Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 251426 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1026 AM EDT WED MAY 25 2016 .SYNOPSIS... An upper level ridge will bring very warm weather to most of the region through Saturday, except for cooler temperatures at times along the immediate coast. A backdoor cold front will bring cooler weather to the region sometime on Sunday, but temperatures should rebound to at or above normal by early next week. A few showers and thunderstorms are possible Thursday night into Friday, and again this weekend but the vast majority of this time will be dry. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ***Summer temperatures push in today across the region*** 1030 AM Update...Most of the fog has cleared out across the area with the exception of one band of fog that is hugging the south coast of RI and moving eastward towards Buzzards Bay and the Cape. If it continues on this trajectory without burning off, portions of Cape Cod along the Cape Cod Canal as well as Martha`s Vineyard and the Elizabeth Islands will see a period of fog later this morning into early afternoon. Visibilities have been generally about a mile with this bank of fog on land, it may be more dense over the water. Made minor adjustments to the temperatures to ease them back as they have not jumped up as quickly as forecast. Otherwise, the previous forecast is on track. Weak ridging at the surface and aloft will cross the region by midday through the afternoon with NW winds aloft. Warm core H925 temps will push across the region, up to +19C to +22C by this afternoon. Once skies become mostly sunny, temps will rise quickly with excellent low and mid level mixing in place. Expect temps to top off in the mid-upper 80s with a few spots touching 90. However, dewpoints falling into the 40s will result in low humidity levels. High clouds will start to push in from the NW during the mid and late afternoon ahead of H5 short wave across far northern New England. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Tonight... Most of the energy from a weak H5 shortwave trough will remain across northern New England. NW flow keeps dry conditions across the region tonight. The mid and upper level clouds will dissipate overnight as SW winds shift back to W-NW and diminish. It will remain mild, with temperatures only bottoming out from the mid 50s well inland to lower-mid 60s across the coastal plain. Thursday... A cold front will slowly push S across the region during the day. Clouds will push in from the W as the front moves in during the afternoon. Short range models vary in their solutions, with mainly dry conditions through the day offered by the ECMWF, but the GFS tends to bring some moisture with a weak H5 shortwave in the W-NW flow aloft. Have mentioned only slight chance PoPs moving into W MA/N Central CT during the mid and late afternoon hours. Have noted marginal instability with this system, plus another day of warm temperatures, so have mentioned widely scattered showers/isolated thunderstorms. It will be another warm day, with somewhat higher dewpoints making it feel a bit more humid. Highs will again be in the mid-upper 80s away from the immediate coast, with a few spots possibly hitting 90 again. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Highlights... * Friday: Very warm w/highs mid-upper 80s northwest of BOS-PVD but a bit cooler across southeast MA/RI * Saturday: Hot and a bit humid w/highs mainly upper 80s to lower 90s away from the immediate south coast * Sunday: Temps uncertain depending on timing of cold front, warmest readings likely CT River Valley w/coolest across Eastern MA coast * A few showers/t-storms possible Thu night/Fri and again Sat/Sun but the vast majority of this time will be dry * At or above normal temperatures likely return early next week Details... Thursday night...Shortwave energy and a burst of elevated instability may result in a few showers/t-storms Thursday night, mainly northwest of a Boston to Providence line. If any activity is able to develop, it will be short-lived with the majority of the night ending up dry. Low temps mainly in the upper 50s to the lower 60s. May see some patchy ground fog develop late in the typically prone locations. Friday...Surface winds shift to the south-southwest behind the warm front as 850T rise to around +14C. Plenty of sunshine should allow highs to warm into the middle to upper 80s northwest of a Boston to Providence line. Southeast of this line...a cooling marine layer may hold highs in the upper 70s to the lower 80s. Dry weather will dominate on Friday, but enough instability combined with a pre-frontal trough may allow a few showers/thunderstorms to develop across W MA/N CT Fri afternoon and evening. Not sure if this activity gets into our region or stays to our west, but highest risk will be across northwest MA. Shear is rather weak so even if we see a few thunderstorms in our western zones, overall severe weather threat is rather low. Saturday...A hot and somewhat humid day is on tap to kick off the Memorial Day Weekend. 850T around +16C, plenty of sunshine, and a westerly component to the surface winds should allow for high temps to reach into the upper 80s to the lower 90s away from the immediate south coast. Dewpoints between 60 and 65 across most of the region will make it feel a bit humid. While most of the day will be dry, a few showers and thunderstorms may develop Saturday afternoon and evening with a pre-frontal trough and CAPE values between 1000 and 2000 J/KG. This will be mainly to the northwest of a Boston to Providence line. Forcing will be rather weak, so areal coverage of any activity that develops may remain limited. Severe weather threat also looks rather low at this time with rather weak 0 to 6 km shear, but too early to rule out a strong thunderstorm or two given decent instability. Sunday...Low confidence on high temperatures given a subtle change in timing of the backdoor cold front will make a big difference in the exact outcome. We can say that the warmest readings will be across the lower CT River Valley and coolest along the eastern MA coast. Good shot though at the CT River Valley seeing high temps reaching well into the 80s, while the eastern MA coast has afternoon temps falling into the 60s. A few showers will remain possible and perhaps even a couple of t-storms across the interior if enough instability develops during the afternoon. Monday and Tuesday...Backdoor cold front does not appear as strong on the latest model runs. It looks to washout across the region early next week. GFS washes out on Monday while the ECMWF waits until Tuesday. Probably should see the return to above normal temps by Tue with rather warm temps aloft. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...High confidence. VFR conditions expected the rest of the day, except on the Cape and Islands where fog may reduce visibilities down to MVFR/IFR at times. Tonight...High confidence. VFR conditions. W-NW winds 10 kt or less. Thursday...High confidence. VFR. Light W-NW winds, except sea breezes possible late morning/afternoon along the coast. KBOS TAF...Moderate to high confidence. An ESE sea breeze has developed and is expected to continue into early afternoon. Southwesterly winds should overcome this by late afternoon. KBDL TAF...High confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday night and Friday...Moderate to high confidence. VFR conditions likely dominate but some brief MVFR conditions possible in a few brief showers/t-storms mainly across the interior. Also, some patchy ground fog possible in the typically prone locations very early Fri AM. Saturday...Moderate to high confidence. VFR conditions likely dominate but a brief period of MVFR-IFR cigs/vsbys possible in a few afternoon and evening showers/thunderstorms. Sunday...Low confidence. MVFR-IFR conditions may develop from east to west behind a backdoor cold front. A few thunderstorms also possible Sun afternoon across the interior. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...High confidence. W winds up to 10 kt will back to SW 10-15 kt this afternoon with gusts up to 20 kt on the southern outer waters. Seas 4 ft or less. Patchy fog mainly along the south coast will result in reduced visibilities at times. Tonight...High confidence. Light southwesterly winds become westerly, gusting up to 20 kt on the southern outer waters this evening. Seas 4 ft or less. Thursday...High confidence. Light W winds shifting to S in the afternoon. Seas remain below 5 ft. Outlook /Thursday Night through Sunday/...High Confidence. Winds and seas will generally remain below Small Craft Advisory thresholds through the period. The main concerns are a period of near-shore southwesterly wind gusts of 20 to 25 knots Saturday afternoon which will result in some choppy seas for mariners. May also see some brief easterly wind gusts between 20 and 25 knots on Sunday behind a backdoor cold front. && .FIRE WEATHER... Today...Expect temperatures will rise quickly, soaring well into the 80s to near 90 across most locations except cooler along the immediate south coast. These temperatures will combine with dewpoints dropping into the 40s resulting in afternoon RH values down to between 20 and 30 percent. A few hours of westerly wind gusts up to 20 to perhaps briefly 25 mph are anticipated. Given Tuesday`s rainfall and marginal criteria, will fall short of needing fire weather headlines. Many locations are close to or already at full green-up. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Air Quality Alert until 11 PM EDT this evening for MAZ020>024. RI...Air Quality Alert until 11 PM EDT this evening for RIZ003-004- 006>008. MARINE...None. && $$ SYNOPSIS...Frank/EVT NEAR TERM...Frank/RLG/EVT SHORT TERM...EVT LONG TERM...Frank AVIATION...Frank/EVT MARINE...Frank/EVT FIRE WEATHER...Staff

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