Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 061734 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1234 PM EST Wed Dec 6 2017 .SYNOPSIS... A cold front pushes offshore today, prompting a return to much cooler temperatures this afternoon. Dry and seasonably chilly weather will continue Thursday into part of Friday. Low pressure will bring the potential for minor snow accumulations Friday night and Saturday across Rhode Island and Southeast Massachusetts, but an impact further back across the interior can not be ruled out. Temperatures will average a bit below normal into early next week with perhaps a coastal storm bring the potential for some rain and/or snow next Tuesday into Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1230 pm update... Cold front has pushed offshore, with drier and cooler air steadily working its way thru the region. With cold air advection persisting, expect temperatures to continue to remain nearly steady or slowly fall during the afternoon. Some mainly mid and high level clouds have lagged behind the cold front. Based on their eastward progress, the clearing should reach the BOS-PVD corridor around 3 pm. For the Cape and Islands, the cloud cover may linger until early evening.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Tonight into Thursday... More of a zonal-type pattern for the area during this timeframe as the pattern appears to push another vort max into the western Great Lakes. This will result in seasonable temps for early Dec. For tonight, clear skies with fairly light winds will result in temperatures in the mid to low 20s away from the coast. Locations along the coast will be a bit more mild as cold air aloft over the relatively warm water will keep mixing up during the overnight. Dry weather will prevail tomorrow as high pressure slides to the south of the area. Winds will remain out of the west which could help with any downsloping component. Temperatures will remain seasonable with upper 30s to mid 40s. Model cross sections do show some moisture in the mid-levels resulting in some clouds during the day. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Highlights... * A bit of accumulating snow possible Fri night/Sat...Low confidence * Chilly with a few snow showers possible Sunday * Potential coastal storm may bring rain/snow to the region next Tue/Wed with unseasonably cold weather to follow Thursday night... Dry and cold weather expected Thu night. Mostly clear to partly cloudy skies along with light winds should allow for low temps to bottom out in the upper teens to middle 20s in most locations by daybreak Friday. Friday... Partial sunshine in the morning should give way to an increase in clouds from the south during the afternoon. This in response to shortwave energy approaching from the west and some weak waves of low pressure off the Carolina coast. Much of the day should remain dry, but a bit of rain/wet snow may work onto the far southeast New England coast late in the day/early evening. High temps will mainly be in the upper 30s to the lower 40s. Friday night and Saturday... Tremendous uncertainty continues in this portion of the forecast. Several pieces of northern stream energy will dig a trough to our west, as low pressure track northeastward off the coast. The majority of the 00z guidance indicates the potential for some light snow or rain/snow mix grazing portions of the region, mainly RI and SE MA. This would bring the potential for a light accumulating snowfall to portions of this region Friday night and Saturday. It is important to remember that there is a lot of uncertainty on how this evolves given that the threat is 72+ hours out on the model guidance. A lot of this will depend upon how far south this trough digs, which will determine how close to the coast low pressure will track. Looking at the individual GEFS/EPS ensemble members reflects this uncertainty nicely. There are some members depicting complete misses, keeping our weather mainly dry as precipitation remains out over the ocean. Other ensemble members bring a light accumulating snowfall to portions of the region with the focus across southeast MA/RI. Finally, there are even a couple of members that show a moderate snowfall back into the interior while the coastal plain is mild enough for a rain/snow mixture. In a nutshell, odds favor a glancing blow Friday night and Saturday with the potential for a light accumulating snow mainly across Rhode Island and Southeast MA. Nonetheless, other options remain on the table. These include a complete miss or the potential for a light to moderate snowfall further back into the interior with boundary layer issues moving onto the coastal plain. Sunday... Vigorous shortwave energy sweeps through the region with perhaps a few snow showers. It will be rather chilly too with high temps mainly in the 30s. Monday through Wednesday... Dry and chilly weather should dominate Monday with high temps mainly in the 30s to near 40. Unsettled weather may return Tuesday into Wednesday as models indicate the potential for a developing coastal storm, that may bring rain and/or snow to the region depending on the track/timing/intensity. Obviously, considerable uncertainty on that given its nearly a week out. Regardless, unseasonably cold air looks to follow for the second half of next week. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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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 Thursday/... 1730Z Update This afternoon...High confidence. VFR for the remainder of the day, except a band of MVFR cigs pass thru Cape and Islands between 18-21Z. Westerly winds gusting around 20 kts along east coastal MA. Tonight into Tomorrow...High confidence. VFR, dry and modest west winds near 15-20 kts by Thursday afternoon. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday Night through Friday: VFR. Breezy. Friday Night: Mainly VFR, with areas IFR possible. Breezy. Chance SN. Saturday: MVFR/IFR conditions possible. Breezy. Chance SN, chance RA. Saturday Night: MVFR/IFR conditions possible. Breezy. Chance SN, chance SHSN. Sunday: MVFR/IFR conditions possible. Breezy. Slight chance SHSN.
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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 Thursday/... SCA headlines continue for the outer coastal waters and RI/BI sounds thru tonight, with W/NW wind gusts 25-30 kts diminishing this afternoon, but rough seas lingering for the overnight. Dry weather on Thursday, but increasing southerly swell will keep seas near or above 5 feet along the southern outer coastal waters, SCA continues into Thu for that area. Outlook /Thursday Night through Sunday/...Moderate to high Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain. Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Rain likely. Local visibility 1 to 3 nm. Saturday: Winds less than 25 kt. Rain likely. Saturday Night: Winds less than 25 kt. Local rough seas. Chance of rain, chance of rain showers. Local visibility 1 to 3 nm. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain showers. Local visibility 1 to 3 nm.
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&& .TIDES/COASTAL FLOODING...
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Astronomical high tides will occur once again during this midday high tide. However winds today will be in a more westerly component, thus reducing in swell during the time of high tide. Minor splashover may occur during the midday high tide but overall impacts appear to be minimal at this time.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 PM EST this afternoon for ANZ230- 231-251. Small Craft Advisory until 7 AM EST Thursday for ANZ235-237- 250. Small Craft Advisory until 7 PM EST Thursday for ANZ254>256.
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&& $$ SYNOPSIS...Frank/Dunten NEAR TERM...Frank/Dunten/NMB SHORT TERM...Dunten LONG TERM...Frank AVIATION...Frank/Dunten/NMB MARINE...Frank/Dunten/NMB TIDES/COASTAL FLOODING...Staff

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