Lexington, Massachusetts, USA
000 FXUS61 KBOX 270157 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 957 PM EDT Tue Mar 26 2024 .SYNOPSIS... Damp and chilly day continues with raw northeast winds, drizzle, and fog, especially across eastern Massachusetts. Considerably milder Wednesday, but a continued risk for showers. A frontal wave will bring more widespread rain Thursday into early Friday, which may lead to renewed flooding concerns. Drying out later Friday into Saturday, but there remains uncertainty in the exact timing. Dry and seasonable next weekend, but blustery on Saturday. && .NEAR TERM /THROUGH WEDNESDAY/... 10 PM update... Another chilly, raw and damp night with cool onshore flow yielding low clouds, drizzle and areas of fog. Noticeable improvement tomorrow/Wed as onshore flow weakens and airmass modifies, courtesy of WAA with 925 mb temps warming from +2C 18z Tuesday to +10C 18z Wed. After patchy morning drizzle and fog, mid level dry air advects across the region, providing a window of dry weather from late morning into the afternoon, including lunch time, before showers arrive late in the day from west to east. Noticeable milder too with highs in the mid to upper 50s, along with light winds. This temps will be 15-20 degs warmer than Tue! Earlier discussion below. Previous Discussion... Moisture continues to be pulled into southern New England this afternoon and evening on NE flow around the occluded low well to our south. Thus, clouds continue even though the bands of light showers and drizzle have diminished by this afternoon. Even so, will continue to see these impact the eastern half of the region, especially east coastal MA off and on. Tonight a subtle shortwave lifts through the broader SW flow ahead of an approaching shortwave. However, it is accompanied by drier air moving in from the south which should limit shower coverage. BUFKIT soundings do show some marginal drying in the low levels along the east coast, but even so would expect spotty drizzle and fog. Lows will be milder than the previous night as increasing dewpoints limit temps to the low to mid 30s. && .SHORT TERM /WEDNESDAY NIGHT/... A subtle mid level disturbance moves overhead Wednesday rotating around a very broad trough over the entire eastern half of the U.S. For much of the day the plume of deeper moisture ahead of the trough remains to our south, while the dynamics also are removed from our area, so shouldn't see much in the way of rain during the day. The exception may be the orographically favored terrain of western MA. Something of note will be the milder temperatures compared to Tuesdays as low level flow moderates. Dewpoints rise into the upper 40s/low 50s and while there is some disagreement between the global and hi- res guidance, even ensembles show a 40-60% chance of surface temps reaching as high as 60 degrees in RI and southeast MA. Wednesday night the plume of moisture (>1" PWATs) originating from the Gulf of Mexico reach southern New England ahead of an area of low pressure moving up the east coast. This is the front end of what will be a prolonged period of widespread moderate rainfall. The synoptic forcing for ascent will be increasing thanks to divergence aloft from a 150 kt upper jet as the upper trough and surface low approach. By sunrise on Thursday, can't rule out a half inch or more of rainfall. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights * Heavy precipitation late week may lead to an elevated risk for flooding across RI and southeastern MA * Trending drier with near normal temperatures this weekend Looking like southern New England is heading into a prolonged period of unsettled weather late this week. Significant ensemble signals in the NAEFS, with standardized anomalies of 3-4 standard deviations. We're looking at quite a bit of moisture and lift sometime from Thursday into Friday a a coastal low pressure moves by to our east. Given this storm track, the greatest risk for rainfall will be across the Cape and islands, but there should be at least some rainfall across most of southern New England during this time. There is potential for another 1-2 inches of rainfall in our region, which will need to be monitored with area waterways already running high from the rainfall this past Saturday. Should confidence in significant rainfall continue to increase, Flood Watch headlines may be needed for portions of southern New England. Still thinking this weekend remains mainly dry, but the picture is not as clear as it once was. A low pressure should move into the Maritimes from east of New England by Saturday. The question then becomes where exactly will the cold front of this low pressure be. At this time, thinking it stalls just to the south of New England. With another low pressure projected to develop over the central USA at this time, providing another mechanism to keep this front nearby. This low pressure itself is projected to pass by to our south on Sunday, but not far enough south to prevent some clouds from reaching our region. Saturday looks to be the windier of the two days, as some cooler air arrives on the back side of the departing low pressure. Weak high pressure should then continue into Monday, before another low pressure possibly arrives towards next Tuesday. Near to slightly above normal temperatures anticipated through this portion of the forecast. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. Tonight...high confidence. IFR/LIFR in low clouds, spotty light rain, drizzle and areas of fog. NE winds ease and become SE late. Wednesday...moderate confidence. Drier on Wednesday with IFR/LIFR early improving to MVFR/VFR by afternoon. Light and variable winds in the morning, becoming SSE in the afternoon. Wednesday night...moderate confidence. VFR to start lowering to IFR/LIFR in increasingly widespread moderate rain showers. Light and variable winds becoming northerly. KBOS TAF...High confidence in trends, some uncertainty in exact timing. KBDL TAF...High confidence in trends, some uncertainty in exact timing. Outlook /Thursday through Sunday/... Wednesday Night: MVFR/IFR conditions possible. Chance RA, patchy BR. Thursday: Mainly IFR, with areas MVFR possible. RA. Thursday Night: MVFR/IFR conditions possible. Windy with local gusts up to 30 kt. Chance RA. Friday: VFR. Windy with gusts up to 35 kt. Chance RA. Friday Night: VFR. Windy with gusts up to 35 kt. Saturday: VFR. Windy with gusts up to 30 kt. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight... High pressure moves over the Maritimes and low pressure south of New England weakens. Winds weaken and shift from NE to SE. Rough seas slowly subside. Vsby limited in areas of light rain/drizzle and fog. Wednesday... Weak high pressure over the waters; winds light and variable. Drizzle and fog during the morning slowly give way to drier weather in the afternoon along with improving vsby. Seas 5-7 ft. Wednesday night... Rain shower coverage increasing through the nighttime hours. Winds light and variable. Seas 4-6 ft. Outlook /Thursday through Sunday/... Wednesday Night: Winds less than 25 kt. Local rough seas. Rain likely, patchy fog. Visibility 1 to 3 nm. Thursday: Winds less than 25 kt. Seas up to 5 ft. Rain. Local visibility 1 to 3 nm. Thursday Night: Low risk for Small Craft Advisory winds with local gusts up to 30 kt. Areas of rough seas. Rain. Friday: Strong winds with gusts up to 30 kt. Rough seas up to 9 ft. Chance of rain. Friday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 8 ft. Slight chance of rain. Saturday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 9 AM EDT Wednesday for ANZ230. Small Craft Advisory until midnight EDT tonight for ANZ231>235- 237. Small Craft Advisory until 8 AM EDT Thursday for ANZ250-251- 254>256. && $$ SYNOPSIS...Belk/BW NEAR TERM...Nocera SHORT TERM...BW LONG TERM...Belk AVIATION...Belk/BW MARINE...Belk/BW
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