Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 020138 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 935 PM EDT FRI JUL 1 2016 .SYNOPSIS... An approaching cold front will bring numerous showers and scattered thunderstorms into this evening, and a few of them may become strong to severe with locally heavy rainfall. High pressure builds in behind the front and dry and very warm weather through much of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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***Severe weather potential has diminished but still can not rule out a low risk for a few strong to marginally severe t-storms through 2 or 3 am*** 935 pm update... Tornado watch for western MA/northern CT has been dropped as the bulk of the showers/thunderstorms have moved east of that region. Main action currently across the eastern half of MA, where a cluster of thunderstorms were producing brief torrential rainfall. However, limited instability has kept this activity below severe limits. Still some uncertainty as to what exactly unfolds overnight. Mainly dry across the western half of the CWA at this time. However, surface cold front and cold pool aloft will be approaching from the west. SPC meso-analysis page shows shear increasing near midnight along with instability. However, drier mid level air will be moving into the region at the same time and act as a limiting factor. So in a nutshell, surface convergence along the front/increasing shear may yield another round of scattered showers/t-storms. However, dry mid level will try limit areal coverage of convection and its intensity. Nonetheless, still the low risk for a few strong to marginally severe storms overnight through 2 or 3 am given increasing shear/low level convergence.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Saturday... Mostly sunny and dry conditions with dry westerly flow in place. 850 mb temps 10-12C support highs in the upper 70s to lower 80s. A refreshing airmass as dewpoints will drop into the upper 40s and 50s. It will become a bit breezy with gusts 20-25 mph. Saturday night... A quiet night with mainly clear skies and diminishing wind. With very dry airmass in place it will be a cool night for July with mins dropping into the 50s with some upper 40s possible colder locations in the CT Valley. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Big Picture... Upper trough over the Northeast USA Sunday-Monday lifts out through the Maritimes. Subtropical high covers the southern half of the country and builds north by midweek. The GFS and ECMWF have different magnitudes for 500 mb contour heights midweek but both show the same trend with above normal values for July. The GGEM is more of an outlier. Details... Sunday-Monday... Upper trough and cold pool with Vertical Totals 26-27C, but cloud moisture limited to a layer either side of 800 mb. Could be diurnal clouds but no showers. Mixing reaches to at least 800 mb each day with temps at that level supporting max sfc temps in the Low to Mid 80s. Tuesday through Friday... Upper ridge builds. The broad area of subsidence will allow dry weather with plenty of sun each day. Mixing will reach above 850 mb, supporting max sfc temps in the upper 80s and lower 90s. An approaching cold front may bring a chance of showers Friday although a west-to-east flow may hamper southward progress of any cold front. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT Short Term /through Saturday Night/... Tonight...Moderate confidence. Cigs lowering to MVFR/IFR south of the Mass Pike later this afternoon into this evening. Patchy fog also developing tonight. Showers this evening move west to east across SNE. Still small potential for a storm or two to become strong or damaging, mainly over CT and Western MA. Improvement expected by 12z in most locations, except for patchy stratus/fog lingering on the outer cape/islands. Saturday...High confidence. Patchy MVFR/IFR lingering over cape/islands early, otherwise VFR. W/NW wind gusts to 20 kt. Saturday night...High confidence. VFR. KBOS TAF...Moderate confidence. Main thunderstorm risk 01-05z. KBDL TAF...Moderate confidence. Main thunderstorm risk 22-03z. Outlook /Sunday through Wednesday/... High confidence. VFR through the period. Patchy IFR in fog possible early each morning. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/...High confidence. Tonight...Pre-frontal southerly wind gusts to 20 kt into this evening with up to 25 kt NE MA outer coastal waters where seas expected to reach 5 ft. SCA will continue here. Biggest concern for mariners is the risk for a few strong thunderstorms this evening, with the potential for 40+ kt gusts. Patchy fog will also limit vsby at times. Saturday and Saturday night...Mainly westerly winds below SCA thresholds. Gusts up to 20 kt during Sat. Outlook /Sunday through Wednesday/... High confidence. Winds remain below 25 knots and seas below 5 feet through the period. && .FIRE WEATHER... After showers and sct t-storms this evening, widespread precipitation looks to be nil over the next 7 days. High pressure and dry conditions appear to take hold of the region Saturday, lasting through the much of next week. Much of this time will be less humid with RH values dropping close to 30 percent for much of this time. Winds overall appear to be light during this period. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 4 AM EDT Saturday for ANZ250. && $$ SYNOPSIS...WTB/KJC NEAR TERM...FRANK SHORT TERM...KJC LONG TERM...WTB AVIATION...WTB/KJC MARINE...WTB/KJC FIRE WEATHER...

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