Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280852 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 452 AM EDT Thu Mar 28 2024 .SYNOPSIS... A frontal wave will bring more widespread rain to the region from tonight, into Thursday, and possibly lingering into early Friday. This additional rainfall may lead to renewed flooding concerns. Rain, possibly mixed with snow ends Friday morning, except possibly linger into the afternoon across eastern MA. Gradual clearing Friday, but windy Friday and Saturday, with a chance for a few showers Saturday night into Sunday morning. A mix of clouds and sunshine Sunday and Monday with near to above normal temperatures. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 245 AM update... Key Points Thursday... * Widespread rain after daybreak & moderate to heavy at times * Minor poor drainage/urban flooding for the late day commute Stalled frontal boundary and associated low level convergence draped across SNE today. Meanwhile, strong upper level jet streak develops over the northeast into Quebec, with jet increasing to 130-140 kt. This will enhance the QG forcing over SNE and will be acting on a moisture plume with PWATs of 1+ inches. This is courtesy of a full latitude trough approaching from the west with strong southern stream jet energy rounding the base of the trough and then rotating up the eastern seaboard. This will induce a wave of low pressure to develop on the frontal boundary over FL/GA early this morning, then intensifying as the wave moves northeast off the Carolina coast late today. All of these ingredients will yield a large rain shield overspreading SNE today, especially after daybreak and continuing throughout the day. Airmass is warm enough to support ptype of all rain, but this system has winter type attributes, including strong mid level Fgen over SNE, which will result in rain moderate to heavy at times. Not expecting excessive rainfall rates, but a steady light to moderate rain, heavy at times. Rainfall totals through 8 pm roughly 0.50-1.00 inches regionwide, with locally up to 1.5 inches possible from eastern CT into RI and eastern MA. Thus, any flooding today will be limited to minor urban/street/highway flooding, especially later in the day. Seasonable temps with highs in the upper 40s to lower 50s. With frontal boundary draped across the area, light NNE winds over eastern MA/RI and NNW winds in CT and western- central MA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... 245 AM update... Key Messages Thursday night & Friday... * Rain continues, moderate to heavy at times * Rain may briefly mix with or change to snow before ending Friday morning Thursday night... Trough amplification with negative tilt evolving as it moves across SNE. This combined with RRQ of upper level jet moving across the area will enhance QG forcing for ascent, yielding widespread rain and moderate to heavy at times across eastern CT into RI and eastern MA. Trough amplification also results in the offshore wave intensifying, with surface winds over SNE backing to the NNW, cooling surface temps into the mid and upper 30s. Furthermore, this combined with height falls will yield column cooling and may result in rain briefly mixing with or changing to snow before ending Friday morning. The NAM offers the most amplified solution and most snow on the backside. Can`t completely discount this outcome, but none of the other hi res guidance supports it. Even the NAM limits subfreezing surface temps to the northern Worcester Hills and Berks, thus any minor snow accumulation would be confined to this area. Otherwise, just some wet snow possible before ending. Storm total qpf will range from 1-2 inches, highest amounts over eastern CT into RI and eastern MA, where there is low risk of up to 3 inches. Winds - light NNE Thu evening shift to the NW overnight and become gusty as offshore wave intensifies. NW winds 15-25 mph overnight, except up to 35 mph across Cape Cod and the Islands. Temps - in the 40s during the early evening, fall into the mid and upper 30s overnight as rain possibly ends as a brief period of wet snow. Any subfreezing temps will be confined to the highest elevations of Worcester county & the Berkshires. Thus, not expecting much if any impact. Although, we will need to watch later model trends. Friday... Models have trended slower with precip departure, as open/negative tilt mid level trough evolves into a closed low just east of Cape Cod. Thus, rain, possibly mixed with wet snow at times may linger across eastern MA into the afternoon. Otherwise, dry weather overspreads the region from west to east with possible late day clearing. Surface cyclone may become a sub 980 mb low late Fri as it approaches Nova Scotia. This may yield NW winds 20-30 mph with gusts possibly up to 50 mph. Hence, a wind advisory may be needed Friday. Seasonable temps Friday with highs in the upper 40s to lower 50s, but gusty NW winds will make it feel quite a bit cooler. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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Highlights * Windy on Saturday with sunshine and seasonable temperatures * Dry and slightly above normal temps through Monday * Unsettled weather returns Tuesday and Wednesday with an opportunity for substantial precipitation Friday night and Saturday Deep 850 hPa low over The Gulf of Maine deepen and stalls in response to upstream blocking. With a ridge building gin from the west the pressure gradient tightens and a strong low-level jet develops over southern New England under northwest flow. This will support a period of gusty northwest winds over the region with 30 to 40+ mph wind gusts possible Friday evening through Saturday morning. The gradient gradually relaxes into Saturday afternoon, but a well mixed boundary layer will continue to support 20 to 30 mph gusts for much of the day Saturday. Drier air mass should support sunny skies for most of the day Saturday with near normal temperatures. Sunday and Monday Winds diminish by Sunday as a mid-level ridge and surface high pressure builds over southern New England. This will support dry weather and slightly above normal temperatures through Monday. For reference, the average high/low temperatures for Boston this time of year is around 50 and 35 degrees respectively. High/low temps on these days are forecast to be slightly higher than those values. Tuesday and Wednesday Latest suite of model guidance continues to support the development of a low-pressure system over The Midwest early next week. As this system moves east/northeast during the middle of next week, southern New England is likely to see another round of substantial precipitation. Details with respect to precip amounts and timing are very vague at this time, so for now just expect a period of unsettled weather for the middle of next week.
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&& .AVIATION /09Z THURSDAY THROUGH MONDAY/...
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Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. 06z update... Today...high confidence. Any VFR cigs and vsby predawn lower to IFR/LIFR by daybreak in widespread rain, moderate to heavy at times. Light and variable winds trend to NNE across RI and eastern MA, NNW across CT and western-central MA. Tonight...high confidence on trends, lower on exact timing and details. At 00z, IFR/LIFR in rain, moderate to heavy at times. Overnight, improving trends to MVFR/VFR across CT into western MA, improving to IFR/MVFR elsewhere. Rain may mix with or change to wet snow at times toward 12z Fri. NNE winds in the evening become NW overnight and increase to 15-25 kt, gusting up to 35 kt Cape Cod and Islands. Friday...high confidence on trends, lower on exact timing and details. At 12z, IFR/MVFR across eastern MA and RI in rain, possibly mixed with wet snow at times before ending during the afternoon. Across CT into western-central MA, MVFR/VFR in the morning in lingering light rain/snow, ends and improves to VFR in the afternoon along with dry weather. NW winds increase to 20-30 kt with gusts up to 40 kt. KBOS TAF...High confidence in trends, some uncertainty in exact timing of details. Rain may briefly mix with some wet snow 09z-15z Fri before ending. KBDL TAF...High confidence in trends, some uncertainty in exact timing of details. Rain may briefly mix with some wet snow 06z-12z Fri before ending. Outlook /Friday Night through Monday/... Friday Night: VFR. Strong winds with areas of gusts up to 40 kt. Saturday: VFR. Strong winds with local gusts up to 40 kt. Saturday Night: VFR. Windy with local gusts up to 30 kt. Sunday through Sunday Night: VFR. Breezy. Monday: VFR. Slight chance RA.
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&& .MARINE...
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Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 245 AM update... * NW Gales possible Friday/Fri night Today...high forecast confidence. Frontal boundary draped across the MA/RI waters, with light NNE winds developing across the eastern waters and NNW over the western waters. Periods of rain early this morning become more widespread later this morning into the afternoon, then moderate to heavy at times lowering vsby. Tonight...high forecast confidence. Light NNW-NNE winds during the evening become NNW all areas after midnight and rapidly increase to 20-30 kt as offshore low intensifies into a gale center from the Carolinas to western Georges Bank by 12z Friday. Rain, heavy at times will limit vsby. Friday...high forecast confidence. Gale center moves from western Georges Bank to near Nova Scotia. NW winds 20-30 kt gusting up to 40 kt possibly at times. Any morning rain/snow moves offshore with dry weather and improved vsby for the afternoon. Outlook /Friday Night through Monday/... Friday Night: Strong winds with gusts up to 35 kt. Rough seas up to 9 ft. Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Sunday through Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Monday: Winds less than 25 kt. Slight chance of rain.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...Flood Watch through late tonight for CTZ004. MA...Flood Watch through late tonight for MAZ004>007-012>024-026. RI...Flood Watch through late tonight for RIZ001>007. MARINE...Gale Watch from Friday morning through Saturday morning for ANZ231>235-237-250-251-254>256. Small Craft Advisory until 8 AM EDT Friday for ANZ250. Small Craft Advisory until 8 AM EDT this morning for ANZ251. Small Craft Advisory until 8 PM EDT this evening for ANZ254>256.
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&& $$ SYNOPSIS...Nocera NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...RM AVIATION...Nocera/KS MARINE...Nocera/KS

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