815  
FXUS61 KBOX 240217  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
1017 PM EDT WED SEP 23 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL PROVIDE WARM AND DRY  
WEATHER INTO THIS WEEKEND, WITH TEMPERATURES AND HUMIDITY PEAKING  
SUNDAY, PROVIDING A TOUCH OF SUMMER-LIKE CONDITIONS. A PATTERN  
CHANGE TOWARD SHOWERY WEATHER ARRIVES SUNDAY NIGHT INTO NEXT WEEK,  
WITH MUCH NEEDED RAINFALL ARRIVING. ALTHOUGH A WASHOUT IS NOT  
EXPECTED WITH MANY HOURS OF DRY WEATHER DURING THIS TIME.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
NO MAJOR CHANGES TO THE FORECAST THIS EVENING. QUIET WEATHER  
CONTINUES. BROUGHT TEMPERATURES BACK IN LINE WITH OBSERVED  
TRENDS.  
 
PREVIOUS DISCUSSION...  
 
DIURNAL CLOUDS ERODING WITH SUNSET AND WILL GIVE WAY TO CLEAR-  
MOSTLY CLEAR CONDITIONS OVERNIGHT. AS PRESSURE GRADIENT RELAXES  
TONIGHT WINDS WILL SLACKEN AND LIKELY DECOUPLE IN THE VALLEYS  
AND LOW LYING AREAS. THIS COMBINED WITH DEW PTS IN THE 50S WILL  
YIELD A SEASONABLY COOL NIGHT AHEAD. THUS HAVE LEANED TOWARD THE  
COOLER MOS GUIDANCE TO DERIVE MIN TEMPS OVERNIGHT. COULD ALSO  
BE SOME PATCHY FOG TOWARD MORNING ESPECIALLY IN THE VALLEYS AND  
LOW LYING AREAS. ON A RELATED NOTE, CIRCUS CLOUDS EXITING THE OH  
VALLEY INTO PA WILL OVERSPREAD SOUTHERN NEW ENGLAND TOWARD  
DAYBREAK AND MAY PROVIDE FOR A VIBRANT SUNRISE ESPECIALLY ACROSS  
CT AND WESTERN-CENTRAL MA.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/
 
 
320 PM UPDATE...  
 
WE EXPECT A FAIRLY PERSISTENT FORECAST BECAUSE OF A BERMUDA HIGH  
1022MB - WHAT YOU SEE IS WHAT YOU GET. OUTSIDE OF A FEW CLOUDS WE  
ARE MOSTLY SUNNY AND WARM. AFTERNOON TEMPERATURES CONTINUE TO TREND  
5 TO 10 DEGREES ABOVE NORMAL - OVERNIGHT TEMPERATURES REMAIN NEAR  
NORMAL IN THE LOW 50S.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
320 PM UPDATE...  
 
HIGHLIGHTS...  
 
* WARMER THAN AVERAGE THROUGH THE WEEKEND WITH TEMPS & HUMIDITY  
PEAKING SUNDAY  
 
* DRY WEATHER LIKELY CONTINUES THRU THE WEEKEND FOLLOWED BY A  
PATTERN CHANGE TOWARD SHOWERY WEATHER SUNDAY NIGHT INTO NEXT WEEK  
 
PRECIPITATION...  
 
DRY WEATHER EXPECTED TO CONTINUE FRI AND SAT. THE ONLY WRINKLE IS  
FOR LATE FRI NIGHT INTO SAT NIGHT WHEN REMNANT MOISTURE FROM BETA  
TRACKS JUST SOUTH OF NEW ENGLAND. ALTHOUGH MUCH OF THE GUIDANCE  
SUGGEST THE MID LEVEL TROUGH WILL LACK THE AMPLITUDE FOR THE DEEP  
MOISTURE TO TRACK THIS FAR NORTH, THUS REMAINING OFFSHORE. THEREFORE  
OTHER THAN A SPOT SHOWER FRI NGT/SAT/SAT NIGHT AND SOME EXTRA  
CLOUDS, EXPECTING A MAINLY DRY FORECAST. MUCH OF SUNDAY WILL LIKELY  
REMAIN DRY AS WELL ESPECIALLY DURING THE DAYLIGHT HOURS. HOWEVER BY  
SUNDAY EVENING/NIGHT A PREFRONTAL TROUGH INDUCED BY AN APPROACHING  
SHORT WAVE MAY TRIGGER A FEW SHOWERS ACROSS THIS REGION. OTHERWISE  
DRY WEATHER SHOULD PREVAIL THRU THE WEEKEND.  
 
THEN BY EARLY NEXT WEEK MODELS (DETERMINISTIC AND ENSEMBLE GUIDANCE)  
CONTINUE TO ADVERTISE A PATTERN CHANGE WITH A FULL LATITUDE TROUGH  
DEVELOPING OVER THE GREAT LAKES AND OH VALLEY. THIS SHOULD SUPPORT  
SHOWERY WEATHER FROM TIME TO TIME ACROSS SOUTHERN NEW ENGLAND, AS  
SHORT WAVE ENERGY TRACKS ACROSS NY STATE WITH ATTENDING SURFACE COLD  
FRONTS ENTERING, STALLING OR WASHING OUT OVER SOUTHERN NEW ENGLAND.  
GIVEN THE DEEP SSW FLOW SETTING UP ALONG THE EASTERN SEABOARD, THIS  
FULL LATITUDE TROUGH SHOULD BE ABLE TO TAP INTO GULF AND ATLANTIC  
MOISTURE FOR SOME MEANINGFUL/APPRECIABLE RAINFALL HERE NEXT WEEK.  
NOT DROUGHT BUSTING BUT MUCH NEEDED RAINFALL WITH ENSEMBLE MEAN QPF  
FROM THE GFS/EC AND CANADIAN OFFERING AT 0.50-1.25 INCHES OF RAIN  
THRU DAY7 (WED). DIFFICULT TO TIME THE SHOWERS FROM INDIVIDUAL SHORT  
WAVES, HOWEVER ENSEMBLES SUGGEST FIRST POTENT SHORT WAVE TO IMPACT  
OUR REGION SUN NIGHT INTO MONDAY. THEN TRAILING SHORT WAVE ENERGY  
LATE TUE INTO WED. NOT A COMPLETE WASHOUT AS THERE WILL BE MANY  
HOURS OF DRY WEATHER, HOWEVER WITH PWATS +1 TO +2 STANDARD  
DEVIATIONS CAN'T RULE OUT HEAVIER DOWNPOURS FROM TIME TO TIME. GIVEN  
POSITION OF MEAN TROUGH OVER GREAT LAKES/OH VALLEY, HIGHEST POPS WILL  
BE ACROSS WESTERN MA/CT.  
 
TEMPERATURES...  
 
REMAINING WARMER THAN NORMAL (LOW 70S/LOW 50S) THRU THE WEEKEND WITH  
HEAT AND HUMIDITY PEAKING SUNDAY. HIGHS FRI 75-80, SHOULD BE AS WARM  
SAT BUT COULD BE SLIGHTLY COOLER PENDING HOW FAR NORTH CLOUDS TRACK  
FROM OFFSHORE FRONTAL WAVE. THERMAL RIDGE THEN MOVES OVER SOUTHERN  
NEW ENGLAND SUNDAY WITH ENSEMBLES ADVECTING +16C 850 MB AIR ACROSS  
THE AREA AND DETERMINISTIC GUIDANCE OFFERING +18C TO +20C AT 925 MB  
OVER THE REGION. CONSERVATIVELY THIS SUPPORTS HIGHS SUNDAY IN THE  
UPPER 70S TO LOWER 80S AWAY FROM THE SOUTH COAST, WITH POTENTIALLY  
MID 80S CT AND MERRIMACK RIVER VALLEYS ALONG WITH DEW PTS IN THE LOW  
TO MID 60S. DEFINITELY AN AIRMASS WITH A SUMMER FEEL. THEN FOR NEXT  
WEEK, WITH MEAN MID LEVEL TROUGH AXIS REMAINING WELL WEST OF NEW  
ENGLAND, CAA AND POST FRONTAL AIRMASS LIKELY HOLDS OFF UNTIL MID TO  
LATE NEXT WEEK. THUS EXPECTING SEASONAL OR NEAR NORMAL TEMPS MON/TUE  
THEN TRENDING COOLER WED.  
 

 
   
AVIATION /02Z THURSDAY THROUGH MONDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
HIGH CONFIDENCE THROUGH FRIDAY  
 
VFR. RELATIVELY LIGHT WEST WINDS TRANSITION TO SOUTHWEST  
THURSDAY, THEN LINGER INTO FRIDAY. WILL NEED TO MONITOR  
POTENTIAL FOR SEABREEZES AT COASTAL TERMINALS TODAY AWAY FROM  
THE IMMEDIATE SOUTH COAST.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY THROUGH SATURDAY: VFR.  
 
SATURDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SLIGHT  
CHANCE SHRA.  
 
SUNDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE.  
 
SUNDAY NIGHT: MAINLY MVFR, WITH LOCAL IFR POSSIBLE. CHANCE  
SHRA.  
 
MONDAY: MAINLY MVFR, WITH LOCAL IFR POSSIBLE. BREEZY. SHRA  
LIKELY.  
 

 
   
MARINE
 
 
SEAS CONTINUE TO DIMINISH AS TEDDY MOVES FARTHER AWAY FROM THE  
WATERS. WITH RELATIVELY LIGHT WINDS, CANCELED THE SMALL CRAFT  
ADVISORY FOR STELLWAGEN BANK. EXPECTING THE REMAINING SMALL  
CRAFT ADVISORIES CAN BE DROPPED LATER TONIGHT. RELATIVELY LIGHT  
WINDS AND SEAS THEN EXPECTED TO CONTINUE THROUGH THURSDAY NIGHT.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY THROUGH SATURDAY: WINDS LESS THAN 25 KT.  
 
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING  
5 FT. SLIGHT CHANCE OF RAIN SHOWERS.  
 
SUNDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
SLIGHT CHANCE OF RAIN SHOWERS.  
 
SUNDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF  
RAIN SHOWERS.  
 
MONDAY: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS. RAIN  
SHOWERS LIKELY.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR ANZ254-255.  
 

 
 

 
SYNOPSIS...NOCERA/GAUCHER  
NEAR TERM...BELK/NOCERA/GAUCHER  
SHORT TERM...GAUCHER  
LONG TERM...NOCERA  
AVIATION...BELK/NOCERA/GAUCHER  
MARINE...BELK/NOCERA/GAUCHER  
 
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