Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 270921 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 521 AM EDT FRI MAY 27 2016 .SYNOPSIS... Very warm to hot afternoon temperatures will continue today and Saturday away from the immediate coast. A backdoor cold front will bring cooler temperatures to eastern MA Sunday but it will remain very warm across the interior, where hit and miss showers and thunderstorms likely develop during the afternoon. The potential exists for a period of heavy rain very late Sunday night into Memorial Day. Dry weather likely follows Tuesday through Thursday, with above normal temperatures trending back to seasonable levels by late in the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... With increasing humidities across the cooler ocean waters along the S coast, experimental GOES-E IR satellite imagery showing increasing chances for low clouds and fog moving across portions of Cape Cod as well as Nantucket and Martha`s Vineyard this morning. Already noting vsbys below 1/2 mile across Nantucket, with some fog into the Vineyard and may push into the mid and outer Cape. Expect these to push offshore around mid to late morning. Stationary front sitting across eastern Mass early this morning should push NE by midday. With the building upper ridge across the Eastern seaboard, will see slowly but steadily increasing humidities along with the warm to hot temperatures across the region. Noting a weak mid level short wave moving into central and western areas this afternoon, so can not rule out some convection developing. Looks like the best chance will occur from northern Worcester county through into N CT and W Mass this afternoon. Have low chance POPs going there. Marginal instability with K indices into the lower 30s, plus TQs to the upper teens /indicative of possible elevated convection/. Also noting brief period of CAPEs up to 800-900 J/kg late in the day. As the front shifts away from the region this afternoon, warmer air works in, with H925 temps up to +20C to +22C by late in the day across central and western. This along with S-SW winds picking up during the day, temps will soar. Expect temps to top off from 85-90 away from the coast, but only in the 70s along the S coast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Tonight...Any isolated convection that may develop will diminish this evening as diurnal heating ends. Expect dry conditions overnight. With dewpoints continuing to slowly rise, expect patchy fog to develop in the normally susceptible locations mainly after midnight. May also more low clouds and ocean fog move in along portions of the south coast. Overnight lows will only fall back to the lower-mid 60s, though may remain a bit lower along the immediate S coast with cooler ocean temperatures. Saturday...Will see hot and humid conditions across the region as mid level ridge builds across W New England. Expecting highs from 90 to 95 degrees away from the immediate coast with SW winds in place. Temps will remain cooler along the S coast, Cape cod and the Islands. With the summer conditions in place, will see another round of showers and thunderstorms developing during the late morning and afternoon. The best shot looks to be from the interior Merrimack Valley to northern Worcester county into the Conn valley. CAPEs will increase to 1300-1400 J/kg, but some limiting factors also in place with the strong ridge in place which could cap activity. Will need to monitor for some storms producing locally gusty winds. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights... * Turning cooler Eastern MA coast Sunday but still very warm inland * Hit and miss showers/t-storms likely across interior southern New England Sunday afternoon/early evening * Period of heavy rain possible very late Sunday night into Memorial Day with even a small risk of localized flooding * Dry weather Tue into Thu with above normal temps trending back to seasonable levels late in the week Details... Saturday night...Isolated to widely scattered showers/t-storms may linger into the evening but should be on the downward trend with the loss of daytime heating. Otherwise, expect mainly dry weather Saturday night but it will be quite mild and muggy for late May. Low temps may only drop into the middle to upper 60s for many locations away from the cooling marine influence of the south coast. Patchy fog likely develops in the typically prone locations with dewpoints in the 60s. Sunday...Still timing differences with the backdoor cold front but appears that it will still be east of the CT River Valley by mid afternoon. So its conceivable that Sunday afternoon temps will have fallen into the 60s along the Eastern MA coast, while the Lower CT River Valley might be in the lower 90s. The morning should mainly be dry, but expect 1000 to 2000 J/KG of Cape to develop across interior southern New England. Despite upper level ridging, decent low level convergence/instability will allow low level moisture to pool a bit. The result should be hit and miss showers/thunderstorms developing across interior southern New England Sun afternoon. The extent of this activity will be determined by how fast the front moves and amount of instability that is able to develop. Highest risk for scattered activity is across western MA/northern CT but it could extend back into portions of central MA/RI if front moves slower. 0 to 6 km shear is weak, so overall severe weather threat is low. However, given decent instability can not rule out a strong thunderstorm or two. Any storms that develop will be slow moving and capable of producing very localized heavy rain. So to sum up Sunday, dry weather expected for much of the day but scattered showers/t-storms likely develop in the afternoon across the interior. While activity should be hit and miss, very localized heavy rainfall and lightning will be the biggest concern with any storm. Sunday night and Memorial Day... Hit and miss convection across the interior should diminish Sunday evening with the loss of daytime heating. Mainly dry weather expected for the first part of the night. Things then become very interesting very late Sunday night into Memorial day. The National Hurricane Center is expecting low pressure between the Bahamas and Bermuda to develop into a tropical or sub tropical cyclone in the next 48 hours. While a direct impact will not occur, an approaching cold front will likely pull a plume of its tropical moisture northward. PWATS may rise to around 2 inches in southern New England. Still plenty of uncertainty on how this unfolds, but a period of heavy rain showers and a few embedded thunderstorms are possible across the region. Fortunately, this appears to be a progressive event but given tropical connection there is a small risk of some localized flooding. Something will have to watch closely, especially given it will be on the end of a Holiday Weekend and a big travel day. Tuesday through Thursday... Looks like dry and warm weather follows behind the cold front on Tuesday with highs mainly in the 80s. It is a long way off, but current guidance favors dry weather Wed into Thu as high pressure builds down from the Canadian Maritimes. This would also generate an easterly low level component to the wind with temperatures likely returning to seasonable normals by Thursday. && .AVIATION /09Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through 12Z...High confidence. Local IFR-LIFR CIGS/VSBYS across outer Cape Cod and Nantucket in low clouds and fog. Otherwise VFR conditions. Today...High confidence. Mainly VFR, except IFR-LIFR CIGS/VSBYS through mid to late morning across portions of outer Cape Cod and Nantucket. Conditions should improve by midday. Low probability for brief MVFR conditions in SCT -SHRA/-TSRA mainly across the interior. Tonight...High confidence. Mainly VFR. Patchy ground fog develops resulting in local MVFR-IFR conditions. Leftover isolated -SHRA/ -TSRA this evening with brief local MVFR conditions, then ending. Saturday...Moderate confidence. Mainly VFR. Local MVFR-IFR conditions in patchy fog through mid morning. Low probability of brief MVFR conditions in SCT afternoon SHRA/TSRA across the interior. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Saturday Night through Tuesday/... Saturday night...Moderate to high confidence. Any isolated convection diminishes early in the evening. Mainly VFR conditions but a period of MVFR to even localized IFR condition may develop late in patchy fog and perhaps a touch of low clouds. Sunday...Moderate confidence. VFR conditions may lower to MVFR thresholds across Eastern New England behind backdoor cold front. Otherwise, mainly VFR across the interior but briefly lower conditions possible in hit and miss showers/t-storms during the afternoon. Sunday night and Memorial Day...Moderate confidence. MVFR-IFR conditions may develop late Sunday night into Memorial Day in a period of rain showers which may be locally heavy. Monday night and Tuesday...Moderate to high confidence in mainly VFR conditions. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...High confidence. Expect S-SW winds in place across the waters through the period, picking up to around 15 KT tonight and continuing on Saturday. Seas look to build to around 5 feet on the southern outer waters tonight, so have issued small craft advisory for those waters. Areas of fog will move across the southern outer waters to E of Cape Cod, with some patchy dense fog possible through mid to late morning today, then again tonight into early Saturday. Outlook /Saturday Night through Tuesday/...High confidence. Winds and seas will generally remain below small craft advisory through the period with a relatively weak pressure gradient. Biggest concern for Mariners will be late Sunday night into Memorial Day, when a period of heavy rain showers/isolated thunderstorms are possible. && .CLIMATE... Still expect highest temperatures of the week on Saturday. Some record highs may be challenged. However, might even see temps getting close to records today as well. Record highs for today May 27... Boston...96 set in 1880 Providence...90 set in 1914 and 1981 Hartford...94 set in 1914 and 1965 Worcester...91 set in 1914 Milton/Blue Hill...92 set in 1914 Record highs for Saturday May 28... Boston...92 set in 1931 Providence...91 set in 1931 Hartford...93 set in 1977 Worcester...88 set in 1911 and 1929 Milton/Blue Hill...90 set in 1929 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert from 11 AM this morning to 11 PM EDT this evening for CTZ002>004. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas from 11 PM this evening to 8 AM EDT Saturday for ANZ255-256. && $$ SYNOPSIS...Frank/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...Frank AVIATION...Frank/EVT MARINE...Frank/EVT CLIMATE...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.