Lexington, Massachusetts, USA
000 FXUS61 KBOX 021120 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 720 AM EDT Tue Aug 2 2022 .SYNOPSIS... Becoming hot, muggy, with brief widely scattered showers and isolated thunderstorms develop ahead of an approaching cold front Tuesday afternoon. Dry and very warm again Wednesday albeit noticeably cooler along portions of the immediate coast. This will be followed by near record high temps and oppressive humidity Thursday some of which may linger into Friday. The threat for scattered showers and thunderstorms increases Friday and may persist at times this weekend into next Monday, but a washout is not expected. Above normal temperatures continue as well, but not at the potential record breaking levels of Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 630 AM Update Forecast remains on track this morning. Muggy start to the day with dewpoint and air temperatures in the mid and upper 60s respectively. GOES night time microphysics reveals areas of low stratus across portions of the interior this morning. Latest observational trends have shown this cloud layer lifting gradually. Expect this trend to continue as the morning progresses. No significant changes to the near-term forecast. A hot muggy day remains in store. See previous discussion for additional details. Previous Discussion Rather expansive area of stratus was located over the eastern 2/3 of southern New England this morning. This stratus should dissipate rather quickly after sunrise, only to be replaced with higher clouds later today. Expecting another rather warm and humid day today, with the risk for some showers and a few thunderstorms as a cold front approaches. Given the timing of this front, these are more likely across the western half of southern New England. There is not a lot of shear to organize to modest CAPE values of 1,000-1,500 J/kg. Thus, not expecting a widespread severe weather event today, but cannot rule out a strong storm or two. These storms should weaken after sunset. Expecting max temperatures to be about 5 degrees higher today due to a persistent southwest wind ahead of a cold front. This will also lead to much higher dewpoints. At this time, thinking we will stay just under the threshold for a Heat Advisory, but it will be close. This will need to be monitored by the day shift, as a subtle increase of only a degree or two in either temperatures or dew points from the current forecast could make all the difference. If you must work outdoors today, please drink plenty of fluids and take frequent breaks out of the sun. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... A cold front will move offshore late this evening and overnight, leading to less humid conditions Wednesday. A few locations across eastern MA could also be slightly cooler, with seabreezes developing by afternoon. Across the interior, max temperatures should be similar to today. Once showers dissipate this evening, rain-free weather should persist through Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights * Potentially record setting heat on Thursday with heat indices over 100. * Oppressive humidity Friday with scattered showers and thunderstorms Friday afternoon. * Above normal temperatures continue this weekend Thursday and Friday Deep southwest flow is forecast to advect an anomalously warm and humid air mass into southern New England for Thursday and Friday. Temperatures at 850 hPa are expected to rise above 20 Celsius on Thursday. With persistent 15-20 knot southwest winds expected in the boundary layer, we can expect diurnal mixing to 850 hPa which will support high temperatures in the upper 90s to perhaps 100 degrees across much of interior southern New England. Lower temperatures forecast across southeastern MA and the south coast in the upper 80s to low 90s. Dewpoints in the upper 60s to low 70s will result in heat indices in the low 100s at some locations. Heat advisory headlines are likely at this time. Dry air in the mid-levels will keep the region dry on Thursday afternoon, but a spot shower/thunderstorm Thursday night can't be ruled out across the western zones. Deep southwest flow continues into Friday and supports surging dewpoints into the low to mid 70s. Temperatures remain above normal, but increasing cloudiness Friday afternoon should limit high temperatures to the upper 80s and low 90s. Nonetheless, the oppressive humidity will have us flirting with heat advisory criteria with heat indices in the upper 90s likely. Weak upper-level disturbance and surface frontal boundary moves across the region late Friday. This will bring the potential for a few thunderstorms and some much needed rainfall across portions of southern New England. Weak boundary layer winds and PWATs close to 150 percent of normal will be supportive of locally heavy downpours. Not expecting any severe storms to develop as both deep-layer shear and synoptic forcing for ascent will be very limited. This Weekend Southwest flow continues to support above normal temperatures this weekend. No strong signals for advisory level heat this weekend, but still hot with highs in the upper 80s to low 90s. Dewpoints remain elevated in the low to mid 70s making for some very uncomfortable sleeping weather. Can't rule out a few isolated convective showers or thunderstorms during the afternoon. Next Week Consensus among long-term models and ensembles if for the southwest flow pattern and above normal temperatures to continue into Monday. Beyond Monday there is a signal for a frontal passage early next week that would bring the next opportunity for substantial rainfall. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today...High confidence. IFR/MVFR stratus deck across the interior and near The Cape/South Coast lift to VFR early this morning. Mainly VFR the rest of the day with a scattered to broken deck of diurnal CU. Widely scattered brief showers and perhaps a few isolated thunderstorms develop this afternoon, which may result in brief/localized lower conditions but areal coverage/duration should be limited. SW winds 10-15 knots. Tonight and Wednesday...High confidence. VFR. KBOS...High confidence in TAF. Moderate confidence in timing dissipation of stratus. KBDL...High confidence in TAF. Outlook /Wednesday Night through Saturday/... Wednesday Night: VFR. Thursday: VFR. Breezy. Thursday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Friday: Mainly VFR, with areas MVFR possible. Chance SHRA, slight chance TSRA. Friday Night: Mainly MVFR, with areas VFR possible. Chance SHRA, slight chance TSRA. Saturday: Mainly MVFR, with areas VFR possible. Breezy. Slight chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Monday evening into Tuesday night...High confidence. Poor visibility early this morning will improve during the day. A cold front brings another chance for showers and slight chance for thunderstorms this afternoon and early evening. A cold front will move across the waters tonight, with fair conditions expected Wednesday. Outlook /Wednesday Night through Saturday/... Wednesday Night through Thursday: Winds less than 25 kt. Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, slight chance of thunderstorms. Friday Night: Winds less than 25 kt. Chance of rain showers, slight chance of thunderstorms. Saturday: Winds less than 25 kt. Slight chance of rain showers. && .CLIMATE... August 4th daily record maximum high temperature. BOS - 96F [1928] ORH - 95F [1944] PVD - 98F [1944] BDL - 96F [1944] August 4th daily record maximum low temperature. BOS - 76F [1930] ORH - 72F [2002] PVD - 74F [2010] BDL - 74F [2006] && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/RM NEAR TERM...Belk/RM SHORT TERM...Belk LONG TERM...RM AVIATION...Belk/RM MARINE...Belk/RM CLIMATE...
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