Special Weather Statement, NWS Boston/Norton, MA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
207 AM EDT MON SEP 5 2011

.SYNOPSIS...
A SLOW MOVING COLD FRONT PUSHING EAST FROM THE GREAT LAKES WILL
BRING A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH MONDAY...MAINLY
ACROSS THE INTERIOR. MORE WIDESPREAD SHOWERS AND THUNDERSTORMS
WITH HEAVY RAIN ARE LIKELY MONDAY NIGHT INTO TUESDAY MORNING AS
THE FRONT MOVES THROUGH THE REGION. THE FRONT MAY PROVIDE THE
FOCUS FOR SHOWERS IN THE SOUTHERN HALF OF THE AREA MIDWEEK. HIGH
PRESSURE IS EXPECTED TO PROVIDE DRY WEATHER INTO THE WEEKEND.
HURRICANE KATIA WILL BE MONITORED CLOSELY AS IT MOVES INTO THE
WESTERN ATLANTIC OFF THE MID ATLANTIC COAST. CURRENT PROJECTIONS
ARE THAT IT MAY THEN TURN NORTHEAST AND PASS WELL SOUTH OF
NANTUCKET...BUT THIS CAN STILL CHANGE...SO STAY TUNED TO THE
LATEST ADVISORIES FROM THE NATIONAL HURRICANE CENTER.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
145 AM UPDATE...
WE STILL HAVE ABOUT 500 J/KG MLCAPE FAR W ZONES AND SHOWERS/SCT
TSTMS ARE LIFTING NWD FROM E NYS. CONVECTION IS LOCATED IN THETA-E
RIDGE AXIS WHICH EXTENDS INTO OUR NW ZONES SO CANT RULE OUT A FEW
SHOWERS OR A TSTM EARLY THIS MORNING...OTHERWISE MAINLY DRY
CONDITIONS WILL PREVAIL FURTHER E.

MAIN FOCUS FOR SHOWERS/TSTMS OVERNIGHT WILL BE NORTH AND WEST OF
THE REGION AS COLD FRONT PUSHES E FROM THE E LAKES.

MILD AND HUMID NIGHT WITH MIN TEMPS MID TO UPPER 60S. PATCHY LATE
NIGHT FOG WILL DEVELOP AGAIN.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
MONDAY...
STRONG NEGATIVELY TILTED TROF AND ASSOCIATED SFC COLD FRONT SLOWS
THROUGH NYS IN RESPONSE TO STRONG ATLANTIC RIDGE. GUIDANCE
SUGGESTS MUCH OF THE FORCING ASSOCIATED WITH THIS SYSTEM STAYS WELL
W OF THE AREA...ALTHOUGH MOST RECENT RUNS SLIGHTLY MORE
PROGRESSIVE. WHILE THE SYSTEM IS OVERALL QUITE ROBUST...AND BEGINS
TO TAP INTO MOISTURE FROM LEE...WITH MUCH OF THE BEST FORCING
REMAINING W...SUSPECT MUCH OF SNE WILL REMAIN DRY THROUGH THE DAY
MON...ESPECIALLY E OF ORH. INSTABILITY LOOKS TO BE LOW TO MODERATE
AT BEST WITH LITTLE ML OR SB CAPE. THIS IS LARGELY DUE TO
MOISTENING UPPER LVLS AND COOL SFC DUE TO FAIR AMOUNT OF CLOUD
COVER EXPECTED BY SUN UP. GIVEN THIS HAVE DROPPED TS CHANCES DOWN
TO ISOLD FOR THE MON TIMEFRAME. IN TERMS OF TEMPS...CLOUDS WILL
LIKELY KEEP AREAS W OF ORH COOL AND IN THE 70S...WHILE ERN
PORTIONS OF THE FA MAY WELL REBOUND INTO THE 80S AGAIN WITH MORE
SUNSHINE EXPECTED.

THE KEY FEATURE WITH THE FORECAST WILL BE RAINFALL POTENTIAL. WITH
MUCH OF THE FORCING REMAINING TO THE E AND DIMINISHING MID LVL
LAPSE RATES NEITHER CONVECTION OR STRATIFORM RAIN LOOK TO BE A
MAJOR ISSUE MUCH OF THE DAY SAVE FOR THE FAR WRN INTERIOR. THIS
SYSTEM DOES HAVE A TROPICAL CONNECTION HOWEVER...DRAWING SOME
MOISTURE FROM LEE AS IT WEAKENS...INCREASING PWATS TO AROUND 2.0
INCHES. GUIDANCE HAS BECOME SLIGHTLY MORE PROGRESSIVE IN TIMING SO
WILL INCREASE POPS TOWARD EVENING. THIS SLIGHTLY FASTER SUGGESTION
FAVORED BY THE ECMWF/GFS/GEFS MEAN IS FAVORED AS THE AMPLITUDE OF
THE TROF WEAKENS SIGNIFICANTLY AS IT PUSHES INTO THE RIDGE
UPSTREAM. SEE HYDROLOGY SECTION BELOW FOR A MORE DETAILED
DISCUSSION OF QPF/HYDRO ISSUES.

MONDAY NIGHT...
ADJUSTED TIMING OF COLD FRONT/UPPER LVL WAVE THROUGH THE REGION
BASED ON A BLEND OF ECMWF/GFS TIMING. THIS SUGGESTS THE FRONT IS
JUST REACHING WRN ZONES BY EVENING...THEN SHIFTING TO THE S COAST
BY AROUND 06Z. MUCH OF THE BEST FORCING FOR PRECIP REMAINS BEHIND
THE FRONT AS LLVL WIND PROFILES HAVE A SLIGHT BEND TOWARD THE
FRONT...SUGGESTING OVERRUNNING. DUE TO THE OVERALL PATTERN LEANING
TOWARD A FASTER FLOW REGIME...SUSPECT PDS OF HEAVY MAIN WILL MOVE
THROUGH WITH THE REGION RATHER QUICKLY ALONG WITH THE FRONT. THE
COOL AND DRIER AIRMASS ASSOCIATED WITH THE UPPER TROF ALSO IS
SLIGHTLY FASTER AT PUSHING IN PER LATEST GUIDANCE. GIVEN THIS
EXPECTING THAT MUCH OF THE REGION WILL BE OUT OF THE MORE
STRATIFORM RAIN TOWARD DAYBREAK. ELEVATED K VALUES SUGGEST SOME
CONDITIONAL INSTABILITY ALOFT...SO WILL CONTINUE WITH ISOLD TS
NEAR FROPA. THE CONVECTIVE POTENTIAL MAY LEAD TO SHORT LIVED ISOLD
HEAVIER BANDS OF RAIN WHICH MAY NEED TO BE MONITORED. AS MENTIONED
EARLIER...SEE HYDRO SECTION BELOW FOR HYDRO ISSUES WITH THIS
FROPA.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
* FRONT EXITS TUE MORNING AND STALLS SOUTH OF THE AREA BRINGING
  CHANCES OF PRECIP TO AREAS MAINLY SOUTH OF THE MASS PIKE MIDWEEK
* LEE REMNANTS MAY STAY TO OUR SW...
* KATIA IS POWERFUL STORM AND WILL NEED TO BE MONITORED...BUT
  LATEST INDICATIONS ARE THAT IT WILL PASS TO SOUTH OF NANTUCKET
  LATE IN WEEK.

OVERVIEW AND MODEL PREFERENCES...
FRONT PASSES ACROSS SOUTHEASTERN AREAS TUE MORNING THEN STALLS.
REMNANTS OF LEE ARE EXPECTED TO REACH THE MID ATLANTIC REGION THEN
POSSIBLY DISSIPATE. CURRENT PROJECTIONS ARE FOR HURRICANE KATIA TO
MAKE A RUN TOWARD NORTH CAROLINA...THEN...HOPEFULLY...BOOMERANG
BACK OUT TO THE EAST-NORTHEAST WITHOUT MAKING LANDFALL...PASSING
A FEW HUNDRED MILES SOUTH OF NANTUCKET IN THE FRIDAY-SATURDAY
TIMEFRAME. THE STALLED FRONT TO THE SOUTH OF NEW ENGLAND MAY
WANDER NORTHWARD MIDWEEK GIVING A CHANCE OF SHOWERS MAINLY TO
SOUTHERN PORTIONS OF THE FORECAST AREA. QUIET WEATHER EXPECTED FOR
THE WEEKEND.

AS FOR MODEL PREFERENCES...WENT MORE WITH A 12Z ECMWF/GFS BLEND FOR
MOST FORECAST PERIODS. THINK THE NAM IS OVERDONE AND TOO SLOW WITH
THE FRONT EXITING THE REGION ON TUE. ONE EXCEPTION IS THAT WE PREFERRED
THE WETTER NAM/ECMWF FOR WED HOWEVER...ESPECIALLY ALONG THE SOUTH
COAST.

DETAILS...
TUESDAY...AM PREFERRING THE QUICKER TIMING OF THE ECMWF AND GFS
WITH THE FRONT EXITING THE SOUTH COAST IN IN THE MORNING HOURS.
FEEL THAT NAM IS TOO SLOW. QPF FROM LOCALLY HEAVY RAIN SHOWERS COULD
BE AS HIGH AS AN INCH IN SOUTHEAST AREAS BUT ECMWF IS MUCH LOWER
AND HPC HAS BACKED OFF ON PRECIPITATION AMOUNTS AS WELL. WILL KEEP
SKIES CLOUDY FOR MOST AREAS BUT EXPECT PARTIAL SUNSHINE LATER IN
THE DAY NORTH OF ROUTE 2 IN NORTHERN MA.

TUESDAY NIGHT THROUGH THURSDAY...THIS IS A MUCH LOWER THAN NORMAL
CONFIDENCE FORECAST. THE FRONT STALLS JUST SOUTH OF SOUTHERN NEW
ENGLAND. THE GFS IS NOW DRY FOR WED BUT THE NAM AND ECMWF ARE
WET...WITH THE FRONT MEANDERING NORTHWARD A BIT. SOME MOSITURE MAY
BE EJECTED NORTHEASTWARD FROM TIME TO TIME FROM THE REMNANTS OF
TROPICAL STORM LEE...BUT THE BULK OF LEE'S IMPACT IS EXPECTED TO
REMAIN WELL TO OUR SOUTHWEST. HAVE FORECASTED A CHANCE OF SHOWERS
MAINLY SOUTH OF THE MASS PIKE THROUGH THE PERIOD. NORTHEAST WINDS
SHOULD HOLD TEMPERATURES TO THE UPPER 60S AND LOWER 70S FOR MAXES
AND 50S FOR MINS.

THURSDAY NIGHT THURSDAY THROUGH SATURDAY NIGHT... THIS TIME FRAME
IS HIGHLY DEPENDENT UPON THE MOVEMENT OF HURRICANE KATIA. PLEASE
REFER TO THE LATEST FORECASTS FROM THE NATIONAL HURRICANE CENTER.

AT THIS TIME...IT APPEARS THAT A WEAK UPPER LEVEL RIDGE OF HIGH
PRESSURE WILL EXIST OVER NORTHERN NEW ENGLAND WITH WEAK HIGH
PRESSURE ALSO AT THE SURFACE. IT SHOULD BE ENOUGH TO PROVIDE SOME
SUNSHINE AND DRY WEATHER. THE GFDL...CMC...GFS...HWRF...AND ECMWF
MODELS HAVE ALL COME INTO LINE WITH EACH OTHER ON THIS 12Z MODEL
CYCLE. THEY BRING KATIA ON A TRACK DANGEROUSLY CLOSE TO NORTH
CAROLINA BUT THEN DO AN ABOUT FACE AND BOOMERANG KATIA TO THE
EAST-NORTHEAST PASSING BETWEEN 300 AND 400 MILES TO THE SOUTH OF
NANTUCKET. WHILE WE HOPE THIS IS THE CASE...MODELS HAVE BEEN
SHIFTING CONSIDERABLY OVER THE PAST SEVERAL DAYS. WE WILL NEED TO
SEE THIS TRACK BECOME ESTABLISHED OVER SEVERAL MODEL CYCLES IN
ORDER TO HAVE SIGNIFICANT CONFIDENCE IN THIS FORECAST. IF THIS
TRACK IS INDEED WHAT HAPPENS...THEN WE COULD HAVE 20-30 KT WINDS
AND SEAS BUILDING TO 10 TO 15 FT ON OUR COASTAL WATERS. EXPECTS
LARGE SWELLS AND DANGEROUS RIP CURRENTS TO BE ARRIVING AS EARLY AS
WEDNESDAY ON THE SOUTHERN COASTAL WATERS.

SUNDAY...HIGH PRESSURE SHOULD STILL REMAIN IN CONTROL PROVIDING
SUNSHINE AND DRY WEATHER. LITTLE CHANGE TO MOSGUIDE TEMPS WITH
HIGHS MAINLY 70 TO 75. CLOUDS WILL INCREASE LATE IN THE DAY AS
ANOTHER FRONT BEGINS TO APPROACH FOR EARLY NEXT WEEK.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
FORECASTER CONFIDENCE LEVELS...
  LOW...LESS THAN 30 PERCENT
  MODERATE...30 PERCENT TO 60 PERCENT
  HIGH...GREATER THAN 60 PERCENT

THROUGH 12Z...
EXPECT CIGS TO DETERIORATE EARLY THIS MORNING WITH AREAS OF IFR
DEVELOPING...ESPECIALLY INTERIOR AND CAPE/ISLANDS. PATCHY FOG ALSO
EXPECTED.

TODAY...
MEDIUM CONFIDENCE. AREAS OF IFR THIS MORNING SHOULD IMPROVE TO A
PERIOD OF VFR THIS AFTERNOON...BUT MVFR MAY PERSIST ACROSS NW
ZONES. SHOWERS MOVE INTO W ZONES THIS AFTERNOON. SW WIND GUSTS TO
25 KT EXPECTED OVER E TERMINALS.

TONIGHT...
MEDIUM TO HIGH CONFIDENCE IN OVERALL TREND OF CONDITIONS LOWERING
TO IFR/LIFR IN STRATUS AND PATCHY FOG AS SHOWERS WITH LOCALLY
HEAVY RAFL MOVE ACROSS THE REGION. CONFIDENCE IS LOWER ON TIMING.

MONDAY...
MEDIUM CONFIDENCE. EXPECT IFR IN SHOWERS AND PATCHY FOG...POSSIBLY
IMPROVING TO VFR N ZONES IN THE AFTERNOON AS DRIER AIR TRIES TO
MOVE IN FROM THE N.

KBOS TERMINAL...
LOW TO MEDIUM CONFIDENCE IN TAF. MAY SEE A BRIEF PERIOD OF MVFR
CIGS THIS MORNING...BUT ANY MVFR SHOULD IMPROVE TO VFR BY MIDDAY.
CONDITIONS LOWERING BACK TO MVFR BY THIS EVENING AS SHOWERS MOVE
IN BUT LOW CONFIDENCE ON TIMING. SW WIND GUSTS TO 20-25 KT THIS
AFTERNOON.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY...MODERATE CONFIDENCE. MVFR CONDITIONS LIKELY IN RAIN
SHOWERS...SOME HEAVY...MAINLY SOUTHERN SECTIONS IN THE MORNING.
CONDITIONS IMPROVING TO VFR MOST TERMINALS DURING THE AFTERNOON.

WEDNESDAY...LOW TO MODERATE CONFIDENCE. VFR NORTH OF THE MASS PIKE.
SOUTH OF THE PIKE...MAINLY VFR WITH PERIODS OF MVFR IN RAIN.

THURSDAY...LOW CONFIDENCE. VFR WITH SCATTERED SHOWERS...MAINLY
SOUTHERN AREAS.

&&

.MARINE...
SEAS GRADUALLY INCREASE IN SWELL OVERNIGHT...WITH EXPECTATION THEY
WILL REACH 5 FT OVER ALL OUTER WATERS BY MORNING. WILL ISSUE AN
SCA FOR THESE SEAS THROUGH THE DAY TOMORROW...ALTHOUGH SWELL WILL
LIKELY CONTINUE TO BUILD THROUGH AT LEAST MON NIGHT. A STRONG LLJ
WILL BUILD OVER THE REGION DURING THE DAY TOMORROW AND SUSPECT
THIS WILL BE TAPPED...ALLOWING GUSTS TO 25 KT ESPECIALLY NEAR
SHORE DURING THE LATE MORNING AND AFTERNOON HOURS. WILL ALSO ISSUE
A SHORTER PERIOD SCA FOR THE NEAR SHORE COASTAL ZONES FROM LATE
MORNING THROUGH THE AFTERNOON MONDAY FOR EXPECTED 25 KT GUSTS.

OUTLOOK...TUESDAY THROUGH FRIDAY...

TUESDAY...SEAS AND WINDS DIMINISH SLIGHTLY AS HIGH PRESSURE STARTS
TO BUILD OVER THE WATERS...BUT SEAS STILL REMAIN ABOVE 5 FEET
PARTICULARLY ON THE OUTER WATERS.

WEDNESDAY AND THURSDAY...SEAS SLOWLY BUILD..TO 10 FT ON THE
SOUTHERN OUTER WATERS...AS LONG PERIOD SWELL REACHES THE COASTAL
WATERS FROM HURRICANE KATIA. NORTHEAST WINDS REMAIN BELOW 25 KT.

FRIDAY...DEPENDING ON THE TIMING OF HURRICANE KATIA PASSING TO THE
SOUTH OF THE REGION...AGAIN BASED ON THE LATEST TRENDS...THERE IS
A CHANCE THAT SOUTHEASTERN WATERS WILL HAVE WINDS OF STRONG SMALL
CRAFT ADVISORY LEVELS. SEAS WILL CONTINUE TO BUILD TO 10 TO 13
FEET ON THE SOUTHERN OUTER WATERS.

&&

.HYDROLOGY...
THE AFOREMENTIONED SLOW MOVING TROF AND SFC FRONT PUSHING E FROM
THE GREAT LAKES WILL CONTINUE TO SLOW AT FIRST AS IT ATTEMPTS TO
PUSH INTO THE UPSTREAM RIDGE. THIS SUGGESTS THAT MUCH OF THE
FORCING/MOISTURE PLUME FROM LEE WILL REMAIN WELL W OF THE FA
THROUGH THE DAY MON. THEREFORE...NOT EXPECTING MUCH IN THE WAY OF
QPF DURING THE DAY MON SAVE FOR EXTREME WRN PORTIONS OF THE AREA.
AS THE PATTERN BREAKS DOWN TOWARDS EVENING...THE SYSTEM LOOKS TO
BE MORE PROGRESSIVE...AND DOES NOT ALLOW FOR BANDS OF HEAVIER RAIN
TO LINGER OVER THE REGION. GUIDANCE /AND SUBSEQUENTLY HPC/ HAS
BACKED OFF ON TOTAL QPF THROUGH THE DAY 3 PERIOD. EVEN WITH PWATS
APPROACHING 2.5 INCHES OVERNIGHT AHEAD OF THE FRONT...THE SYSTEM
LOOKS LIKE IT MAY BE MOVING FAST ENOUGH TO PUSH HEAVIER BANDS
THROUGH BEFORE CAUSING SERIOUS RIVER/SMALL STREAM RISES.
URBAN/SMALL STREAM ISSUES MAY BE THE KEY TO WATCH...AS THE
AFOREMENTIONED ISOLD ELEVATED CONVECTION COULD TAP THE TROPICAL
MOISTURE AND ALLOW BRIEF HEAVY DOWNPOURS.

FFG IS GENERALLY 1.5+ AND 2+ INCHES PER HOUR AND 3 HOUR
TOTALS RESPECTIVELY...AND 3+ INCHES FOR 6 HOUR TOTALS EVEN IN WRN
MA WHERE THE HEAVIER RAINS FROM IRENE FELL. GIVEN THE LEAN TOWARD
A MORE PROGRESSIVE AND LOWER TOTAL QPF SOLN OF LATE WILL HOLD OFF
ON A FLOOD OR FLASH FLOOD WATCH FOR NOW. THIS WAS AGREED UPON BY
NEIGHBORING OFFICES AS WELL. WILL HAVE TO MONITOR GUIDANCE SHOULD
IT BEGIN TO LEAN TOWARD THE MORE AMPLIFIED AND SLOWER NAM...WHICH
FAVORS A VERY STRONG SLY LLJ ADVECTING THE TROPICAL MOISTURE AHEAD
OF THE FRONT OVERNIGHT. A WATCH STILL MAY BE NECESSARY IF THE
SYSTEM LOOKS TO BE SLOWER THAN CURRENTLY SUGGESTED.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 8 PM EDT THIS
     EVENING FOR ANZ230>234-236-251.
     SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT THIS
     EVENING FOR ANZ235-237-250.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
     ANZ254>256.

&&

SYNOPSIS...DOODY/GAF
NEAR TERM...KJC/DOODY
SHORT TERM...DOODY
LONG TERM...GAF
AVIATION...KJC/GAF
MARINE...DOODY/GAF
HYDROLOGY...

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>