Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 260835 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 335 AM EST Wed Jan 26 2022 .SYNOPSIS...
-- Changed Discussion --
High pressure brings an arctic airmass into the region today and tonight. Not quite as cold Thursday afternoon along with less wind, but nonetheless remaining colder than normal. Then all eyes turn to a powerful coastal storm Friday night into Saturday night, which will likely impact at least a portion of the region with heavy snow, strong winds, coastal flooding and dangerous seas. However, still some uncertainty on the exact storm track and intensity, which will have a direct impact on snow amounts and other storm details. Drier weather returns with below normal temperatures Sunday.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
330 AM update... Today... Arctic airmass slowly overspreads the region, on cold NNW drainage flow with 925 mb temps lowering to about -14C to -16C by days end. This strong low level cold air advection will preclude much if any temp rise from temps early this morning. Given this and shallow nature of the cold airmass, leaned toward the colder guidance sources to derive high temps today. This only yields highs in the low to mid 20s, upper teens for much of western-central MA. It will feel even colder in response to NNW winds 10 to 20 mph, highest winds over Cape Cod and the Islands.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
-- Changed Discussion --
Tonight... Arctic 1030+ mb high builds into the region, yielding a cold night ahead with lows mainly ranging from -5 to +5 across much of the region. NNW winds will trend more northerly and diminish. Thus, not much of a wind chill overnight, nevertheless, very cold overnight. Given diminishing winds, mostly clear conditions and a very dry airmass, derived lows tonight from the colder MOS guidance. Before winds diminish, NNW winds trending northerly, very cold air on this trajectory over the relatively warm SSTs, will yield OES across the outer Cape and possibly into coastal Plymouth county. The NSSL WRF and ARW are most aggressive with OES, and offer a coating up to an inch possible in spots across the outer Cape and coastal Plymouth county. This seems reasonable given 340 wind direction, delta-T of 24 degs from top of the mixed layer (-18C) to SSTs of +6C, and very little directional shear in the boundary layer. Otherwise, dry weather prevails. Thursday... A very cold start to the day, but slight improvement as ridge axis aloft moves east of the region along with surface high sliding offshore, offering weak return warm advection flow to setup. Temps only a few degs higher than today, but light SSW winds and plenty of sunshine will help offset the colder than normal temps.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 06z update... Today...High confidence VFR, dry weather and NW winds 10-20 kt, highest winds over Cape Cod and the islands. Given this wind trajectory, ocean effect snow showers likely remain just offshore of Cape Cod. Tonight...High confidence. VFR, dry weather with NNW winds at 5-15 kts. Gusts up to 20 kts across the Cape/Islands. This more northerly wind trajectory likely results in ocean effect snow showers and MVFR conditions coming onshore to Cape Cod and possibly coastal Plymouth county. A coating to an inch is possible. Thursday...High confidence. VFR, dry light and variable winds becoming SSW. Across the outer Cape, MVFR cigs and vsbys possible in morning ocean effect snow showers. KBOS Terminal...High Confidence in TAF. KBDL Terminal...High Confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday Night: VFR. Breezy. Friday: Mainly VFR, with areas MVFR possible. Slight chance SN. Friday Night: Mainly VFR, with local IFR possible. Windy with gusts up to 35 kt. Chance SN. Saturday: Mainly VFR, with areas MVFR possible. Strong winds with gusts up to 60 kt. SN likely. Saturday Night: Mainly VFR, with local MVFR possible. Strong winds with gusts up to 45 kt. Chance SN. Sunday: VFR. Windy with areas of gusts up to 30 kt.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 330 AM update... Today...arctic high pressure approaches from the west, yielding NNW 10-20 kt winds across MA and RI waters, along with light freezing spray. Tonight...arctic high continues building east into New England. More of a northerly wind 10-20 kt produces ocean effect snow showers over the eastern MA waters, along with light freezing spray. Thursday...high pressure moves offshore with light and variable winds becoming SSW wind and light, generally 15 kt or less. Outlook /Thursday Night through Sunday/... Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas locally approaching 5 ft. Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain, slight chance of snow. Friday Night: Low risk for gale force winds with gusts up to 40 kt. Local rough seas. Snow likely, rain. Saturday: gale force winds with gusts up to 45 kt. Rough seas up to 20 ft. Snow, rain. Saturday Night: Strong winds with areas of gusts up to 45 kt. Rough seas up to 20 ft. Snow likely, chance of freezing spray. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 15 ft. Chance of freezing spray, slight chance of snow.
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 3 AM EST Thursday for ANZ250-254.
-- End Changed Discussion --
&& $$ SYNOPSIS...Nocera/BW NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...BW AVIATION...Nocera/BW MARINE...Nocera/BW

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.