Lexington, Massachusetts, USA
000 FXUS61 KBOX 211732 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 132 PM EDT Thu Mar 21 2024 .SYNOPSIS... Dry conditions for today and Friday. Though southern New England is located between two pressure systems and will experience strong west/northwest gusts through this evening, before diminishing on Friday. Due to the dry and gusty conditions today, all of southern New England is placed under elevated fire weather concerns. A more active weather pattern then evolves for Friday night into the weekend. A strong frontal system may bring the risk for minor accumulating snow in the interior late Friday night, but transition to widespread soaking rain Saturday into Saturday evening, capable of poor drainage flooding and rises on rivers and streams. Drying out Sunday into early next week but temperatures will average below normal with persistent onshore flow. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... * Second day of spring features gusty winds, below normal highs, and elevated fire weather concerns. Main weather concerns today are the gusty winds and low values of relative humidity, leading to elevated fire weather concerns for this afternoon. First off, southern New England is placed between two pressure systems, a building high over the Ohio River Valley and a deepening low across northern Maine. Forecast soundings based on BUFKIT continue to show a deep and well-mixed boundary layer to 850mb. Wind gusts today will be in the neighborhood of 30 to 40 mph, with the potential of nearing 50mph for towns along the east slope of the Berkshires. In collaboration with NWS Albany we continued our Wind Advisory for western Massachusetts, which includes Berkshire County, as well as the western most of the following counties; Franklin, Hampshire, and Hampden. With a well-mixed boundary layer we are able to transport the low dewpoint temperature to the surface, which is in the single digits. And because of that, our minimum relative humidity values are 25 to 35 percent. And after speaking with our fire weather partners and neighboring WFOs, we have agreed to issue a special weather statement (SPS) for elevated fire weather concerns for today. You can find more information regarding fire weather are the bottom of the AFD. While there will be a fair amount of sunshine, temperatures this afternoon will struggle to reach the 40 degree mark. In fact, those living along the coast will have the better chance of recording a high temperature of 38F to 42F, areas west of I-95 are generally in the middle to upper 30s this afternoon. It is also important to consider the gusts, it will allow it to feel as if it were in the teens and 20s. Brr, never fun talking about wind chills when the calendar reads spring. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... * Gusty wind and below normal temperatures this evening into the overnight hours. * Sunny, light wind, and potentially a renewed fire weather threat for Friday. Overnight: High pressure moves in from the west and will help ease the tight pressure gradient force over southern New England, thus allowing winds to drop off. Gusts diminish, 15 to 25 mph, by the end of the night. Continued CAA overnight will result in below normal low temperatures, forecast ranges from the teens across the interior and the 20s over the coastal plain. Friday: An 1030+mb area of high pressure settles over the northeast and allows for wind speeds to become light. Expecting a mainly sunny day due to the dry airmass, though this will lead to a second day of low values of relative humidity. It is possible an SPS for elevated fire weather concerns could become needed if our partners deem it necessary. The good news, winds are light, less than 15 mph from the west/southwest. Afternoon high temperatures are a few degrees warmer than today, generally expect highs in the low 40s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Highlights: * Minor snow accum possible late Fri night into early Sat in the interior * Widespread rain, heavy at times Sat into Sat evening capable of minor urban and poor drainage flooding and some river flooding * Trending drier for Sun into early next week, but blustery with below normal temps Friday Night into Saturday Night... Potent northern stream trough moves into New Eng with enough interaction with southern branch to bring a plume of anomalous PWATs northward into SNE. Meanwhile southern stream low pres is forecast to lift northward along the mid Atlc coast Sat then track south and east of Nantucket Sat night. Inverted trough extending north from the low pres combined with coupled upper level jet structure will result in strong forcing for ascent, acting on anomalous moisture to bring heavy rainfall to SNE Sat into Sat evening. Initial warm advection and deepening moisture ahead of the approaching mid level trough will result in precip developing from west to east mainly after midnight Fri night. The column is cold enough to support a few hours of snow north and west of I-95 corridor where a coating to one half inch is possible before snow changes to rain. Snow will persist longer further in the interior, with 1-3 inches possible north of the Route 2 corridor in far northern MA, especially over the higher terrain. Snow will change to rain here Sat morning and there could also be a period of freezing rain during the snow to rain transition. The bigger impact from this storm will be the heavy rainfall during Sat into Sat evening which will be focused along and to the west of the surface boundary/inverted trough. The heaviest rain will initially be focused across the interior during Sat but shift to the SE New Eng late Sat and especially Sat evening as low pres tracks south of Nantucket. Deterministic and ensemble guidance suggesting potential for 1.5 to 3 inches of rainfall. However, where this axis of heaviest rainfall sets up remains uncertain. GEFS and CMC ensemble probs of 2+ inches favor areas south of the MA Pike while ECMWF ensembles have heaviest rainfall in the interior. Still need to iron out these details but the heavy rainfall may lead to areas of minor urban and poor drainage flooding. In addition, MMEFS probabilistic hydrographs based on the GEFS are indicating high probs (70-80 percent) of minor flood for the Pawtuxet and Wood River basins in RI, with 30-40 percent probs of moderate flood. Rain will be ending from west to east Sat night as colder air begins to move back into the region. If cold air comes in quicker it is possible rain could change to a period of snow before ending, mainly interior where some minor accum are possible. But this is a low confidence forecast at this time. Regarding potential for coastal flooding Sat, it is looking like a rather low risk at this time. Along the south coast, the tide in question is the Sat evening high tide. Providence would need a 2.5 ft surge to reach minor flood, and we are currently forecasting a 1- 2 ft surge. No concern along the E coast for the Sat and Sat night high tides. Sunday into Wednesday... Deterministic guidance continues to trend drier for Sun into early next week as ocean storm remains well offshore with high pres building to the north. However, ensemble guidance still showing low probs for measurable QPF across SE New Eng Sun-Mon so we continued low pops in the grids. Still a chance that a piece of moisture could wrap around the low pres and back in across SE New Eng sometime Mon or Tue so will have to watch this. The shower chances increase again toward midweek as a shortwave approaches from the west. Persistent onshore flow will keep temps below normal. Not expecting any coastal flooding issues for the east coast Sun into early next week as forecast surge is much less than what is needed to reach minor flood. && .AVIATION /17Z THURSDAY THROUGH MONDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. Through 00Z...High confidence VFR with strong W to WNW winds at 15-25 kts. Gusts of 30-40 kts gradually ease to 25-35 kts by this evening. Tonight...High confidence. VFR with winds out of the WNW to NW at 10-20 kts, with gusts of 20-30 kts for most of the night. Anticipate that the gusty winds cease by roughly 08-12Z. Friday... High confidence. VFR with NW winds at 5-10 kts shifting to the W by late morning. Should continue to shift to the SW by the afternoon. Increasing mid/high clouds during the afternoon. Friday Night...High confidence in trends, moderate in exact timing. VFR to start, but will have conditions deteriorate as precipitation spreads in. Should see MVFR to IFR after 06Z with light snow to start for most. Will stay as snow across the higher terrain, but transition over to all rain elsewhere fairly quickly. KBOS TAF... High confidence in TAF. VFR with WNW winds at 20-25 kts through the day and winds gusting 35 kts. Should ease tonight, but still will be gusty until the Fri AM push. Winds shift to the SW Fri afternoon. KBDL TAF...High confidence in TAF. VFR with WNW/NW winds 15-20 kts and gusts 30 kts through the day. Winds ease tonight, but still remain gusty until the Fri AM push. Winds shift to the W/SW Fri afternoon. Outlook /Saturday through Monday/... Saturday: Mainly IFR, with areas MVFR possible. Windy with gusts up to 35 kt. RA. Saturday Night: Mainly VFR, with local IFR possible. Strong winds with local gusts up to 40 kt. Chance RA, slight chance SN. Sunday: VFR. Windy with gusts up to 35 kt. Sunday Night: VFR. Strong winds with local gusts up to 40 kt. Slight chance RA. Monday: VFR. Windy with gusts up to 35 kt. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Friday... High Confidence. Dry conditions throughout this period. A Gale Warning continues for all waters, with the exception of Narragansett Bay through this evening. Today, west/northwest gusts up to 40 knots with increasing seas between 5-8 feet near shore, and 8-11 feet off shore. Friday the wind becomes west/southwest with gust below 25 knots and diminishing seas. Outlook /Friday Night through Monday/... Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Friday Night: Winds less than 25 kt. Chance of rain. Saturday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Rain. Local visibility 1 to 3 nm. Saturday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 14 ft. Rain. Areas of visibility 1 to 3 nm. Sunday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 14 ft. Slight chance of rain. Sunday Night through Monday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 13 ft. Slight chance of rain. && .FIRE WEATHER... Elevated fire weather concerns today and also potentially into Friday. Today offers a combination of gusty NW winds between 35 and 50 mph and lowest RHs around 20-35 percent. In addition, rainfall received on Wednesday were less than 0.2 inches. In collaboration with our neighboring WFOs and state partners, a special weather statement for Elevated Fire Weather Concerns goes into effect from 11am to 8pm . For Friday, NW to W winds are lighter but RHs project to be lower in the upper teens to 30 percent range. Will reassess with incoming guidance before coordinating with our fire weather partners over the coming days. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Wind Advisory until 8 PM EDT this evening for MAZ002-008-009. RI...None. MARINE...Gale Warning until 8 PM EDT this evening for ANZ230. Gale Warning until 2 AM EDT Friday for ANZ231>235-237-250-251- 254>256. Small Craft Advisory until 2 AM EDT Friday for ANZ236. && $$ SYNOPSIS...KJC/Dooley NEAR TERM...KJC/Dooley SHORT TERM...Dooley LONG TERM...KJC AVIATION...BL MARINE...KJC/Dooley FIRE WEATHER...Dooley
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