Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261402 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1002 AM EDT Thu Apr 26 2018 .SYNOPSIS... A weak high pressure ridge will bring a return to mainly dry weather later this morning through tonight with seasonable temperatures. Another fast moving low pressure system will bring a period of widespread showers to the region Friday afternoon and evening. Milder temperatures return Saturday, but a cold front will bring a brief shot of cooler air to the region Sunday into Monday. A significant warming trend will occur Tuesday into Wednesday with dry weather expected. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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10 am update... Clearing out, drying out, becoming breezy. Wet weather and foggy conditions exiting with lead vortmax associated with mid-level trof axis, will linger longest along E/SE coastal MA and over adjacent waters. Primary vortmax to follow however mid-level drying evident per water vapor satellite. Beneath right entrance region of accompanying H3 jet streak, if any additional shower activity, mainly N New England within better deep layer moisture and favorable ascent ahead of primary vortmax, perhaps along the Berkshire with orographic lift of available moisture. K-indices an excellent indicator of those areas favorable of seeing later day wet weather. Otherwise clearing out with boundary layer mixing. Rapid improvement already from visible satellite / web cams / observing stations. Weak low-level CAA above partial clearing, the high angle sun warming highs into the 60s. Expect steep lapse rates to H8 allowing mix- down of faster winds, drier air. Some gusts already occurring. Lowering dewpoints, breezy W winds, potential for gusts up to 30 mph as primary vortmax sweeps N portions of S New England, a local W flow enhancement. Highs again getting up around the mid 60s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Tonight.. Weak high pressure crosses the region, so expect partly cloudy skies on average. West winds will be briefly gusty this evening mainly along the immediate S coast, but will become light by around midnight. Fast flow aloft continues as mid level long wave trough starts to dig across the western Great Lakes. Noting another short wave in this fast flow, with associated surface low pressure shifting NE out of the Carolinas after midnight. Expect dry conditions through the night, though mid and high clouds will increase after midnight across western areas. Low temps will range through the lower-mid 40s, typical for late April. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Highlights... * A period of widespread showers Fri afternoon/eve with localized brief heavy rainfall possible * Mainly dry and milder during the day Sat with just few showers possible across the interior * Scattered showers possible Sat night into Sun but not a washout * Mainly dry and cool Sun night into Mon * Dry with a significant warming trend Tue/Wed Details... Friday and Friday night... While much of Friday morning may end up dry...shortwave energy lifting northeastward will result in a period of widespread showers focused Friday afternoon/evening. Despite the shortwave energy gradually deamplifying a modest southerly LLJ/PWAT axis will develop ahead of it. Guidance has trended stronger and further west with the axis of the LLJ along with some elevated instability. These ingredients should combined for a period of widespread showers Friday afternoon/evening. Brief localized heavy rainfall is possible and perhaps even an isolated t-storm or two. Greatest risk for that will be across southeast New England on the nose of the LLJ. High temperatures may reach the lower to middle 60s for a time during the late morning/early afternoon...but readings should drop back into the 50s once the rain arrives and some fog should develop. The bulk of the rain should come to an end after midnight...but areas of fog may linger. Saturday... An approaching cold front will result in a milder southwest flow of air into southern New England. Partial sunshine and good mixing ahead of the front should allow afternoon high temperatures to reach into the upper 60s to the lower 70s away from the marine influence of the south coast. Mainly dry weather expected Saturday...but enough forcing/marginal instability may allow for a few showers to develop during the afternoon across the interior. Saturday night and Sunday... The guidance has trended slower with the passage of the cold frontal passage. While confidence is low...the slower movement of the front may allow for a bit better moisture return and perhaps a period of scattered showers Saturday night into Sun. The main idea is that while it does not look like a washout...a period of scattered showers is certainly possible. Highs Sun may reach well into the 50s to the lower 60s given the slower movement of the cold front. Sunday night and Monday... The latest model suite has slowed the departure of the deep upper trough across the northeast. Therefore...cool weather is on tap for Sunday night and Monday. Low temperatures Sun night probably will bottom out well down into the 30s...so some frost is possible. Highs on Monday should be mainly in the upper 50s to around 60. Mainly dry weather expected...although a few spot showers are possible on Mon given cold pool aloft overhead. Tuesday and Wednesday... A significant warmup is still in the cards for the region as the upper trough quickly departs and is replaced by upper level ridging. This should allow highs to probably break 70 across much of the region Tue and perhaps 80+ in some locations by Wed. Weak pressure gradient will likely allow for localized sea breezes at times...resulting in cooler temperatures along the immediate coast. Nonetheless...summerlike warmth is a good bet by the middle of next week away from localized marine influences. Dry weather is also anticipated Tue/Wed as upper level ridge will result in little synoptic forcing for any precipitation. && .AVIATION /14Z 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 Tonight/...High confidence. Rest of today... IFR/LIFR quickly eroding N/E to VFR. At latest 16z for NE MA, Outer Cape, ACK ... mainly near-shore. Increasing W winds, gusts up around 20-25 kts, should scour towards noon. Highest gusts along high terrain. Tonight... VFR. W winds, gradually diminishing, can`t rule out gusts up to 20 kts. Mid-high CIGs on the increase after midnight. KBOS Terminal...IFR quickly improves next hour or two, lifting to VFR as W winds increase. Can`t rule out gusts up to 25 kts. KBDL Terminal...Conditions improved. Should see W winds increase towards noon, potential gusts up to 25 kts. Outlook /Friday through Monday/...Moderate to High confidence. Thursday: Mainly VFR, with local IFR possible. Breezy. Slight chance SHRA, patchy FG. Thursday Night: VFR. Breezy. Friday: Mainly VFR, with local IFR possible. Breezy. SHRA. Friday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA, isolated TSRA, patchy FG. Saturday: VFR. Breezy. Saturday Night: VFR. Chance SHRA. Sunday: VFR. Breezy. Slight chance SHRA. Sunday Night through Monday: VFR. Breezy.
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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 Tonight/...High confidence. Today... SW winds diminishing as rain moves out. Lower visibility / fog will linger over cooler waters towards noon prior to W winds increasing during the latter half of the day. Drier air, should scour out. Improving weather. Gusts up to 25 kts forecast. Tonight...High confidence. W winds gusting to 25 kt early then diminishing. Seas will slowly subside but remain at or above 5 ft. Good visibility. Outlook /Friday through Monday/...Moderate to High confidence. Thursday: Winds less than 25 kt. Rough seas up to 11 ft. Patchy fog. Local visibility 1 nm or less. Thursday Night: Winds less than 25 kt. Areas of rough seas. Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, isolated thunderstorms. Friday Night: Winds less than 25 kt. Areas of rough seas. Chance of rain showers, isolated thunderstorms, patchy fog. Local visibility 1 nm or less. Saturday: Winds less than 25 kt. Seas up to 5 ft. Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers. Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
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&& .EQUIPMENT...
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The NOAA Weather Radio transmitter serving Providence is out of service due to phone line problems. The phone company has prioritized the issues and is working to get the weather broadcast back on the air as soon as possible. The transmitter serving Hyannis is back in service.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ232. Small Craft Advisory until 1 AM EDT Friday for ANZ233-234. Small Craft Advisory until noon EDT today for ANZ236. Small Craft Advisory until 6 PM EDT Friday for ANZ235-237-250- 254>256. Small Craft Advisory until 2 AM EDT Friday for ANZ251.
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&& $$ SYNOPSIS...Frank/EVT NEAR TERM...Frank/Sipprell/EVT SHORT TERM...EVT LONG TERM...Frank AVIATION...Frank/Sipprell/EVT MARINE...Frank/Sipprell/EVT EQUIPMENT...WFO BOX Staff

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