599  
FXUS61 KBOX 250201  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
1001 PM EDT SAT JUN 24 2017  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE BRINGS MOSTLY CLEAR CONDITIONS AND LIGHT WINDS  
TONIGHT, AS WELL AS LOWER HUMIDITY. A FAST MOVING DISTURBANCE  
MOVES ACROSS NEW YORK AND NORTHERN NEW ENGLAND LATE SUNDAY,  
BRINGING SCATTERED SHOWERS TO NORTHERN PARTS OF OUR AREA. A WEAK  
COOL FRONT MOVES ACROSS THE AREA LATE TUESDAY. THEN A WARMING  
TREND BEGINS FOR THE LATTER HALF OF THE WEEK WITH A RETURN TO  
SUMMER HEAT AND HUMIDITY BY FRIDAY. THUNDERSTORM CHANCES WILL  
ALSO INCREASE LATE IN THE WEEK AS A SLOW-MOVING COLD FRONT MOVES  
ACROSS SOUTHERN NEW ENGLAND FRIDAY INTO SATURDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
 
 
10 PM UPDATE...  
 
COOL, DRY, COMFORTABLE NIGHT AHEAD. A FEW SHOWERS LINGER INTO W  
NEW ENGLAND ASSOCIATED WITH MID-LEVEL ASCENT UPON LINGERING  
MOISTURE. LIGHT SHOWERS / SPRINKLES NOTED FOR W MA AND W CT AS  
WE GO THROUGH THE REMAINDER OF THE EVENING, DISSIPATING AROUND  
MIDNIGHT.  
 
OTHERWISE DRY AIR ADVECTION CONTINUING TO PROCEED AS WINDS REMAIN  
LIGHT BENEATH CLEAR CONDITIONS. AN OPPORTUNITY FOR RADIATIONAL  
COOLING, CLOSELY EVALUATING SURFACE DEWPOINTS TO GET AN IDEA OF  
HOW COOL IT CAN GET. LEANED TOWARDS LOWEST OF GUIDANCE, LOWS DOWN  
AROUND THE MID TO UPPER 50S WITH SPOTS NOTORIOUSLY KNOWN FOR  
RADIATING OUT EFFECTIVELY (I.E., MARTHAS VINEYARD) POTENTIALLY  
FALLING INTO THE LOW 50S.  
 

 
   
SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/
 
 
BROAD CYCLONIC FLOW ACROSS THE NORTHERN USA, BUT WITH A STRONG  
120-KNOT JET MOVING THROUGH THE FLOW AND DRIVING FEATURES  
QUICKLY THROUGH THE FLOW.  
 
SHORTWAVE OVER THE GREAT LAKES SUNDAY MORNING RACES NORTHEAST,  
CROSSING UPSTATE NY IN THE AFTERNOON AND NORTHERN NEW ENGLAND  
SUNDAY NIGHT. THIS SHORTWAVE WILL CARRY ENOUGH COLD AIR AT 500  
MB TO DESTABILIZE THE AIRMASS ACROSS THESE AREAS SUNDAY. THE  
INSTABILITY PARAMETERS ARE CONSISTENT WITH THIS, AND FAVOR  
THUNDER TO OUR NORTH AND WEST BUT NOT IN SOUTHERN NEW ENGLAND.  
EVEN SO, WE WILL BE IN THE RIGHT ENTRANCE REGION OF THE UPPER  
JET, WHICH WILL FAVOR UPPER VENTING AND GENERATE SOME LIFT. WE  
WILL FORECAST A CHANCE OF AFTERNOON/EVENING SHOWERS, PRIMARILY  
ACROSS WESTERN AND CENTRAL MASS.  
 
THE MIXED LAYER IS FORECAST TO REACH TO AT LEAST 800 MB AND  
POSSIBLY 750 MB. WINDS IN LAYER WILL BE 15-20 KNOTS, SO EXPECT  
SOUTHWEST WINDS GUSTING TO THOSE SPEEDS IN THE AFTERNOON.  
TEMPERATURES AT 800 MB WILL BE 7-9C, EQUIV TO 12-14C AT 850 MB.  
THIS WOULD SUGGEST MAX SFC TEMPS IN THE LOW TO MID 80S.  
 
AFTER THE SHORTWAVE PASSES TO OUR NORTH, ANY SHOWERS SHOULD  
DIMINISH. FOR MOST FOLKS, IT SHOULD BE A FAIR NIGHT WITH TEMPS  
IN THE 50S.  
 

 
   
LONG TERM /MONDAY THROUGH SATURDAY/
 
 
HIGHLIGHTS...  
 
* COOLER WITH A FEW SHOWERS/ISOLD T-STORM POSSIBLE MON INTO WED  
* WARMING TREND TOWARD END OF THE WEEK WITH RETURN TO SUMMER  
HEAT/HUMIDITY BY FRI  
 
DETAILS...  
 
MONDAY INTO TUESDAY NIGHT...  
 
AN UPPER LEVEL TROUGH MOVES EASTWARD FROM THE GREAT LAKES ON  
MONDAY AND EXITS NEW ENGLAND TUESDAY NIGHT. TEMPERATURES COOL  
ALOFT MONDAY, MAKING FOR SOMEWHAT UNSTABLE AIR. THE COLUMN WILL  
BE LACKING A LOT OF MOISTURE, AS INDICATED BY LOW K INDICES.  
THE BEST CHANCES FOR ANY SHOWERS OR AN ISOLATED THUNDERSTORM  
WILL BE IN WESTERN AND NORTHERN MA MONDAY AFTERNOON/EVENING.  
ON TUESDAY, WITH THE AXIS OF THE COLD POOL ALOFT OVER NEW  
ENGLAND, THERE IS A BETTER CHANCE OF SCATTERED SHOWERS AND  
THUNDERSTORMS ACROSS THE ENTIRE REGION. TOTAL TOTALS INDICES  
REACH THE LOWER 50S ACROSS THE NORTHWESTERN TWO-THIRDS OF  
SOUTHERN NEW ENGLAND. HIGHS MAINLY 75 TO 80 BOTH DAYS OVER THE  
INTERIOR WITH COMFORTABLE OVERNIGHT LOWS IN THE 50S EXCEPT NEAR  
60 OVER CAPE COD.  
 
WEDNESDAY INTO THURSDAY MORNING...  
 
LOOKS LIKE A DRY PATTERN WEDNESDAY INTO THURSDAY MORNING WITH  
THE UPPER TROUGH HAVING EXITED AND A SURFACE HIGH PRESSURE  
RIDGE BUILDING OVER THE MID-ATLANTIC STATES. K INDICES WILL BE  
VERY LOW AND SURFACE DEWPOINTS WILL BE IN THE UPPER 40S TO LOWER  
50S. HIGHS WEDNESDAY WILL WARM A BIT...INTO THE LOWER 80S.  
MINIMUM RELATIVE HUMIDITIES WILL APPROACH 30 PERCENT BUT WINDS  
SHOULD BE LIGHT, PREVENTING FIRE WEATHER CONCERNS.  
 
THURSDAY AFTERNOON AND FRIDAY...  
 
ON THURSDAY, HEAT AND HUMIDITY BEGINS TO RETURN AROUND THE  
WESTERN PERIPHERY OF HIGH PRESSURE NEAR BERMUDA AND IN ADVANCE  
OF AN APPROACHING LOW PRESSURE/COLD FRONT SYSTEM IN THE EASTERN  
GREAT LAKES. HIGH TEMPERATURES ARE FORECAST TO REACH THE MID AND  
UPPER 80S. A STRONG SOUTHWESTERLY LOW LEVEL JET WILL DEVELOP  
DURING THE DAY, WITH MODELS INDICATING 40-50 KTS AT 925 MB.  
MIXING SHOULD ALLOW WIND GUSTS TO REACH 25-30 MPH AT THE  
SURFACE, ESPECIALLY IN EASTERN MA AND RI. HAVE RAISED WINDS  
ABOVE GUIDANCE VALUES.  
 
WITH SOUTH-SOUTHEAST SURFACE WINDS AND STRONG SOUTHWEST TO WEST  
WINDS ALOFT, FORECAST 0-3KM HELICITIES ARE ABOVE 300 M2/S2  
ACROSS OUR REGION WITH SIGNIFICANT 0-1KM VALUES AS WELL. THE  
SETUP IS THERE FOR POTENTIAL SEVERE WEATHER. HOWEVER, THE DAY IS  
DRY TO START. BUT BOTH THE GFS AND ECMWF SHOW A RAPID INFLUX OF  
34-36 K INDICES INTO WESTERN SECTIONS BETWEEN 18-22Z THURSDAY  
LATE AFTERNOON. THE IMPLICATION IS THAT CONVECTION FORMS OVER  
THE EASTERN GREAT LAKES, MOVES ACROSS NEW YORK STATE AND INTO  
CT/WESTERN MA LATE IN THE DAY. THE SOURCE OF THE  
CONVECTION...THE COLD FRONT...WILL REMAIN WELL TO OUR WEST SO IT  
SHOULD WEAKEN AS IT HEADS EAST THURSDAY NIGHT, BUT WITH A HIGH  
SHEAR/HIGH HELICITY ENVIRONMENT IN PLACE HERE, WE WILL NEED TO  
WATCH FOR ISOLATED SEVERE THUNDERSTORM POTENTIAL.  
 
ON FRIDAY, SUMMERTIME HEAT AND HUMIDITY WILL HAVE PEAKED WITH  
HIGHS REACHING THE UPPER 80S AND LOWER 90S AND DEWPOINTS  
REACHING THE UPPER 60S TO NEAR 70 IN THE CT RIVER VALLEY BY  
EVENING. DEPENDING ON MODEL SOLUTIONS, THE COLD FRONT WILL BE  
EITHER APPROACHING OR MOVING THROUGH ON FRIDAY AFTERNOON.  
THERE SHOULD BE STRONG CAPE AND STILL SOME 0-3KM HELICITY NEAR  
OR ABOVE 150. AM FORECASTING 40-50 PERCENT CHANCES OF  
THUNDERSTORMS. THE POTENTIAL DOES EXIST FOR SEVERE STORMS FRIDAY  
INTO FRIDAY EVENING.  
 
SATURDAY...  
 
THE SATURDAY FORECAST DEPENDS ON THE TIMING OF THE  
AFOREMENTIONED COLD FRONT. THE 12Z MODEL RUNS HAVE SLOWED THIS  
FRONT DOWN AND CONSEQUENTLY, ANOTHER VERY WARM DAY IS FORECAST,  
WITH HIGHS IN THE MID AND UPPER 80S AND CONTINUING CHANCES OF  
SHOWERS AND THUNDERSTORMS. COOLER WEATHER MAY WAIT UNTIL LATE IN  
THE WEEKEND, BEYOND THIS FORECAST PERIOD.  
 

 
   
AVIATION /02Z SUNDAY THROUGH THURSDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH MONDAY NIGHT/...HIGH CONFIDENCE.  
 
TONIGHT...  
VFR. MAINLY SKC. LIGHT W WINDS. INITIAL RISK OF -SHRA OVER W MA  
AND W CT TOWARDS 3-4Z, PUSHING E AS FEW-SCT LOW-END VFR CIGS,  
ERODING.  
 
SUNDAY...  
VFR. SKC INITIALLY BECOMING SCT-BKN ACROSS THE INTERIOR TOWARDS  
MIDDAY AND CONTINUING THROUGH AFTERNOON. SCT SHRA MAINLY N/W OF  
BDL-SFZ-BOS WITH A LOWER RISK OF TSRA. SW WINDS BECOMING BREEZY  
WITH GUSTS UP TO 20 KTS. LOW RISK MVFR WITH -SHRA, HIGHER  
CONFIDENCE OVER HIGH TERRAIN TERMINALS.  
 
SUNDAY NIGHT...  
VFR. SCT-BKN CIGS DISSIPATING ALONG WITH -SHRA CHANCES. W/SW  
WINDS DIMINISHING.  
 
MONDAY INTO MONDAY NIGHT...  
VFR. REPEAT OF SUNDAY INTO SUNDAY NIGHT. MOSTLY SKC INITIALLY  
WITH SCT-BKN CIGS DEVELOPING MIDDAY AND CONTINUING THROUGH  
AFTERNOON WITH THE THREAT OF -SHRA AND A LOWER THREAT OF TSRA  
MAINLY N/W OF BDL-SFZ-BOS. HOWEVER MID TO HIGH LEVEL CIGS WILL  
BE ON THE INCREASE FROM THE W LATE MONDAY NIGHT INTO TUESDAY MORN.  
 
KBOS TERMINAL...FOR BOTH SUNDAY AND MONDAY, WILL KEEP MOST OF  
THE -SHRA ACTIVITY AND LOWER RISK OF TSRA N/W. BLUSTERY SW WINDS  
DURING THE DAYLIGHT HOURS WITH GUSTS UP AROUND 20 KTS.  
 
KBDL TERMINAL...SIMILAR THINKING AS DESCRIBED ABOVE FOR KBOS.  
 
OUTLOOK /TUESDAY THROUGH THURSDAY/...HIGH CONFIDENCE.  
 
TUESDAY...  
MAINLY VFR. A FEW DIURNALLY DRIVEN SHOWERS AND PERHAPS AN ISOLD  
T-STORM NORTHWEST SECTIONS MONDAY AND ACROSS MUCH OF THE REGION  
TUESDAY.  
 
WEDNESDAY...  
VFR.  
 
THURSDAY...  
VFR TO START, ALTHOUGH SOME PATCHY FOG POSSIBLE ALONG THE SOUTH  
COAST EARLY. AREAS OF MVFR CIGS AND VSBYS IN SCATTERED SHOWERS  
AND T-STORMS DEVELOPING IN WESTERN MA AND WESTERN CT LATE IN THE  
AFTERNOON AND SPREADING EASTWARD THU NIGHT.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH MONDAY NIGHT/...HIGH CONFIDENCE.  
 
GENERAL TREND OF LIGHT WINDS OUT OF THE W DURING THE OVERNIGHT  
PERIODS WHILE BECOMING BLUSTERY OUT OF THE SW THROUGH THE DAY  
WITH POTENTIAL FOR GUSTS UP AROUND 20 KTS. THIS AS FRONTAL WAVES  
EMERGE FROM THE W ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE  
OVER THE GREAT LAKES WHILE HIGH PRESSURE REMAINS DOMINANT OVER  
THE NW ATLANTIC.  
 
ROUGH SEAS AND SWELL LINGER OVER THE S/SE WATERS THROUGH SUNDAY  
AROUND 5 TO 6 FEET. SMALL CRAFT FOR HAZARDOUS SEAS ACCORDINGLY.  
 
OUTLOOK /TUESDAY THROUGH THURSDAY/...  
 
TUESDAY THROUGH WEDNESDAY...HIGH CONFIDENCE.  
QUIET BOATING WEATHER WITH WINDS AND SEAS BELOW SCA. A FEW  
HOURS OF NEARSHORE LOWER 20 KNOT WIND GUSTS ARE POSSIBLE EACH  
AFTERNOON.  
 
THURSDAY...MODERATE CONFIDENCE.  
SOUTHWEST WINDS WILL GUST TO NEAR SMALL CRAFT ADVISORY LEVELS  
AS OUR REGION IS IN BETWEEN HIGH PRESSURE OVER BERMUDA AND LOW  
PRESSURE OVER THE EASTERN GREAT LAKES. SEAS WILL BE INCREASING  
TO 4 TO 6 FT OVER THE OUTER WATERS, TOO. CHANCE OF SHOWERS AND  
THUNDERSTORMS THURSDAY NIGHT.  
 

 
   
TIDES/COASTAL FLOODING
 
 
ASTRONOMICAL TIDES ARE RATHER HIGH THROUGH THIS WEEKEND DURING THE  
NIGHT TIME CYCLES. BOSTON HAS A 12.4 FT HIGH TIDE FORECAST AROUND  
MIDNIGHT TONIGHT AND 12.2 FT JUST AFTER MIDNIGHT SUNDAY NIGHT.  
 
WHILE MOST PLACES HAD THEIR HIGHEST ASTRONOMICAL TIDE OF THE  
YEAR LAST MONTH, A FEW SPOTS ALONG OUR COAST WILL HAVE IT WITH  
THIS JUNE SET OF HIGHEST TIDES. EITHER WAY, THE DIFFERENCE  
BETWEEN THE MAY AND JUNE HIGHEST TIDES IS SMALL.  
 
WHILE OFFSHORE WINDS ARE FORECAST, CURRENT CONDITIONS SUGGEST A  
0.4 SURGE WHICH WILL RESULT IN MINOR SPLASHOVER. THUS WILL  
CONTINUE A COASTAL FLOOD STATEMENT FOR TONIGHT'S HIGH TIDE.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 PM EDT SUNDAY  
FOR ANZ254>256.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT SUNDAY  
FOR ANZ235-237.  
 

 
 

 
 
SYNOPSIS...WTB/GAF  
NEAR TERM...WTB/SIPPRELL/GAF  
SHORT TERM...WTB  
LONG TERM...GAF  
AVIATION...WTB/GAF/SIPPRELL  
MARINE...WTB/GAF/SIPPRELL  
TIDES/COASTAL FLOODING...WFO BOX STAFF  
 
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