Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230243 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1043 PM EDT WED APR 22 2015 .SYNOPSIS... A COLD FRONT IN THE HUDSON AND DELAWARE VALLEYS WILL MOVE NORTHEAST ACROSS SOUTHERN NEW ENGLAND THIS EVENING BRINGING SHOWERS AND ISOLATED THUNDER. UNSEASONABLY COOL WEATHER CONTINUES INTO AT LEAST EARLY NEXT WEEK WITH SPOTTY SHOWERS OR SPRINKLES. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 1045 PM UPDATE... NUMEROUS SHOWERS CONTINUED TO MOVE ACROSS SOUTHERN NEW ENGLAND THIS EVENING. FINALLY SEEING THE COLD FRONT WITHIN THE RADAR DATA. THIS FRONT WAS IN CENTRAL MA AND CT AT THE TIME OF THIS WRITING. ONCE THIS FRONT MOVES PAST A GIVEN LOCATION THIS EVENING...WE SHOULD SEE THE COVERAGE OF SHOWERS DROP OFF RATHER QUICKLY. MOST OF THE INSTABILITY AND BEST DYNAMICS ARE OFFSHORE NOW...AS EVIDENCED BY THE LIGHTNING DATA. MAIN CHANGES WITH THIS FORECAST WERE TO TRY TO TIME THE FRONT ACROSS SOUTHERN NEW ENGLAND...AND THE ATTENDANT RAINFALL CHANCES. MID LEVEL COLD POOL APPROACHES NW AND N CENTRAL MA AFTER 06Z... MAY SEE A FEW MORE SHOWERS DEVELOP WITH THE UNSTABLE AIR ALOFT. WILL ALSO KEEP AN EYE ON TEMPERATURES THERE. CURRENT FORECAST HAS TEMPS DROPPING TO THE LOWER-MID 30S...NOT SURE IF THIS WILL BE REALIZED BY DAYBREAK WITH CLOUDS HANGING IN. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... CUTOFF UPPER LOW SPINS OVER NEW ENGLAND DURING THIS PERIOD. THIS WILL HOLD THE COLD POOL ALOFT OVER THE REGION. DAYTIME HEATING MAY DESTABILIZE THE AIRMASS AND GENERATE A FEW WIDELY SCATTERED RAIN SHOWERS. MIXING MAY REACH AS HIGH AS 800 MB...WHERE TEMPERATURES OF -8C TO -10C WOULD SUPPORT MAX SFC TEMPS IN THE UPPER 40S AND LOWER 50S. WINDS IN THIS MIXED LAYER ARE FORECAST AT 20-25 KNOTS...GUSTS WITHIN THIS RANGE ARE EXPECTED DURING THE LATE MORNING AND AFTERNOON. THE COLD AIRMASS STAYS IN PLACE THURSDAY NIGHT. SUFFICIENT MOISTURE IN THE COLUMN TO SUGGEST AT LEAST SOME SKY COVER OVERNIGHT AND SUFFICIENT PRESSURE GRADIENT TO MAINTAIN SOME WIND. WHILE RADIATIONAL COOLING IS QUESTIONABLE...ADVECTION COOLING IS STILL IN PLAY. MIN TEMPS UNDER THE COLD POOL CLOUDS LAST NIGHT WERE AT OR BELOW FREEZING. EXPECT WE WILL BE CLOSE TO THAT THURSDAY NIGHT WITH MINS IN THE UPPER 20S AND 30S. IF SKIES DID CLEAR AND WE WERE TO RADIATE...SFC TEMPS WOULD FALL TO THE MID 20S OVER A WIDE PORTION OF THE INTERIOR. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... HIGHLIGHTS... * UNSEASONABLY COOL TEMPERATURES CONTINUE THROUGH MOST IF NOT ALL OF THIS PERIOD * SPOTTY LIGHT SHOWERS MAINLY NEAR AND N OF THE MASS PIKE FRIDAY INTO EARLY SUNDAY * BETTER CHANCE FOR SHOWERS LATE SUNDAY INTO TUESDAY AS UPPER LOW PRESSURE RETROGRADES OUT OF THE MARITIMES OVERVIEW AND MODEL PREFERENCES... NEGATIVE NAO AND AO TELECONNECTIONS CONTINUE WITH NO END IN SIGHT...SO HIGH AMPLITUDE BLOCKING PATTERN LOOKS TO HOLD ON AS SEEN ON THE 12Z MODEL GUIDANCE THROUGH MOST IF NOT ALL OF THIS FORECAST PERIOD. NOTING THE H5 CUTOFF LOW THAT SPINS ACROSS NORTHERN NEW ENGLAND INTO SOUTHERN QUEBEC SHIFTS E INTO THE MARITIMES SOMETIME THIS WEEKEND...ONLY TO RETROGRADE BACK ACROSS NORTHERN NEW ENGLAND EARLY NEXT WEEK. THIS WILL KEEP COOL CONDITIONS WITH BRIEF SPOTTY LIGHT SHOWERS MAINLY FROM THE MASS PIKE NORTHWARD AS THE LOW TRIES TO EXIT. HOWEVER...WITH RENEWAL OF UPPER LOW ENERGY SHIFTING BACK TOWARD THE REGION AS WELL AS A WIND SHIFT TO THE N TO NE AND EVENTUALLY E...WILL BRING BETTER SHOT FOR SHOWERS LATE THIS WEEKEND INTO TUESDAY AS MORE LOW LEVEL MOISTURE WORKS IN OFF THE OCEAN. AS THE BIG UPPER LOW SPINS ACROSS THE NE AND MID ATLC COAST... SEVERAL SYSTEMS THAT TRY TO WORK E OUT OF THE ROCKIES AND SOUTHERN PLAINS STATES WILL BE SHUNTED TOWARD THE SE U.S. THROUGH EARLY NEXT WEEK. THE UPPER SYSTEM WILL TRY TO SHIFT E AGAIN BUT NOT UNTIL LATER TUESDAY...AT LEAST AT THIS POINT. LEANED TO A BLEND OF AVAILABLE GUIDANCE...WHICH SHOWS GOOD CONSISTENCY WITH OUR PREVIOUS FORECAST INTO THIS WEEKEND. STILL SOME TIMING ISSUES INTO THE EARLY AND MIDDLE PORTIONS OF NEXT WEEK SO LOWER THAN AVERAGE CONFIDENCE BEYOND MONDAY. DETAILS... * FRIDAY THROUGH SUNDAY...MODERATE CONFIDENCE. H5 CUTOFF LOW/COLD POOL CONTINUES TO KEEP TEMPS BELOW SEASONAL NORMALS FOR LATE APRIL ESPECIALLY FOR DAYTIME HIGHS. READINGS WILL ONLY TOP OFF MAINLY IN THE 50S...RUNNING A GOOD 5 TO 10 DEGREES BELOW NORMAL. AS IS THE CASE WITH A COLD POOL ALOFT...WILL LIKELY SEE DIURNAL CLOUDS DEVELOP DURING THE DAY ALONG WITH SPOTTY LIGHT SHOWERS THAT WILL DEVELOP. AT THIS POINT...LOOKS LIKE THE BEST CHANCE WILL BE NEAR AND N OF THE MASS PIKE...BUT CAN NOT RULE OUT A QUICK SPRINKLE EVEN S OF THERE. ON FRIDAY NIGHT...SKIES DO BECOME PARTLY CLOUDY AND...WITH LIGHT/VRBL WINDS...MAY SEE TEMPS DROP ESPECIALLY ACROSS CENTRAL AND WESTERN MA INTO N CENTRAL/NE CT. LOWS FORECAST TO FALL CLOSE TO OR A BIT BELOW FREEZING AND...THIS LATE INTO THE SEASON...MAY NEED FROST/FREEZE HEADLINES. MODEL SOLUTIONS TRYING TO SIGNAL THE SLOW EXIT OF THE UPPER SYSTEM SOMETIME SUNDAY...BUT TIMING IS UNCERTAIN. AT THIS POINT...THE LOW DOES MOVE A BIT FURTHER NE OF THE REGION SO COULD BE A BIT DRIER ESPECIALLY THE FURTHER S ONE IS FROM THE MA/NH/VT BORDER. ALSO LOOKS LIKE FEWER DIURNAL CLOUDS THAT DAY...MAINLY ACROSS N CT/RI/SE MA SO A FEW SPOTS MIGHT TOUCH 60. * MONDAY THROUGH WEDNESDAY...LOW CONFIDENCE. GUIDANCE SHOWING A BIT BETTER AGREEMENT ON THEIR SOLUTIONS DURING THIS TIMEFRAME WITH THE RETROGRESSION OF THE UPPER LOW BACK OUT OF THE MARITIMES INTO NORTHERN NEW ENGLAND AGAIN. HOWEVER...THIS TIME WINDS LOOK TO SHIFT TO N-NE AND EVEN E OVER TIME. THIS WILL KEEP TEMPS COOL BUT COULD BRING A BETTER SHOT FOR SHOWERS ESPECIALLY ACROSS EASTERN AND CENTRAL AREAS. THIS WILL KEEP A GOOD AMOUNT OF CLOUDINESS AS WELL. MODELS TRY TO BREAK DOWN THE UPPER LOW AGAIN AROUND THE WEDNESDAY TIMEFRAME...BUT RATHER WIDE SOLUTIONS FURTHER S AND W OF THE REGION ALONG WITH ANOTHER LONG WAVE TROUGH REPLACING THE CUTOFF ACROSS FROM THE GREAT LAKES TO SE U.S. BY LATE NEXT WEEK. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. .SHORT TERM /THROUGH THURSDAY NIGHT/... TONIGHT...GENERALLY HIGH CONFIDENCE. VFR CONDITIONS WILL BE PREDOMINANT...THOUGH WILL SEE LOCAL MVFR CIGS/VSBYS IN SHOWERS. EXPECT WINDS TO SHIFT TO W-NW AS COLD FRONT CONTINUES TO MOVE E. THURSDAY...HIGH CONFIDENCE IN VFR CONDITIONS. BRIEF...SPOTTY DIURNAL SHOWERS POSSIBLE...MAINLY IN NORTHERN/WESTERN MASS. THURSDAY NIGHT...HIGH CONFIDENCE. VFR. KBOS TAF...HIGH CONFIDENCE IN OVERALL TAF. MODERATE CONFIDENCE IN TIMING OF SHOWERS. KBDL TAF...HIGH CONFIDENCE IN OVERALL TAF. MODERATE CONFIDENCE IN TIMING OF SHOWERS. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY-SATURDAY...MODERATE CONFIDENCE. MAINLY VFR. CONDITIONS MAY LOWER TO MVFR QUICKLY IN BRIEF LIGHT SHOWERS FROM MIDDAY THROUGH THE EARLY EVENING HOURS EACH DAY. SUNDAY-MONDAY...MODERATE CONFIDENCE. MAINLY VFR...BUT COULD LOWER BRIEFLY IN SHOWERS SUNDAY NIGHT INTO MONDAY. BEST SHOT ACROSS CENTRAL AND E MA INTO RI/NE CT DURING MONDAY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... TONIGHT AND THURSDAY...HIGH CONFIDENCE. SOUTHEAST SWELL CONTINUES TO INFLUENCE OUR WATERS...MAINTAINING 5 TO 7 FOOT SEAS...ESPECIALLY ON OUR EXPOSED SOUTHERN WATERS. GUSTY WINDS WILL GRADUALLY DIMINISH THIS EVENING...BUT SEAS SHOULD LINGER ON THE EXPOSED WATERS. WEST WINDS THEN PICK UP AGAIN ON THURSDAY WITH GUSTS NEAR 25 KNOTS. RATHER THAN GO OFF-AGAIN/ON- AGAIN WITH THE SMALL CRAFT HEADLINES...WE WILL MAINTAIN THEM FOR MOST WATERS THROUGH THURSDAY. EXCEPTION WILL BE BOSTON HARBOR AND NARRAGANSETT BAY FOR WHICH THE HEADLINES ARE MORE DIRECTLY TIED TO THE DIURNAL WINDS. THE OTHER CONCERN WILL BE FOR A BAND OF SHOWERS EARLY TONIGHT. IF ENOUGH INSTABILITY CAN BE REALIZED...A FEW OF THE HEAVIER SHOWERS MAY CONTAIN GUSTY WINDS/SMALL HAIL. LOW RISK OF A FEW THUNDERSTORMS AS WELL. THURSDAY NIGHT...HIGH CONFIDENCE. WEST WINDS DIMINISH A LITTLE BUT REMAIN GUSTING NEAR 20 KNOTS ON THE SOUTHERN WATERS. SEAS/SWELL SUBSIDE A LITTLE BUT MAINTAIN 5-6 FEET ON THE SOUTHERN AND SOUTHEAST OUTER WATERS. OUTLOOK...FRIDAY THROUGH MONDAY...HIGH CONFIDENCE FRIDAY AND SATURDAY...EXPECT W-NW WINDS GUSTING TO 20-25 KT WITH SEAS REMAINING AOA 5 FT MAINLY OVER THE OUTER WATERS. EXPECT WINDS AND SEAS TO DIMINISH LATE SAT/SAT NIGHT. SUNDAY AND MONDAY...WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT CRITERIA. WINDS VEER TO N LATE MON/MON NIGHT. && .HYDROLOGY... A COMBINATION OF RAINFALL AND SNOWMELT ACROSS NORTHERN NEW ENGLAND WAS MAKING ITS WAY DOWN THE CONNECTICUT RIVER. THIS COMBINED WITH TIDAL INFLUENCES AT THE MOUTH OF THE RIVER WILL RESULT IN MINOR FLOODING ACROSS PORTIONS OF THE LOWER CONNECTICUT RIVER. THE RIVER NEAR HARTFORD IS EXPECTED TO APPROACH ITS FLOOD STAGE TOWARD DAYBREAK THURSDAY. NEAR MIDDLE HADDAM...THE TIDAL INFLUENCE WILL BE STRONGER. MINOR FLOODING IS ONGOING DURING AT LEAST A PART OF EACH TIDE CYCLE. THIS IS EXPECTED IS EXPECTED TO CONTINUE THROUGH AT LEAST SATURDAY MORNING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EDT THURSDAY FOR ANZ231>235- 237. SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ250-254>256. SMALL CRAFT ADVISORY UNTIL 7 AM EDT THURSDAY FOR ANZ251. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/BELK/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...BELK/WTB/EVT MARINE...BELK/WTB/EVT HYDROLOGY...STAFF

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