Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220744 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 244 AM EST Mon Jan 22 2018 .SYNOPSIS... Some light precipitation is expected today and tonight. Most of it will be rain, but light icing is likely over interior high terrain especially tonight into early Tuesday. A fast moving storm system will bring a period of heavy rain to the region Tuesday along with strong winds across SE New England. Blustery, dry and colder weather follows Wednesday through Friday, then a warming trend next weekend. A cold front may bring showers by next Sunday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 1040 PM Update... Leading edge of overrunning precip pushing into the Berkshires and Litchfield hills as seen on latest NE regional 88D radar imagery, though not seeing any ground truth of it reaching the ground yet. Have kept slight CHC POPs going for now from around midnight onward, but will monitor the precip progression. T/Td spreads are lower, down to 4 degrees or less across the CT valley with some patchy fog from about KPSF-KORE and northward into S VT/S NH on 03Z obs. As lower layer continues to moisten, will likely see more patchy fog develop so have included that in the overnight forecast. The temps were mainly near or below freezing across N central and W Mass at 03Z, so will likely see some mixture at the onset of the precip but should be very light at least to start. Will follow suggestion from previous shift and issued Special Weather Statements as needed. Remainder of forecast was updated to bring conditions current. Previous discussion... High pressure is situated to provide dry weather much of the night. Low level flow remains light most of this time, but shows signs of overrunning after midnight. Meanwhile, satellite images and sfc observations show a cloud deck over Eastern PA edging northeast. Between this and the favorable development of lift overnight, expect increasing clouds through the night. Can not rule out some light precip late, especially in Western MA and CT, but the chance before 12Z is rather low so we used slight chance pops. If any precipitation were to form late tonight, temperature profiles suggest rain in the south and a snow/sleet/freezing rain mix north. Clouds will limit the overnight cooling, and cold air damming signal does not show much until late night. We maintain a range of upper 20s north to mid 30s south coast. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... Monday... High pressure over Quebec Monday and increasing cold air damming into New England. The damming seems focused on Northern New England, but could further expand into our area as well during Monday morning. Our temperature profiles support rain most places, but a rain/snow mix north of the Mass Pike. The GFS and ECMWF bring a front south into Southern New England or just to our south. This shows increasing lift potential, thus increasing pops. We show chance pops all areas Monday morning and likely pops in the afternoon in Western and Central Mass and adjoining CT. An east wind should be enough to keep ptype as rain, but it may be marginal in Western Mass/Northern Worcester County. Even with better lift, the focus of southerly low level winds and moisture remains to our west across New York State through the day. So we continue to expect QPF amounts up to 0.1 inches. Monday night... Evening cooling and the stalled front to our south may allow a brief period of freezing rain in Central and Western Mass, especially along and north of the Route 2 corridor. The front moves north during the night with winds shifting from the south. This will bring slowly rising temperatures overnight ending the icing risk. South-southwest winds 35-40 knots move up over the region during the late night. This transports 1 inch PW values into the area. Expect increasing chance of rain toward morning with categorical pops...75 pct or higher...over Western Mass and Western CT. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Blustery and colder Wed, and especially Thu/Fri, but dry * Much milder next weekend with showers possible by Sunday Tuesday night... Cold front will be in the vicinity of the Cape/Islands Tue evening then moving offshore. Some lingering showers are possible here early, and a few rain to snow showers possible western MA in the evening as mid level trough swings through. Otherwise, gradual clearing will develop although some lower clouds may linger across NW MA. Gusty west winds will develop overnight as low level cold advection increases. Wednesday through Friday... Blustery and colder pattern as longwave trough develops over the NE but mainly dry weather expected with dry column and subsidence. Near normal temps Wed, then trending below normal Thu/Fri. Core of the coldest air aloft on Thu with 850 mb temps near -15C. This will result in highs Thu mainly in the 20s to near 30 with gusty winds making it feel considerably colder, while Thu night wind chills drop into the single numbers and subzero higher terrain. Temps recover Fri as heights begin to rise and low level temps moderate but a cold start will hold temps from the upper 20s to mid 30s. Saturday and Sunday... Return to milder airmass and well above normal temps as high pres moves offshore and mid level ridge builds north along the east coast. 850 mb temp anomalies 1-2SD and EPS/GEFS ensembles have fairly high probs of 50s in the coastal plain by Sun. Deterministic GFS looks too fast with next approaching trough and not supported by majority of GEFS members so we leaned toward slower ECWMF solution given downstream ridging in place over the western Atlantic. Next chance of showers assocd with the mid level trough and attending cold front should hold off until Sunday or possibly Sat night. Very low risk of some icing distant interior if precip comes in Sat night but any freezing precip would probably be localized and this is a very low probability. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/... Overnight...High confidence. Mainly VFR conditions with light/variable winds becoming S along the S coast toward daybreak. Expect CIGS/VSBYS lowering to MVFR across the E slopes of the Berkshires and CT valley by around 05Z, then will slowly shift E across central and NE Mass. Will see a spotty light mix of -RA/-SN/-FZRA/-PE mainly across the E slopes of the Berkshires to N Worcester county and the Merrimack valley through daybreak. Monday...Moderate confidence. MVFR cigs with areas of IFR cigs developing in the afternoon. Increasing chance of light rain through the day. Generally MVFR vsbys in rain and some mixed rain/snow. Light wind becomes light East-Northeast. Monday night...Moderate confidence. MVFR conditions with areas of IFR. Rain most places with a chance of freezing rain early in northern areas of Massachusetts such as vicinity of FIT and ORE. Winds turn from the Southeast and South toward morning. KBOS Terminal...Moderate to high confidence in TAF. KBDL Terminal...Moderate to high confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday Night: Mainly VFR, with local MVFR/IFR possible in the evening across Cape/Islands. Windy with gusts to 30 kt. Slight chance SHRA in the evening. Wednesday: VFR. Windy with gusts to 30 kt. Wednesday Night through Friday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/...Moderate confidence. Tonight and Monday... Light winds shift from the south late at night and from the southeast Monday. Speeds remain below 15 knots. Seas 2 feet or less. Vsby lowers to 3-5 miles in rain during Monday afternoon. Monday night... Southeast to south wind increasing, but remaining below 25 knots. Seas building to 4 feet. Rain with vsbys 3-5 miles. Outlook /Tuesday Night through Friday/... Tuesday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 12 ft. Slight chance of rain showers. Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 11 ft. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Thursday through Thursday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Friday: Winds less than 25 kt. Local rough seas. && .HYDROLOGY... A Flood Warning remains in effect for the Connecticut River at Middle Haddam, where ice jams are causing river fluctuations. No significant change from earlier forecasts. For details on specific area rivers, including observed and forecast river stages, please visit the Advanced Hydrologic Prediction Service (AHPS) graphs on our website. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Watch from Tuesday morning through late Tuesday night for ANZ232>235-237-250-254>256. Gale Watch from Tuesday morning through Tuesday evening for ANZ230-236. Gale Watch from Tuesday morning through late Tuesday night for ANZ231-251. && $$ SYNOPSIS...KJC NEAR TERM...Doody/EVT SHORT TERM...WTB LONG TERM...KJC AVIATION...WTB/KJC/EVT MARINE...WTB/KJC/EVT HYDROLOGY...

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