676
FXUS61 KBOX 240222
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1022 PM EDT THU MAY 23 2013
SYNOPSIS
A COLD FRONT WILL MOVE SLOWLY INTO NEW ENGLAND FRIDAY. LOW
PRESSURE WILL DEVELOP ON THIS FRONT...CAUSING THE SYSTEM TO LINGER
ACROSS THE REGION THROUGH THE WEEKEND. THIS WILL BRING SHOWERS AND
COOLER CONDITIONS...WITH A FEW THUNDERSTORMS POSSIBLE. SOME OF THE
RAINFALL WILL BE HEAVY AT TIMES. CONDITIONS SHOULD IMPROVE ON
MONDAY. DRY WEATHER AND SEASONABLE TEMPS ARE EXPECTED INTO THE
MIDDLE OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
10 PM UPDATE...
MAIN CHANGE WITH THIS FORECAST PACKAGE WAS TO ISSUE A FLASH FLOOD
WATCH FOR THE WESTERN HALF OF SOUTHERN NEW ENGLAND. PORTIONS OF
THE WATCH AREA HAD ALREADY SEEN MORE THAN 1 INCH OF RAIN EARLIER
TODAY. EXPECTING ANOTHER AREA OF MODERATE TO HEAVY RAINFALL TO
IMPACT THIS REGION LATER TONIGHT.
BASED ON LATEST MODEL GUIDANCE...INCREASED POPS FOR MEASURABLE
RAINFALL SLIGHTLY. ALSO TRIED TO ADJUST TIMING BASED ON RADAR
DATA. ADJUSTED TEMPERATURES AND DEW POINTS TO REFLECT LATEST
OBSERVED TRENDS.
PREVIOUS DISCUSSION...
TONIGHT...COLD FRONT MOVES SLOWLY EAST FROM CENTRAL NEW YORK AND
WILL APPROACH WESTERN NEW ENG TOWARD DAYBREAK AS MID LEVEL TROF
AMPLIFIES OVER THE GRT LAKES. SNE WILL BE UNDER THE RIGHT
ENTRANCE REGION OF THE UPPER JET WHICH WILL PROVIDE GOOD FORCING
ACTING ON HIGH PWAT AIRMASS TO BRING LOCALLY HEAVY RAINFALL TO
SNE. SHOWERS AND ISOLD TSTMS WILL BE ONGOING ACROSS THE INTERIOR
IN THE EVENING...THEN FOCUS WILL SHIFT TO THE COASTAL PLAIN AFTER
MIDNIGHT AS LOW LEVEL JET STRENGTHENS ACROSS SE NEW ENG.
INSTABILITY WILL BE WEAKENING OVERNIGHT AND EVEN ELEVATED
INSTABILITY PARAMETERS ARE MARGINAL. STILL CAN NOT RULE OUT ISOLD
TSTMS GIVEN DEEP SYNOPTIC FORCING...BUT LACK OF INSTABILITY SHOULD
LIMIT RAINFALL RATES. AREAS OF URBAN AND POOR DRAINAGE FLOODING
LIKELY OVERNIGHT IN EASTERN NEW ENG.
SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/
HIGH AMPLITUDE TROF FORECAST TO CLOSE OFF OVER THE MID ATLC
REGION ON FRIDAY WITH SOUTHERLY FLOW ALOFT. SFC LOW DEVELOPS ON
THE FRONT WHICH WILL SLOW ITS EWD PROGRESS ACROSS SNE. LOW LEVEL
JET WILL BE SITUATED JUST E OF CAPE COD IN THE MORNING WITH AXIS
OF HEAVY RAINFALL CONFINED TO THE CAPE/ISLANDS...BEFORE MOVING E
IN THE AFTERNOON. HOWEVER...SHOWERS WILL PERSIST ALL DAY ACROSS
MUCH OF THE REGION WITH DEEP MOISTURE AXIS IN PLACE AND SFC WAVE
MOVING ALONG FRONTAL BOUNDARY. IN FACT...THIS HAS A WINTER LOOK
TO IT WITH DECENT LOW LEVEL FRONTOGENESIS AND DEFORMATION AXIS
SETTING UP ACROSS WESTERN NEW ENG NW OF SFC LOW. TEMPS WILL
LIKELY FALL INTO THE 50S OVER NW HIGHER TERRAIN AS FRONT MOVES TO
THE EAST...BUT SHOULD REACH WELL INTO 60S TO AROUND 70 ACROSS SE
NEW ENG WHICH WILL REMAIN E OF THE BOUNDARY FOR MOST OF THE DAY.
THE FRONT SHOULD REACH THE I95 CORRIDOR BY LATE AFTERNOON.
LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
HIGHLIGHTS...
* SLOW MOVING UPPER LEVEL SYSTEM WILL KEEP SHOWERS AND COOLER
TEMPS FOR THE WEEKEND
* IMPROVEMENTS BEGIN ON MONDAY...WITH DRIER BUT COOL CONDITIONS
* MODERATING TEMPERATURES ARRIVE BY LATE NEXT WEEK
OVERVIEW AND MODEL PREFERENCES...
ALL OPERATIONAL MODELS NOW ON BOARD WITH DEVELOPING AMPLIFIED
UPPER LEVEL PATTERN ACROSS THE LOWER 48...WITH DIGGING TROUGHS ON
THE EAST AND WEST COASTS WITH BUILDING RIDGE ACROSS THE CENTRAL
U.S. THROUGH A GOOD PORTION OF THIS PERIOD. H5 CUTOFF LOW DEVELOPS
ACROSS THE MID ATLC THEN SLOWLY MOVES INTO THE REGION THIS
WEEKEND...WITH SURFACE LOW DEVELOPING ALONG SLOWLY MOVING COLD
FRONT. LOWERED CONFIDENCE ON TIMING THE EXIT OF THE LOW...
HOWEVER. BY EARLY NEXT WEEK...THOUGH...SHOULD SEE IMPROVING
CONDITIONS BUT COOL TEMPS. TEMPS START TO MODERATE BY MID WEEK.
WENT ALONG WITH 12Z GFS/00Z ECMWF AND THEIR ENSEMBLES...WHICH IS
PRETTY CLOSE TO THE WPC GUIDANCE.
DETAILS...
FRIDAY NIGHT THROUGH SUNDAY...CONTINUED CLOUDY SKIES WITH SHOWERS
AND COOL TEMPS WILL CONTINUE THROUGH MOST OF THE HOLIDAY WEEKEND.
SURFACE LOW PRES TRAPPED WITH ITS UPPER LEVEL CUTOFF LOW WILL
SLOWLY MOVE ACROSS THE REGION...WITH PERIODS OF HEAVY RAINFALL
ANYTIME DURING THIS TIMEFRAME. CURRENT QPF FORECAST SUGGESTS
POSSIBILITY OF 1-2 INCHES OF GENERAL RAIN WITH THE HIGHEST AMOUNTS
ACROSS THE CT VALLEY AND SW NH. HOWEVER...WITH THE CHANCE OF
THUNDER...COULD SEE LOCALIZED FLOODING ESPECIALLY ACROSS CENTRAL
AND WESTERN AREAS WITH GOOD LOW LEVEL MOISTURE INFLOW. WILL
CONTINUE TO MONITOR FOR POTENTIAL OF FLOODING ALONG RIVERS AND LOW
LYING AREAS.
TEMPS WILL BECOME RATHER CHILLY ACROSS S NH/W MA SAT NIGHT AS LOW
PRES SPINS ACROSS E MA...WITH N-NW WINDS IN PLACE. MOS GUIDANCE
SUGGESTS READINGS FALLING BACK TO THE MID-UPPER 30S ACROSS THE
HIGHER TERRAIN. CAN NOT RULE OUT THE REMOTE POSSIBILITY OF SOME
MIXING OVER THE HIGHEST TERRAIN OF SW NH.
FOR NOW...LOOKS LIKE THE LOW AND UPPER LEVEL SYSTEM WILL SLOWLY
MOVE NE DURING SUNDAY...BUT PRECIP WILL LINGER INTO SUN NIGHT
BEFORE TAPERING OFF FROM SW-NE OVERNIGHT SUN. DAYTIME HIGHS WILL
ONLY BE IN THE 50S THROUGH THE WEEKEND.
MONDAY...TRANSITION DAY AS HIGH PRES BUILDS OUT OF CENTRAL CANADA.
MAY STILL SEE SOME WIDELY SCT SHOWERS ACROSS S NH/NE MA EARLY BUT
WILL PUSH NE. WILL CONTINUE COOL...BUT READINGS SHOULD REACH THE
60S.
TUESDAY-THURSDAY...HIGH PRES WILL SHIFT TO THE MID ATLC COAST THEN
OFFSHORE DURING THIS TIMEFRAME. EXPECT A DRY FORECAST WITH SLOWLY
MODERATING TEMPS.
AVIATION /02Z FRIDAY THROUGH TUESDAY/
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
OVERVIEW...MODERATE CONFIDENCE.
TONIGHT...EXPECT VFR-MVFR CIGS THIS EVENING TO LOWER TO IFR-LIFR
WITH AREAS OF FOG AND MVFR-IFR VSBYS DEVELOPING. AREAS OF
SHOWERS/SCT TSTMS ACROSS CT VALLEY INTO SW NH WILL EXPAND E
OVERNIGHT WITH STRONG SW FLOW AT SURFACE AND ALOFT. LOCALLY HEAVY
RAINFALL LIKELY. LOCAL LLWS POSSIBLE LATE TONIGHT ACROSS CAPE AND
ISLANDS AS LOW LEVEL JET STRENGTHENS ACROSS REGION.
FRIDAY...MVFR-IFR CIGS/VSBYS CONTINUE THROUGH THE DAY. WINDS SHIFT
TO W-NW ACROSS WESTERN AREAS DURING THE AFTERNOON...THEN LATE IN
THE DAY ACROSS THE E. LOCALLY HEAVY RAINFALL MAINLY IN THE
MORNING. LLWS LIKELY ACROSS CAPE/ISLANDS THROUGH MIDDAY.
KBOS TERMINAL...MODERATE CONFIDENCE. EXPECT LOWERING CIGS TO IFR
TONIGHT WITH SHOWERS INCREASING. SCT TSTMS POSSIBLE.
KBDL TERMINAL...HIGH CONFIDENCE. EXPECT MVFR CIGS/VSBYS THIS
EVENING TO BECOME IFR AS WIDESPREAD SHOWERS CONTINUE THROUGH A
GOOD PORTION OF THE NIGHT. A FEW TSTMS THROUGH MIDNIGHT POSSIBLE.
PRECIP SHOULD LESSEN FRIDAY MORNING...BUT SOME LIGHT SHOWERS
LINGER.
OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY...
FRIDAY NIGHT THROUGH SUNDAY...LOW TO MODERATE CONFIDENCE. VERY
UNSETTLED PATTERN WITH VARIABILITY BETWEEN VFR CONDITIONS AND
MVFR/IFR CONDITIONS IN SHRA/SCT TSRA/FOG. IMPROVING CONDITIONS
DURING SUNDAY NIGHT FROM SW TO NE.
MONDAY-TUESDAY...MODERATE TO HIGH CONFIDENCE. VFR. LOW PROB OF
MVFR CIGS ACROSS S NH/N MA EARLY MON THEN IMPROVING. LOW
CONFIDENCE ON SEA BREEZE DEVELOPMENT.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
HIGH CONFIDENCE THROUGH FRIDAY.
LOW LEVEL JET WILL BRING NEAR SCA GUSTS ON THE WATERS THROUGH
TONIGHT...DIMINISHING WEST OF THE CANAL LATER TONIGHT AS THE LLJ
MOVES TO THE EAST. STRONG LOW LEVEL INVERSION WILL LIMIT GUSTS SO
GALES NOT EXPECTED. PERSISTENT SW FLOW WILL RESULT IN BUILDING
SEAS THROUGH FRIDAY. WINDS WILL DIMINISH ON FRIDAY AS THE LLJ
MOVES E OF THE WATERS. EXPECT LOW VSBYS IN FOG AND LOCALLY HEAVY
SHOWERS. ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE.
OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY...
FRIDAY NIGHT...LOW TO MODERATE CONFIDENCE. LOW PRES AND COLD FRONT
WILL SLOWLY CROSS THE WATERS...THEN STALL ALONG THE EASTERN NEAR
SHORE WATERS. EXPECT SW GUSTS UP TO 20 KT EARLY...THEN WILL
DIMINISH. LOW PROB FOR THUNDER. AREAS OF LOW VSBYS IN HEAVIER
SHOWERS AND PATCHY FOG. SEAS WILL REMAIN AOA 5 FT MAINLY OVER THE
OPEN WATERS.
SATURDAY-SUNDAY...LOW CONFIDENCE MAINLY FOR TIMING. AS LOW PRES
STALLS ACROSS E MA/MASS BAY...WILL SEE LIGHT/VRBL WINDS EXCEPT
N-NW OVER THE WESTERN WATERS LATER SAT...WHICH WILL SHIFT TOWARD
THE EASTERN WATERS DURING SUN. SEAS REMAIN HIGH. LOW CHANCE OF
TSTMS SAT-SAT NIGHT. LOW PROB OF GUSTS UP TO 25 KT SUN.
MONDAY-TUESDAY...LOW TO MODERATE CONFIDENCE. WINDS BECOME W WITH
GUSTS UP TO 20 KT MON...THEN DIMINISH MON NIGHT-TUE. SEAS AROUND 5
FT ON THE OUTER WATERS MON...THEN SUBSIDING.
TIDES/COASTAL FLOODING
EAST COAST OF MA THIS WEEKEND...
ASTRONOMICAL HIGH TIDES WILL OCCUR THIS WEEKEND INTO EARLY NEXT
WEEK. WITH SURFACE LOW WOBBLING OVER SOUTHERN NEW ENGLAND SATURDAY
AND INTO SUNDAY...EXPECT GUSTY NORTHERLY TO NORTHWEST WINDS
ESPECIALLY DURING THE DAYTIMES HOURS. AT BOSTON...A HIGH TIDE OF
11.9FT WILL OCCUR ON FRIDAY NIGHT AT 11:21 PM AND 12.2 FT EARLY
SUNDAY MORNING AT 12:12 AM. EXPECT A LIGHT SOUTHERLY WINDS DURING
THE FRIDAY HIGH TIDE SO THIS IS LESS THAN A CONCERN. LOOKING AT
THE SUNDAY MORNING HIGH TIDE...NORTHERLY TO NORTHWESTERLY WINDS
MAY HELP INCREASE THE SURGE ESPECIALLY FOR CAPE COD BAY. RIGHT NOW
ONLY EXPECT MINOR SPLASHOVER ACROSS NORTH FACING BEACHES. WILL
NEED TO CONTINUE TO MONITOR AND UPDATE WITH THE LATEST FORECAST
GUIDANCE.
BOX WATCHES/WARNINGS/ADVISORIES
CT...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR CTZ002>004.
MA...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR MAZ002>004-
008>012-026.
NH...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR NHZ011-015.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT FRIDAY FOR ANZ232.
SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ233-234.
SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ230-
236.
SMALL CRAFT ADVISORY UNTIL 4 AM EDT FRIDAY FOR ANZ231-251.
SMALL CRAFT ADVISORY UNTIL 6 PM EDT FRIDAY FOR ANZ235-237.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT FRIDAY FOR ANZ250.
SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ254>256.
SYNOPSIS...KJC/EVT
NEAR TERM...BELK/EVT/KJC
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT
MARINE...KJC/EVT
TIDES/COASTAL FLOODING...STAFF
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