Area Forecast Discussion
Issued by NWS Boston, MA

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554 FXUS61 KBOX 161457 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 957 AM EST Sat Dec 16 2017 .SYNOPSIS... Blustery and cold conditions today with less wind Sunday as high pressure builds across the region. A weak warm front may bring some light snow Sunday night and mixed rain/snow Monday. Temperatures will be milder on Tuesday ahead of a cold front, then turning blustery and colder Wednesday into Thursday. Temperatures will moderate again on Friday as light rain moves in ahead of another cold front. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1000 AM Update... Overall trend in the forecast remains on track for this afternoon. Mostly sunny skies to start, but low level moisture off the Great Lakes will continue to stream eastward. Thus anticipate clouds to build into the region limiting diurnal heating this afternoon. Otherwise updated snow forecast with latest trends in the hi-res guidance. Increased snow chances across western MA, CT and southern RI. These showers will be brief but cannot rule out a dusting for the region. Previous Discussion... Another northern stream shortwave drops south across New Eng this afternoon. Sunshine will give way to more clouds in the afternoon as area of low and mid level moisture moves into the region ahead of the shortwave. While most of the day will be dry, a few snow showers are possible, mainly in western New Eng where column moisture is a bit greater. The shortwave will also result in some gusty winds today and a reinforcement of the colder airmass with 850 mb temps holding around -12C to -13C. Highs will range from upper 20s to mid 30s. Gusts to 25-30 mph developing.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... Tonight... Gusty winds will gradually diminish tonight as high pres approaches from the NW. Good drying moves in which will result in clearing skies although a few high clouds may move in from the SW. Another cold night with lows down into the single numbers in western MA where winds will decouple sooner, with mostly teens elsewhere. Sunday... High pres builds to the north resulting in light winds but a cold day as 925 mb temps around -8/-9C. With northerly winds and cold start to the day, temps will only recover to the mid 20s to lower 30s, mildest near the south coast. Expect lots of sunshine but high clouds will be increasing in the afternoon. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Overview... Continue to see a broad, progressive mid level steering flow across most of the lower 48, especially over the northern tier states, while cutoff H5 low tries to set up across the SW states through Monday. Another stronger H5 short wave dives SE out of central Canada by mid week, but the question will be whether some of its associated moisture will work far enough south to bring another round of precipitation across. Broad long wave ridge moves across the northern tier states by around Thursday as another surface high moves quickly across. Once again, another short wave in the steering flow. An associated warm front may push across late next week as H5 heights rise and winds shift to W-SW. Low pressure may also form across the Great Lakes, with some precip trying to shift E. Temperatures will start off below seasonal normals early next week, then will briefly warm on Tuesday as the low passes N of the region. Readings drop below normal again around mid week. Beyond Wednesday, models showing a broad model solution spread, so have below average confidence with the forecast. Details... Sunday night and Monday... Weak, elongated short wave moves quickly eastward out of the Ohio Valley, bringing some light precip with it. Still some model solution spread in handling this short wave, with the GFS and NAM being weak and diffuse while both the GGEM and ECMWF are showing a more organized albeit weak low moving across the region with a more robust moisture field. Noting the QPF remains light, with most of the higher amounts pushing in N and W of the region late Sun night and Mon as the surface low moves across northern New England Monday. Do see the layer moistening up rather well, as seen on both the GFS and NAM BUFKIT soundings, reaching through the dendritic growth zone (which was generally between 850 and 650-700 hPa). So, should see light snow developing across the region by around midnight across central and western areas, pushing E after midnight. At this point, looks like snow amounts will generally be below an inch though some spots could reach an inch across the E slopes of the Berkshires as well as over portions of NE Mass. May see precip taper off to patchy drizzle briefly as the main area shifts E during Monday. After overnight lows in the upper teens and 20s, expect highs to recover to the 30s across most areas, except 40-45 across the S coast with the continued zonal flow aloft and corresponding H5 heights around 550 dm. Tuesday through Thursday... Digging H5 short wave in the W-NW flow across central Canada will dive SE during Tuesday. Associated weak surface low forecast to remain N of the region, but the southern edge of the precip may push into central and northern areas. Light QPF amounts are currently forecast. Temps will moderate, so should see mainly light rain, but could mix with or change to snow showers as it ends early Tue night. Leftover precip should push offshore during the early morning hours on Wed, then colder air returns with gusty W-NW winds during Wed. Gusts up to around 25 kt are possible during the day, but possibly up to 30 kt across Cape Cod and the islands. Broad high pressure will cross the region on Thursday with dry conditions and temps running up to 5 degrees below normal. Thursday night and Friday... As the high moves offshore Thu night, will start to see a change in the upper level pattern. Another long wave trough will push into the central U.S., extending to the 4 corners region. This will cause the steering flow to shift to W-SW during this timeframe with increasing H5 heights and milder temps toward late next week. Surface low pres develops the western Lakes, with low level southerly winds bringing moisture to the upper Mississippi valley during Thu. Will still see NW flow early across New England, but as the high moves offshore, winds shift to S-SW. Temps will respond during Fri, with highs ranging from around 40 across the E slopes of the Berkshires into N central Mass up to around 50 along the S coast. Big question during this timeframe will be whether moisture from off the Carolinas will start to feed N as winds shift ahead of the developing low to the W, bringing some precip along with it. Model solution spread continues, to lower confidence on timing and track of precip. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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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 Sunday/...High confidence. Today...VFR. BKN CIGS 035-050 developing in the afternoon. Low risk of a snow shower western MA/CT and southern RI. West wind gusts up to 25 kt developing, possibly up to 30 kt on the outer Cape and Nantucket. Tonight and Sunday...VFR with diminishing wind. KBOS Terminal...High confidence. KBDL Terminal...High confidence. Cannot rule out the potential for a snow shower this afternoon. Outlook /Sunday Night through Wednesday/... Sunday Night: Mainly VFR, with areas IFR possible. Chance SN. Monday: MVFR-IFR conditions possible. Chance SN. Chance RN S coast in the afternoon. Monday Night: Mainly VFR, with local IFR possible. Patchy BR. Tuesday: Mainly VFR, with areas MVFR possible. Breezy. Slight chance SHRA. Tuesday Night: VFR. Windy with local gusts to 30 kt. Slight chance SHRA, slight chance SHSN. Wednesday: VFR. Windy with local gusts to 30 kt.
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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 Sunday/...High confidence. Today and Tonight...W-NW gusts to 25-30 kt, with a few marginal gale force gusts near 35 kt possible over southern waters. Strong winds lingering into this evening before diminishing after midnight. SCA all waters. Sunday...Light NW winds with seas below SCA. Outlook /Sunday Night through Wednesday/... Sunday Night: Winds less than 25 kt. Slight chance of snow. Areas of visibility 1 to 3 nm. Monday: Winds less than 25 kt. Chance of rain, chance of snow. Areas of visibility 1 to 3 nm. Monday Night: Winds less than 25 kt. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Slight chance of rain showers. Wednesday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST Sunday for ANZ231>234-251. Small Craft Advisory until 7 PM EST this evening for ANZ230- 236. Small Craft Advisory until 3 AM EST Sunday for ANZ235-237-250. Small Craft Advisory until 6 AM EST Sunday for ANZ254>256. && $$ SYNOPSIS...KJC/EVT NEAR TERM...KJC/Dunten SHORT TERM...KJC LONG TERM...EVT AVIATION...KJC/EVT MARINE...KJC/EVT is the U.S. government's official web portal to all federal, state and local government web resources and services.