Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261114 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 714 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/... 710 am update... Last of the steady rain across eastern MA will be exiting the region over the next hour or two. Otherwise, a few spot showers may linger this morning. Areas of fog still impacting the region with a few localized spots where it was dense. Rapid improvement should occur over the next few hours as increased mixing allows drier air to scour it out. Clouds will be slower to depart...but should see partial sunshine emerge in most areas by afternoon. Skies will become partly to mostly sunny this afternoon for most areas. It will be a more typical spring day as temperatures rebound into the middle to upper 60s across much of the region. As winds shift to SW to W during the day, may see wind gusts up to around 25 mph mainly during the afternoon, possibly a bit higher for a time along the immediate S coast. && .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 /11Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...Moderate to High confidence. Today...LIFR conditions dominated very early this morning...but should see improvement to high end IFR-MVFR by mid morning and mainly VFR by afternoon. High confidence in the improvement given dry westerly flow mixing down...but uncertainty revolves around the specific timing. W-SW winds will gust up to 20-25 kt along the immediate S coast, Cape Cod and the islands as well as the higher terrain. Tonight...VFR conditions. W wind gusts up to around 20 kt. Mid and high clouds increase after midnight across western areas. KBOS Terminal...High confidence in TAF but lower confidence in timing. LIFR conditions should improve to high end IFR-MVFR by mid morning and mainly VFR this afternoon. Specific timing is uncertain. KBDL Terminal...High confidence in TAF but lower confidence in timing. IFR conditions should improve to MVFR by mid morning and then mainly VFR this afternoon. Outlook /Friday through Monday/...Moderate to High confidence. Friday: VFR in the morning will be replaced by MVFR-IFR conditions form west to east during the afternoon/early evening as rain showers move across the region with even the low risk of an isolated t-storm. Areas of fog also expected to develop late. Friday Night: Mainly MVFR-IFR conditions. SHRA mainly in the evening, but areas of fog and low clouds may persist longer. Saturday: VFR. Saturday Night: VFR. Chance SHRA. Sunday: VFR. Slight chance SHRA. Sunday Night through Monday: VFR. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Through 12Z...Moderate confidence. Small Craft Advisories for all waters except Boston Harbor and Cape Cod Bay. Expect E-SE winds gusting up to 25 kt. Rough seas up to 10 to 12 ft. Rain showers along with areas of fog. Visibility locally below 1 nm at times across the southern waters. Today...Moderate to high confidence. S-SW winds gusting to 25-30 kt then will briefly diminish around midday before shifting to W and gusting up to around 20 kt mainly on the outer waters. Seas will remain at 5 feet or greater through the day across the open waters as well as the south bays and sounds. Visibilities at or below 1 nm at times through mid to late morning in patchy fog and showers, then improving. 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. Friday: Winds less than 25 kt. Seas up to 5 ft. Rain showers develop by late afternoon with an isolated t-storm or two possible. Areas of fog. Local visibility 1 to 3 nm. Friday Night: Winds less than 25 kt. Areas of rough seas. Rain showers likely with perhaps isolated thunderstorm. Areas of fog. Visibility 1 to 3 nm. 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. && .EQUIPMENT... 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. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Dense Fog Advisory until 9 AM EDT this morning for MAZ020>024. RI...Dense Fog Advisory until 9 AM EDT this morning for RIZ006>008. 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. && $$ SYNOPSIS...EVT/Frank NEAR TERM...Frank/EVT SHORT TERM...EVT LONG TERM...Frank AVIATION...EVT/Frank MARINE...EVT/Frank EQUIPMENT...Staff

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