Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 141329 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 929 AM EDT Wed Mar 14 2018 .SYNOPSIS... Low pressure center over Nova Scotia will lift north today. An upper level disturbance rotates through late today and tonight, allowing the risk for accumulating snow showers to continue through tonight. Expect mainly dry and cooler than normal weather into the weekend and early next week. Another coastal storm may impact the region sometime next late Tuesday or Tuesday night. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Radar indicating snow shower activity along the Berkshires and extending into the east slopes. Expect this to continue into the afternoon hours, Winter Weather Advisory continues for potential 3-5 inches of snow accumulation. Radar and surface obs indicate some lighter snow showers making it east of the Advisory area, with visibility as low as around 2 miles. Expanded the likely pops to include the Worcester Hills where most of this activity is occurring. Elsewhere mainly a chance to slight chance pop for snow. Could see up to an inch of snowfall over the Worcester Hills, elsewhere up to a coating is possible. Early morning discussion follows... *** Snowfall Mainly For The East Slopes Of The Berkshires *** Primary low pres is moving through Nova Scotia and into the Maritimes early this morning. However, weak deformation/lift in the low-mid lvls continues to support very light SN across N MA and across the E slopes of the Berkshires where there is enhanced upslope. The former should be coming to an end by sunrise as drier air continues to infiltrate the DGZ and subsidence thanks to rising heights increases. However, with upslope and trapped moisture through the Berkshires, will maintain a Winter WX Advisory through the day. Mesoscale QPF suggests as much as 3-5 inches along the Berkshire border which supports this issuance. Otherwise today, blustery with occasional SHSN, although mainly dry due to the implied subsidence and drying in the lowest 400hPa per latest Bufkit soundings. Breaks of sun expected. Breezy conditions continue with H92 momentum hovering between 30-45 kt which should be tapped. Highest gusts likely over the Cape/Islands where wind advisories will continue. Highs likely to remain in the low-mid 30s thanks to an established snowpack.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... *** Snow Squalls Likely This Evening And Overnight *** This evening and overnight... Robust H5 shortwave rotates to the SE through the evening and early overnight hours. The mid lvl cooling that results leads to steepening low lvl lapse rates, as high as 6.5-7.5C/km from the SFC through H7. Slight warm advection and southerly moisture flux also re-saturates the column as well, allowing PWATs to reach back to near 1 std deviation above normal. Combine this with a lingering LLJ around 35-40 kt, and we have the perfect setup for brief heavy snow showers and squalls to develop. This is supported by high values on the BTV Snow Squall Parameter. Peak timing will be from about 23Z (7PM local) to about 09Z (5AM local). Typical snow squall impacts possible, with brief heavy snow leading quick accumulations of 1-3 inches possible as well as quick changes in visibility/windy conditions leading to hazardous travel. Will issue an overview SPS for this risk this morning, but will have to handle squalls as they develop with short-fused updates this evening. Note that the nature of these are such that they are hit-or-miss, some may see little to no impact while others see higher impact. Overnight mins remain in the upper 20s to low 30s thanks to the increase in clouds and lingering snow showers. Thu... Shortwave rotates out to sea. The resulting AVA allows for rising heights and return to implied subsidence. Therefore risk for snow/rain showers is much lower on Thu and most areas are likely to remain dry after early AM SHSN dissipate. Breezy however, with gusts 20-30 mph lingering through the day. Some W downsloping may allow a few spots to reach the low 40s for highs, but will be inhibited by snowpack. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Big Picture... Longwave scale shows trough east/ridge west through the weekend. The pattern then flattens early to mid next week. Shortwave scale shows closed lows over the Maritimes and the Pacific Northwest, with a ridge over the Plains. This converts to a more zonal flow with shortwaves passing south of New England over the weekend and the middle of next week. Mass fields amongst the models are similar through Saturday, then diverge through the first half of next week. Confidence is high Saturday, but diminishes to low early next week. Details... Thursday night through Sunday... Maritime low moves off, but trough lingers over New England and the Maritimes Friday and possibly Saturday. A shortwave moves through the trough Friday bringing a cold pool aloft and cold advection in the lower atmosphere. Another shortwave moves through Sunday with briefly milder temps. Expect a generally dry period, the Friday shortwave could generate an isolated rain or snow shower. Expect mixing to about 900 mb, possibly to 850 mb Friday in the cold advection. Temperatures aloft during this time should top out in the 30s, except upper 30s and low 40s on Sunday. Winds in the mixed layer reach 30 knots Friday, diminishing to 20 knots by Sunday. Monday-Tuesday... Northern jet stream pushes high pressure south from Canada over New England. This will bring dry weather Monday, but trend max temperatures back into the 30s. Shortwave moving west to east in the southern stream will approach during this period, and could spread precipitation into our area late Tuesday and Tuesday night. But the models show different timing of the weather systems, and all of this comes during Day 7 or later. We will show chance pops for late Tuesday and Tuesday night. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/...High confidence. Through 21Z today... Mainly VFR. Some BKN-OVC MVFR CIGS mainly in the Worcester Hills and Berkshires throughout the day, but VFR dominates. Breezy with W winds 10-20 kt sustained and gusts 25-40 kt. 21Z Today Through 09Z Thu... Mixed MVFR/VFR conditions in lower CIGS and brief SHSN. These SHSN could lead to a localized snowfall 1-3 inches along with reductions in vsby to IFR/LIFR at times. These will be hit or miss, so not all sites see these heavier SHSN. 09Z Thu through the rest of Thu... Mainly VFR. Blustery conditions continue, but weaker winds thank previous days. KBOS Terminal...Mainly VFR until this evening during which a few SHSN with brief heavy bursts of SN possible. This would yield MVFR/IFR conditions at times. Otherwise, windy with gusts 25-30 kt at times through the day. KBDL Terminal...High confidence in TAF. Occasional late afternoon/evening SHSN. Outlook /Thursday Night through Sunday/... Thursday Night through Friday: VFR. Windy with local gusts to 30 kt. Friday Night: VFR. Windy with areas gusts to 30 kt. Saturday: VFR. Windy with local gusts to 30 kt. Saturday Night through Sunday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/...High confidence. Through Tonight... Gale force winds out of the W-SW continue today except Narragansett bay. Note that this evening there may be a brief lull where gusts generally fall below Gales, but these will increase again overnight, so Gale Warnings have been extended to account for this secondary burst of stronger winds. Thu... Winds gradually recede to mainly below Gale strength. However, gusts still reach around 30 kt and seas remain elevated so Small Craft Advisories will have to follow. Outlook /Thursday Night through Sunday/...Moderate confidence. Thursday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Friday Night: Strong winds with gusts up to 30 kt. Areas of rough seas. Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...Wind Advisory until 5 PM EDT this afternoon for MAZ024. Wind Advisory until 5 PM EDT this afternoon for MAZ022-023. Winter Weather Advisory until 8 PM EDT this evening for MAZ002- 008-009. RI...None. MARINE...Gale Warning until 8 AM EDT Thursday for ANZ231>235-237- 254>256. Gale Warning until 6 PM EDT this evening for ANZ230. Small Craft Advisory until 8 PM EDT this evening for ANZ236. Gale Warning until 8 PM EDT this evening for ANZ250-251.
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&& $$ SYNOPSIS...WTB/Doody NEAR TERM...WTB/Doody/NMB SHORT TERM... LONG TERM...WTB AVIATION...WTB/Doody MARINE...WTB/Doody is the U.S. government's official web portal to all federal, state and local government web resources and services.