Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261108 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 708 AM EDT Tue Mar 26 2024 .SYNOPSIS... Another chilly day is on tap for Tuesday, with raw northeast winds along with some spotty light showers, drizzle and fog, especially across eastern Massachusetts. Considerably milder Wednesday, but 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 TONIGHT/... 2 AM update... Key Points... * Cool/Raw Tue with spotty light showers/drizzle, esp eastern MA * Highs Tue only in the upper 30s/lower 40s Details... Tuesday... Occluded low well south of New England begins to rotate deeper moisture into SNE today, especially across eastern MA via WAA aloft wrapping cyclonically around the offshore. This combined with moist ENE low level flow into SNE, will result in bands of light showers coming onshore, along with areas of drizzle and fog. Not a washout, but definitely nuisance precip across eastern/central MA into RI, with precip not as widespread westward into CT and western MA. Raw/damp ENE winds 15-25 mph, except gusts up to 35 mph Cape Cod and Islands continue today, slowly easing late in the day as pressure gradient relaxes. However, this will result in another chilly day with highs only in the upper 30s to lower 40s, mid 30s high terrain. These temps are about 10 degs cooler than normal. It will feel coolest along/near the coast given the chilly onshore winds. && .SHORT TERM /WEDNESDAY/... 2 AM update... Key Points... * Remaining damp Tue night * Milder Wednesday and not as wet Tuesday night... Synoptic scale lift arrives later tonight in response to s/wv trough approaching from the west. However, deep layer moisture is lacking and this should preclude widespread showers, hence more scattered in areal coverage, along with areas of drizzle and fog. Thus, damp weather at times. Not as chilly as airmass slowly modifies. Lows in the 30s. As previous forecaster noted, the higher terrain could see lows near freezing. Thus, low risk of spotty light freezing rain/drizzle at the highest elevations of the Worcester Hills and east slopes of the Berks. Although, with cold air damming setup weakening overnight, probability is very low for any freezing rain/drizzle. Otherwise, ptype will be all rain. Light NE winds become light and variable late. Wednesday... Some synoptic scale lift moving across SNE from S/WV energy in the SW flow aloft, but deep layer moisture is lacking. Thus, other than morning drizzle and fog, late morning into the afternoon should feature mainly dry weather, especially across RI and eastern MA. Farther to the west, deeper moisture may result in scattered showers across western MA/CT. Clouds likely dominate but milder, in response to low level flow becoming SSE, supporting highs in the mid to upper 50s. It will feel milder as dew pts climb into the 40s, compared to the 20s early Tue. Light and variable winds early becoming SSE in the afternoon. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights * Heavy precipitation late week may lead to an elevated risk for flooding across southeastern MA and Rhode Island * Trending drier with near normal temperatures this weekend Wednesday night through Friday An active period of weather develops late Wednesday into Thursday as a robust short-wave trough digs into the southeastern US. This will support the development of an elongated region of low pressure nearly parallel to the east coast that will track north/northeast through the end of the week. A strong region of frontogenesis oriented north to south is forecast to develop within the trough axis and extend from the Carolinas to southern New England. As the upper-level short-wave trough becomes negatively tilted early Thursday, the elongated region of low-pressure will slowly track north/northeast through Friday. With above normal moisture situated over southern New England (PWAT ~1.25 inches) , this synoptic setup may support a steady period of rain over southern New England from roughly Wednesday night through Friday morning. Latest ensemble mean precipitation forecasts are indicating the potential for a widespread 1 to 3 inches of rainfall between Wednesday night and early Friday afternoon. Currently, southeast MA and RI are in the bullseye for model precipitation with ensemble means between 2 and 3 inches. If we consult ensemble probabilities from the LREF and NBM, there is above a 30 and 50 % chance respectively between the two ensembles for 24 hour precipitation to exceed 2 inches across southeastern MA and RI between Thursday and Friday morning. With several rivers in these locations already in flood stage, additional rainfall of this magnitude may prolong or exacerbate ongoing flooding. There is still a fair amount of uncertainty in the forecast given the dynamic nature of the system, but the ensemble probabilities alone are enough to raise some concerns for the end of the week. Should confidence in significant rainfall continue to increase, Flood Watch headlines may be needed for portions of southern New England. We will have a better idea of what to expect as we enter the time range of hi-resolution ensemble guidance during the next 24 to 36 hours. Aside from the rainfall to end the week, temperatures are forecast to be near normal with highs in the upper 40s/low 50s and lows in the upper 30s/low 40s Wednesday night through Friday. Friday night through the Weekend The elongated region of low-pressure expected to produce late week precip will continue to traverse north/northeast to end the week. North/northwest flow develops behind the system and ushers drier air over the region that should support partial sunshine for the weekend. While temperatures will be close to normal in the upper 40s/low 50s on Saturday and Sunday, efficient boundary layer mixing in the post frontal air mass is likely to support breezy northwest winds this weekend. Saturday looks to be the windier of the two days with gusts from 20 to 30 mph possible. Model guidance relaxes the pressure gradient on Sunday with more modest wind gusts closer to 20 mph. Forecast currently looks quiet to start the week next Monday, but ensembles suggest there may be more active weather beyond day 7. Stay tuned for further details later this week. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/...
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Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. Today...high confidence on trends, lower on exact details and timing. MVFR/IFR conditions overspread the region from SE to NW today, with much of the region IFR by late today, with areas of LIFR possible late across Cape and Islands. Bands of light rain overspread the much of the region today from southeast to northwest. In between the showers there will be areas of drizzle and fog, especially this afternoon across the hilly terrain of Worcester Hills and east slopes of the Berks, with IFR/MVFR vsbys. NE winds remain gusty 15-25 kt, except up to 35 kt along the coast, slowly easing late in the day. Tonight...high confidence. A comb of IFR/LIFR in low clouds, spotty light rain, drizzle and areas of fog. NE winds ease and become SE late. Wednesday...moderate confidence. Not as damp and drier in the afternoon across RI and eastern MA. IFR/LIFR in the morning lifts to MVFR/VFR in the afternoon, with light and variable winds in the AM becoming SSE in the afternoon. KBOS TAF...High confidence in trends, some uncertainty in exact timing and details. KBDL TAF...High confidence in trends, some uncertainty in exact timing and details. Outlook /Wednesday Night through Saturday/... Wednesday Night: MVFR/IFR conditions possible. RA likely. Thursday: Mainly MVFR, with areas IFR possible. RA. Thursday Night: MVFR/IFR conditions possible. Windy with gusts up to 35 kt. RA likely. Friday: Mainly VFR, with local IFR possible. Windy with gusts up to 35 kt. Chance RA. Friday Night through Saturday: VFR. Windy with gusts up to 35 kt. Slight chance RA.
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&& .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 2 AM update... * High Seas & NE Gales Tue Morning... Tuesday... Offshore low well south of New England will continue to generate ENE gales across the MA/RI waters into Tue morning, then slowly slackening Tue afternoon. Given the large easterly fetch, very rough/dangerous seas persist, 15-20 ft seas SE of Nantucket and Cape Cod. Vsby reduced at times in light rain, drizzle and fog. Tuesday night... High pressure over the Maritimes and low pressure south of New England both weaken. This will result in winds slackening and shifting 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 yielding light and variable winds. Drizzle and fog during the morning, slowly gives way to drier weather in the afternoon along with improving vsby. Outlook /Wednesday Night through Saturday/... Wednesday Night: Winds less than 25 kt. Local rough seas. Rain likely. Thursday: Winds less than 25 kt. Seas up to 5 ft. Rain. Thursday Night: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Rain likely. Friday: Moderate risk for gale force winds with gusts up to 35 kt. Rough seas up to 9 ft. Chance of rain. Friday Night: Moderate risk for gale force winds with gusts up to 35 kt. Rough seas up to 10 ft. Chance of rain. Saturday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Slight chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ230- 236. Gale Warning until 2 PM EDT this afternoon for ANZ231>235- 254>256. Small Craft Advisory until midnight EDT tonight for ANZ237. Small Craft Advisory until 8 AM EDT Wednesday for ANZ250-251. && $$ SYNOPSIS...Nocera NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...RM AVIATION...RM MARINE...Nocera/BW

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