Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 181742 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 142 PM EDT MON AUG 18 2014 .SYNOPSIS... DRY AND SEASONABLY WARM WEATHER INTO WEDNESDAY...THEN A COOLING TREND IS EXPECTED THURSDAY AND FRIDAY AS CLOUDS INCREASE ALONG WITH ONSHORE WINDS AND THE RISK OF A FEW SHOWERS. DRY WEATHER LIKELY RETURNS NEXT WEEKEND BUT WITH COOLER THAN NORMAL TEMPERATURES... AS HIGH PRESSURE BUILDS SOUTHWARD FROM THE CANADIAN MARITIMES. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 145 PM UPDATE... LITTLE CHANGE TO THE FORECAST. ENERGY THROUGH THE W-PERIPHERY OF CYCLONIC FLOW IS LENDING TO AN ENHANCEMENT OF LOW- TO MID-LEVEL WINDS. WITH BOUNDARY LAYER MIXING DUE TO DAYTIME HEATING...SEEING THE MIX-DOWN OF FASTER MOMENTUM TO THE SURFACE WITH GUSTS BEING OBSERVED OF 20 MPH ALONG WITH THE DEVELOPMENT OF SCATTERED TO BROKEN CUMULUS. SEA-BREEZES HAVE DEVELOPED ACROSS THE S-SHORELINE AND LIKELY TO DEVELOP TO THE E TOWARDS THE LATE AFTERNOON. THE WEAK PRESSURE GRADIENT UP AGAINST BRISK NW-FLOW WILL LIKELY RESULT IN SEA- BREEZES ONLY AFFECTING IMMEDIATE COASTLINES. NEAR-TERM MESOSCALE GUIDANCE INCLUDING THE WRF CAPTURE THIS WELL. FAVOR THE WRF-NMM WINDS OVERALL. HIGHS UP TO AROUND THE MID- TO UPPER-70S ARE STILL EXPECTED. SHOULD SEE PRESENT TEMPERATURES WARM JUST A COUPLE OF DEGREES MORE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... TONIGHT AND TOMORROW... UPPER LEVEL FLOW BECOMES MORE ZONAL DURING THIS TIME FRAME. UPPER LEVEL SYSTEM MOVING ACROSS THE OHIO VALLEY TODAY WILL STAY SOUTH OF THE REGION AND MOVE ACROSS THE MID-ATLANTIC TOMORROW THANKS TO A STRONG GREENLAND BLOCK. AT THE SURFACE...HIGH PRESSURE WILL REMAIN OVERHEAD. ANTICIPATE LIGHT WINDS AND MOSTLY CLEAR SKIES ASIDE FROM SOME DIURNAL CU. PATCHY GROUND FOG MAY DEVELOP IN THE TYPICAL PRONE REGIONS OVERNIGHT. TEMPERATURES TONIGHT WILL DROP INTO THE 50S TO LOW 60S AND WILL WARM INTO THE UPPER 70S TO LOW 80S TOMORROW. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HIGHLIGHTS... * DRY AND SEASONABLY WARM WEDNESDAY * COOLER THU AND FRI WITH A RISK OF A FEW SHOWERS * DRYING TREND NEXT WEEKEND BUT COOLER THAN NORMAL SYNOPTIC OVERVIEW AND MODEL EVALUATION... MAIN WEATHER FEATURE THIS PERIOD WILL BE A HIGH AMPLITUDE RIDGE OF +2 TO +3 STANDARD DEVIATIONS ABOVE CLIMO OVER GREENLAND AND THE DAVIS STRAIT. THIS RESULTS IN A REX TYPE BLOCK PATTERN TO DEVELOP OVER THE NORTHEAST STATES INTO SOUTHEAST CANADA. THIS SHIFTS THE JET STREAM/STORM TRACK/FRONTAL BOUNDARY SOUTH OF NEW ENGLAND...ALLOWING MAINLY DRY WEATHER AS COOL MARITIME HIGH PRESSURE BUILDS SOUTHWARD INTO NEW ENGLAND. REGARDING MODEL GUIDANCE...GEFS AND ECENS ENSEMBLES IN GOOD AGREEMENT ON THE LARGE SCALE FLOW THIS PERIOD. AS FOR THE DETERMINISTIC RUNS OF THE GFS AND ECMWF...TYPICAL TIMING AND AMPLITUDE DIFFERENCES AT THIS TIME RANGE...BUT OVERALL IN GOOD AGREEMENT ON THE OVERALL PATTERN AND THEME. THUS ABOVE AVERAGE FORECAST CONFIDENCE THIS PERIOD. SENSIBLE WEATHER DETAILS... WED... SHORT WAVE RIDGING PERSIST OVER NEW ENGLAND TO YIELD DRY WEATHER AND SEASONABLY WARM TEMPS...U70S TO L80S. WEAK HIGH PRES OVER THE AREA WILL SUPPORT LIGHT WINDS BUT ALSO AFTERNOON SEABREEZES KEEPING THE COASTLINE SLIGHTLY COOLER. FAIRLY COMFORTABLE WITH DEW PTS IN THE U50S TO L60S. SHORT WAVE TROUGH AND DEEPER MOISTURE FROM THE GREAT LAKES APPROACHES NEW ENGLAND LATE IN THE DAY AND ESPECIALLY WED NIGHT. THUS A LOW RISK OF A FEW SHOWERS ACROSS WESTERN CT-MA- SOUTHWEST NH. ELSEWHERE DRY WEATHER SHOULD PREVAIL. NOT EXPECTING ANY THUNDER GIVEN THE LACK OF SFC BASED AND INSTABILITY ALOFT. THU INTO FRI... SHORT WAVE TROUGH TRACKS FROM THE GREAT LAKES TO SOUTHERN NEW ENGLAND. THE BULK OF THE DEEP LAYER MOISTURE AND SURFACE LOW TRACK WELL SOUTH OF NEW ENGLAND. HOWEVER THE ONSHORE FLOW AND ESPECIALLY THE UPSLOPE COMPONENT ACROSS THE HIGHER TERRAIN OF WESTERN CT-MA INTO SOUTHWEST NH ALONG WITH CYCLONIC FLOW ALOFT MAY YIELD PERIODIC SHOWERS. GREATEST RISK WILL BE ACROSS THE INTERIOR. ELSEWHERE LOWER RISK OF SHOWERS. OVERALL NOT A WASHOUT JUST A FEW SPOTTY SHOWERS... PERHAPS MORE NUMEROUS OVER THE HIGHER TERRAIN. GIVEN THE COOL ONSHORE WINDS...SB INSTABILITY IS NIL AND MID LEVEL LAPSE RATES ARE LESS THAN 6C/KM. THUS NOT ANTICIPATING ANY THUNDER. NEXT WEEKEND... MEAN MID LEVEL TROUGH AXIS EXPECTED TO MOVE OFFSHORE AND ALLOWS 1024 MB MARITIME HIGH TO BUILD SOUTHWARD INTO NEW ENGLAND. THIS PROMOTES A DRYING TREND BUT ALSO COOLER THAN NORMAL TEMPS WITH HIGHS MAINLY IN THE LOW TO MID 70S. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH TUESDAY...HIGH CONFIDENCE. 18Z UPDATE... VFR. NW WINDS WITH GUSTS UP TO 20 KTS ACROSS THE INTERIOR. SEA- BREEZE ACTIVITY ALONG THE IMMEDIATE SHORELINES FROM NOW UNTIL 22Z. WINDS LIKELY TO BE LIGHT AND VARIABLE WITH SEA-BREEZE INCURSION. SCT-BKN CIGS AROUND 5-6 KFT. OVERNIGHT...LIGHT N WINDS ANTICIPATED UNDER SKC. PATCHY MVFR-IFR GROUND FOG IS POSSIBLE. LIGHT AND VARIABLE WINDS CONTINUE INTO TUESDAY ALLOWING SEA-BREEZE ENCROACHMENT BEGINNING AROUND 14Z... WASHING OUT INTO OVERNIGHT HOURS. SCT CIGS AROUND 5-6 KFT DURING THE DAY...MAINLY SKC INTO WEDNESDAY MORNING WITH SOME FILTERING MID- TO HIGH-LEVEL CLOUDS. KBOS TERMINAL...MODERATE CONFIDENCE. WEAKENING NW-FLOW IN AND AROUND THE TERMINAL INDICATES POTENTIAL SEA-BREEZE SETUP TOWARDS 20Z. SEA-BREEZE MAY STRUGGLE TO REACH THE TERMINAL...PERHAPS PARKING OVER THE E-END OF RUNWAYS. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH FRIDAY... WED...HIGH CONFIDENCE FOR VFR/DRY WEATHER AND AFTERNOON SEA BREEZES. WED NIGHT/THU/FRI...MODERATE CONFIDENCE. MAINLY VFR WITH A LOW RISK OF MVFR AT TIMES IN SCT SHOWERS...ESPECIALLY WESTERN NEW ENGLAND IN HIGHER TERRAIN. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TODAY THROUGH TUESDAY...HIGH CONFIDENCE. QUIET BOATING WEATHER IS EXPECTED. NORTHWEST FLOW WITH OCCASIONAL GUSTS TO 20 KTS IN THE AFTERNOON. SEA BREEZES POSSIBLE MON AFTERNOON AND TUESDAY AFTERNOON. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...MODERATE TO HIGH CONFIDENCE. STORM TRACK REMAINS SOUTH OF NEW ENGLAND WITH A SERIES OF WEAK LOWS EXITING THE MID ATLC COAST AND TRACKING SOUTH OF 40N LATITUDE. HOWEVER HIGH PRES BUILDING SOUTH FROM QUEBEC COMBINED WITH THESE SERIES OF WEAK LOWS SOUTH OF NEW ENGLAND MAY RESULT IN ENE WINDS UP TO 20-25 KT ACROSS THE SOUTH COASTAL WATERS THU NIGHT INTO FRI. AS FOR VSBY MAINLY GOOD BUT MAY LOWER IN PATCHY FOG AND ISOLATED SHOWER WED NIGHT THRU FRI. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...SIPPRELL SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/DUNTEN

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