480
FXUS61 KBOX 081058
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
658 AM EDT WED APR 8 2020
SYNOPSIS
WEAK AREA OF LOW PRESSURE TRACKING OVER OR JUST SOUTH OF NEW ENGLAND
WILL SPREAD A PERIOD OF RAIN ACROSS THE REGION THIS MORNING. AS THE
LOW DEPARTS A DRYING TREND DEVELOPS THIS AFTERNOON ALONG WITH A FEW
BREAKS OF SUNSHINE LATE IN THE DAY. ANOTHER SYSTEM MOVES IN
THURSDAY, BRINGING MORE RAIN AND SCATTERED THUNDERSTORMS. SCATTERED
SHOWERS ARE POSSIBLE THURSDAY NIGHT THROUGH FRIDAY. DRIER WEATHER
FOR THIS WEEKEND BEFORE OUR NEXT WET WEATHER SYSTEM EARLY NEXT
WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
700 AM UPDATE ...
THE BACK EDGE OF THE PRECIP IS MOVING QUICKLY INTO
WESTERN/CENTRAL MA AND CT. PRECIP AMOUNTS HAVE GENERALLY ADDED
UP TO A FEW HUNDREDTHS IN NORTHERN ZONES TO A FEW TENTHS IN
NORTH WESTERN CT. NO MAJOR CHANGES TO THE FORECAST THIS MORNING.
PREVIOUS DISCUSSION...
TODAY ...
MID LEVEL WARM FRONT AND ASSOCIATED SURFACE WAVE MOVING ACROSS OR
JUST SOUTH OF THE REGION THIS MORNING. GIVEN NW FLOW ALOFT DEEP
LAYER MOISTURE AND INSTABILITY WILL STRUGGLE TO ADVECT NORTHEAST.
THEREFORE LOWEST POPS AND LEAST QPF WILL BE ACROSS NORTHEAST MA. IN
ADDITION CONVECTION CURRENTLY OVER SOUTHEAST PA INTO NJ APPEARS TO
BE PRECLUDING DEEP LAYER MOISTURE AND INSTABILITY FROM ADVECTING
NORTHEAST. FURTHERMORE, LEFTOVER DRY AIR (DEW PTS IN THE 30S) FROM
TUE INITIALLY ERODING LEADING EDGE OF PRECIP AS IT ATTEMPTS TO ENTER
EASTERN MA DURING THE PREDAWN HOURS. THUS LEANING TOWARD THE LOWER
QPF GUIDANCE. 00Z HREF PROBABILITY MATCHED MEAN SEEMS REASONABLE
WITH GREATEST QPF FROM WESTERN MA INTO CT, RI AND SOUTHEAST MA
INCLUDING CAPE COD AND ISLANDS WHERE UP TO 0.25 INCHES OF QPF IS
POSSIBLE. MEANWHILE OVER ESSEX COUNTY OF NORTHEAST MA ONLY A FEW
HUNDREDS IS LIKELY.
PROGRESSIVE NW FLOW ALOFT WILL RESULT IN A SHORT DURATION PERIOD OF
RAIN WITH DRYING TREND FOR THE AFTERNOON. BACK EDGE OF PRECIP SHIELD
CURRENTLY FROM UTICA NY TO LAKE GEORGE AREA. LOW LEVEL WINDS BECOME
LIGHT NORTHEAST THIS AFTERNOON BEHIND DEPARTING FRONTAL WAVE.
TYPICALLY THIS WOULD KEEP LOW CLOUDS LOCK IN ACROSS THE REGION.
HOWEVER GIVEN LOW LEVEL DRY AIR CURRENTLY OVER THE REGION WITH DEW
PTS IN THE 30S, LOWER CLOUDS WILL BE CONFINED TO WESTERN MA/CT INTO
RI AND SOUTHEAST MA THIS MORNING. THUS PARTIAL CLEARING WILL ADVECT
FROM NORTH-NORTHEAST TO SOUTHWEST THIS AFTERNOON AND ESPECIALLY LATE
IN THE DAY WHEN SOME BREAKS OF SUNSHINE ARE POSSIBLE. MODELS HAVE
BEEN TRENDING MILDER WITH EACH RUN. AS A RESULT WILL FOLLOW THESE
TRENDS WITH HIGHS TODAY IN THE LOW TO MID 50S, UPPER 50S POSSIBLE
HARTFORD TO SPRINGFIELD. NOT AS WARM AS THE PAST TWO DAYS BUT VERY
CLOSE TO NORMAL. COOLEST TEMPS ALONG THE IMMEDIATE EASTERN MA
COASTLINE INCLUDING BOSTON GIVEN THE NORTHEAST WINDS, LIMITING HIGHS
HERE TO THE UPPER 40S.
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/
TONIGHT ...
WEAK SHORT WAVE RIDGING PROVIDES THE REGION WITH DRY WEATHER AND
SEASONABLE TEMPERATURES. GIVEN LIGHT WINDS AND DEW PTS 35-40 (AT OR
ABOVE THE AVERAGE NIGHTTIME LOWS), RISK FOR PATCHY FOG ESPECIALLY
ALONG THE COAST WHERE HIGHEST DEW PTS WILL BE OBSERVED.
THURSDAY ...
CLOSED LOW JUST NORTH OF THE GREAT LAKES INTO SOUTHERN ONTARIO
EJECTS A VERY STRONG SHORT WAVE INTO NEW ENGLAND DURING THE
AFTERNOON. VERY STRONG JET DYNAMICS WITH THIS SYSTEM THAT INDUCES
979 MB TRIPLE PT/SECONDARY OVER NORTHEAST MA AROUND 21Z THU. STRONG
CYCLONIC CURVATURE TO THE MID/UPPER LEVEL FLOW COUPLED WITH PWAT
PLUME OF 1+ INCHES AND STEEP MID LEVEL LAPSE RATES SUGGEST A GOOD
BET FOR ELEVATED CONVECTION AND BRIEF HEAVY SHOWERS. IN FACT COULD
BE A FINE LINE OF LOW TOP CONVECTION. KEY FOR SURFACE BASED
CONVECTION WILL BE HOW FAR NORTH DOES WARM SECTOR TRACK BEFORE
TRIPLE PT LOW PINCHES OFF WARM SECTOR FROM ADVECTING NORTHWARD. SOME
OF THE HIGH RES GUIDANCE HINT AT WARM SECTOR BRIEFLY ADVECTING INTO
RI AND EASTERN MA WITH SURFACE TEMPS AND DEW PTS CLIMBING INTO THE
50S! SOME OF THE GUIDANCE HAS TRENDED FARTHER NORTH-NORTHEAST WITH
TRIPLE PT/SECONDARY LOW. THIS WOULD RESULT IN WARM SECTOR SURGING
FARTHER NORTH INCREASING THE THREAT OF STRONG TO SEVERE STORMS. SPC
DAY 2 FORECAST HAS ALSO TRENDED NORTHWARD WITH MARGINAL RISK NOW
INTO NYC AREA. WILL JUST HAVE TO WATCH HOW THIS EVOLVES. AS OF NOW
SB INSTABILITY APPEARS TO BE LACKING.
BREEZY CONDITIONS WILL DEVELOP IN THE WARM SECTOR LATE THU MORNING
INTO THU AFTERNOON WITH SOUTH WINDS 10-15 MPH GUSTING UP TO 25-35
MPH AT TIMES, THEN ABRUPTLY SHIFTS TO THE WEST LATE IN THE DAY WITH
THE FROPA.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
HIGHLIGHTS...
* GUSTY WINDS, LIGHT RAIN, AND HIGH ELEVATION SNOW ON FRIDAY WITH A
FEW RUMBLES OF THUNDER POSSIBLE
* POTENTIAL FOR MINOR COASTAL FLOODING THROUGH EARLY FRIDAY AROUND
HIGH TIDE ACROSS THE EAST AND SOUTH COASTS OF MA AND RI.
SEE THE TIDES AND COASTAL FLOODING SECTION BELOW FOR MORE DETAILS.
* TEMPERATURES RUNNING NEAR TO BELOW NORMAL THROUGH SATURDAY, THEN A
WARM UP SUNDAY- TUESDAY
* RAIN AND GUSTY WINDS RETURN MONDAY
DETAILS...
THURSDAY NIGHT AND FRIDAY...
BY LATE THURSDAY EVENING/EARLY OVERNIGHT HOURS THE COLD FRONT WILL
HAVE EXITED OFFSHORE USHERING IN A DRIER AIRMASS AND LEAVING
CLEARING SKIES IN ITS WAKE. STRONG JET DYNAMICS REMAIN, NOW OUT OF
THE W/NW. THIS BRINGS MID LEVEL CAA AND STEEPENING LAPSE RATES,
HELPING TO MIX DOWN A STRONG 40-50 KT 850 MB LLJ. THE STRONGEST
WINDS SHOULD REMAIN ALOFT DURING THE OVERNIGHT HOURS, BUT WITH
DIURNAL HEATING ON FRIDAY AND THE COLD POOL ALOFT THE BOUNDARY LAYER
SHOULD MIX VERY WELL ALL THE WAY UP TO AT LEAST 750 MB. THIS WILL
ALLOW FOR WIDESPREAD VERY STRONG WIND GUSTS TO MIX DOWN, POTENTIALLY
NECESSITATING A WIND ADVISORY OR EVEN A HIGH WIND WARNING; 40-50
MPH GUSTS ARE LIKELY.
EVEN THOUGH THE SFC LOW WILL BE WELL TO OUR NORTH, THE UPPER LOW
LINGERS OVERHEAD KEEPING CYCLONIC FLOW IN PLACE WITH WRAPAROUND
MOISTURE AND THE STRONG LLJ. THIS WILL MEAN SCATTERED RAIN SHOWERS,
ESPECIALLY DURING THE DAY. THIS AS DIURNAL HEATING OF THE SFC
TOGETHER WITH THE COLD POOL ALOFT CONTRIBUTE TO SOME SFC BASED
INSTABILITY WHICH COULD BRING ABOUT A THUNDERSTORMS OR TWO AS WELL.
SATURDAY AND SUNDAY...
NICE WEEKEND IN STORE, THOUGH SUNDAY LOOKS TO BE THE NICER OF THE
TWO DAYS (WARMER WITH LESS WIND). A RIDGE OF HIGH PRESSURE BEGINS TO
MOVE OVERHEAD EARLY SATURDAY, AND THIS MEANS THE PRESSURE GRADIENT
WILL BE SLOWLY RELAXING, SO WINDS LIKELY REMAIN BREEZY ON SATURDAY
BEFORE CALMING SATURDAY NIGHT AND SUNDAY. TEMPERATURES REMAIN IN THE
LOW 50S ON SATURDAY UNDER NW FLOW ON THE DOWNSTREAM SIDE OF THE
RIDGE. BY SUNDAY THOUGH, THE RIDGE AXIS APPROACHES AND SW RETURN
FLOW WARMS US UP INTO THE UPPER 50S. LOW TEMPERATURES ON SUNDAY
MORNING WERE TRENDED TOWARD THE COLDER MOS GUIDANCE TO ACCOUNT FOR
LIKELY RADIATIONAL COOLING UNDER CLEAR SKIES AND LIGHT WINDS...INTO
THE UPPER 20S AND LOW 30S.
MONDAY AND TUESDAY...
THE MILD TEMPERATURES CONTINUE ON MONDAY AND TUESDAY. HOWEVER, IT
COMES WITH THE RETURN OF WIDESPREAD RAIN. A DEEP MID LEVEL TROUGH
AND SFC LOW WILL BRING RAIN AND GUSTY WINDS AROUND MONDAY, WITH
ANOTHER POTENTIALLY WET DISTURBANCE RIGHT ON ITS HEELS.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
12Z UPDATE ... HIGH CONFIDENCE IN TRENDS, LOWER ON EXACT
DETAILS.
THIS MORNING ... RAIN IN MVFR FROM WESTERN MA INTO CT/RI AND
SOUTHEAST MA. VFR ELSEWHERE WITH LIGHT RAIN. LIGHT AND VARIABLE
WINDS TRENDING LIGHT NE.
THIS AFTERNOON ... TRENDING TOWARD VFR ALONG WITH DRIER WEATHER.
LIGHT NE WIND.
TONIGHT ... VFR IN THE EVENING BUT TRENDING TOWARD MVFR/IFR
INCLUDING PATCHY FOG. MAINLY DRY WEATHER PREVAILS.
THURSDAY ... STRONG COLD FRONT APPROACHES THE REGION AND SWEEPS
THRU THE AREA LATE IN THE DAY. MAINLY MVFR BUT IFR POSSIBLE IN
HILLY TERRAIN. WIDESPREAD SHOWERS DEVELOPING WEST TO EAST THRU
THE DAY WITH A FINE LINE OF LOW TOP SHOWERS/THUNDERSTORMS
POSSIBLE ALONG AND AHEAD OF THE FRONT. LLWS LIKELY GIVEN
MAGNITUDE OF LOW LEVEL SOUTHERLY JET. STRONG WIND SHIFT LATE IN
THE DAY WITH THE FRONTAL PASSAGE FROM SOUTH TO WEST.
KBOS TERMINAL...HIGH CONFIDENCE IN THE TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN THE TAF.
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...
THURSDAY NIGHT: VFR. STRONG WINDS WITH LOCAL GUSTS UP TO 40 KT.
FRIDAY: VFR. STRONG WINDS WITH GUSTS UP TO 45 KT. SLIGHT CHANCE
SHRA, ISOLATED TSRA.
FRIDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. WINDY WITH
GUSTS UP TO 35 KT.
SATURDAY THROUGH SATURDAY NIGHT: VFR. BREEZY.
SUNDAY: VFR.
MARINE
TODAY ... WEAK SURFACE LOW TRACKS SOUTH OF NEW ENGLAND THIS MORNING
THEN EASTWARD TO GEORGES BANK THIS AFTERNOON. MORNING RAIN GIVES WAY
TO A DRYING TREND IN THE AFTERNOON. LIGHT SSW WINDS BECOME NE THIS
AFTERNOON.
TONIGHT ... WEAK HIGH PRESSURE OVER THE WATERS PROVIDES DRY QUIET
WEATHER.
THURSDAY ... STRONG COLD FRONT SWEEPS ACROSS THE WATER LATE THU WITH
WIDESPREAD SHOWERS AND EMBEDDED THUNDER LIKELY. STRONG SSW WINDS
AHEAD OF THE FRONT ABRUPTLY SHIFTS TO THE WNW AND REMAINS STRONG
AND GUSTY.
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...
THURSDAY NIGHT: MODERATE RISK FOR GALE FORCE WINDS WITH GUSTS
UP TO 40 KT. ROUGH SEAS UP TO 11 FT. SLIGHT CHANCE OF RAIN
SHOWERS.
FRIDAY: MODERATE RISK FOR GALE FORCE WINDS WITH GUSTS UP TO
40 KT. ROUGH SEAS UP TO 12 FT. SLIGHT CHANCE OF RAIN SHOWERS,
ISOLATED THUNDERSTORMS.
FRIDAY NIGHT: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. AREAS OF ROUGH SEAS.
SATURDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. LOCAL ROUGH SEAS.
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT.
SUNDAY: WINDS LESS THAN 25 KT.
TIDES/COASTAL FLOODING
4 AM UPDATE:
NEXT 4 TIDES (MIDDAY AND MIDNIGHT TODAY AND THURSDAY) ARE
ASTRONOMICALLY HIGH AND RUN THE RISK OF MINOR COASTAL
FLOODING/INUNDATION. MIDDAY TODAY AND THEN MIDNIGHT TONIGHT MAIN
RISK IS EASTERN MA AND AGAIN TONIGHT GIVEN LIGHT ONSHORE FLOW. THEN
TOMORROW WITH SOUTHERLY SURFACE WINDS RISK SHIFTS TO THE SOUTH COAST
OF MA/RI.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT FRIDAY FOR MAZ019-022.
COASTAL FLOOD ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT
FRIDAY FOR MAZ015-016.
COASTAL FLOOD ADVISORY UNTIL 8 AM EDT FRIDAY FOR MAZ007.
RI...COASTAL FLOOD ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT
FRIDAY FOR RIZ002-004>007.
MARINE...GALE WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY EVENING FOR
ANZ232-250-254-255.
GALE WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY EVENING FOR
ANZ233>235-237-256.
GALE WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY AFTERNOON
FOR ANZ231-251.
SYNOPSIS...NOCERA/BW
NEAR TERM...NOCERA/BW
SHORT TERM...NOCERA
LONG TERM...BW
AVIATION...NOCERA/BW
MARINE...NOCERA/BW
TIDES/COASTAL FLOODING...
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