Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 200744 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 344 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 /UNTIL 6 PM THIS EVENING/... 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 /6 PM THIS EVENING 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. OVERVIEW AND MODEL PREFERENCES... WITH THE LATEST /20.00Z/ GUIDANCE SUITE...THE DIFFERENCES REGARDING A DIGGING TROF LATE IN THE WEEK ARE DIMINISHING. THE ECMWF...AND SOME ENSEMBLES ARE LESS AMPLIFIED AS THE TROF TRIES TO DIG INTO BUILDING RIDGE BOTH ACROSS THE SW CONUS AND SE ATLANTIC ASSOCIATED WITH THE BERMUDA HIGH. THEREFORE...THE TIMING OF A COLD FRONT FOR WED-THU APPEARS TO BE FASTER WITH HIGH PRES NOW DOMINATING THE LATTER PART OF THE WEEK. GIVEN THIS IDEA FITS THE PATTERN BETTER...FEEL A BLEND OF THIS LATEST ECMWF WITH OTHER OPERATIONAL GUIDANCE IS THE BEST COURSE OF ACTION WITH THIS UPDATE. THEREFORE...THE PERIOD WILL BE DOMINATED BY THESE TWO BUILDING RIDGES...ALLOWING FOR AN INFLUENCE OF THE BERMUDA HIGH THROUGH AT LEAST MID WEEK. THE WARMING/HIGHER HUMIDITY TREND IS FAVORED AS THE FLOW PATTERN WILL ALLOW H85 TEMPS TO REACH ALMOST +19C BY THU. IT IS NOT UNTIL THAT SLOWLY WEAKENING TROF ARRIVES LATE IN THE WEAK THAT A DRIER..ZONAL..AND COOLER AIRMASS IS ALLOWED TO MOVE IN. DETAILS... MON NIGHT INTO WED... GRADUALLY WARMING TEMPERATURES THANKS TO SW FLOW IS EXPECTED...ALONG WITH INCREASING DWPTS...REACHING THE UPPER 60S BY WED. H85 TEMPS OF +16C TUE SUGGEST TEMPS IN THE MID 80S WHERE SUNSHINE ALLOWS FULL MIXING...WHILE +18C SUGGESTS SOME HIGHS AROUND 90F ON WED. THE KEY EACH OF THESE DAYS WILL BE THEIR CONVECTIVE POTENTIAL. EACH DAY THE H7 TEMPS INCREASE...TO ABOUT +8C ON TUE...THEN NEAR +10C BY WED...SUGGESTING A BUILDING CAPPING INVERSION. ALSO...RRQ OF THE UPPER JET AND SLACKENING IN THE MASS FIELDS REMAINS TO THE N AND W EACH DAY. THEREFORE...SUSPECT THAT THE BEST CHANCE FOR ACTIVITY IS TO THE N AND W. ALSO...SHEAR IS MINIMAL AT BEST /GENERALLY BELOW 15 KT/ SO ANY CONVECTIVE ACTIVITY THAT IS ABLE TO OCCUR WILL LIKELY COLLAPSE QUICKLY. IN SUM...WILL GO WITH SOME LOW POPS..MAINLY ACROSS THE W EACH DAY...WITH SLIGHTLY HIGHER POPS ON WED THANKS TO THE FACT THAT ALL OF THESE FEATURES LINE UP SLIGHTLY BETTER. OVERNIGHT...SOME FOG IS POSSIBLE...PARTICULARLY TUE NIGHT AND WED NIGHT. THU... BETTER CHANCE FOR CONVECTIVE ACTIVITY AS UPPER LVL JET STREAK LINES UP IT/S RRQ OVER SRN NEW ENGLAND...WITH SFC BASED CAPE VALUES 1000-1500J/KG. SHEAR MAGNITUDES ARE HIGHER AS WELL...ON THE ORDER OF 40 KT. ALL AS A SFC COLD FRONT PUSHES THROUGH THE AREA. WILL HIGHLIGHT CHANCE POPS WITH THE POSSIBILITY OF CONVECTION. ALTHOUGH A SEVERE THREAT IS THERE...HAVE HIGHEST CONFIDENCE IN HEAVY RAIN AS PWATS APPROACH 2.0 INCHES. WITH THE LATEST RUNS...WILL BEGIN TO BRING IN DRIER AIR BY THU EVENING. FRI INTO THE WEEKEND... WITH THE MORE PROGRESSIVE SOLUTION NOW FAVORED...THE SHORTWAVE TROF IS EXPECTED TO LIFT TO THE NE AS ONCE AGAIN...THE SW RIDGE REGAINS CONTROL. HOWEVER...DO EXPECT THAT SOME DRIER...COOLER AIR WILL MOVE IN WITH HIGH PRES MOVING OVER FROM THE W-NW. THEREFORE...EXPECT A RETURN TO LOWER HUMIDITIES AND NEAR SEASONABLE TEMPERATURES UNTIL SW FLOW RETURNS BY SUN. && .AVIATION /08Z 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... MON NIGHT INTO WED...MODERATE CONFIDENCE. MAINLY VFR. HOWEVER OVERNIGHT EACH NIGHT...THE THREAT FOR FOG WITH IFR/MVFR CONDITIONS IS POSSIBLE...PARTICULARLY ALONG THE S COAST. ISOLATED SHOWER/T-STORM POSSIBLE WED AFTERNOON MAINLY IN THE W. WED NIGHT INTO THU...MODERATE CONFIDENCE. A COLD FRONT CROSSES THE REGION...WITH A BETTER CHANCE FOR MORE WIDESPREAD SHOWERS OR THUNDERSTORMS AND MVFR/IFR CONDITIONS. && .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... MON NIGHT THROUGH TUE...HIGH CONFIDENCE. HIGH PRES OVER THE WATERS SHOULD LEAD TO MAINLY QUIET BOATING WEATHER...WITH SW WINDS AND SEAS GENERALLY BELOW SMALL CRAFT ADVISORY THRESHOLDS. SOME FOG POSSIBLE BOTH MON AND TUE NIGHT WITH REDUCED VSBYS. WED AND THU...MODERATE CONFIDENCE. SW FLOW IS EXPECTED TO INCREASE WED AHEAD OF A COLD FRONT WHICH WILL CROSS THE WATERS EARLY THU. WINDS NEAR THE SE COAST OF MA MAY GUST TO AROUND 25 KT AT TIMES...POTENTIALLY REQUIRING A SMALL CRAFT ADVISORY. SEAS SHOULD REMAIN BELOW 5 FT THROUGH THE PERIOD HOWEVER. SOME SHOWERS AND THUNDERSTORMS ARE POSSIBLE OVER THE WATERS PARTICULARLY LATE WED NIGHT AND THU. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK SHORT TERM...BELK LONG TERM...DOODY AVIATION...BELK/DOODY MARINE...BELK/DOODY

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