Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
738 FXUS61 KBOX 221623 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1223 PM EDT FRI MAY 22 2015 .SYNOPSIS... CLEARING ACROSS THE REGION AS RAIN EXITS OFFSHORE. A COLD FRONT WILL SWEEP THE REGION THIS AFTERNOON AHEAD OF WHICH AN ISOLATED SHOWER IS POSSIBLE INTO EARLY EVENING. BEHIND THIS FRONT...FROST AND MAYBE EVEN RECORD-BREAKING COLD...IS POSSIBLE FRIDAY NIGHT INTO SATURDAY MORNING. DRY AND SEASONABLE FOR SUNDAY. A CHANCE OF SHOWERS MAINLY TO THE NORTH AND WEST FOR MEMORIAL DAY...NOT ANTICIPATING TO BE A WASHOUT. COULD BE WARM AND MUGGY WHILE REMAINING MOSTLY DRY FOR MIDWEEK...AN UNCERTAIN FORECAST FOR THE LATE-WEEK PERIOD. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
1220 PM UPDATE... NO MAJOR CHANGES TO THE ONGOING FORECAST. DIURNAL STRATOCUMULUS STARTING TO DEVELOP ACROSS SOUTHERN NEW ENGLAND. PREVIOUS DISCUSSION... HOWEVER LATER THIS AFTERNOON WILL HAVE TO WATCH VORTEX SWIRLING SOUTHWARD FROM ONTARIO AND QUEBEC. THIS WILL PROVIDE CYCLONIC FLOW AND A COLD FRONT ENTERING THE REGION THIS AFTERNOON. ALSO TEMPS WILL BE RAPIDLY COOLING ALOFT WITH 500 MB TEMPS DROPPING TO -24C BY DAYS END! THIS WILL PROVIDE STEEPENING MID LEVEL LAPSE RATES. HOWEVER THE COLUMN BECOMES FAIRLY DRY THIS AFTERNOON. SO WHILE THERE WILL LIKELY BE MODEST BUILD-UPS THIS AFTERNOON...DEEP DRY AIR ALOFT WILL PROVIDE A CAP/LID ON CONVECTION. THUS OTHER THAN A SPOT SHOWER THIS AFTERNOON/EARLY EVENING... EXPECTING A PLEASANT DRY AFTERNOON WITH SEASONABLY MILD TEMPS.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... *** NEAR RECORD COLD TEMPS TONIGHT INTO EARLY SAT MORNING *** TONIGHT... OTHER THAN A SPOT EVENING SHOWER ASSOCIATED WITH THE FRONTAL PASSAGE...DRY WEATHER PREVAILS IN THE POST FRONTAL AIRMASS LATER THIS EVENING AND OVERNIGHT. STRONG COLD AIR ADVECTION BEHIND DEPARTING FRONTAL BOUNDARY WITH 850 TEMPS FALLING TO -4C TO -6C BY 12Z SAT! THESE VALUES ARE -3 SD BELOW CLIMO! MORE TYPICAL OF A FALL- LIKE AIRMASS. TEMPS ACROSS NORTHWEST MA WILL LIKELY APPROACH FREEZING. THUS HAVE ISSUED A FREEZE WATCH FOR THIS AREA. TRICKY FORECAST AS PGRAD MAY PRECLUDE WINDS FROM DECOUPLING...YIELDING TEMPS NOT AS COLD AND PRECLUDING A FROST FORMING AND/OR A HARD FREEZE. GIVEN HOW ANOMALOUSLY COLD THIS AIRMASS WILL BE COMBINED WITH UNCERTAINTY ISSUED A FREEZE WATCH TO INCREASE PUBLIC AWARENESS. AS FOR TEMPS...MANY LOCATIONS WILL FALL WITHIN 3-5 DEGREES OF RECORD LOW VALUES. NOT VERY SUMMER-LIKE FOR MEMORIAL DAY WEEKEND. SATURDAY... A CHILLY START TO THE DAY BUT CORE OF THE COLD AIRMASS AND ASSOCIATED VORTEX MOVE OFFSHORE. THIS WILL PROVIDE HEIGHT RISES OVER THE AREA YIELDING PLENTY OF SUNSHINE AND A NICE REBOUND IN TEMPS. MORNING LOWS IN THE 30S AND 40S SHOULD CLIMB WELL INTO THE 60S FOR THE AFTERNOON. A BIT BREEZY WITH WEST WINDS 10 TO 20 MPH...BECOMING SW LATE IN THE DAY. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... */ HIGHLIGHTS... - DRY AND SEASONABLE FOR SUNDAY WITH INCREASING CLOUDS LATE - SHOWERS MEMORIAL DAY MAINLY N/W...NOT A WASHOUT! - MUGGY AND DRY PATTERN POTENTIALLY PREVAILING FOR MIDWEEK - A LOW CONFIDENCE FORECAST FOR THE LATE-WEEK PERIOD. */ DISCUSSION... CONTINUANCE OF A CONSENSUS BLEND OF DETERMINISTIC/ENSEMBLE GUIDANCE. CHALLENGES IN OBTAINING CONFIDENCE WITH THE WEAKER MARITIME FLOW AND OVERALL FLAT-FLOW REGIME AS WELL AS INTERPRETING AND ANTICIPATING CONVECTION. BUT THE PATTERN ECHOES SOME SIMILARITY TO EARLY MAY WITH THE CONVERGENT FLOW AND WET-WEATHER HELD N BY THE BERMUDA RIDGE. FLY IN THE OINTMENT THOUGH IS POSSIBLE WITH THE CUTOFF RETROGRADING LOW LATE IN THE FORECAST PERIOD. BREAKING IT ALL OUT BELOW. WILL KEEP IT DRY AND SEASONABLE FOR THE WEEKEND BENEATH INFLUENTIAL BERMUDA HIGH WITH BREEZY SW-FLOW ALONG ITS W-PERIPHERY. ISENTROPIC ASCENT THROUGH THE LOW- TO MID-LEVELS. TOP-DOWN MOISTENING WITH INCREASING AND THICKENING CLOUDS TOWARDS LATE. AS WE GO INTO MEMORIAL DAY...THERE IS A CHANCE OF SHOWERS. BUT HOLD UP. NOT A WASHOUT. ENHANCING RIDGE AHEAD OF AN OPEN-WAVE DISTURBANCE ACROSS THE W-HALF OF THE CONUS STRENGTHENS THE SURFACE BERMUDA HIGH. THINK THIS WILL INCREASE THE SUBSIDENCE AND DRY AIR ACROSS OUR AREA KEEPING THE SW WARM-MOIST CONVEYOR-BELT FLOW TO THE N/W. ITS LEADING EDGE WARM-FRONT WITH A COLLOCATED CONVERGENT NOSE OF A LOW-LEVEL-JET IS THE FOCUS OF LOW- TO MID-LEVEL FORCING THE BETTER OF WHICH IS CLOSER TO FAVORABLE DYNAMICS AND ASSOCIATED DEEP-LAYER LIFT WITH THE OPEN-WAVE IMPULSE TO THE W. SO PER DISCUSSION ABOVE AND EVALUATING CIPS ANALOGS...CONFIDENCE IS THAT BETTER WET-WEATHER CHANCES WILL BE N/W. NOT SURE ON TIMING BUT THINKING LATE MONDAY INTO MONDAY NIGHT. WONDER WITH THE INCREASING SUBSIDENCE INVERSION WHETHER THERE WILL BE ISSUES ALONG THE COAST WITH MARITIME STRATUS/FOG. WITH A PREVALENT RIDGE AGAINST THE VORTEX OVER N CANADA...FEEL THE CONVERGENT FLOW PATTERN THROUGH WHICH MID-LEVEL DISTURBANCES BECOME STRETCHED REMAINS N. S NEW ENGLAND REMAINS WITHIN THE WARM-SECTOR WITH MUGGY YET DRY CONDITIONS. BETTER WET-WEATHER CHANCES REMAIN N AND W FOR THE MIDWEEK PERIOD. CONFIDENCE IS GAINED PER CIPS ANALOGS BUT CONVECTION IS A TRICKY BEAST. CAN NOT RULE OUT EVOLUTION OF ANY CONVECTION ANTICIPATED N AND W TO EVOLVE S AND E WITH THE STEERING FLOW TOWARDS BETTER MOIST-INSTABILITY AXES...THOUGH PERHAPS ERODING INTO AN ENVIRONMENT OF SUBSIDENCE AND DRY AIR. FAVOR THE CANADIAN AND ECMWF BLEND OVER THE GFS. BY LATE WEEK...RIDGE POTENTIALLY ERODES WITH THE RETROGRADGING CUT- OFF LOW. FLAT-FLOW REGIME PREVAILING? PERHAPS MARITIME-CONVERGENT FLOW REMAINS N KEEPING US BENEATH A ZONE OF DRY AIR / SUBSIDENCE? LOW CONFIDENCE AT THIS TIME BUT PREFER THE ECMWF FOR THE FORECAST TIME-FRAME. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH FRIDAY/... 16Z UPDATE... TODAY... VFR. COLD FRONT SWEEPS THE TERMINALS THIS AFTERNOON. LOW RISK OF AN ISOLATED -SHRA. WINDS BACK OUT OF THE NW AND BECOME BLUSTERY. TONIGHT...WNW WINDS INCREASE UP TO 25 KT IN GUSTS. SPOT SHOWER POSSIBLE UNTIL 03Z OR SO. OTHERWISE VFR AND DRY WEATHER. SATURDAY...WEST WINDS UP TO 20 KT IN GUSTS. VFR AND DRY WEATHER PREVAIL. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... VFR. BREEZY SW-WINDS. CIGS LOWERING AND THICKENING LATE. MONDAY INTO MONDAY NIGHT...MODERATE CONFIDENCE. LOW-END VFR TOWARDS THE LATER-HALF WITH INCREASING -SHRA CHANCES MAINLY TO THE N AND W. LOW CONFIDENCE BUT PERHAPS IFR-LIFR MARINE STRATUS / FOG ACROSS THE S/SE-COAST. TUESDAY INTO TUESDAY NIGHT...MODERATE CONFIDENCE. VFR. -SHRA CHANCES N AND W. CONTINUED LOW CONFIDENCE WITH IFR-LIFR MARINE STRATUS / FOG ACROSS THE S/SE-COAST.
-- End Changed Discussion --
&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SATURDAY/... TODAY...LIGHT AND VARIABLE WINDS THIS MORNING BECOME WSW THIS AFTERNOON AND INCREASE TO 25 KT LATE IN THE DAY IN GUSTS. LIGHT RAIN EARLY THIS MORNING GIVES WAY TO DRY WEATHER AND GOOD VSBY BY MID MORNING. TONIGHT...COLD FRONT SWEEPS ACROSS THE WATERS WITH WNW WINDS GUSTING UP TO 25 KT. GOOD VSBY. SAT...WNW WINDS 15 TO 20 KT POSSIBLY GUSTING UP TO 25 EARLY BECOMES WSW 15 TO 20 KT DURING THE AFTERNOON. NO PRECIP AND GOOD VSBY. OUTLOOK...SATURDAY THROUGH TUESDAY... SATURDAY NIGHT INTO SUNDAY NIGHT...HIGH CONFIDENCE. SW-WINDS WITH GUSTS UP TO 20 KTS ESPECIALLY DURING THE DAY AND ALONG THE NEAR-SHORE WATERS. LOOKING AT WAVES POTENTIALLY BUILDING IN EXCESS OF 5 FEET ON THE OUTER WATERS. MONDAY INTO TUESDAY NIGHT...MODERATE CONFIDENCE. SW-FLOW WITH GUSTS IN EXCESS OF 20 KTS ESPECIALLY DURING THE DAY AND ALONG THE NEAR-SHORE WATERS. THE PERSISTENT FETCH COULD POTENTIALLY YIELD A PROLONGED PERIOD OF WAVES IN EXCESS OF 5-FEET ON THE OUTER WATERS. && .CLIMATE... RECORD LOWS FOR MAY 23RD... BOSTON - 40 /1967/ HARTFORD - 37 /1976/ PROVIDENCE - 40 /1950/ WORCESTER - 32 /1929/ && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...FREEZE WATCH FROM LATE TONIGHT THROUGH SATURDAY MORNING FOR MAZ002-003. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 11 AM EDT SATURDAY FOR ANZ231>235-237-250-251-254>256. SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 8 AM EDT SATURDAY FOR ANZ230-236. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...BELK/NOCERA/SIPPRELL SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...BELK/NOCERA/SIPPRELL CLIMATE...STAFF

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.