Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 142003 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 303 PM EST Tue Nov 14 2017 .SYNOPSIS... Upper low and cold pool centered over Northern New England will move east tonight. High pressure brings drier air and clearing later tonight and Wednesday. Low pressure from the Northern Plains sweeps east, eventually redeveloping along the New England coast Thursday and bringing rain to the region. Another area of high pressure brings dry weather Friday, followed by rain Saturday from another storm approaching from the west. Drier weather follows for the start of next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Upper level low and cold pool are centered over Northern New England with -26C isotherm clipping northern Massachusetts. This low will move off through the Maritimes by morning, and as a consequence temperatures aloft will warm by several degrees. High pressure surface and aloft will build in overnight. Moisture levels diminish after 06z, suggesting a clearing trend in the sky cover after midnight. Winds will be light in the interior. Even on Cape Cod/islands where winds remain brisk this evening, expect the winds to diminish overnight. With clearing skies and light wind, expect temperatures in Western Mass and CT to radiate for a few hours and reach near the dew point. Farther east where clouds persist longer, temps will remain a few degrees above dew point. Overall range should be mid 20s northwest to near 40 Nantucket. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday... High pressure overhead will bring mainly clear skies and light wind. The actual center of the high will pass to our north, allowing the gradient wind to turn from the east through the day. Mixing to 925 mb will tap temps equiv to 850 mb temps of -7C to -10C. This supports max sfc temps in the low to mid 40s. Some question remains as to lingering clouds over the Cape and Islands. RH fields at 925 mb show 90-95 pct values there during Wednesday while 850 mb RH values are high mainly to the east of the Outer Cape. We will show 50 to 55 pct sky cover over the Cape and Islands with less cover for the remainder of our region. Wednesday night... High pressure maintains dry weather much of the night as it moves off to the east. The next shortwave comes from the Canadian Prairies and reaches the Great Lakes Wednesday night. The surface weather system moves from the Great Lakes to Quebec Wednesday night. The nose of the upper jet approaches the New England border around 06z with favorable jet dynamics over our area during the late night. Low level moisture increases during this same period. Precipitable water values only climb a little above normal by morning, and the low level jet forcing is concentrated in Northern NY overnight, so expect slow eastern progress into Southern New England. All of the operational models keep measureable QPF to our west through 06Z, then move the measureable values into at least western and central sections by 12Z. We move chance pops into Western sections by 3 AM and to Eastern Mass by 12Z. Likely pops to Western Mass and CT by 10-11Z. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Scattered showers move across late Wed night/Thu ahead of cold front * Light snow showers possible across higher terrain early Sat * Widespread rainfall likely Sat afternoon and Sat night * Some showers linger through at least midday Sunday Details... Thursday... Leading edge of precip reaches Southern New England early Thursday. Brought likely POPs in by around 12Z across central and western areas, then should push E during the afternoon. QPF amounts should run about 0.2" or less through this timeframe. Winds pick up on Thu as temps rebound. As the cold front moves across Thu afternoon, winds shift to W-NW. Milder air starts to work in ahead of the cold front. Thursday night and Friday... Strong cold air advection works in Thu night with increasing NW winds. Also noting strong low level NW jet moving across, with H85 winds up to 30-40 kt, but some question how much this will mix down. Appears that low level mixing develops during Fri afternoon, but from about H9 and lower. Could see gusts up to around 20 kt, highest across the inland terrain, but will be blustery along the coast especially Cape Cod and the islands. With mostly sunny to sunny skies on Friday, temps will only top off in the mid-upper 30s across the higher terrain ranging to the lower to mid 40s across the coastal plain. Friday night-Saturday night... Ridge axis at the surface and aloft shifts E. Expect increasing clouds during Fri night, but timing is in question. Noting widening model solution spread in the progression of the next system toward the region. GFS appears to be fast outlier in bring in leading edge of precip ahead of next cold front sometime Saturday, while GGEM and ECMWF is slower in moving low pressure out of the eastern Great Lakes around or after 00Z Sun. This is mainly due to both the GGEM and ECMWF trying to develop H5 cutoff low pres across southern Quebec/eastern Great Lakes while digging the mid level trough S to the Carolinas. 00Z GFS remains progressive. Could see leading edge of precip move into western areas after 06Z Sat, with best chance for precip during Sat, even though the surface low pres is slow to exit the eastern Great Lakes due to the possible mid level cutoff low. With temps running in the lower-mid 30s well inland late Fri night, might see some snow showers at the onset of any precip that may reach into N central and W Mass mainly across the higher terrain. Little if any snow accumulation is expected. Most precip should hold off until the daylight hours Sat as temps rebound to the 40s well inland ranging to the mid 50s along the S coast. Sunday-Monday... The slower model members hold off bringing the cold front through until Sunday morning. Scattered showers may linger into midday Sunday, and may mix with some snow showers across the E slopes of the Berkshires before ending around midday Sunday. Will become blustery as well, especially along the coast and across the higher terrain Sun afternoon. Expect mainly dry conditions on Monday, though a few showers may linger along the immediate S coast. Will still see gusty W-NW winds during Monday as well. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Tonight and Wednesday...High confidence VFR with dry weather. Clearing trend between 9 PM/02Z and 2 am/07Z. Light wind. Dry weather Wednesday with winds turning move from the east and southeast by afternoon. Increasing thin cirrus. Wednesday night... High confidence. VFR the first part of the night with increasing sky cover. Cloud bases 4000-6000 feet. After midnight cigs should lower to MVFR levels, about 2000-2500 feet. Showers enter from the Berkshires/Litchfield Hills late at night with 4-6 mile vsbys in showers reaching the CT Valley late. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Thursday through Sunday/...High confidence. Thursday: Mainly MVFR, with local IFR possible. Breezy. SHRA likely. Thursday Night through Friday: VFR. Windy with gusts to 30 kt. Friday Night: Mainly VFR, with local MVFR possible. Breezy. Saturday: Mainly MVFR, with areas VFR possible. Windy with local gusts to 30 kt. SHRA likely. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... High pressure builds over the waters tonight and Wednesday, then moves off to the east Wednesday night. Expect winds to remain below 25 knots through the period, and below 20 knots tonight and Wednesday. Seas have lingered at 5 feet on the outer waters east of Massachusetts and look to remain that way through Wednesday night. We have issues a Small Craft Advisory for Seas for this area. No headlines on the remaining waters. Rain will move in from the west late Wednesday night. Outlook /Thursday through Sunday/... Thursday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Rain showers likely. Thursday Night: Moderate risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Friday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Friday Night: Winds less than 25 kt. Local rough seas. Saturday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Rain showers likely. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas until 8 PM EST Wednesday for ANZ250-254-255.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT

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