Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 202255 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 655 PM EDT Fri Oct 20 2017 .SYNOPSIS...
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High pressure centered over the Eastern USA will move offshore during the weekend. The high will bring warm dry weather for over the weekend. A cold front brings showers Tuesday and Wednesday. Cooler drier weather returns late in the week.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Clear skies and light winds across the region will bring dry weather and cooling temperatures overnight. Observed dew points this evening were in the 30s, except for some 40s along the South Coast. With radiational cooling favored, we expect min temps to reach 35-40 in Western Mass and upper 30s to mid 40s in interior sections farther east. Min temps 45 to 52 along the coastline.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Saturday... Subtropical ridge currently over the southeast states builds northward up the eastern seaboard Saturday. Surface high moves from eastern PA early Sat to south of New England during the afternoon, yielding light SW winds across the area. Surface pressures higher tomorrow (1024 mb) than today (1017 mb) across New England. This will result in less blyr mixing but entire column continues to warm with 925 mb temps warming from +11C today to +16C tomorrow. This will yield highs in the mid to upper 70s, likely falling shy of the records but still very pleasant with dew pts in the 40s, light winds and lots of sunshine. Record highs are 80 at Worcester, 81 at Providence, and 82 at Hartford and Boston...all set back in 1920. Saturday night... High pressure lingers over the area so expect dry weather along with temps falling quickly with sunset given light winds, dry atmosphere and clear skies. Although not as cool as tonight as southwest winds Sat bring dew pts up into the 40s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... 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-Monday... High pressure to our east with a light southerly flow across Southern New England. The period will be subsident with warm tempertures 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. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/...Generally high confidence. 2 PM update... High pressure provides VFR, dry weather and light winds tonight, Sat and Sat night. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Sunday through Wednesday/... Sunday...VFR. 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. && .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. 4 PM update... Very tranquil boating weather for late Oct with high pressure building across the area through Sat night. Expecting light winds, dry weather and good vsby thru this period. Outlook /Sunday through Wednesday/...High confidence. Sunday through 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. && .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/Nocera NEAR TERM...WTB/Nocera SHORT TERM...Nocera LONG TERM...WTB AVIATION...WTB/Nocera MARINE...WTB/Nocera FIRE WEATHER... CLIMATE...

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