOWS IN THE UPPER
40S TO LOWER 50S IN MORE CANADIAN MARITIME AIRMASS.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
BACK DOOR COLD FRONT RETREATS NORTH AS A WARM FRONT SUNDAY.
RESULTANT SE-S LOW LEVEL FLOW AND RIDGING ALOFT SHOULD ALLOW FOR
TEMPERATURES ACROSS THE INTERIOR TO RETURN TO NEAR NORMAL
LEVELS...WHILE COASTAL AREAS REMAIN BELOW NORMAL WITH THE ONSHORE
FLOW. APPEARS THERE WILL BE JUST ENOUGH LOW LEVEL INSTABILITY TO
ALLOW FOR ISOLATED ELEVATION DRIVEN SHRA/TSRA ACROSS FAR WESTERN
ZONES. BLENDED MAV/MET MOS FOR HIGHS SUNDAY.

MID-UPPER LEVEL RIDGE AXIS SLIDES OFFSHORE SUNDAY NIGHT...WITH SW
FLOW SETTING UP ALOFT. SHORTWAVES WORKING THERE WAY UP THE BACKSIDE
OF THE RIDGE WARRANT CHANCE POPS FOR SHRA. USED A MAV/MET BLEND FOR
LOWS.

A SECOND WARM FRONT TRIES TO LIFT THROUGH MONDAY/MONDAY NIGHT AS IT
WEAKENS/DISSIPATES. SHORTWAVES MOVING UP THE BACK SIDE OF THE RIDGE
WARRANT CHANCE POPS FOR SHRA WITH SUFFICIENT INSTABILITY OVER
WESTERN ZONES TO HAVE DIURNAL CHANCE OF THUNDER AS WELL. REMAIN IN
SW FLOW ALOFT WITH A SIMILAR PATTERN ON TUESDAY. USED A BLEND OF
MEX/MEX ENSEMBLE MEAN GUIDANCE WITH HPC GUIDANCE FOR HIGHS/LOWS
MON-TUE.

MODELS COME INTO DISAGREEMENT WED-FRI ON PLACEMENT OF SLOW MOVING
SFC COLD FRONT WITH THE GFS WANTING TO HAND IT UP TO OUR WEST...AND
THE ECMWF MOVING THE FRONT THROUGH THE REGION...THEN STALLING IT OUT
JUST TO OUR S/E. WENT WITH HPC IDEA OF A COMPROMISE...WITH FIRST
FRONT PASSING THROUGH WEDNESDAY...THEN WASHING OUT...WITH A SECOND
COLD FRONT THEN HANGING OUT TO OUR WEST THURSDAY-FRIDAY. THE MODELS
ARE IN BETTER AGREEMENT ON IDEA OF MEAN SW FLOW ALOFT...THOUGH THE
ECMWF IS MORE AGGRESSIVE IN BUILDING IN A RIDGE FROM THE S WED
NIGHT/THU. LEANED TOWARDS ECMWF IDEA...AS IT HISTORICALLY IS A
BETTER VERIFYING MODEL THAT FAR OUT...PLUS THIS IDEA IS ALSO
CONSISTENT WITH THE FIRST COLD FRONT WASHING OUT AFTER IT PASSES
THROUGH WEDNESDAY.

THE NET RESULT IS UNSETTLED CONDITIONS WITH SCT SHRA IN RESPONSE TO
SHORTWAVES MOVING UP THE BACKSIDE OF THE RIDGE AND ISO DIURNAL TSRA
ACROSS WESTERN ZONES. HAVE HIGHER POPS OVER THE NW 1/2 OF THE CWA AS
IT IS CLOSER TO THE SFC BOUNDARY. FOR TEMPERATURES CONTINUED USING
BLEND OF MEX/MEX ENSEMBLE MEAN WITH HPC GUIDANCE.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
FORECASTER CONFIDENCE LEVELS...
  LOW...LESS THAN 30 PERCENT
  MEDIUM...30 PERCENT TO 60 PERCENT
  HIGH...GREATER THAN 60 PERCENT

MEDIUM CONFIDENCE ON 18Z TAFS. LOW STRATUS HAS REMAINED IN PLACE
OVER MOST OF MASSACHUSETTS AND SRN NH...WITH BREAKS IN CLOUDS
DEVELOPING OVER CT/RI AND CAPE COD. LOW STRATUS DECK IS EXPECTED
TO CONTINUE TO RETREAT NORTHWARD LATE THIS AFTERNOON. AS IT
DOES...CONDITIONS ARE EXPECTED TO IMPROVE TO VFR FOR A FEW HOURS
MID-LATE AFTERNOON OVER MOST TERMINALS. STRATUS DECK OVER THE
OCEAN IS ADVANCING NORTHWARD AS WELL...SO COASTAL TERMINALS ARE
LIKELY TO RETURN TO MVFR OR LOWER CONDITIONS THIS AFTERNOON.

BREAKS IN CLOUDS WILL ENHANCE SURFACE INSTABILITY...WITH A CHANCE
OF DEVELOPING SHOWERS/TSTMS. SO FAR ALL ACTIVITY HAS DEVELOPED
WEST OF THE REGION...OVER THE LOWER HUDSON VALLEY...BUT CU FIELDS
ARE DEVELOPING OVER PORTIONS OF MASS/CT WHERE BREAKS IN STRATUS
HAVE DEVELOPED. INCLUDED CB GROUPS IN WESTERN AND INLAND
TERMINALS. AMENDMENTS WILL BE ISSUED IF HIGHER CONFIDENCE DEVELOPS
OF SHOWERS/TSTMS IMPACTING ANY SPECIFIC TERMINALS.

TONIGHT...MEDIUM CONFIDENCE. ACROSS EASTERN AND CENTRAL
AREAS...EXPECT MVFR-VFR CONDITIONS EARLY LOWERING TO IFR-LIFR
CIGS/VSBYS IN AREAS OF FOG ESPECIALLY ALONG THE COAST.  ACROSS
WESTERN AREAS...SHOULD SEE VFR CONDITIONS EARLY...THEN AREAS OF
MVFR-IFR CIGS/VSBYS...MAINLY AFTER MIDNIGHT. SCATTERED EVENING
SHOWERS/TSTMS ACROSS WESTERN AREAS.

LIGHT WINDS EXPECTED THROUGH THE PERIOD. WIND DIRECTION MAY BE
VARIABLE WITH NO SIGNIFICANT STEERING PATTERN.

KBOS TERMINAL...MEDIUM CONFIDENCE. MVFR CEILINGS MAY BREAK OUT TO
VFR EARLIER THAN FORECAST. SOME SHOWERS OR A THUNDERSTORM MAY
DEVELOP LATE THIS AFTERNOON. LIFR CONDITIONS SHOULD REDEVELOP
THIS EVENING AS THE BOUNDARY LAYER COOLS.

OUTLOOK...SATURDAY THROUGH TUESDAY...

SATURDAY...MEDIUM CONFIDENCE.  MVFR TO IFR CONDITIONS IN LOW CLOUDS
AND FOG PATCHES SATURDAY MORNING SHOULD IMPROVE TO MAINLY VFR BY
LATE MORNING OR EARLY AFTERNOON.  SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED INLAND FROM THE COAST MAINLY SATURDAY
AFTERNOON/EARLY EVENING.

SATURDAY NIGHT THROUGH EARLY MONDAY...MEDIUM CONFIDENCE.  MAINLY
MVFR TO IFR CONDITIONS IN LOW CLOUDS...FOG PATCHES AND PERHAPS ABOUT
SCATTERED SHOWERS.

MONDAY AFTERNOON INTO TUESDAY...MEDIUM CONFIDENCE WITH MAINLY VFR
CONDITIONS EXPECTED.

&&

.MARINE...
TONIGHT AND SATURDAY...WEAK GRADIENT SHOULD KEEP WINDS AND SEAS
BELOW SCA THRESHOLDS.  HOWEVER...AREAS OF FOG WILL LIKELY REDUCE
VISIBILITIES FOR MARINERS LATE TONIGHT INTO SAT MORNING. VSBY SHOULD
IMPROVE BY LATE MORNING OR EARLY AFTERNOON...AND PARTICULARLY IN
WAKE OF BACKDOOR COLD FRONT LATE IN THE DAY.

SATURDAY NIGHT...A BACK DOOR COLD FRONT SHOULD RESULT IN A BRIEF
PERIOD OF NORTHEAST WIND GUSTS OF 20 TO 25 KNOTS.  MARGINAL 5 FOOT
SEAS MAY ALSO AFFECT THE EASTERN OUTER-WATERS FOR A TIME.

OUTLOOK...SUNDAY THROUGH WEDNESDAY...
RELATIVELY RELAXED PRESSURE GRADIENT SHOULD ALLOW FOR SUB-SCA
CONDITIONS OVER THE WATERS SUNDAY AND SUNDAY NIGHT.

PERSISTENT SOUTHERLY FLOW SHOULD BRING SCA SEAS ON THE OUTER WATERS
MONDAY-WEDNESDAY...WITH SUB-SCA SEAS ELSEWHERE.

WINDS SHOULD ALSO REMAIN BELOW SCA LEVELS THROUGH THE PERIOD...
EXCEPT FOR POSSIBLY THE OUTER WATERS TUE-WED WHERE GUSTS TO 25 KT
ARE POSSIBLE...WITH STRENGTHENING S FLOW.

&&

.EQUIPMENT...
WFO BOX WILL BE IN SERVICE BACKUP BY WFO OKX THROUGH AT LEAST LATE
THIS AFTERNOON. KBOX DOPPLER RADAR DATA MAY BE SPORADIC AS WELL.

&&

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

&&

SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
EQUIPMENT...

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TAUNTON MA
ISSUED BY NATIONAL WEATHER SERVICE UPTON NY
350 PM EDT FRI MAY 20 2011

CTZ002>004-MAZ002>024-026-NHZ011-012-015-RIZ001>008-212000-
HARTFORD CT-TOLLAND CT-WINDHAM CT-WESTERN FRANKLIN MA-
EASTERN FRANKLIN MA-NORTHERN WORCESTER MA-CENTRAL MIDDLESEX MA-
WESTERN ESSEX MA-EASTERN ESSEX MA-WESTERN HAMPSHIRE MA-
WESTERN HAMPDEN MA-EASTERN HAMPSHIRE MA-EASTERN HAMPDEN MA-
SOUTHERN WORCESTER MA-WESTERN NORFOLK MA-SOUTHEAST MIDDLESEX MA-
SUFFOLK MA-EASTERN NORFOLK MA-NORTHERN BRISTOL MA-
WESTERN PLYMOUTH MA-EASTERN PLYMOUTH MA-SOUTHERN BRISTOL MA-
SOUTHERN PLYMOUTH MA-BARNSTABLE MA-DUKES MA-NANTUCKET MA-
NORTHERN MIDDLESEX MA-CHESHIRE NH-EASTERN HILLSBOROUGH NH-
WESTERN AND CENTRAL HILLSBOROUGH NH-NORTHWEST PROVIDENCE RI-
SOUTHEAST PROVIDENCE RI-WESTERN KENT RI-EASTERN KENT RI-BRISTOL RI-
WASHINGTON RI-NEWPORT RI-BLOCK ISLAND RI-
350 PM EDT FRI MAY 20 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHERN
CONNECTICUT...CENTRAL MASSACHUSETTS...EASTERN
MASSACHUSETTS...NORTHEASTERN MASSACHUSETTS...SOUTHEASTERN
MASSACHUSETTS...WESTERN MASSACHUSETTS...SOUTHERN NEW
HAMPSHIRE...NORTHERN RHODE ISLAND AND SOUTHERN RHODE ISLAND.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED INTO THIS
EVENING. A FEW OF THE STRONGER STORMS MAY CONTAIN SMALL HAIL AND
LOCALLY HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED AGAIN MAINLY
SATURDAY AFTERNOON AND EVENING INLAND FROM THE COAST. A FEW OF THE
STRONGER STORMS MAY CONTAIN SMALL HAIL AND LOCALLY HEAVY RAINFALL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

ANZ230>237-250-251-254>256-212000-
BOSTON HARBOR-CAPE COD BAY-NANTUCKET SOUND-VINEYARD SOUND-
BUZZARDS BAY-RHODE ISLAND SOUND-NARRAGANSETT BAY-BLOCK ISLAND SOUND-
COASTAL WATERS EAST OF IPSWICH BAY AND THE STELLWAGEN BANK NATIONAL
MARINE SANCTUARY-MASSACHUSETTS BAY AND IPSWICH BAY-
COASTAL WATERS FROM PROVINCETOWN MA TO CHATHAM MA TO NANTUCKET MA
OUT 20 NM-
COASTAL WATERS EXTENDING OUT TO 25 NM SOUTH OF MARTHAS VINEYARD AND
NANTUCKET-
COASTAL WATERS FROM MONTAUK NY TO MARTHAS VINEYARD EXTENDING OUT TO
20 NM SOUTH OF BLOCK ISLAND-
350 PM EDT FRI MAY 20 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MASSACHUSETTS COASTAL WATERS
AND RHODE ISLAND COASTAL WATERS.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

AREAS OF DENSE FOG WILL AFFECT PARTS OF THE REGION LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

AREAS OF DENSE FOG WILL AFFECT PARTS OF THE REGION SATURDAY
MORNING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TAUNTON MA
ISSUED BY NATIONAL WEATHER SERVICE NEW YORK NY
456 PM EDT FRI MAY 20 2011

CTZ002-202200-
HARTFORD-
456 PM EDT FRI MAY 20 2011

...STRONG THUNDERSTORMS WILL IMPACT SOUTHWESTERN HARTFORD COUNTY...

AT 454 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM SOUTHINGTON TO
BERLIN...OR ALONG A LINE EXTENDING FROM WOLCOTT TO MIDDLETOWN...AND
MOVING WEST AT 10 MPH.

PEOPLE IN SOUTHWESTERN HARTFORD COUNTY...INCLUDING SOUTHINGTON...
BERLIN...NEWINGTON...NEW BRITAIN...FARMINGTON...PLAINVILLE AND
BRISTOL...SHOULD MONITOR THE WEATHER SITUATION CLOSELY. LISTEN FOR
POSSIBLE WARNINGS AND BE PREPARED TO TAKE APPROPRIATE ACTION SHOULD
SEVERE WEATHER THREATEN.

SMALL HAIL IS EXPECTED WITH THESE STORMS. IN ADDITION...VERY HEAVY
RAIN...WITH RAINFALL RATES OF UP TO ONE AND ONE HALF INCHES AN
HOUR...IS OCCURRING WITH THESE STORMS. THIS WILL CAUSE PONDING OF
WATER ON ROADWAYS... AND MINOR FLOODING OF POOR DRAINAGE AREAS.

LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS. REMEMBER...IF YOU CAN
HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING. MOVE
TO SAFE SHELTER IMMEDIATELY.

LAT...LON 4177 7279 4164 7258 4162 7270 4160 7272
      4159 7275 4158 7276 4158 7279 4157 7280
      4156 7294 4157 7295 4164 7294 4164 7299
      4175 7301

MALOIT