Area Forecast Discussion
Issued by NWS Boston, MA

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883 FXUS61 KBOX 210610 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 210 AM EDT Sat Oct 21 2017 .SYNOPSIS...
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High pressure centered over the Eastern USA will move offshore this weekend, bringing warm, dry weather to our region. A cold front brings showers Tuesday and Wednesday. Cooler drier weather returns late next week.
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&& .NEAR TERM /THROUGH TODAY/...
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High pressure remains in control of our weather, although the center does start to move farther east of our region. This should mean a west to southwest wind across our region. While max temperatures should be higher today, and about 10-15 degrees above normal, it remains probable that today`s record high temperatures are safe. Overall, still a very pleasant day for the second half of October with plenty of sunshine.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/...
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Center of a high pressure continues to move east of southern New England during this time. Dry weather with mostly clear skies will continue, with only some passing high clouds at times. South to southwest winds also continue, meaning temperatures remain well above normal.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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Big Picture... Ridge over the Eastern USA early in the week with above normal 500- mb heights foretells a mild dry start to the week. High amplitude trough digs over the Central USA during this time with a closed low forming over the Great Lakes by Tuesday. The low then sweeps east across New England Thursday-Friday. As the upper low approaches and then moves overhead, 500-mb heights over us will lower substantially, from the 580s to the 550s, which suggests much cooler temperatures later in the week. Mass fields begin to diverge Tuesday as the upper low formation takes off to our west-southwest. Thermal fields are similar through Wednesday then diverge. High confidence in forecast Sunday and Monday...confidence then diminishes through moderate the rest of the week. Details... Sunday Night-Monday... High pressure to our east with a light southerly flow across Southern New England. The period will be subsident with warm temperatures aloft. Main question will be the depth of the mixed layer with shallow mixing promoting cooler temps. Mixing to 900 mb would tap a 10C equivalent, while 925 mb would tap an 8-9C equivalent. Expect max temps in the 70s, possibly 80 if the mixing goes deeper. Dew points in the 50s suggests min temps mainly in the 50s. Tuesday-Wednesday... The digging upper trough, associated surface cold front, increased southerly flow ahead of the front, and increased moisture in that flow all point to a chance of showers Tuesday and Tuesday night with lingering showers Wednesday. Precipitable water values climb to 1.5 inches Tuesday and may reach 2.0 inches just ahead of the cold front Tuesday night. Totals are forecast to reach upper 40s and LI values marginally sub-zero, so thunder is not out of the question, especially just ahead of the front. Thursday-Friday... Upper trough moves across on Thursday. High pressure builds on Friday. Could be some leftover showers Thursday especially in Eastern Mass. Dry weather Friday.
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&& .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. High pressure provides VFR, dry weather and relatively light winds through Sunday. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Sunday Night through Wednesday/... Sunday Night: VFR with local IFR in fog. Monday: VFR. Monday Night: VFR, with local IFR possible in fog. Chance SHRA late. Tuesday: MVFR, with local IFR possible. Breezy. Likely SHRA. Tuesday Night: MVFR, with local IFR possible. Breezy. Likely SHRA. Wednesday: Breezy. Chance SHRA.
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&& .MARINE...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. Very tranquil boating weather for late Oct with high pressure moving across the waters through Sat night. Expecting light winds, dry weather and good vsby through this period. Outlook /Sunday Night through Wednesday/...High confidence. Sunday Night: Winds less than 25 kt. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Chance of rain showers. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 11 ft. Rain showers likely. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 12 ft. Rain showers likely.
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&& .FIRE WEATHER... Dry weather continues through at least Sunday with minimum RH values Saturday down to 25 to 35 percent. However with high pressure nearby winds will be very light. Thus fire weather parameters remaining below headline criteria. && .CLIMATE... Record high temperatures for Saturday, October 21: BOS 82 in 1920 BDL 82 in 1920 PVD 81 in 1920 ORH 80 in 1920 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/Belk NEAR TERM...WTB/Belk SHORT TERM...Belk LONG TERM...WTB AVIATION...WTB/Belk MARINE...WTB/Belk FIRE WEATHER...Staff CLIMATE...Staff

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