Area Forecast Discussion
Issued by NWS Boston, MA

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869 FXUS61 KBOX 091140 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 640 AM EST Fri Dec 9 2016 .SYNOPSIS... Mainly dry, but unseasonably cold temperatures are on tap for our region through Saturday. Some mixed wintry precipitation is looking more likely Sunday evening into the day on Monday, but some uncertainty remains. Cooler conditions return by the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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645 AM Update...The forecast is generally on track this morning. Made a few minor updates to the sky cover and temperature forecasts to adjust for current trends. Increased sky cover out west a bit based on satellite trends. Colder air will continue to overspread southern New England. This will steepen low level lapse rates, and result in gusty west to northwest winds. The challenge has been trying to gauge how effective the momentum transfer will be. Winds early this morning were not that strong at the lower elevations, but gusting up to around 30 kt already at elevations about 1000 ft, or higher. Should the momentum transfer be maximized, we might come quite close to wind advisory criteria for gusts. At this time, am more confident in gusts just shy of needing advisories. This will need to be watched closely by the next shift. Other than the winds, expecting some diurnal clouds to develop across our region. Clouds will be more prevalent toward the Berkshires, where deeper moisture was pooling from the Great Lakes. Temperatures expected to be about 5-10 degrees lower than Thursday. The gusty winds however, will produce wind chill values in the teens and 20s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Our region should remain in between the major weather features tonight and Saturday. Mid level flow is fairly zonal, with a stronger shortwave arriving Saturday. At the surface, high pressure remains to our southwest, with a low pressure over the Maritimes. Expecting gusty northwest winds to continue, although not quite as strong as today. Not much chance for precipitation, due to lacking humidity. However, there should be enough moisture for some clouds as the shortwave arrives. Temperatures will be 10-15 degrees below normal. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... * Wintry precipitation likely Sunday evening into Monday * Another system may bring precip sometime Tuesday or Wednesday * Another round of unseasonably cold weather late in the week 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 mainly snow to much of the area, changing to rain along the coastal plain. The second one, a coastal system, may bring another round of snow/rain to the region sometime Tuesday or Wednesday. Or it may stay far enough to the south that there may not be much, if any, precipitation. An arctic front will bring below normal temperatures back to the region late next week. 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 slowly offshore. Then a shortwave moves through the upper level flow over the area early Monday. There is still some uncertainty with the track of the associated low pressure system and the potential development and location of a secondary low pressure system. Expect the models to start coming into better agreement later today as the energy responsible for the system moves onshore and is better sampled. The track of the primary low and any secondary low development will affect thermal profiles. So this is leading to a bit of uncertainty with the p-type through the event. At this time, believe it will be a mainly snow or rain scenario, but there is a low probability of a period of ice during the transition as the warmer air moves in aloft. While it is still a bit too early to detail exact snow amounts, confidence is high that a portion of the area could have accumulations in the 3 to 6 inch range. Most of the area should see at least a dusting of snow, with the possible exception being the Islands. Monday night and Tuesday...The 00Z runs of the models/ensembles indicate high pressure will build into the region and be the dominant feature during this time. However, this is a change from previous runs which had a bit more activity, especially during Tuesday. So this period remains a bit uncertain and unsettled. Wednesday and Thursday...Confidence remains rather low for this period. A broad upper level trough in the Great Lakes moves eastward over southeastern Canada and the northeastern U.S. A strong shortwave will rotate through this trough bringing another period of unsettled weather to southern New England. The low pressure system associated with this shortwave looks to be a coastal low at this point, but there is significant spread in the ensembles as to how close this system comes to southern New England. Beyond the potential precipitation event, another shot of arctic air is expected to move into the region. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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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 Saturday/... Today into Tonight...High confidence. VFR. NW winds continuing. Sustained around 10 to 15 kts, gusts up to 35 kts, diminishing late towards Saturday morning. SCT-BKN low end VFR cigs. Saturday...High confidence. VFR. NW winds diminishing. KBOS TAF...W/NW flow increases. Gusts up to 35 kts possible. KBDL TAF...W/NW flow increases. Gusts up to 30 kts possible. Outlook /Saturday Night through Tuesday/... Saturday night through Sunday...High confidence. Mainly VFR conditions expected. Lowering clouds and approaching precipitation may result in a trend towards MVFR after noon on Sunday. Sunday evening through Monday...Moderate confidence. MVFR/IFR develop in snow Sunday night. Snow may change to rain across portions of the coastal plain Monday. Accumulating snow is likely across the interior. Some improvement is possible late Monday as precipitation comes to an end. Tuesday...Low confidence. Improving conditions. Mainly VFR.
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&& .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...High confidence. W/NW winds on the increase with the likelihood of gales on most of the outer waters. Latest buoy reports show gusts already right around gale force. Will be expanding the gale warnings, soon. Rough seas also building through today. Winds and seas gradually diminish Saturday. Outlook /Saturday Night through Tuesday/... Saturday night and Sunday...High confidence. Winds and seas continue to diminish. 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 and small craft advisories will be necessary. There is a moderate probability of N-NW gales. Tuesday...Moderate confidence. NW winds and seas slowly diminish. Small craft advisories will likely continue through much of Tuesday. In addition, there is a moderate probability of N-NW gales during the morning. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 AM EST Saturday for ANZ231>234. Small Craft Advisory until 4 AM EST Saturday for ANZ230-236. Small Craft Advisory until 6 PM EST Saturday for ANZ235-237. Gale Warning until 10 PM EST this evening for ANZ250-254. Gale Warning until 6 PM EST this evening for ANZ251-255-256. && $$ SYNOPSIS...Belk/RLG NEAR TERM...Belk/RLG SHORT TERM...Belk LONG TERM...RLG AVIATION...Belk/RLG MARINE...Belk/RLG

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