Lexington, Massachusetts, USA
000 FXUS61 KBOX 241716 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 116 PM EDT Sun Mar 24 2024 .SYNOPSIS... Mainly dry today and Monday but windy along the coast, especially Cape and Islands. Then an unsettled pattern for Tuesday through Friday with multiple chances of rain. Moisture from the ocean backs into the region Tuesday with focus for light rain across eastern New England, then showers region wide on Wednesday. A coastal low pressure may then bring more widespread rain sometime Thursday into Friday. Drying out next weekend. && .NEAR TERM /THROUGH TONIGHT/... Forecast is on track with the main adjustment being to lower temps a few degrees as we've not warmed up quite as much as expected; should top out in the upper 30s to near 40. Previous Discussion... Highlights: * Chilly despite sunshine making a return. Trending towards a more sun-filled day, but the sky will have a milky-white look due to higher clouds across eastern Massachusetts and Rhode Island. * SPS issued through 8am for possible icy conditions as temperatures are expected to fall below freezing. Motorists and pedestrians should exercise caution if heading out on the roadway overnight as untreated surfaces may become slick. The system that brought widespread 2-3 inches of rainfall yesterday is now racing north into the Canadian Maritime. For us, surface high pressure is building in out of the west. Given our position between the two systems, there is a rather tight pressure gradient, thus the continued gusty conditions. After reviewing latest high-res guidance in BUFKIT, did opt to extend the Wind Advisory for Cape Cod and the Island through 6AM as there could be periodic gusts to 50 MPH. The stronger gusts end this morning with the rest of the day featuring a north/northwest gust 25 to 35 MPH. Elsewhere, the wind gust are between 15 and 25 MPH. It will be a dry day, though expect the larger rivers to continue to rise due to the runoff from smaller creeks and streams finally reaching these larger rivers. Sunshine returns, though it likely is more of a milky-white sky across eastern Massachusetts and possibly into Rhode Island. These high clouds are the outer fridge of the departing low pressure system from yesterday. Despite the sunshine, temperatures will remain below normal once again with afternoon high temperatures only reaching the upper 30s to low 40s. The normal high for late March are between 45 and 50 degrees. && .SHORT TERM /MONDAY/... Highlights: * Generally dry period with below normal temperatures. A quiet night ahead with surface high pressure expanding over Quebec. Mainly clear sky cover to the west and easing winds will help temperatures fall well into the mid-teens, while the coastal plain of Massachusetts and Rhode Island are noticeably 'warmer' with overnight low temperatures in the upper 20s to mid 30s. Part of what keeps this area warmer is the mix boundary layer, with a north to north/northeast wind 10 to 15 MPH. During the overnight hours a coastal low pressure system moves north but will likely get 'stuck' southeast of the Benchmark due to the surface high over Quebec strengthening to 1040mb. Once again, we are situated between two pressure systems, increasing the wind speeds. Do anticipate the more gusty winds, up to 35 mph, are felt across southeast Massachusetts, Cape Cod, and Islands through Monday afternoon. Over all a dry day. Depending on how far north and west the 995mb low can reach will dictate whether or not we see light rain for some areas of southeast Massachusetts. Ensembles show less than 20 percent of 0.01 just off shore, mainly outer Cape Cod and Nantucket. Kept POPs at slight chance or less for Monday afternoon for sites like; MVY, ACK, HYA, and CHH. As for temperatures, the northeast flow will keep 925mb temperatures fairly low, -4C to -6C, around 10th percentile, based off sounding climatology from CHH. Afternoon highs reach the low and mid 40s. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights: * Below normal temps Tue, with spotty light rain expanding westward across eastern half SNE * Milder Wed with showers at times * A coastal storm may bring more rain Thu into Fri Monday night into Wednesday... Stagnant pattern persists into Tue with SNE caught between Maritimes high pres to the north and ocean storm well to the south. Gusty NE winds will continue into Tue while deeper moisture begins to back in from the east. This can be seen with plume of higher 1"+ PWATs expanding westward toward New Eng. This will lead to increasing chances of light rain developing over the Cape/Islands by late Monday night then pushing west into eastern New Eng Tue. Some uncertainty remains how far west the moisture gets, but higher confidence in at least some spotty light rain for eastern half of SNE on Tue and rest of the region Tue night. Then on Wed, weak ridging aloft breaks down as broad longwave trough approaches from the west sending weak impulses and increasing toward New Eng within the SW flow aloft. So another unsettled day Wed with a few showers at times. Certainly not a washout for Tue/Wed but it will likely be wet at times with lots of low clouds. Below normal temps Tue with NE flow and cloud cover holding temps in the upper 30s to mid 40s, then milder Wed as global ensembles indicate high probs of temps in the 50s. Thursday through Saturday.... More wet weather expected Thu into Fri as a fairly robust southern stream shortwave rotating around the longwave trough leads to developing low pres tracking NE along the eastern seaboard. There is obvious uncertainty with the track of low pres at this time range and where axis of rainfall sets up as well as timing of when rain exits. GEFS, ECMWF and CMC ensembles all indicate high probs of 0.50"+ QPF Thu into Thu night, and at least moderate probs of 1"+ QPF for SE New Eng so it is looking wet during this time. Rain may be pushing offshore during Fri but timing of when this occurs is uncertain so we kept PoPs going through Fri. It appears we finally dry out next Sat as trough axis lifts to the NE with dry NW flow developing. && .AVIATION /17Z SUNDAY THROUGH THURSDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. 18Z update... This afternoon through Monday night...High confidence. VFR. Expecting a lull in gusts this afternoon/evening but another round of 25-35kt gusts is expected overnight into Mon. Otherwise, VFR through Monday night. KBOS TAF...High confidence. KBDL TAF...High confidence. Outlook /Tuesday through Thursday/... Tuesday: MVFR/IFR conditions possible. Windy with gusts up to 30 kt. Chance RA, slight chance FZRA. Tuesday Night: Mainly IFR, with areas VFR possible. Breezy. Chance RA, slight chance FZRA. Wednesday: MVFR/IFR conditions possible. Chance RA. Wednesday Night: Mainly MVFR, with local IFR possible. Chance RA. Thursday: MVFR/IFR conditions possible. Chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today: Dry conditions. Low pressure system to the north continues northerly gales with gusts to 40 knots. Seas on the outer waters are greater than 12 feet, near shore waves are 6 to 10 feet. Tonight: Low pressure developing to the south will increase gusts and seas. NE winds 20-35 kts gusting 35 to 40 kts with seas increasing to 12-14 ft. Monday: Low pressure system moves north and continues gusty NE gales on the southern and eastern outer waters. Northeast waters gusts near 30 knots. Seas on the outer waters are greater than 14 feet, near shore waves are 6 to 10 feet. Outlook /Monday Night through Thursday/... Monday: Low risk for gale force winds with gusts up to 40 kt. Rough seas up to 15 ft. Monday Night: Strong winds with gusts up to 40 kt. Rough seas up to 15 ft. Slight chance of rain. Tuesday: Strong winds with gusts up to 35 kt. Rough seas up to 14 ft. Chance of rain. Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 12 ft. Chance of rain. Wednesday: Winds less than 25 kt. Rough seas up to 9 ft. Chance of rain. Wednesday Night: Winds less than 25 kt. Areas of rough seas. Chance of rain. Thursday: Winds less than 25 kt. Seas up to 5 ft. Rain likely. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT Monday for ANZ230-231-236- 237-251. Gale Warning from 1 AM to 8 PM EDT Monday for ANZ232>235. Gale Warning until 8 PM EDT Monday for ANZ254>256. && $$ SYNOPSIS...KJC/Dooley NEAR TERM...BW/Dooley SHORT TERM...Dooley LONG TERM...KJC AVIATION...KJC/BW MARINE...KJC/Dooley
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