694  
FXUS61 KBOX 291413  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
1013 AM EDT WED MAR 29 2017  
   
SYNOPSIS
 
 
RAIN HAS ENDED IN NEW ENGLAND, ALTHOUGH CLOUDS LINGERED AT SUNRISE.  
EXPECT A CLEARING TREND THROUGH THE DAY WITH DRY WEATHER CONTINUING  
THROUGH THURSDAY. LOW PRESSURE FROM THE OHIO VALLEY PASSES S OF NEW  
ENGLAND SATURDAY. THIS BRINGS A MIX OF PRECIPITATION FRIDAY AND  
SATURDAY. HIGH PRESSURE BRINGS DRY WEATHER SUNDAY AND MONDAY, FOLLOWED  
BY ANOTHER APPROACHING STORM ON TUESDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
10 AM UPDATE...  
 
MIX OF SUN AND CLOUDS OVER MUCH OF S NEW ENGLAND WITH BLUSTERY  
NW WINDS.  
 
EVALUATING, FAIR AMOUNT OF MOISTURE WITHIN THE H925-85 LAYER AS  
CYCLONIC FLOW PREVAILS THROUGH WHICH POTENT MID-LEVEL IMPULSES  
TRAVERSE. JUST LOOKING AT HIGH-RES GOES-16 DATA, SUBSIDENCE  
BEHIND THE MORNING MID-LEVEL WAVE NOW MOVING S AND OFFSHORE IS  
ALLOWING FOR SOME PARTIAL CLEARING, BUT CAN SEE N AND UPSTREAM  
OVER THE ST LAWRENCE VALLEY THE NEXT WAVE COMING S. THE WAVE MAY  
SKIRT S NEW ENGLAND. HOWEVER GIVEN COLD AIR ADVECTION AND THE  
ANTICIPATED BOUNDARY LAYER MIXING OF RESIDUAL MOISTURE BENEATH  
INCREASING HIGH PRESSURE AND DRY-SUBSIDENCE INVERSION THAT WE  
SHOULD SEE BROKEN CLOUD DECKS LIFTING UP AROUND 5 KFT AGL.  
 
AS THE PRIOR FORECASTER MENTIONED, COLD AIR CLOUDINESS. PLUS THE  
ADDITIONAL ENERGY SKIRTING S LATER TODAY MAY TOUCH OFF SOME LIGHT  
SHOWER ACTIVITY. PREVAILED LIGHT RAIN ACCORDINGLY TO LINGER ALONG  
THE E COAST. SO ALL IN ALL, AM FORECASTING TEMPERATURES TO BE JUST  
A DEGREE OR TO LOWER FOR HIGHS STILL ANTICIPATED AROUND THE UPPER  
40S TO LOW 50S.  
 
FEELING A BIT COOLER. NW BLUSTERY WINDS GUSTING AS HIGH AS 30 MPH  
ESPECIALLY ALONG THE HIGH TERRAIN AND OVER THE E COAST BENEATH  
THE CRUX OF HEIGHTENED N/W WINDS WITHIN THE LOW LEVELS BEHIND  
THE DEPARTING LOW. GOING TO FEEL ROUGHLY AROUND 5 DEGREES COLDER.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/
 
 
OVERNIGHT...  
 
CLEARING OCCURS DURING THE EVENING HOURS AS DIURNAL/CAA  
CLOUDINESS ERODES. THIS WILL BEGIN TO ALLOW SOME DECOUPLING  
ALTHOUGH IT MAY TAKE UNTIL AFTER MIDNIGHT FOR MOST PLACES TO  
DROP TO NEAR CALM AS PRES GRADIENT REMAINS RELATIVELY TIGHT  
THROUGH ABOUT 06Z. THIS WILL LIMIT TIMING FOR RADIATIONAL  
COOLING. THEREFORE, THE FLOOR FOR MOST OVERNIGHT LOWS IS IN THE  
MID 20S, ALTHOUGH A FEW SPOTS (MAINLY THE MOST SHELTERED  
VALLEYS) COULD DROP A BIT LOWER.  
 
THURSDAY...  
 
ANOTHER SEASONABLE DAY FOR THE MOST PART ALTHOUGH WITH GENERALLY  
WEAKER WINDS. GUSTS MAINLY HOLD 15-20 MPH. HIGHS PER SLIGHT  
WARMING TO AN AVERAGE OF -4C AT H85, LOOK TO REMAIN IN THE UPPER  
40S TO AROUND 50, ALTHOUGH A FEW SPOTS MAY DO A BIT BETTER GIVEN  
MORE SUNSHINE AND LESS IN THE WAY OF DIURNALLY DRIVEN CLOUDS.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
 
 
BIG PICTURE...  
 
LONGWAVE FLOW IS NEARLY WEST-EAST WITH A SLIGHT TROUGH OVER THE  
NORTHEAST USA. SHORTWAVE SCALE FLOW SHOWS SPLIT NORTHERN AND  
SOUTHERN JET STREAMS DIRECTING AT LEAST THREE AND POSSIBLY FOUR  
SHORTWAVES THROUGH NEW ENGLAND THROUGH EARLY NEXT WEEK.  
 
MODEL MASS FIELDS ARE SIMILAR THROUGH THE WEEKEND, THEN DIVERGE LATE  
IN THE FORECAST PERIOD WITH THE APPROACH OF THE NEXT WEATHER SYSTEM  
TUESDAY. PATTERN CONFIDENCE IS MODERATE THROUGH THE WEEKEND,  
DIMINISHING TO LOW BY TUESDAY.  
 
DETAILS...  
 
THURSDAY NIGHT...  
 
HIGH PRESSURE OVER THE REGION SHIFTS EAST OVERNIGHT. THE OVERALL  
PATTERN SUGGESTS WARM ADVECTION PRECIP STARTING FRIDAY MORNING. EVEN  
SO, THE MAIN SYSTEM RETURN FLOW CONTINUES TO FOCUS ON NY/PA/NJ  
THROUGH 12Z, EVEN AS THE MODELS MOVE QPF ACROSS SOUTHERN NEW ENGLAND  
DURING 06Z TO 12Z. MODEL OMEGA FIELDS SHOW WEAK LIFT OVER THE REGION  
DURING LATE THURSDAY NIGHT, BUT RH FIELDS SHOW A DRY LAYER BELOW  
THIS LIFT. ALL OF THIS LEADS TO CONCERN THAT THE MODELS ARE  
UNIFORMLY RUSHING PCPN IN TOO SOON. WE HAVE SLOWED THE ONSET BY A  
FEW HOURS, BUT CONTINUE TO BRING CHANCE POPS TO THE WESTERN HILLS,  
CT RIVER VALLEY, AND CENTRAL HILLS OVERNIGHT. COLD AIR DAMMING  
SIGNAL IN THE PRESSURE PATTERN OVER THE INTERIOR, AND LIGHT  
NORTHERLY LOW LEVEL AGEOSTROPHIC FLOW. WITHIN THE CONTEXT OF CHANCE  
POPS, WE EXPECT ENOUGH COLD AIR FOR A SNOW PTYPE IN THE INTERIOR AND  
A RAIN/SNOW MIX ALONG THE COASTAL PLAIN.  
 
FRIDAY THROUGH SATURDAY...  
 
MODELS AGREE ON CLOSED LOW OVER ILLINOIS/INDIANA FRIDAY MORNING WITH  
SURFACE LOW OVER THE MIDWEST. THE MIDWEST LOW IS FORECAST TO  
REDEVELOP ALONG THE MID ATLANTIC COAST, LIKELY IN RESPONSE TO THE  
COLD AIR OVER INTERIOR NEW ENGLAND.  
 
STRONG LOW LEVEL SOUTHERLY JET AT 45-50 KNOTS IN THE OHIO VALLEY  
INTO WESTERN NY. MEANWHILE SOUTHERLY FLOW INTO NEW ENGLAND IS QUITE  
LIGHT FRIDAY MORNING, THEN SLOWLY INCREASES THROUGH THE AFTERNOON.  
THE STRONGER 25-45 KNOT ONSHORE FLOW WAITS UNTIL LATE IN THE DAY AND  
DURING FRIDAY NIGHT AS THE COASTAL LOW DEVELOPS. STRONGER WINDS  
DEVELOP ALOFT AND MOVE OVER THE SOUTH COAST AND SOUTHERN WATERS  
FRIDAY NIGHT AND SATURDAY MORNING. THERE IS CONCERN THAT THE MODELS  
ARE NOT FULLY ACCOUNTING FOR THE POTENTIAL THAT THIS WIND REACHES  
THE SURFACE AT THAT TIME. EXPECT GREATER CONFIDENCE FOR PRECIP  
FRIDAY NIGHT AND SATURDAY MORNING.  
 
WE WILL FEATURE INCREASING POPS THROUGH THE DAY FRIDAY WITH HIGHEST  
VALUES FRIDAY NIGHT AND SATURDAY AS THE COASTAL REDEVELOPMENT PASSES  
OFFSHORE.  
 
INCREASING LOW LEVEL AGEOSTROPHIC FLOW FROM THE NORTH DURING THE  
AFTERNOON AND NIGHT...REACHING 25-35 KNOTS AT NIGHT. THIS SHOULD  
MAINTAIN AND BUILD LOW LEVEL COLD AIR FOR FRIDAY NIGHT. THIS BUILDS  
CONFIDENCE IN A SNOW/ICE EVENT FOR THE INTERIOR, WHILE THE ONSHORE  
EASTERLY WIND KEEPS COASTAL AREAS ABOVE FREEZING. THERE IS  
POTENTIAL FOR SEVERAL INCHES OF ACCUMULATION INLAND, ESPECIALLY IN  
NORTHERN/WESTERN MASSACHUSETTS.  
 
SUNDAY AND MONDAY...  
 
NORTHERN STREAM SHORTWAVE MOVES OVERHEAD AND CARRIES AN APPRECIABLE  
COLD POOL ALOFT, ESPECIALLY OVER NORTHEAST MA. MEANWHILE THE SURFACE  
LAYER SHOWS LESS COLD ADVECTION THAN ALOFT. SO WITH CLEARING SKIES  
MIXING SHOULD BRING TEMPS INTO THE 40S AND NEAR 50. THIS COMBINATION  
SHOULD DESTABILIZE THE AIRMASS AND SUPPORT DIURNAL CUMULUS DURING  
SUNDAY. IT IS POSSIBLE WE ARE UNDERESTIMATING THE SKY COVER FOR  
SUNDAY...THIS WILL DEPEND ON THE AMOUNT OF LINGERING MOISTURE FOR  
CLOUDS.  
 
HIGH PRESSURE AND LIGHTER WIND WILL MOVE IN FOR MONDAY WITH SUNNY  
SKIES. MIXING WILL SUPPORT MAX SFC TEMPS IN THE UPPER 40S AND LOWER  
50S.  
 
TUESDAY...  
 
LOW PRESSURE EJECTING FROM THE SOUTHWEST USA IS PROJECTED TO  
APPROACH OUR AREA ON TUESDAY. THIS SYSTEM BEARS SOME SIMILARITY TO  
THE FRIDAY-SATURDAY SYSTEM, INCLUDING A COLD AIR DAMMING SIGNAL AND  
A COASTAL REDEVELOPMENT. THIS COULD BE ANOTHER COASTAL RAIN/INLAND  
MIX SITUATION, BUT CURRENTLY EXPECTED TEMPERATURES SUPPORT ALL RAIN.  
MUCH TOO EARLY TO LOCK ONTO A SOLUTION FOR THIS.  
 

 
   
AVIATION /14Z 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/...  
 
15Z UPDATE...  
 
TODAY...  
IFR CIGS LIFTING TO LOW-END VFR SCT-BKN AROUND 5 KFT AGL. WITH  
IFR CIGS -DZ MAY ACCOMPANYING. INCREASING NW WINDS. GUSTS UP TO  
30 KTS TOWARDS EVENING INTO THE OVERNIGHT AS CIGS ERODE.  
 
THURSDAY...HIGH CONFIDENCE.  
VFR. NW FLOW WEAKER THAN TODAY.  
 
KBOS TAF...IMPROVING CIGS THROUGH THE DAY WITH INCREASING NW FLOW.  
 
KBDL TAF...IMPROVING CIGS THROUGH THE DAY WITH INCREASING NW FLOW.  
 
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...  
 
THURSDAY NIGHT THROUGH SATURDAY...MODERATE CONFIDENCE.  
 
VFR THURSDAY EVENING WILL LOWER TO MVFR FRIDAY AND IFR/LIFR FRIDAY  
NIGHT AND SATURDAY. INLAND AREAS WILL SEE A RAIN/SNOW MIX FRIDAY  
CHANGE TO SNOW/SLEET/FREEZING RAIN FRIDAY NIGHT WITH SEVERAL INCHES  
OF SNOW/SLEET POSSIBLE IN THE WESTERN AND CENTRAL HILLS. MORE LIKELY  
RAIN IN THE COASTAL PLAIN WITH A PERIOD OF SNOW/RAIN MIX FRIDAY  
NIGHT. PRECIPITATION TAPERS OFF WEST TO EAST SATURDAY AFTERNOON.  
GUSTY EASTERLY WINDS IN THE COASTAL PLAIN FRIDAY NIGHT AND SATURDAY,  
BECOMING NORTHERLY SATURDAY NIGHT.  
 
SUNDAY...MODERATE CONFIDENCE.  
 
CONDITIONS TREND TO VFR WITH AT LEAST PARTIAL CLEARING. NORTHWEST  
WINDS WITH GUSTS 20 KNOTS OR LESS.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH THURSDAY/...  
 
10 AM UPDATE...NO MAJOR CHANGES TO THE FORECAST.  
 
TODAY AND TONIGHT...HIGH CONFIDENCE.  
 
WINDS WILL INCREASE ACROSS THE WATERS THROUGH THE DAY, BUT WILL  
PEAK BY LATE THIS AFTERNOON AND EARLY IN THE OVERNIGHT. NW GUSTS  
AT PEAK WILL REACH 25-30 MPH WITH A FEW GUSTS JUST SHY OF GALES.  
SEAS INCREASE WITH THIS WIND AS WELL, PEAKING EARLY THU MORNING  
AT 8-10FT ON THE SE OCEAN WATERS. SMALL CRAFT ADVISORIES REMAIN  
AS ISSUED.  
 
THU...HIGH CONFIDENCE.  
NW WINDS DIMINISH AND WAVES SLACKEN THROUGH THE DAY. SMALL CRAFT  
ADVISORIES ARE LIKELY TO BE DROPPED THROUGH THE DAYLIGHT HOURS.  
 
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...  
 
THURSDAY NIGHT... HIGH CONFIDENCE.  
 
LINGERING 5 FOOT SEAS ON THE OUTER WATERS. DIMINISHING WIND AS HIGH  
PRESSURE BUILDS IN. A SMALL CRAFT ADVISORY IS POSSIBLE FOR LEFTOVER  
SEAS THURSDAY EVENING.  
 
FRIDAY-SATURDAY...MODERATE CONFIDENCE.  
 
MIDWEST WEATHER SYSTEM REDEVELOPS ALONG THE MID ATLANTIC COAST  
FRIDAY NIGHT AND PASSES THE WATERS ON SATURDAY. WINDS REMAIN BELOW  
25 KNOTS FRIDAY, BUT BECOME EAST AND MAY INCREASE TO 30 KNOTS FRIDAY  
NIGHT AND SATURDAY. WINDS TURN FROM THE NORTH AS THE SYSTEM MOVES  
PAST. EXPECT SEAS TO BUILD FRIDAY NIGHT AND SATURDAY WITH HEIGHTS 5  
TO 10 FEET POSSIBLE.  
 
WINDS OF 40-50 KNOTS ARE POSSIBLE ALOFT, ABOUT 2000-3000 FEET ABOVE  
THE SURFACE. THERE IS AT LEAST A LOW CONCERN FOR 35 KNOT GUSTS  
FRIDAY NIGHT AND SATURDAY PRIMARILY OVER THE SOUTHERN WATERS.  
 
SUNDAY...MODERATE CONFIDENCE.  
 
LOW PRESSURE MOVES AWAY FROM NEW ENGLAND, WITH DIMINISHING WINDS  
OVER THE WATERS. LINGERING 5-6 FOOT SEAS ON THE OUTER WATERS MAY  
REQUIRE A SMALL CRAFT ADVISORY THERE.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THURSDAY FOR ANZ231>234-  
251.  
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 8 AM EDT  
THURSDAY FOR ANZ230.  
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT  
THURSDAY FOR ANZ235>237.  
SMALL CRAFT ADVISORY UNTIL 8 PM EDT THURSDAY FOR ANZ250-254.  
SMALL CRAFT ADVISORY UNTIL 2 PM EDT THURSDAY FOR ANZ255-256.  
 

 
 

 
 
SYNOPSIS...WTB/DOODY  
NEAR TERM...WTB/DOODY/SIPPRELL  
SHORT TERM...DOODY  
LONG TERM...WTB  
AVIATION...WTB/DOODY/SIPPRELL  
MARINE...WTB/DOODY/SIPPRELL  
 
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