Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 081455 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 955 AM EST Thu Dec 8 2016 .SYNOPSIS... A strong front crosses the region late today. Mainly dry, but unseasonably cold temperatures are on tap for our region Friday into Saturday. Low pressure will likely bring some rain/snow Sunday into Monday. A shot of arctic air is then expected by mid to late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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10 am update... Definitely hazy on the drive into work this morning. No surprise given the light winds and shallow inversion discerned from the 12z sounding this morning. Many locations dropping down at or below 1 to 2 miles in visibility, some places still low given how light the winds continue to be and the trapped cold air within the sheltered valleys. Expect that this fog should lift as we go through the day as temperatures warm. Back to the 12z soundings, fair amount of dry air within the low levels. Seeing returns from WSR-88D emerging out of a mid-level deck around 5-7 kft agl attendant to some weak forcing out ahead of a stretch mid-level shortwave through the overall cyclonic flow. Accompanying cold frontal boundary with limited moisture given a continental-origin airmass associated, likely not going to see much in any way of sprinkle / flurry activity except across the high terrain. Much of the activity falling in the form of virga. Mostly cloudy most of today with some cloud break late. A westerly flow, looking at seasonable temperatures with highs getting up around the low 40s. It`ll be late when westerly flow turns towards NW associated with a reinforcing arctic front and colder air. So one last day of normal conditions and then we`ll begin the downward temperature trend going into this weekend.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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Tonight... Arctic cold front moves offshore during the night. Lowering humidity, meaning even less risk for precipitation. West winds will increase slightly, in response to the increased pressure gradient. There should be enough of a surface inversion to prevent the maximum momentum transfer. Below normal temperatures. Friday... Colder air will continue to overspread Southern New England. More sunshine early in the day will lead to deeper mixing, and stronger west to northwest winds. Diurnal clouds expected to develop through the day. Temperatures should only rise at most 10 degrees from morning lows. Mainly dry weather should continue. There is the possibility for a stray snow shower across the interior, but not a large one.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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*/ Highlights... * Unseasonably cold but mainly dry Saturday * Wintry precipitation possible Sunday into Monday * Another system may bring precip Tuesday into Wednesday */ Overview... Models and ensemble members are in generally good agreement on much of the long term, particularly with the synoptic pattern. After starting the period with below normal temperatures, two systems may bring precipitation to southern New England. The first one moves through the region Sunday into Monday, bringing a period of snow to much of the area, changing to rain along the coastal plain. The second one may bring another round of snow/rain to the region Tuesday into Wednesday. Or it may stay far enough to the north that there will be little, if any, precipitation. Then an arctic front will bring below normal temperatures to the region once again. */ Daily Discussion... Friday night through Saturday... Northwesterly flow keeps below normal temperatures in the region through this period. High temperatures Saturday will have trouble getting above freezing. Most areas will be below freezing for most of this time. The south coast may see high temperatures just above freezing. Low temperatures should fall into the teens Friday and Saturday nights. Otherwise, high pressure will keep dry weather in the area. Sunday and Monday... Much of the day Sunday should be fairly dry as weak upper ridging moves over southern New England and high pressure moves offshore. Then a shortwave will move through the upper level flow over the area late Sunday into early Monday. Low pressure moves eastward just south of southern New England during this time, keeping cold air in the region. Thermal profiles continue to indicate a snow or rain scenario with all snow across the interior and a period of snow followed by a change to rain across the coastal plain. Ensemble QPF amounts indicate a rather minor snow event, with the highest confidence in 1-3 inch snow totals, and a low probability of up to 6 inches in the highest terrain. Confidence is relatively high for a precipitation event to occur, however, confidence is low in the details. Tuesday and Wednesday... Confidence remains rather low for this period, especially with changes seen since last night`s model runs. The 00Z GFS and its ensembles indicate a low pressure system moving through Quebec will bring an arctic cold front through southern New England. If this solution is correct, it will result in another precipitation event. The 00Z ECMWF on the other hand indicates brings a shortwave over the area resulting in some light precip, but keeps the low pressure system well north of the area. Again, confidence is quite low. Expect below normal temperatures to come in Wednesday.
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&& .AVIATION /15Z THURSDAY 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 night/...High confidence. 15z update... Rest of today... MVFR-IFR vsbys dissipating across the CT River Valley 15-16z. Then all terminals VFR with W winds, increasing late with gusts 15-20 kts especially along the S/SE coast. BKN-OVC cigs becoming SCT late. Low risk of very light shower activity over high terrain and along the coast. Tonight... Blustery W/NW winds continuing along the immediate coast and high terrain with gusts up to 25 kts, otherwise VFR with overall light winds. Friday... Mainly VFR. Low risk for brief MVFR cigs toward the Berkshires. NW winds increasing across the interior with gusts up to 35 kts possible into afternoon. KBOS TAF...W flow increasing towards late and continuing overnight around 270-280 with gusts up to 25 kts. KBDL TAF...Morning fog/haze should lift towards noon, 15-16z, and thereafter VFR. Increasing W winds towards late dropping off over- night. Outlook /Friday Night through Monday/... Friday night through Saturday...High confidence. Mainly VFR conditions expected. A period of lower clouds Friday night may result in some MVFR conditions. Sunday and Monday...Moderate confidence. VFR conditions to start. Conditions may lower to MVFR/IFR later Sunday afternoon and Sunday night in rain and/or snow. Some improvement is possible late Monday as precipitation comes to an end.
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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 Friday/...High confidence. 10 am update...No major changes to the forecast which is on track. Today and Tonight... With cold frontal passage late today, expect an increase in W-NW winds late in the day and continuing into tonight. Gusts up to 25-30 kt likely at times. Conditions may briefly diminish below Small Craft Advisory levels across the outer RI coastal waters today. That said, will continue the Advisory through today, with the expectation of increasing winds and seas later this afternoon. Small Craft Advisories will start across most of the other coastal waters this afternoon. Friday... Strong cold advection will result in widespread NW wind gusts of 25 to 35 knots. Not enough confidence 35 kt will be widespread enough, long enough, to convert the Gale Watches over the eastern outer MA coastal waters to Gale Warnings. Will let the next shift take another look. Outlook /Friday Night through Monday/... Friday night...High confidence. Small craft advisories are likely with winds gusting over 25 knots and seas on the outer waters 5 to 6 feet. There is a moderate probability of NW gales. Saturday and Sunday...Moderate confidence. Winds and seas slowly diminish, but generally remain above SCA criteria until late Saturday night. Monday...Moderate confidence. Seas below 5 feet will slowly increase once again from the south as low pressure approaches the waters. Winds increase as well, with small craft advisories likely. There is a moderate probability of N gales.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 7 PM this evening to 1 AM EST Saturday for ANZ231>234. Small Craft Advisory from 7 PM this evening to midnight EST Friday night for ANZ230-236. Small Craft Advisory from 3 PM this afternoon to 1 AM EST Saturday for ANZ235-237. Gale Watch from Friday morning through late Friday night for ANZ250-251-254. Small Craft Advisory from 1 PM this afternoon to 9 AM EST Friday for ANZ250-254. Small Craft Advisory from 7 PM this evening to 9 AM EST Friday for ANZ251. Small Craft Advisory from 1 PM this afternoon to 1 AM EST Saturday for ANZ255. Small Craft Advisory until 1 AM EST Saturday for ANZ256. && $$ SYNOPSIS...Belk/RLG NEAR TERM...Belk/RLG/Sipprell SHORT TERM...Belk LONG TERM...RLG AVIATION...Belk/RLG/Sipprell MARINE...Belk/RLG

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