Area Forecast Discussion

000 FXUS61 KBOX 261757 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 157 PM EDT Fri Apr 26 2024 .SYNOPSIS... High pressure across the northeastern states allows for dry weather, chilly nights, and comfortable afternoons through the first-half of the weekend. Unsettled pattern sets up for Sunday into early next week with shower chances. Temperatures turn milder for some but a back door cold front likely keeps the warmest air over western SNE Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1100 AM Update: Another stellar day today weatherwise as high pressure dominates. Conditions hould again be very similar to yesterday, with bluebird skies and lots of sun, sea- breezes near the coasts, although temperatures a few degrees milder than yesterday. Seabreeze on the eastern MA coast already has developed and should take place closer to early/midafternoon along the South Coast of RI/MA and Narrangasett Bay. Sea breezes will also keep coastal areas colder with higher dewpoints in the low to mid 30s, compared to quite low dewpoints in the upper single digits to mid teens inland. Tried to better show the trend in dewpoints by blending in some the WRF-ARW dewpoints into the official forecast. But overall another pleasant day on tap. Previous discussion: A quiet and sunny day ahead with surface high pressure firmly in place over southern New England. Nearly a carbon copy forecast from Thursday. After starting with temperatures in the 20s and low 30s, today warms into the upper 50s and low 60s for most, though coastal towns remain cooler. Why? An on shore wind/ sea breeze develops by mid-morning. Here temperatures reach the low 50s. With a sprawling high pressure system the mean wind direction of the boundary layer is tough to nail down, do think wind direction is a bit variable today, though eastern Massachusetts sees an easterly wind due to the sea breeze. Southern Rhode Island and south coast of Massachusetts seas more of a southerly wind, once again due to the sea breeze. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Copy & Paste: Yet another dry, clear, and cold night across southern New England. That said, do not think temperatures dip as low as it has done the past two nights. Given repetitiveness of the forecast, leaned on the biased-correct CONSMOS and made manual adjustments to our prone locations that radiate on clear and calm nights. Overall, widespread lows in the middle and upper 30s for the coastal plain and upper 20s and low 30s across the interior. Where we could see temperatures drop lower, our known radiators; I-495 corridor, hallows of eastern CT, and Martha`s Vineyard - Here temperatures may drop between 28F and 32F. Given the limited area, will hold off this morning on issuing a Freeze Watch. This situation might be better handled with a Frost Advisory, but will leave that up to the day crew after reviewing the latest data. As for Saturday, a sunny and comfortable one with surface high pressure anchored south of Block Island. Light winds and clear skies will allow for temperatures to climb into the low and middle 60s away from the coast. At the coast, a sea breeze likely to develop given persistent pattern, highs will only reach the middle and upper 50s. By late afternoon a mid-level shortwave approaches from the west with a surface warm front. Day light hours remain dry, though mid and high clouds begin to move in from west to east during the late afternoon. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Key Points... * Scattered showers Saturday night become more hit-and-miss Sunday into Monday; more widespread rain chances through mid week with potential for a thunderstorm. * Warming trend through next week but a back door cold front likely keeps warmest air confined to western SNE. Details... Sunday and Monday... A passing warm front and weak isentropic lift will lead to widely scattered showers across southern New England Saturday night. Lack of strong forcing will limit rainfall amounts to a few hundredths to a few tenths focused over western MA/CT with lesser amounts to the east. This comes as high pressure sinks south of the region and the trough of low pressure drops from Canada into New England Sunday into Monday. Thus, despite being on the periphery of a mid level ridge can`t rule out some hit-and-miss showers each day with a good amount of cloudcover. The biggest impact of the track of this low will be a backdoor cold front that, despite a steadily warming mid level airmass (850 mb temps up to +10C by Monday for some), will keep the more significant warm up confined to western MA/CT on Monday. There remains a high degree of uncertainty with respect to high temperatures, especially Monday as the front looks to drop through Sunday night. Tuesday through Thursday... Guidance is looking slower to kick steering flow back to southerly for Tuesday which is not increasing confidence in the temperature forecast beyond Monday either. A seasonable airmass does look to remain in place though, with highs in the low to mid 60s for Tuesday and warming further Wed/Thu. Again, this will be highly dependent on the how the pattern evolves beyond Monday which remains uncertain. What is largely agreed upon is our mid level ridging finally breaking down with a shortwave and frontal system moving through on Tuesday bringing the return of more widespread rain showers. Some thunderstorms are possible, mainly over western MA/CT where there exists several hundred J/kg of CAPE but forcing does not look especially strong. && .AVIATION /18Z FRIDAY THROUGH TUESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18z TAF Update: Through Tonight: High confidence. VFR SKC. For this afternoon, light and variable winds, with seabreezes near the coasts should trending light S by 00z. Light S winds for all areas overnight. Saturday: High confidence. VFR, although with an increasing canopy of high clouds late- day. Light SW winds increase thru the day to around 7-10 kt; though sea-breezes again develop near the coasts between 14-16z Sat. Saturday Night: High confidence in trends though moderate on exact timing. Cigs start VFR but will be steadily lowering. Best chance at sub-VFR ceilings and light rain showers is after 06z and mainly from ORH westward; cigs could be as low as IFR but think MVFR predominate for those interior western terminals. Still think we`re looking at OVC VFR for eastern terminals. SW winds around 8-12 kt to start, but decrease to around 5-8 kt late. Low prob of low level wind shear south of I-90. KBOS TAF...High confidence in TAF. VFR. Sea breeze winds will continue around 110-120 degrees at 10-12 kt until about 00z with SSE winds. Winds become light southerly tonight. Seabreezes again likely for Sat, following similar 14-16z timeframe as prior days. KBDL TAF...High confidence in TAF. VFR. Light north winds most of today, but will trend southerly around 4-7 kt late today into tonight. Outlook /Saturday Night through Tuesday/... Saturday Night: Mainly VFR, with local IFR possible. Chance SHRA. Sunday: Mainly VFR, with local IFR possible. Slight chance SHRA. Sunday Night through Monday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Tuesday: Mainly VFR, with areas MVFR possible. Slight chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Saturday... High confidence. Tranquil boating conditions through Saturday as high pressure builds southeastward into the coastal waters. Today: Sunny. Light north winds (easterly near shore) early today, this afternoon, winds turn southerly around 10-15 kt. Seas 3 ft or less. Tonight: Dry. Winds becomes more westerly and are less than 10 knots. Seas 2 ft or less. Saturday: Sunny. Increasing southwest winds 10 to 15 knots, seas 2-3 ft. Outlook /Saturday Night through Tuesday/... Saturday Night through Sunday Night: Winds less than 25 kt. Slight chance of rain showers. Monday: Winds less than 25 kt. Monday Night: Winds less than 25 kt. Slight chance of rain showers. Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...BW/Dooley NEAR TERM...Loconto/BW/Dooley SHORT TERM...Dooley LONG TERM...BW AVIATION...Loconto/KP MARINE...Loconto/KP NWS BOX Office Area Forecast Discussion