Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230828 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 428 AM EDT THU APR 23 2015 .SYNOPSIS... UNSEASONABLY COOL WEATHER CONTINUES INTO AT LEAST EARLY NEXT WEEK WITH SPOTTY SHOWERS OR SPRINKLES. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... CUTOFF UPPER LOW CONTINUES TO SPIN OVER NEW ENGLAND...KEEPING AN UNSEASONABLY STRONG COLD POOL ALOFT IN PLACE. 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 KT. SO GUSTS WITHIN THIS RANGE ARE EXPECTED FROM LATE MORNING INTO THIS AFTERNOON. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... THE UNSEASONABLY COLD AIRMASS REMAINS IN PLACE TONIGHT INTO FRIDAY. 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 FARTHER UPSTREAM. WE STILL EXPECT MIN TEMPERATURES IN THE UPPER 20S AND 30S. IF SKIES DID CLEAR AND WE WERE TO RADIATE...SURFACE TEMPERATURES WOULD FALL TO THE MID 20S OVER A WIDE PORTION OF THE INTERIOR. THIS SETS UP A LITTLE PREDICAMENT. THE STRONGER WINDS AND AT LEAST PARTIAL CLOUD COVER SHOULD NEGATE THE POSSIBILITY OF FROST ACROSS A LARGE PORTION OF THE REGION. BASED ON THE MEDIAN DATE OF THE LAST FREEZE...AM ONLY CONCERNED FOR PORTIONS OF NORTHERN CT...RI AND SOUTHEAST MA AT THIS TIME. THINKING THERE WILL BE PATCHY FROST...BUT PROBABLY NOT ENOUGH TO WARRANT A FROST ADVISORY. A FEW OF THE NORMALLY COLDER LOCATIONS COULD REACH FREEZING. HOWEVER... CONFIDENCE IN THIS IS NOT YET HIGH ENOUGH FOR ANY KIND OF AN ADVISORY OR WARNING. WILL LET THE DAY SHIFT TAKE ANOTHER LOOK AT THIS POTENTIAL. AS WITH TODAY...WILL LIKELY SEE ANOTHER ROUND OF DIURNAL CLOUDS DEVELOP DURING FRIDAY...ALONG WITH MORE SPOTTY LIGHT SHOWERS. AT THIS POINT...LOOKS LIKE THE BEST CHANCE WILL BE NEAR AND NORTH OF THE MASS PIKE...BUT CAN NOT RULE OUT A QUICK SPRINKLE EVEN SOUTH OF THERE. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * BELOW NORMAL TEMPERATURES THROUGH NEXT WEEK * SPOTTY DIURNAL SHOWERS THIS WEEKEND INTO MID-NEXT WEEK * LOW CONFIDENCE ON COASTAL SYSTEM THURS/FRIDAY. OVERVIEW... OVERALL THE 00Z MODELS HANDLE THE DEEP CLOSED LOW MOVING ACROSS THE NORTHEAST COMPARABLY ON FRI AND GRADUALLY SHIFT THE ENERGY OFFSHORE SOUTHEAST CANADA ON SAT INTO SUNDAY. A GENERAL MODEL COMPROMISE IS PREFERRED FOR THIS TIME PERIOD. BEYOND THE WEEKEND THE FOCUS IS ON THE UPPER LEVEL LOW...WHICH WILL MIGRATE BACK TOWARDS THE NORTHEAST BY MONDAY...AND A CLOSED LOW OVER THE DESERT SOUTHWEST. THE FORECAST CHALLENGE FOR NEXT WEEK WILL BE THE MIGRATION OF THIS DESERT LOW ACROSS THE SOUTHERN PLAINS AND ITS INTENSIFICATION ACROSS THE SOUTHEAST AS IT WRAPS UP INTO THE CLOSED LOW. A KEY COMPONENT OF THE SYSTEM`S INTENSIFICATION WILL BE THE INCORPORATION OF SOUTHEASTWARD-MOVING SHORTWAVE ENERGY AND WHERE THIS NORTHERN STREAM ENERGY WILL PHASE WITH THE CUTOFF SYSTEM. CURRENTLY THE 00Z GFS IS FASTER AND PHASES OVER THE PLAINS WHERE THE EC IS LESS AMPLIFIED/MORE PROGRESSIVE AND ALLOWS THE ENERGY TO BE THE KICKER TO PUSH THE CUTOFF LOW OUT TO SEA. TELECONNECTION INDICES OF -NAO/+PNA DO NOT TRULY SUPPORT THE EC SOLUTION...SO TRENDED CLOSER TO WPC AND THE GFS FOR THIS FORECAST. DETAILS... * SATURDAY INTO SUNDAY...HIGH CONFIDENCE. STRONG CUTOFF LOW WILL CONTINUE TO IMPACT THE NORTHEAST DURING THIS TIME PERIOD. UPPER LEVEL RIDGE OVER THE CENTER CONUS WILL BUILD PUSHING THE BULK OF THE ENERGY OFFSHORE SAT/SUN. THIS MAY LIMIT SHOWER CHANCES AS BEST COLD POOL AND FORCING WILL BE NORTHEAST OF THE AREA. A STRENGTHENED SURFACE LOW WILL PASS SOUTH OVER THE MID- ATLANTIC DURING THIS TIME PERIOD KEEPING MOST OF THE MOISTURE TO THE SOUTH. REGARDLESS APPEARS THAT THIS SURFACE LOW WILL GET CAUGHT IN THE OVERALL UPPER FLOW PATTERN AND RETROGRADE THE LOW BACK TOWARDS NEW ENGLAND BY EARLY NEXT WEEK. THIS LOW AND ITS ASSOCIATED COLD POOL WILL CONTINUE TO KEEP TEMPS BELOW AVERAGE FOR MUCH OF THE FORECAST. A FEW SITES MAY WARM INTO THE 60S OVER THE WEEKEND AS THE COLD POOL WILL BE EAST OF THE AREA. ANTICIPATE CLEARING SKIES OVERNIGHT WITH DIURNAL CU DURING THE DAY. STILL CANT RULE OUT AN ISOLATED SHOWER DURING THE AFTERNOON HOURS...BUT NOTHING TO CANCEL WEEKEND PLANS OVER. AREAS THAT HAVE THE BEST CHANCE FOR ANY PRECIP WILL BE THE NORTHEAST HALF OF THE REGION...CLOSER TO THE LOW PRESSURE. * MONDAY INTO TUESDAY...MODERATE CONFIDENCE. GUIDANCE BEGINS TO SPLIT THE UPPER LEVEL PATTERN OUT WEST DURING THIS PORTION OF THE FORECAST AS MENTIONED ABOVE. FOR NEW ENGLAND...THE UPPER LEVEL LOW WILL RETROGRADE INCREASING THE CHANCES OF PRECIP AS SEVERAL POTENT SHORTWAVES MORE THROUGH THE FLOW. CHANCE FOR SHOWERS WILL BE HIGHER THAN FOR THIS UPCOMING WEEKEND. TEMPERATURES WILL CONTINUE TO BE COOLER THAN NORMAL. WEDNESDAY AND BEYOND...LOW CONFIDENCE. LOTS OF UNCERTAINTY IN THIS PORTION OF THE FORECAST. EVERYTHING IS DEPENDENT ON HOW THE CUT-OFF LOW IN THE DESERT SOUTHWEST BEHAVES. CURRENTLY BELIEVE WED IS A TRANSITION DAY WITH BELOW NORMAL TEMPS CONTINUING. WATCHING THE DEVELOPMENT OF A COASTAL LOW ON THURSDAY PER THE GFS...WHERE THE 00Z EC SEEMS TO LOST THE LOW VS ITS 12Z COUNTERPART. REGARDLESS BELIEVE BELOW AVG TEMPS WILL CONTINUE. && .AVIATION /08Z 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/... TODAY...HIGH CONFIDENCE IN VFR CONDITIONS. BRIEF...SPOTTY DIURNAL SHOWERS POSSIBLE...MAINLY OVER NORTHERN/WESTERN MASS. TONIGHT...HIGH CONFIDENCE. VFR. FRIDAY...MODERATE CONFIDENCE. MAINLY VFR. CONDITIONS MAY BRIEFLY LOWER TO MVFR IN LIGHT SHOWERS FROM MIDDAY THROUGH THE EARLY EVENING HOURS. 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...SATURDAY THOUGH MONDAY... SAT AND SUNDAY...HIGH CONFIDENCE. MAINLY VFR. CONDITIONS COULD LOWER TO MVFR QUICKLY IN A BRIEF DIURNALLY DRIVEN SHOWER OR TWO. SEA BREEZE DEVELOPMENT IS POSSIBLE ALONG THE EAST COAST. MONDAY...MODERATE CONFIDENCE. VFR WITH MVFR CONDITIONS IN SCT SHOWERS. && .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/... TODAY...HIGH CONFIDENCE ACROSS THE OUTER COASTAL WATERS. MODERATE CONFIDENCE CLOSER TO SHORE. THE MAIN ISSUE WILL BE MIXING POTENTIAL OVER THE COASTAL WATERS. MARGINAL SMALL CRAFT ADVISORY GUSTS OF 25 KT POSSIBLE. JUST NOT CONFIDENT ENOUGH WE WILL SEE THE REQUIRED DURATION OF THE GUSTS TO WARRANT AN ADVISORY. MUCH EASIER DECISION ACROSS THE OUTER COASTAL WATERS...WHERE LINGERING SWELL HAS SEAS OVER 5 FEET. TONIGHT...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. FRIDAY...EXPECT W-NW WINDS GUSTING TO 20-25 KT WITH SEAS REMAINING AT OR ABOVE 5 FT...MAINLY OVER THE OUTER WATERS. OUTLOOK...SATURDAY THOUGH MONDAY... SATURDAY INTO MONDAY...HIGH CONFIDENCE. UPPER LEVEL LOW WILL CONTINUE TO SPIN ACROSS THE NORTHEAST. HIT OR MISS SHOWERS POSSIBLE DURING EACH DAY. HOWEVER EXPECTING BOTH WIND AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. && .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 LATER THIS MORNING. 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 MIDNIGHT EDT TONIGHT FOR ANZ232. SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR ANZ231- 233-234. SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL NOON EDT FRIDAY FOR ANZ250-254>256. SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR ANZ251. && $$ SYNOPSIS...BELK/DUNTEN NEAR TERM...BELK SHORT TERM...BELK LONG TERM...DUNTEN AVIATION...BELK/DUNTEN MARINE...BELK/DUNTEN HYDROLOGY...STAFF

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