Area Forecast Discussion
Issued by NWS Boston, MA

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775 FXUS61 KBOX 160623 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 223 AM EDT Mon Oct 16 2017 .SYNOPSIS... A strong cold front sweeps across the region overnight and will bring scattered showers into early Monday morning. Behind the front, it turns sharply cooler and brisk Monday afternoon with temperatures dropping down close to freezing by daybreak Tuesday. Gradual warm up through the week, possibly into the weekend, while overall dry and quiet with scattered cloud decks and breezy winds from time to time. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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145 AM Update... Cold front crossing N central and W Mass into N central CT at 05Z. Winds have shifting to NW from KORE-KCEF-KBDL with sct -SHRA reported from NE and central Mass into N central through SW CT. Dewpts have dropped to the mid-upper 50s across the northern Berkshires into SW NH. Will continue to monitor for potential of gusty W-NW winds as front passes through the pre dawn hours. Could see brief gusts up to around 35-40 mph. Showers are progressing steadily SE as seen on latest NE regional 88D radar imagery. 00Z GFS appears to be in track with frontal timing at this point. Will see more patchy showers move into W CT from the lower Hudson Valley, while the showers further E may pick up a bit as the front approaches the S coast, allowing more moisture to be fed ahead of the front over the next few hours. Appears to be covered pretty well on the latest forecast update. Previous Discussion... Gusty SW winds continue along the southern near shore waters. Gusts up to 32 kt at KEWB, 34 kt at KFMH and 32 kt at KPVC, with a peak wind of 35 kt at KPYM and 31 kt at KCQX. Also noting gusts to around 30 kt across portions of E Mass into RI, so very good low level mixing continues this evening. Ahead of the front, temps running in the 60s to around 70, mildest across E Mass.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
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Today... A few left over showers will be possible across the far SE New England coast during the first part of Monday morning. Otherwise, expect some strato-cumulus to work into the region in the cool advection pattern but will also see some peeks of sunshine. Temperatures late Monday morning and afternoon will mainly be in the upper 50s to the lower 60s, but a bit cooler in the higher terrain. Northwest wind gusts of 20 to 30 mph will make it feel chilly compared to our recent mild weather. Tonight... High pressure will build in from the west allowing winds to gradually diminish, except across the southeast New England coast. Cool airmass in place should allow overnight low temps to drop to around 30 to the lower 30s in the normally coolest outlying locations. Some frost/freeze headlines will likely be needed where the growing season is technically still in place. Lastly, it will be milder across the Cape/Nantucket as NNW winds will result in ocean effect cloudiness and holding low temps in the 40s. 850T to seas surface temperature differential around 20C may even yield an isolated shower or two.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... */ Highlights... - Gradual warm-up through the week into the weekend - Perhaps a pattern change into late October, more active, cooler */ Overview and Discussion... Change is on the horizon. A deeper polar low upstream shifting from the Siberian Peninsula E into Alaska diminishes downshearing storm development over the W CONUS and rather promotes ridging into late October. Concurrent with a strong MJO phase 4/5/6 signal, and the expectation is for mild, moist Pacific air to pump into the W CONUS ahead of deep troughing over the NE Pacific. Meanwhile this also promotes downshear deeper troughing over the E CONUS. But prior to, as the polar low matures E into Alaska, individual upstream Pacific origin waves continue to slam into the Cascades later emerging downstream and undergoing cyclogenesis NE into Canada. High pressure is promoted over the SE CONUS beneath preferred H5 ridging. Subsequent SW pump of warmer air across the Central into E CONUS as far N/E into NE Canada. Looking at a suppressed environment over S New England. Aside from a series of weak frontal passages concurrent with breezy winds, Tuesday night into Wednesday, and again Thursday night into Friday with light shower activity over N New England high terrain, otherwise little to no wet-weather activity given abundant dry air through the following weekend. Main story is the warming temperature trend for late October beginning near- seasonable with highs around the low to mid 60s warming into the 70s, possibly into the 80s by the weekend. Consensus of model guidance preferred which signals the low to mid level high situated over the SE CONUS out to Bermuda round which the heat pump flows, breaking down early next week as Pacific energy shears off into the SW CONUS as high pressure builds around the coast of CA. The pattern flips and troughing becomes promoted into the NE CONUS. Looking at the next cold frontal passage and chance of wet weather potentially beginning around Monday night into Tuesday. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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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 Tuesday/...High confidence. Through 12Z... CIGS have been gradually rising across most of the region with some IFR CIGS lingering across the immediate S coast, Cape Cod and the islands at 05Z, with mainly VFR VSBYS. Will see slowly improving CIGS as cold front passes, though sct -SHRA may bring brief MVFR VSBYS. Winds quickly shift to W-NW and may briefly gust up to around 35 kt. Cold front should push to our just off the S coast by around 12Z. Today... Sct -SHRA across S coastal areas move offshore by midday, though a few may linger into early afternoon along the immediate S coast and the islands. Any leftover patchy MVFR VSBYS will improve by midday. SW winds shift to NW as front passes. Gusts around 20 to 25 kt. Tonight... Patchy SCT-BKN VFR clouds linger across Cape Cod, KACK and KMVY early, then should push offshore. N-NW wind gusts up to 20-25 kt along the immediate coast through around midnight, lingering through the night across Cape/Islands. Tuesday... VFR with mostly clear to clear skies. N wind gusts up to around 20 kt across Cape/Islands Tue morning, then diminish. KBOS Terminal...SW wind gusts up to 25 kt through around 09Z, then will shift to W-NW with brief gust up to 30 kt possible as cold front passes. MVFR CIGS through around 09Z-10Z, then improve to VFR. May see some NW wind gusts up to around 20 kt early tonight. KBDL Terminal...N-NW winds around 10-15 kt, may gust up to 20 kt through 09Z. Sct -SHRA push S of the terminal with MVFR CIGS/VSBYS improving to VFR. Expect N-NW wind 10-15 kt into this evening, then slowly diminishing after 04Z tonight. Outlook /Tuesday Night through Friday/...Moderate confidence. Tuesday through Friday... VFR. W winds. Breezy at times, around late Tuesday and again late Thursday
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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 Tuesday/...High confidence. Through 12Z... SW winds gusting up to 25-30 kt will continue overnight, with brief gale force gusts across the southern near shore waters especially Buzzards Bay, Vineyard Sound and Nantucket Sound as well as the eastern open waters through around 09Z or so, then diminish. Small crafts continued for all waters. Scattered showers move across the waters ahead and with the cold front. Winds quickly shift to W-NW with the frontal passage mainly across the eastern waters around 09Z-11Z. Local visibility restrictions in showers and patchy fog through daybreak. Today and Tonight... Behind the cold front, NW gusts 20 to 30 kts, especially over the open waters. Strongest winds immediately behind the front and then Tonight with colder air aloft building S over the warm waters. SMALL CRAFT ADVISORIES may need to be extended. Outlook /Tuesday Night through Friday/...Moderate confidence. Overall W winds, breezy at times around late Tuesday and again late Thursday. Waves for the most part below 5 feet, only issues worth noting are on the S/SE outer waters early Tuesday, possibly again Thursday night into Friday. Otherwise good boating weather.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until noon EDT today for ANZ231>235-237- 251. Small Craft Advisory until 8 AM EDT this morning for ANZ230- 236. Small Craft Advisory until 8 AM EDT Tuesday for ANZ250-254>256.
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&& $$ SYNOPSIS...Frank/Sipprell NEAR TERM...EVT SHORT TERM...Frank LONG TERM...Sipprell AVIATION...Frank/Sipprell/EVT MARINE...Frank/Sipprell/EVT

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