Lexington, Massachusetts, USA
000 FXUS61 KBOX 270551 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 151 AM EDT Wed Mar 27 2024 .SYNOPSIS... Damp and chilly with patchy drizzle and fog Wednesday morning, gives way to a period of dry and milder weather from late morning into the afternoon. A frontal wave will bring more widespread rain to the region from late Wednesday, through Thursday and possibly lingering into early Friday. This additional rainfall may lead to renewed flooding concerns. Drying out later Friday and remaining mainly dry over the weekend into early next week. Temperatures will be seasonable, but remaining breezy at times. && .NEAR TERM /THROUGH TODAY/... Key Messages... * Much milder this afternoon, 15-20 degs warmer than Tue * Mainly dry weather late morning into early/mid aftn 2 AM update... 1040 mb high over southeast Quebec early this morning wedge down into SNE is providing shallow cool air across the region, with NE flow and temps in the 30s. Meanwhile, SW flow aloft overriding this shallow cool layer is providing WAA spotty light rain/mist/drizzle, along with areas of fog. Thus, another dreary morning on tap. However, all models agree on mid level dry air overspreading the region this afternoon. This won't result in sunshine (although, some brightening in the overcast is possible at times), but a period of dry weather is expected from late morning into the afternoon. This will be short lived, as deeper moisture and lift arrive later in the day in the SW flow aloft. This will result in showers redeveloping between 4 pm and 8 pm from west to east. As NE winds this morning shift to the SSE this afternoon, combined with warm air aloft (925 mb temps warming from +2C 18z Tue to +10C Wed at 18z) will result in temps about 15-20 degs warmer than Tue along with lighter winds! This will yield highs in the mid to upper 50s. If enough breaks of sunshine burn through the clouds, a few locations could warm to 60. Dew pts rising from the 30s into the 40s will also contribute to the milder conditions. && .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/... Key Messages... * Widespread rain likely * Axis of heaviest rain remains uncertain 2 AM update... Rain becomes more widespread Wed night, as strong subtropical jet (up to 140 kt) moves up the eastern seaboard and advects PWATs greater than 1 inch across the area. On Thu the axis of highest PWATs sets up across southeast MA per ensembles, however strong Fgen farther to the west across CT/RI into central MA, resembling a winter type system, but ptype all rain for this even. 00z models continue to disagree on the exact placement of these features, thus axis of heaviest rain remains uncertain. 1-2 inches of rain possible with locally up to 3" not out of the question given strong upper jet with RRQ over SNE, coupled with strong mid level Fgen and above avg PWATs. If 2-3" of rainfall materializes, renewed flooding is possible as rivers and streams are running above normal, including saturated soils and elevated ground water levels. Axis of heaviest rain will hinge on amplitude of mid/upper level trough and how much mid level flow can back along the eastern seaboard. For what it's worth, 00z HREF has heaviest rain from eastern CT into RI and eastern MA. Light winds Wed night with mild temps in response to dew pts in the 40s. Winds remain light on Thu along with temps at or slightly milder than normal, with highs in the upper 40s to lower 50s. && .LONG TERM /THURSDAY NIGHT 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 /06Z WEDNESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. 06z update... Wednesday...high confidence on trends, lower on exact timing and details. IFR/LIFR in areas of drizzle and fog this morning, slowly lifts to MVFR/VFR beginning 15z-18z. Mainly dry after 15z, but scattered showers enter region 20z-00z from west to east. NNE winds become SSE this afternoon. Wednesday night...high confidence. MVFR/VFR at 00z lowering to IFR/MVFR as showers overspread the region tonight. LIFR possible across the hilly terrain of CT and MA. Light SSE winds. Thursday...high confidence. Widespread IFR/LIFR in rain, heavy at times possibly across eastern CT into RI and eastern MA. Light/variable wind becoming NNE. KBOS TAF...High confidence in trends, some uncertainty in exact timing of details. KBDL TAF...High confidence in trends, some uncertainty in exact timing of details. Outlook /Thursday Night through Sunday/... 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. 2 AM update... Key Messages... * NNE winds finally shift to the SSE Wed afternoon * Heavy rain possible late Wed night and Thursday Wednesday...high pressure over southeast Quebec and low pressure off the Mid Atlantic coast both weaken today, resulting in diminishing winds and direction shifting from NE to SSE this afternoon. Areas of drizzle and fog will reduce vsby this morning, then improving this afternoon. Wed night...weak high pressure remains over the MA/RI waters, resulting in light winds. Showers become widespread, limiting vsby. Thu...low pressure near the Carolina coast intensifies as it moves offshore. This results in light/variable winds becoming light NNE across the MA/RI waters. Rain, heavy at times limits vsby. Outlook /Thursday Night 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 this morning for ANZ230. Small Craft Advisory until 8 AM EDT Thursday for ANZ250-251- 254>256. && $$ SYNOPSIS...Nocera NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...Belk AVIATION...Belk/Nocera MARINE...Belk/Nocera
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