142
FXUS61 KBOX 161106
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
706 AM EDT WED OCT 16 2019
SYNOPSIS
HIGH PRESSURE JUST OFFSHORE WILL PROVIDE DRY WEATHER THIS
MORNING. HOWEVER A POWERFUL COASTAL STORM DEVELOPS ALONG THE NJ
COAST LATE TODAY AND THEN MOVES NORTHEAST UP THE I-95 CORRIDOR
OF CT, RI AND MA TONIGHT INTO THURSDAY. THIS WILL BRING PERIODS
OF VERY HEAVY RAIN AND STRONG TO PERHAPS DAMAGING WINDS TO THE
REGION BEFORE EXITING THE REGION LATER THURSDAY. HIGH PRESSURE
BUILDS IN WITH COOL, WINDY CONDITIONS THE REST OF THURSDAY
THROUGH FRIDAY. MILDER TEMPERATURES WITH CONTINUED DRY
CONDITIONS EXPECTED THIS WEEKEND AS HIGH PRESSURE MOVES
OVERHEAD. THERE WILL BE A CHANCE FOR SHOWERS MONDAY NIGHT AND
TUESDAY AS THE NEXT WEATHER SYSTEM APPROACHES FROM THE WEST.
NEAR TERM /UNTIL 6 PM THIS EVENING/
650 AM UPDATE...
LIGHT/VARIABLE OR CALM WINDS WERE THE RULE ACROSS THE REGION AT
10Z, ALONG WITH SOME PATCHY FOG ACROSS SOME OF THE NORMAL FOG
SPOTS IN NE CT/N RI INTO INTERIOR E MASS. NOTING VSBY DOWN TO 1
3/4SM AT KPYM AND 3SM AT KOWD. OTHERWISE, SKIES WERE MAINLY
CLEAR AT SUNRISE AS SEEN ON THE 10Z GOES-EAST NIGHTTIME
MICROPHYSICS RGB SATELLITE IMAGERY.
TEMPS HAVE FALLEN TO THE 30S ACROSS MOST AREAS AWAY FROM THE
IMMEDIATE COAST, EXCEPT 44 DEGREES AT KORH AT 10Z, WHILE THE
IMMEDIATE COAST HAD READINGS UP TO THE MID 40S AND UP TO 50
DEGREES AT KPVC.
EXPECT CLEAR SKIES THROUGH MID MORNING, THEN HIGH CLOUDS WILL
FILTER ACROSS WESTERN AREAS BY MIDDAY. TEMPS SHOULD REACH THE
50S FOR MOST AREAS, EXCEPT AROUND 60 DEGREES ACROSS INTERIOR E
MASS AND ALONG PORTIONS OF THE S COAST.
PREVIOUS DISCUSSION...
TODAY...
TEMPS WILL REBOUND TO 60-65 THIS AFTERNOON (VERY CLOSE TO
NORMAL) AS MORNING SUNSHINE COMBINES WITH INCREASING ONSHORE
FLOW THIS AFTERNOON WITH SST STILL IN THE UPPER 50S TO LOWER
60S, HELPING TO ERODE SHALLOW LOW LEVEL COLD AIR OVER THE REGION
THIS MORNING.
THEN INCREASING CLOUDS THIS AFTERNOON FOLLOWED BY RAIN
OVERSPREADING THE REGION AROUND 5 PM WESTERN CT/MA AND CLOSER TO
8/9PM FOR RI AND EASTERN MA. THIS IS IN RESPONSE TO STRONG JET
DYNAMICS APPROACHING THE REGION FROM THE SOUTHWEST.
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/
400 AM UPDATE...
*** STRONG TO DAMAGING WINDS POSSIBLE TONIGHT AND THURSDAY ***
*** HEAVY RAIN TONIGHT WITH LOCALIZED 3-4" AMOUNTS POSSIBLE ***
SIGNIFICANT COASTAL STORM TO IMPACT THE REGION TONIGHT INTO THU WITH
STRONG TO PERHAPS DAMAGING WINDS ALONG WITH VERY HEAVY RAIN LIKELY
YIELDING POOR DRAINAGE/URBAN FLOODING. POWERFUL COASTAL STORM THE
RESULT OF STRONG JET DYNAMICS YIELDING A NEGATIVE TILT MID LEVEL
TROUGH AND SUPPORTING EXPLOSIVE CYCLOGENESIS. SECONDARY LOW PRES
BEGINS TO DEVELOP OVER THE MID ATLC REGION LATER THIS MORNING AT
ABOUT 1007 MB AND THEN RAPIDLY DEEPENS ABOUT 32 MB IN 24 HRS WITH A
975 BOMB CYCLONE OVER NORTHEAST MA/SOUTHEAST NH! THIS WILL LIKELY
HAVE SOME WEATHER IMPACTS HERE TONIGHT INTO THU. HERE ARE THE
DETAILS.
MODELS ...
VERY GOOD AGREEMENT FROM BOTH GLOBAL AND HI RES GUIDANCE ON
SIGNIFICANT TROUGH AMPLIFICATION WITH MID LEVEL HEIGHTS CRASHING AND
GIVING WAY TO EXPLOSIVE CYCLOGENESIS FROM THE NJ COAST THIS EVENING
AND THEN COASTAL LOW TRACKING ALONG OR NEAR THE I-95 CORRIDOR OF
CT/RI AND EASTERN MA OVERNIGHT.
STRONG TO DAMAGING WIND THREAT ...
WIND THREAT WILL COME IN TWO SURGES, FIRST PULSE WILL BE WITH
ANOMALOUS LOW LEVEL SE JET UP TO 70-75 KT MOVING ACROSS RI AND
EASTERN MA 03Z-06Z TONIGHT. MODEL SOUNDINGS SUGGEST LOW LEVEL LAPSE
RATES ARE NEARLY NEUTRAL WITH LOW LEVEL JET NOT MIXING DOWN TO THE
SURFACE. HOWEVER OUR MECHANISMS AT WORK HERE WHICH INCLUDE STRONG
PRESSURE/RISE COUPLET THAT WILL ENHANCE ISALLOBARIC WIND COMPONENT.
IN ADDITION ISOLATED ELEVATED CONVECTION POSSIBLE ON THE NOSE OF
APPROACHING DRY SLOT. THUS VERY HEAVY RAINFALL MAY ENHANCE WIND
TRANSFER FROM ALOFT. FINALLY WITH TREES REMAINING FULLY LEAVED LESS
WIND REQUIRED FOR TREE DAMAGE AND POSSIBLE POWER OUTAGES. GIVEN THE
REASONING ABOVE WILL HOIST A WIND ADVISORY TONIGHT FOR THE ENTIRE
COASTLINE OF MA/RI WITH STRONGEST WINDS LIKELY OVER CAPE COD AND
ISLANDS. LOW PROB OF HIGH WIND CRITERIA OCCURRING SO LATER SHIFTS
WILL HAVE MONITOR MODEL TRENDS. HIGHEST RISK OF STRONG TO DAMAGING
WINDS MAY ARRIVE AROUND DAYBREAK THU OR SHORTLY THEREAFTER AS VERY
STRONG PRESSURE/RISE COUPLET MOVES ACROSS THE AREA. THIS COMBINED
WITH WINDS SHIFTING TO THE WEST AND LOW LEVEL COOL AIR ADVECTION
STEEPENING LAPSE RATES, RISK FOR 60+ MPH GUSTS EXIST ESPECIALLY OVER
CAPE COD AND ISLANDS WHERE RELATIVELY WARM SST WILL PROMOTE DEEP
BLYR MIXING PER MODEL SOUNDINGS. THUS HAVE OPTED FOR A HIGH WIND
WATCH HERE AND WIND ADVISORIES WESTWARD INTO RI AND EASTERN MA
INCLUDING THE BOSTON TO PROVIDENCE CORRIDOR. LATER SHIFTS MAY NEED
TO EXPAND WIND ADVISORY WESTWARD INTO CT AND WESTERN-CENTRAL MA.
HEAVY RAIN/FLOOD THREAT ...
GOOD MODEL AGREEMENT (GLOBAL AND HI RES) FOR RAIN TO OVERSPREAD THE
REGION 4-7 PM ACROSS CT AND WESTERN-CENTRAL MA, THEN INTO RI AND
EASTERN MA 7-10 PM. VERY STRONG JET DYNAMICS COMBINED WITH PWATS
NEAR 1.5 INCHES AND INSTABILITY ALOFT FROM APPROACHING DRY SLOT WILL
RESULT IN PERIODS OF VERY HEAVY RAINFALL TONIGHT FROM APPROXIMATELY
10 PM TO 5 AM FROM SOUTHWEST TO NORTHEAST. BOTH GLOBAL AND HI RES
GUIDANCE SUPPORTING RAINFALL AMOUNTS FROM 1.5 TO 3 INCHES WITH
ISOLATED AMOUNTS UP TO 4 TO 5 INCHES POSSIBLE IN THE UPSLOPE REGIONS
OF THE WORCESTER HILLS AND EAST SLOPES OF THE BERKSHIRES. RIVER AND
STREAMFLOWS ARE RUNNING BELOW NORMAL SO LOTS OF CAPACITY TO TAKE ON
HEAVY RAINFALL. THEREFORE NOT EXPECTING ANY RIVER/STREAM FLOODING SO
NO FLOOD HEADLINES AT THIS TIME. HOWEVER RAINFALL AMOUNTS OF THIS
MAGNITUDE WILL RESULT IN POOR DRAINAGE/URBAN FLOODING. WHAT WILL
LIKELY MINIMIZE FLOOD IMPACTS IS THAT THE HEAVIEST RAINFALL WILL
LIKELY FALL AFTER THE LATE DAY COMMUTE TODAY AND THEN END BEFORE THE
MORNING COMMUTE THU.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
OVERVIEW...
H5 CUTOFF LOW PRES APPROACHING THE MID MAINE COAST WITH LONG WAVE
TROUGH EXTENDING TO THE CAROLINA COAST BY AROUND 00Z FRI WHICH
SLOWLY LIFTS NE TO NEAR PRINCE EDWARD ISLAND AND THE GULF OF ST.
LAWRENCE BY FRI NIGHT. HIGH AMPLITUDE RIDGE BUILDS FROM HUDSON BAY
TO THE OHIO/TENNESSEE VALLEYS FRI NIGHT, SHIFTING SLOWLY E WHILE
ANOTHER DIGGING MID LEVEL TROUGH DEVELOPS FROM THE NORTHERN ROCKIES
TO THE CENTRAL PLAINS AND N TX DURING THE WEEKEND.
ACROSS THE NE U.S., MID LEVEL STEERING FLOW BECOMES RATHER BROAD AND
SOMEWHAT PROGRESSIVE DURING THE UPCOMING WEEKEND. RIDGING BUILDS IN
RESPONSE TO DIGGING TROUGH/CUTOFF LOW ACROSS THE CENTRAL U.S. LATE
THIS WEEKEND INTO EARLY NEXT WEEK. SOME MODEL SPREAD WITH POSITION
AND TRACK OF APPROACHING WARM FRONT AS LOW DEVELOPS ACROSS N GREAT
LAKES INTO S ONTARIO LATE MON NIGHT/TUE.
ANOTHER SYSTEM MAY APPROACH LATE THIS WEEKEND OR EARLY NEXT WEEK AS
ANOTHER CUTOFF MID LEVEL LOW DEVELOPS AND SHIFTS SLOWLY E OUT OF THE
GREAT LAKES. SOME QUESTIONS ON TIMING AND TRACK OF THE ASSOCIATED
SURFACE SYSTEM AND FRONT, WHICH WILL BE DEPENDENT UPON THE EXIT OF
THE HIGH AMPLITUDE RIDGE AXIS. COULD SEE ANOTHER AREA OF LOCALLY
HEAVY RAINFALL WITH THE POTENTIAL OF A TROPICAL MOISTURE PLUME THAT
MAY WORK NE OUT OF THE GULF OF MEXICO.
CONFIDENCE REMAINS HIGH FOR THE EARLY PORTION OF THIS FORECAST, FROM
THURSDAY NIGHT THROUGH MOST OF THE WEEKEND, THEN LOWERS WITH MODEL
SOLUTION SPREAD INCREASING. TIMING ISSUES WITH THE RE-BUILDING OF
THE HIGH AMPLITUDE RIDGE THAT SLOWLY CROSSES NEW ENGLAND THIS
WEEKEND, THEN THE SUBSEQUENT APPROACH OF THE WARM FRONT SOMETIME
EARLY NEXT WEEK. THIS LENDS TO LOWER CONFIDENCE DURING THE SUNDAY
NIGHT THROUGH TUESDAY TIMEFRAME.
DETAILS...
THURSDAY NIGHT THROUGH FRIDAY...
H5 CUTOFF LOW AND ASSOCIATED SURFACE SYSTEM WILL PUSH OUT OF EASTERN
MASS INTO THE NH SEACOAST AND SW MAINE THU EVENING, MOVING ALONG THE
MAINE COAST THEN INTO THE MARITIMES BY FRI MORNING.
HOWEVER, UNSTABLE CONDITIONS WILL LINGER THANKS TO THE COLD POOL
ALOFT ACROSS THE REGION AND THE STRONG CYCLONIC FLOW, SCATTERED
SHOWERS WILL LINGER ACROSS N MASS TO THE E SLOPES OF THE BERKSHIRES
THU NIGHT, THEN WILL DIMINISH OVERNIGHT INTO EARLY FRIDAY MORNING.
LAPSE RATES INCREASE AGAIN BY MID MORNING FRIDAY, SO COULD SEE NW
WINDS GUSTING FROM 25 TO 35 KT, POSSIBLY A BIT HIGHER ALONG THE
COAST DURING FRIDAY.
WITH COOLER AIR WORKING IN ON THE NW WIND FLOW, EXPECT TEMPS TO
BOTTOM OUT IN THE 40S THU NIGHT, THEN WILL RISE TO THE 50S ACROSS
MOST LOCATIONS, BUT A FEW SPOTS ACROSS THE E SLOPES OF THE
BERKSHIRES MAY NOT BREAK 50.
SATURDAY AND SUNDAY...
LARGE HIGH PRESSURE BUILDS SLOWLY ACROSS THE NORTHEAST THIS WEEKEND.
SHOULD SEE MAINLY CLEAR SKIES SATURDAY INTO EARLY SUNDAY, THEN SOME
CLOUDS MAY START TO PUSH IN DURING THE MIDDAY AND AFTERNOON HOURS.
LIGHT WINDS SATURDAY NIGHT INTO EARLY SUNDAY MAY ALLOW TEMPS TO DROP
TO THE MID-UPPER 30S IN THE NORMALLY COLDER VALLEY LOCATIONS.
TEMPS WILL REMAIN ON THE COOL SIDE ON SATURDAY AS H925 TEMPS FROM
+6C TO +8C TRANSLATES TO HIGHS RANGING FROM THE MID-UPPER 50S ACROSS
THE HIGHER INLAND TERRAIN AND ALONG THE COAST, RANGING TO AROUND 60
ACROSS INTERIOR E MASS INTO RI AS WELL AS THE MID AND LOWER CT
VALLEY. ON SUNDAY, H925 TEMPS RISE TO +9C TO +11C, SO READINGS WILL
TOP OFF IN THE LOWER-MID 60S, UP TO 5 DEGREES ABOVE SEASONAL
NORMALS.
SUNDAY NIGHT THROUGH TUESDAY...
ANOTHER CUTOFF MID LEVEL LOW AND ASSOCIATED FRONTAL SYSTEM MAY
APPROACH LATE SUNDAY NIGHT, WITH ANOTHER ROUND OF SHOWERS POSSIBLE
MONDAY INTO TUESDAY.
WITH E-SE WIND FLOW IN PLACE, WHICH SHIFTS TO S-SW AS H5 RIDGE AXIS
SHIFTS E, MAY SEE ANOTHER SHOT OF PRECIP PUSHING NORTHWARD. NOTING A
POTENT PWAT MOISTURE PLUME WORKING UP THE EASTERN SEABOARD FROM THE
GULF OF MEXICO LATE MON NIGHT INTO TUE. GEFS PWAT VALUES SIGNALING
UP TO 3-4 SD ABOVE NORMAL FOR MID-LATE OCTOBER BY 12Z TUE (ABOUT 1.6
TO 1.8 INCHES AS SEEN ON 00Z GFS MODEL). STILL QUITE A BIT OF TIME
TO SEE IF THIS SIGNAL CONTINUES.
WITH THE DIGGING MID LEVEL TROUGH TO THE W OF THE REGION, THE
GENERAL S-SW WIND FLOW WILL ALLOW THIS PRECIP TO SHIFT ACROSS THE
REGION. SOME TIMING ISSUES REMAIN IN PLACE DUE TO MODEL SOLUTION
SPREAD.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
SHORT TERM /THROUGH THURSDAY/...
11Z UPDATE ...
TODAY...
A FEW ISOLATED SPOTS ACROSS NE CT INTO N RI AND INTERIOR SE
MASS REPORTED MVFR CIGS/VSBYS AT 10Z, WHICH SHOULD IMPROVE TO
VFR BY AROUND 13Z. OTHERWISE, VFR CONDITIONS EXPECTED THROUGH
EARLY THIS AFTERNOON WITH LIGHT WINDS. CONDITIONS WILL LOWER TO
MVFR AS RAIN MOVES INTO WESTERN CT/MA AROUND 21Z AND BY 00Z
ACROSS RI AND EASTERN MA. IFR POSSIBLY BY 00Z ACROSS WESTERN
MA/RI. RAIN WILL QUICKLY BECOME HEAVY AT TIMES. EAST TO
SOUTHEAST WINDS DEVELOP THIS AFTERNOON, INCREASING TO 25 KT
ALONG THE COAST BY 00Z.
TONIGHT...
MAINLY IFR IN PERIODS OF VERY HEAVY RAIN AND LIFR AT TIMES. SE
WINDS UP TO 45 KT ALONG THE COAST INCLUDING CAPE COD AND
ISLANDS. LLWS AWAY FROM THE COAST WHERE SURFACE WINDS NOT AS
STRONG. ISOLATED TSRA POSSIBLE 00Z-09Z SOUTHWEST TO NORTHEAST.
THURSDAY...
MVFR/IFR AT DAYBREAK TRENDING TO VFR/MVFR WITH SCATTERED
SHOWERS. STRONG WEST WINDS DEVELOPING AROUND SUNRISE AND
CONTINUING THRU THE MORNING INTO THE AFTERNOON WITH GUSTS UP TO
40 KT POSSIBLE EXCEPT UP TO 50 KT POSSIBLE CAPE COD AND THE
ISLANDS.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SOME UNCERTAINTY ON HOW
STRONG WINDS WILL BECOME TONIGHT AND THU.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF. SOME UNCERTAINTY ON HOW
STRONG WINDS WILL BECOME TONIGHT AND THU.
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...MODERATE CONFIDENCE.
THURSDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. STRONG
WINDS WITH LOCAL GUSTS UP TO 40 KT.
FRIDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. WINDY WITH LOCAL
GUSTS UP TO 30 KT.
FRIDAY NIGHT: VFR. BREEZY.
SATURDAY THROUGH SUNDAY: VFR.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE.
*** STORM WATCH POSTED TONIGHT & THU EASTERN MA WATERS ***
TODAY...
HIGH PRES EAST OF MA PROVIDES LIGHT WINDS THIS MORNING AND DRY
WEATHER BUT ESE WINDS INCREASE UP TO 25 KT BY SUNSET ALONG WITH RAIN
OVERSPREADING RI WATERS LATE.
TONIGHT...
POWERFUL LOW PRES DEVELOPS OFF THE NJ COAST AND THEN TRACKS UP THE I-
95 CORRIDOR OF CT/RI/MA TONIGHT INTO THU. ESE STORM FORCE GUSTS ARE
POSSIBLE OUTER WATERS OF MA, GALES ELSEWHERE. VERY HEAVY RAIN WILL
REDUCE VSBY.
THURSDAY...
975 MB LOW OVER NORTHEAST MA/SOUTHEAST MA THU MORNING THEN LIFTING
INTO NORTHERN NEW ENGLAND. STORM FORCE WEST WINDS POSSIBLE. POOR
VSBY IN SHOWERS AND FOG EARLY WILL IMPROVE WITH WIND SHIFT TO THE
WEST.
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...MODERATE CONFIDENCE.
THURSDAY NIGHT: STRONG WINDS WITH GUSTS UP TO 40 KT. ROUGH SEAS
UP TO 16 FT. SLIGHT CHANCE OF RAIN SHOWERS.
FRIDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 30 KT. AREAS OF ROUGH SEAS.
FRIDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT.
SATURDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
SATURDAY NIGHT THROUGH SUNDAY: WINDS LESS THAN 25 KT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...WIND ADVISORY FROM 10 PM THIS EVENING TO 6 PM EDT THURSDAY FOR
MAZ020-021.
WIND ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT THURSDAY FOR
MAZ007-014>016-019.
WIND ADVISORY FROM 7 AM TO 5 PM EDT THURSDAY FOR MAZ005-006-
012-013-017-018.
WIND ADVISORY FROM 10 PM THIS EVENING TO 7 AM EDT THURSDAY FOR
MAZ022>024.
HIGH WIND WATCH FROM THURSDAY MORNING THROUGH THURSDAY
AFTERNOON FOR MAZ022>024.
RI...WIND ADVISORY FROM 10 PM THIS EVENING TO 6 PM EDT THURSDAY FOR
RIZ004>008.
WIND ADVISORY FROM 7 AM TO 5 PM EDT THURSDAY FOR RIZ001>003.
MARINE...STORM WATCH FROM THURSDAY MORNING THROUGH THURSDAY AFTERNOON
FOR ANZ232-233-254-255.
GALE WARNING FROM 1 AM TO 8 PM EDT THURSDAY FOR ANZ230.
GALE WARNING FROM 11 PM THIS EVENING TO 8 PM EDT THURSDAY FOR
ANZ231.
GALE WARNING FROM MIDNIGHT TONIGHT TO 8 PM EDT THURSDAY FOR
ANZ236.
GALE WARNING FROM 7 PM THIS EVENING TO 4 AM EDT FRIDAY FOR
ANZ235-237.
GALE WARNING FROM 10 PM THIS EVENING TO 4 AM EDT FRIDAY FOR
ANZ234.
STORM WATCH FROM THIS EVENING THROUGH LATE TONIGHT FOR ANZ250-
251.
GALE WARNING FROM 7 PM THIS EVENING TO 6 AM EDT FRIDAY FOR
ANZ256.
SYNOPSIS...NOCERA/EVT
NEAR TERM...NOCERA/EVT
SHORT TERM...NOCERA
LONG TERM...EVT
AVIATION...NOCERA/EVT
MARINE...NOCERA/EVT
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