Lexington, Massachusetts, USA
000 FXUS61 KBOX 051811 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 211 PM EDT Fri Aug 5 2022 .SYNOPSIS... Heat and humidity will be the main weather story right into early next week. This hot stretch continues today, with even higher humidity. The greatest potential for showers and thunderstorms will be today into Saturday, with localized heavy rainfall possible at times. It may be Tuesday, or later, before this heat and oppressive humidity finally breaks in a significant way. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 205 PM Update... * Isolated to scattered thunderstorms with locally heavy developing this afternoon, but many locations will remain dry Oppressive heat & humidity were in place across the region at mid-afternoon. Current temps were mainly in the upper 80s to the lower 90s and with high dewpoints in place current heat Indices were well up into the 90s to near 100. Temps and heat indices will likely climb a few more degrees by late afternoon and Heat Advisories continue for the region. In addition...isolated thunderstorms were beginning to develop at mid-afternoon. Capes were on the order of 1500 to 2000 J/KG and there was a subtle shortwave embedded in the flow. Tough to pinpoint the areas with the best shot of activity given the limited upper level forcing. However, an area along a developing sea breeze front across eastern MA/RI might be one area to watch. Also some terrain/mesoscale interactions will be another area to watch. Overall severe weather threat should be quite limited given very weak wind fields, but locally heavy rainfall is certainly possible given Pwats around 2 inches and slow movement of any storms. This activity will be hit or miss and many locations will remain dry. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... With the weak wind fields in place, expecting thunderstorms to diminish quickly after sunset. The same cannot be said for the possibility of showers tonight. Showers and thunderstorms redevelop for Saturday. Have little confidence in trying to time out the risk for specific locations given the rather soupy environment. Have greater concern for downpours than severe weather yet again Saturday. Above normal temperatures and near oppressive humidity continues. Will likely need to extend Heat Advisories for some areas Saturday. These areas could change daily, so will take any extensions on a daily basis. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights * Oppressive heat and humidity continues through Monday. Additional heat headlines likely for Sunday, and possibly Monday. * Slow-moving frontal boundary early next week may support a period of unsettled weather * Temperatures moderate closer to normal mid-week. Sunday and Monday Little change in the weather pattern for Sunday and Monday as deep southwest flow continues to pump warm moist air into southern New England. Dewpoints remain in the low 70s while afternoon temperature stop out in the low to mid 90s. This will translate to heat indices in the mid to upper 90s for both Sunday and Monday. Thus, additional heat headlines are likely for some areas on these days. Most areas are expected to stay dry during this time frame, but with the unstable atmosphere, we can't rule out a brief spot shower or thunderstorm during the afternoon. Next Week Quite a bit of uncertainty beyond Monday as global models are struggling to come to a consensus on how to resolve a slow moving cold frontal boundary early next week. GFS supports an earlier arrival Monday night, while the EURO supports a later arrival on Tuesday. Have leaned on NBM on guidance due to the uncertainty. The expectation is that this frontal boundary will support periods of wet/unsettled weather in the Tuesday to Thursday time frame. Additionally as an upper-level trough associated with this boundary digs into the Northeast, we should see temperatures return to something closer to normal. While the models are in quite a disagreement early in the week, there is better agreement later in the weak for coastal low developing off the east coast. Perhaps this will introduce an opportunity for so much needed rainfall! Check back for more details in the coming days. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 18z TAF Update... This afternoon into tonight...Moderate Confidence. VFR conditions persist outside the isolated to scattered thunderstorms that will develop into early this evening. This activity should diminish with the loss of daytime heating. Otherwise...the main concern will be for areas of fog developing later tonight which may be locally dense in the typically prone spots. The threat for widespread low clouds though will probably be confined to areas near the south coast with the best shot at Nantucket. Winds becoming Light/Calm tonight except more from the SW at 5-10 knots across the Cape and Islands. Saturday...High Confidence. Mainly VFR once the areas of fog burnoff shortly after sunrise. However, isolated to widely scattered showers/t-storms will be possible in the afternoon with the greatest risk in northern MA and interior southern New England. S-SW winds 10 to 15 knots, but there may be a couple hour window for sea breezes across the eastern and especially northeast MA coast. Any sea breezes should be overcome as the day wears along. Saturday night...High Confidence. Mainly VFR and think the main threat for low clouds/fog will be confined to areas near the south coast, Cape and Islands. Winds will be from the WSW 5-10 knots. KBOS...Moderate Confidence in TAF. KBDL...Moderate Confidence in TAF. Outlook /Saturday Night through Tuesday/... Saturday Night through Sunday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Monday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA. Monday Night: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA, isolated TSRA. Tuesday: Mainly MVFR, with local VFR possible. Breezy. Chance SHRA, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. High confidence. Areas of fog should dissipate this morning. Winds and seas to remain relatively tranquil through Saturday. Outlook /Saturday Night through Tuesday/... Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Seas up to 5 ft. Slight chance of rain showers. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Monday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, isolated thunderstorms. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. && .CLIMATE... August 5th daily record maximum high temperatures... BOS - 100F [1955] ORH - 96F [1944] PVD - 100F [1944] BDL - 101F [1955] August 5th daily record maximum low temperatures... BOS - 76F [1938] ORH - 73F [1938] PVD - 77F [1938] BDL - 76F [1938] && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004. MA...Heat Advisory until 8 PM EDT this evening for MAZ002>023-026. Air Quality Alert until 11 PM EDT this evening for MAZ007-015- 016. RI...Heat Advisory until 8 PM EDT this evening for RIZ001>007. MARINE...None. && $$ SYNOPSIS...Belk/RM NEAR TERM...Frank SHORT TERM...Belk LONG TERM...RM AVIATION...Frank/RM MARINE...Belk/RM CLIMATE...Staff
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