Area Forecast Discussion
Issued by NWS Boston, MA

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896 FXUS61 KBOX 010001 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 701 PM EST Wed Nov 30 2016 .SYNOPSIS... Widespread rain will be locally heavy at times through the overnight hours. Dry conditions return Thu and continue into much of the weekend, with a trend toward cooler temperatures. For early next week, an uncertain forecast but cool weather is expected with some potential for wintry precipitation sometime Sunday night into Tuesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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7 PM Update...The forecast is generally on track this evening. A few minor edits were made to the winds, to bring them more in line with current trends. Widespread rain continues across much of southern New England with the heaviest rain along and north of the Mass Pike. 1) Rain heavy at times persists into the overnight hours... Approaching shortwave was increasing the forcing for ascent and has allowed widespread rain to develop across the region late this afternoon. A strengthening east to southeast low level jet/PWATS that were both 2-3 standard deviations above normal will set the stage for another soaking rain this evening. Unlike yesterday`s rain event, this one will persist through the overnight hours. After midnight, the easterly low level jet will become south southwest and increase to between 55 and 65 knots across the southeast New England coast. This in response to a surface wave of low pressure that will track across RI/southeast MA. The result will be more rain, some of which will be heavy at times. Rainfall amounts look to average between 0.75 and 1.50 inches, but localized 2+ inch amounts are possible. It is difficult to determine where the axis of heaviest rain will setup. There appears to one area across our western/northern MA and into northern CT where an impressive band of mid level frontogenesis sets up. There are also indications of a second band near the south coast, on the nose of the strong low level jet coupled with surface convergence along the wave of low pressure. There is even a low risk of an isolated thunderstorm or two. While no significant problems are anticipated, brief localized poor drainage street flooding is possible. 2) Gusty winds across Cape/Islands toward daybreak... The core of the powerful southwest low level jet will cross the Cape/Islands between 8z and 12z. As is typically the case, there is an inversion in place but some of that wind will mix down. We think a few hours of southwest wind gusts of 30 to 40 mph near 12z will be the general rule. Opted to hold off on a wind advisory for now, but there still is a low risk especially if any convective elements can bring down the stronger winds from aloft. Later shifts will have to monitor closely. 3) Temperatures... Another night of interesting temperature trends across the region. Temps should mainly be in the 40s to around 50 on the south coast this evening. However, the track of the surface low will allow portions of RI/SE MA to warm sector toward daybreak. Temps in these locations may be around 60 near daybreak, while most of the interior remains in the cool sector and in the 40s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Thursday... A much better day is in store as intensifying low pressure lifts into the Canadian Maritimes. Skies will become partly sunny during the morning, but a scattered to broken deck of strato-cumulus clouds will likely move into the region from the west during the afternoon. This should yield partly to mostly cloudy skies with the clouds most abundant across the interior. Despite cold advection aloft, given the mild start it will take sometime for that to be reflected at the surface. Temps most of the day should be well up into the 50s. It will be a bit breezy though with Bufkit soundings supporting westerly wind gusts of 20 to 35 mph. Nonetheless, not a bad day for the first day of December. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... * Dry with cooling temperatures through the weekend * Low confidence in wintry precip Sun. night into Mon. There is continued uncertainty with regards to precipitation in the mid range models. The Canadian, GFS, and GEFS members all keep southern New England dry throughout the long term period. The EPS members have two low pressures approaching southern New England sometime Sunday night into Monday, one from the north and the other from the south. However, the members are well spread out as far as path and timing. The operational ECMWF indicates a similar solution but slower, delayed until Tuesday into Wednesday. Reading previous forecast discussions, this time period has been very uncertain with models flip flopping, so will keep with a blend of the models for the forecast. Friday through Sunday...High confidence. The upper level low and its surface reflections will move into the Maritimes, leaving southern New England in a tight pressure gradient between the departing low and a strong high pressure across the southeastern CONUS. This will result in rather blustery weather, in addition to temperatures returning to near normal or just below normal. Friday will be the warmest day with temperatures diminishing through the weekend. Sunday night through Wednesday...Low confidence. As stated above, there is quite a bit of spread in the models and the ensembles, leaving a lot of uncertainty for this period of the forecast. Option one - a continuation of the weekend - seasonable temperatures and dry. Option two - a period of wintry precipitation Sunday night and Monday. Option three - a period of wintry precipitation, but not until Tuesday and Wednesday. Which one it will be remains to be seen. Will need to keep an eye on the models over the next few days. && .AVIATION /00Z 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/... Tonight...Moderate to high confidence. IFR conditions will prevail this evening in widespread rain and patchy fog. LLWS will also be a concern especially after midnight along the southeast New England coast. The inversion will keep most of the stronger winds aloft, but a brief period of southwest wind gusts of 25 to 35 knots may develop toward daybreak across the Cape/Islands. Thursday...High confidence. Lingering MVFR-IFR conditions will improve to mainly VFR by mid to late morning. VFR will then dominate through Thursday, but a scattered to broken deck of strato- cumulus clouds may result in brief marginal MVFR CIGS. KBOS TAF...Moderate to high confidence in TAF. KBDL TAF...Moderate to high confidence in TAF. Outlook /Thursday Night through Monday/... Thursday night through Sunday...High confidence. Mainly VFR. Blustery W-NW winds expected. Sunday night and Monday...Low confidence. As stated in the long term section there is much uncertainty. Could be VFR and dry or a mix of MVFR/IFR and wintry precip especially across the interior.
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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 Thursday/... Tonight...Moderate to high confidence. Approaching low pressure will allow easterly winds to increase tonight with speeds of 25 to 35 knots. There may be a brief lull in the wind gusts, but they will then shift to the south toward daybreak as most of our waters warm sector resulting in another round of 25 to 35 knot gusts. Small craft headlines are posted all open waters, except for Gales on the eastern outer-waters for a period of 35 knot wind gusts. Thursday...High confidence. Westerly wind gusts of 25 to 35 knots expected in the cold air advection pattern as intensifying low pressure lifts towards the Canadian Maritimes. Small craft headlines all waters, except will continue Gales for our eastern most outer-waters through the morning. Seas on the order of 6 to 10 feet expected across our outer-waters. Outlook /Thursday Night through Monday/... Moderate confidence. Small craft conditions to start. Then winds and seas gradually diminish throughout the period, falling below small craft criteria for a period Sunday. Then there is a possibility that a low pressure system approaches the waters with a resulting increase in seas and wind. There is also a possibility that high pressure builds into the region and winds and seas remain below small craft criteria. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EST Thursday for ANZ231>235- 237-251-256. Small Craft Advisory from 8 AM to 5 PM EST Thursday for ANZ230- 236. Gale Warning from 1 AM to noon EST Thursday for ANZ250-254-255. && $$ SYNOPSIS...Frank/RLG NEAR TERM...Frank/RLG SHORT TERM...Frank LONG TERM...RLG AVIATION...Frank/RLG MARINE...Frank/RLG is the U.S. government's official web portal to all federal, state and local government web resources and services.