Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 200718 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 318 AM EDT SUN JUL 20 2014 .SYNOPSIS... LOW PRESSURE LIFTING NORTHEAST FROM THE MID-ATLANTIC WILL BRING MOSTLY CLOUDY CONDITIONS ACROSS MUCH OF NEW ENGLAND WITH LIGHT SHOWERS FOR THE IMMEDIATE SOUTH AND SOUTHEAST COASTLINE THROUGH LATE TODAY. THEREAFTER...HIGH PRESSURE BUILDS INTO THE REGION BRINGING WITH IT DRY WEATHER ALONG WITH WARM AND HUMID CONDITIONS THROUGH MIDWEEK. A COLD FRONT FROM CANADA TRACKS THROUGH SOUTHERN NEW ENGLAND DURING THURSDAY...WITH HIGH PRESSURE RETURNING ON FRIDAY. && .NEAR TERM /THROUGH TODAY/... LATEST RADAR DATA SHOWING AN AREA OF LIGHT RAINFALL MOVING NORTHEAST FROM NORTHEAST PA. THIS AREA OF RAINFALL IS ASSOCIATED WITH A MID LEVEL SHORTWAVE WHICH WILL CROSS SOUTHERN NEW ENGLAND THIS MORNING. THERE WAS ANOTHER AREA OF LIGHT RAINFALL OVER SOUTHEAST MA AND THE ADJACENT COASTAL WATERS. MOST AREAS WERE NOT EXPERIENCING MEASURABLE RAINFALL SO FAR...BUT CANNOT COMPLETELY RULE OUT SOMETHING MORE THAN SPRINKLES THIS MORNING. SURFACE HIGH PRESSURE RIDGE SHOULD HOLD FAIRLY STRONG OVER SOUTHERN NEW ENGLAND TODAY. THIS WILL SHUNT THE GREATEST RISK FOR MEASURABLE RAINFALL TOWARD THE CAPE AND ISLANDS LATER TODAY. A LOW PRESSURE IS ANTICIPATED TO MOVE FROM THE MID ATLANTIC COAST THIS MORNING...PASSING WELL SOUTHEAST OF NANTUCKET THIS EVENING. WITH LOTS OF CLOUDS AND A CONTINUED EAST TO SOUTHEAST FLOW...MAX TEMPERATURES WILL GENERALLY BE 5-10 DEGREES BELOW NORMAL TODAY. && .SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/... TONIGHT...MID-LEVEL TROUGH WITH ACCOMPANYING LOW MOVING NORTHEAST INTO NOVA SCOTIA. SHOULD SEE THE RETURN OF HIGH PRESSURE DESPITE SOME LINGERING INFLUENCE OF THE TROUGH ACROSS THE EASTERN GREAT LAKES DOWN THROUGH THE OHIO RIVER VALLEY. ANTICIPATED LIGHT WINDS AND CLEARING CONDITIONS COULD MAKE FOR A PERIOD OF EFFECTIVE RADIATIONAL COOLING. WILL FORECAST LOWS NEAR TO SLIGHTLY BELOW NORMAL. MONDAY...SURFACE HIGH PRESSURE LOOKS TO BE IN CONTROL ACROSS SOUTHERN NEW ENGLAND. WITH A MID LEVEL CAP IN PLACE...EXPECTING SOME DIURNAL CUMULUS...BUT LOW PROBABILITY FOR SHOWERS. ONSHORE FLOW WILL KEEP MAX TEMPERATURES ON THE COOL SIDE TOWARD THE COASTS. ELSEWHERE...SEASONABLE MAX TEMPERATURES ARE EXPECTED WITH MORE SUNSHINE. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGHLIGHTS... * DRY TO START THE WORK WEEK. * BECOMING WARMER AND MORE HUMID THROUGH MID WEEK. * BEST CHANCE OF SHOWERS AND THUNDERSTORMS IN THE WEDNESDAY TO THURSDAY NIGHT TIMEFRAME WITH THE APPROACH AND PASSAGE OF A COLD FRONT. DETAILS... TUE...DURING TUE STARTING OFF WITH SURFACE HIGH PRESSURE OVER THE AREA WHICH SLIDES OFFSHORE DURING THE DAY...MEANWHILE LARGE UPPER RIDGE IN THE CENTRAL/WESTERN U.S. BUILDS SOMEWHAT INTO OUR AREA. THIS WILL RESULT IN INCREASING HEAT AND HUMIDITY. HOWEVER WITH MODELS SHOWING THE POTENTIAL FOR A MID LEVEL CAP CONVECTION SHOULD BE DIFFICULT TO ACHIEVE. CONTINUE PREV FORECAST W/MAINLY DRY FORECAST. H85 TEMPS ON TUE AROUND +18C...SO WITH ENOUGH SUNSHINE AND MIXING TEMPS ARE LIKELY TO APPROACH 90F IN SPOTS. LOW LEVEL SW FLOW SHOULD BE FAIRLY WEAK...SO THERE IS THE POTENTIAL FOR SEABREEZE DEVELOPMENT. PATCHY STRATUS/FOG MAY AGAIN DEVELOP TUESDAY NIGHT. WED INTO THU...CONTINUED INCREASE IN MOISTURE AS SW FLOW DEVELOPS OVER SOUTHERN NEW ENGLAND...AHEAD OF AN APPROACHING COLD FRONT AND POSSIBLE OPEN WAVE ALONG THE FRONT. AIRMASS BECOMES UNSTABLE...HOWEVER FRONT OR FOCUS FOR LIFT NOT QUITE INTO OUR AREA YET ON WED...SO GENERALLY SLIGHT CHANCE POPS FOR CONVECTION LOOK GOOD FOR THAT TIMEFRAME. H85 TEMPS ON WED AROUND +19C...SO WITH ENOUGH SUNSHINE AND MIXING TEMPS ARE LIKELY TO REACH AROUND 90F IN SPOTS...DEWPOINTS IN THE 60S SO IT WILL ALSO BE MUGGY. MODELS INDICATE THAT THE FRONT AND POTENTIAL OPEN WAVE REACH OUR AREA DURING THE WED NIGHT/THU TIMEFRAME. UPPER TROUGH WILL BE CROSSING OUR AREA DURING THIS TIMEFRAME AS WELL...RESULTING IN A BETTER CHANCE FOR SHOWERS/TSTMS WED NIGHT INTO PROBABLY THU NIGHT. PRECIPITABLE WATER INCREASES TO AROUND 2 INCHES...LENDING THE POTENTIAL FOR LOCALLY HEAVY DOWNPOURS ON THU. FRI...LATEST OPERATIONAL MODELS INCLUDING 00Z AND 12Z ECMWF ARE A BIT QUICKER WITH THE SURFACE FRONT AND ASSOCIATED LOW PRESSURE CENTER...INDICATING THEY MAY BE OFFSHORE FOR 12Z FRI WITH HIGH PRESSURE BUILDING IN FROM THE W IN ITS WAKE. HOWEVER THE UPPER TROUGH MAY LINGER...WHICH COULD CONTRIBUTE TO A POSSIBILITY OF SPOT DIURNAL SHOWERS. WILL CONTINUE SLIGHT CHANCE FOR SHOWERS ON FRI. NEXT WEEKEND... WITH LATEST MODEL SUITE INCLUDING 00Z/12Z ECMWF MUCH QUICKER WITH PREVIOUSLY MENTIONED COLD FRONT...A PERIOD OF HIGH PRESSURE AND UPPER LEVEL RIDGING MAY BRING DRY CONDITIONS FOR SATURDAY. HOWEVER...THE APPROACH OF ANOTHER FRONT MAY BRING UNSETTLED WEATHER FOR SUNDAY. && .AVIATION /06Z 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/...HIGH CONFIDENCE. VFR. 5-10 KT EASTERLY FLOW FOR A MAJORITY OF THE FORECAST PERIOD. BKN-OVC 10 KFT CIGS OR HIGHER EXCEPT ACROSS THE IMMEDIATE S/SE COASTLINE WHERE A CHANCE SHRA IS POSSIBLE THROUGH LATE TODAY ALONG WITH THE POSSIBILITY OF AT LEAST LOW-END VFR CIGS...POSSIBLY DOWN TO MVFR AT A FEW LOCATIONS. DRIER CONDITIONS ARRIVE TONIGHT AND CONTINUE THROUGH MONDAY. VFR CONTINUES. KBOS TAF...HIGH CONFIDENCE IN TAF. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MODERATE CONFIDENCE. WHILE VFR WILL LIKELY DOMINATE MOST DAYS...SOME OVERNIGHT FOG/STRATUS MAY LEAD TO MVFR/IFR CONDITIONS MON NIGHT AND TUE NIGHT. MAIN AREA OF CONCERN IS SOUTH COASTAL LOCATIONS. CHANCE FOR LOCALIZED MVFR/IFR CONDITIONS IN SHOWERS AND THUNDERSTORMS WED AND THU. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THROUGH MONDAY...HIGH CONFIDENCE. WAVE MODELS CONTINUE TO OVERFORECAST WAVE HEIGHTS OFF OUR COAST BY ABOUT A FOOT. LOWERED THE WAVE HEIGHT GUIDANCE BY 20 PERCENT THROUGH MONDAY. TRANQUIL BOATING WEATHER CONTINUES WITH EASTERLY WINDS AROUND 5-15 KT. WINDS AND SEAS BELOW SMALL CRAFT ADVISORY LEVELS. WILL SEE A CHANCE OF SHOWERS ACROSS THE S/SE WATERS AND ADJACENT SHOWERS TODAY. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... THE AREA OF LOW PRESSURE WILL MOVE FURTHER OFFSHORE...WITH SURFACE HIGH PRESSURE BUILDING OVER THE WATERS. MODERATE CONFIDENCE THAT WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS DURING MONDAY NIGHT THROUGH THROUGH THE DAY ON WEDNESDAY. BUT A FEW WIND GUSTS AND HIGHER SEAS ARE POSSIBLE ON WED AS THE SW WINDS INCREASE. PATCHY FOG MAY LEAD TO VSBY RESTRICTIONS DURING MON AND TUE NIGHTS. FOR WEDNESDAY NIGHT AND THURSDAY THE APPROACH OF A COLD FRONT AND ASSOCIATED LOW PRESSURE WILL BRING INCREASING SW FLOW...AND THE CHANCE FOR SCA WINDS/SEAS AS WELL AS SCATTERED SHOWERS/TSTMS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...BELK/NMB NEAR TERM...BELK SHORT TERM...BELK LONG TERM...NMB AVIATION...BELK/NMB MARINE...BELK/NMB

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