####018008584#### FXUS61 KBOX 040625 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 225 AM EDT Sat May 4 2024 .SYNOPSIS... High pressure brings dry weather with cooler onshore breezes through Saturday. A slow-moving frontal boundary brings clouds and rain showers on Sunday into early Monday, along with a period of cooler high temperatures. Though clouds and off and on showers may linger in southeast New England in vicinity of the slowing front, drier weather prevails for most of interior Southern New England. Turning warmer on Tuesday with abundant sunshine, and though temperatures will be significantly cooler near the coast, interior areas could see high temperatures reach near 80 degrees. Our next chance for rain is around midweek. && .NEAR TERM /THROUGH TODAY/... 3AM Update: Today Almost a repeat of yesterday with high pressure just to the north continuing to support a steady east/northeasterly flow over southern New England. Expect similar temperature patterns today with cooler high temps along the east coast in the mid to upper 50s with gradually warmer temps to the west reaching the upper 60s in the CT River Valley. Skies likely to be partly sunny with low-level moisture coming off the ocean supporting SCT to BKN cloud cover for much of the day. && .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/... Tonight Overcast skies fill back in overnight as the boundary layer cools. This will limit temperatures from falling to far, so expect seasonable low temps in the low to mid 40s across much of the region. High pressure drops to the southeast which will result in easterly winds gradually shifting to the southeast as we approach the dawn hours. Tomorrow Winds shift from southeast to south during the day tomorrow allowing for a surge of moisture across the region. This will support increasing moisture with PWATs rising close to an inch across the region. Precip chances increase gradually from west to east across the region as northern stream short wave energy traverses over The Northeast. Latest suite of model guidance suggests shower chances will peak during the mid-afternoon hours with the steadiest precipitation taking place tomorrow night (see long-term AFD). Skies will be overcast for much of the day tomorrow which will support cooler temperature sin the mid to upper 50s across the region. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights: * Cool with rain Sunday into early Mon, then gradual clearing Monday afternoon, although clouds may linger over southeast MA * Tue looks to be the pick of the week, with abundant sunshine and highs in the 70s to near 80, although much cooler at the coast * Lots of clouds Wed, Thu & Fri along with the risk of periodic showers and cooler Temperatures... Warm westerly flow aloft Monday with 850 mb temps well above normal, about +11C at 18z. Timing of clearing will be crucial to temp forecast. Ensembles supporting 80-100% probability of 70+ highs Monday in the CT River Valley and Merrimack River Valley. More uncertainty southeast across RI and southeast MA given departure timing of clouds. Not quite as warm aloft Tue, but still above normal with +8C to +9C at 850 mb, but warmer blyr temps of +16 to +17C at 925 mb, along with NW winds providing downslope flow. This results in ensembles offering 90-100% probabilities of 70+ highs away from the coastline, where afternoon seabreezes will yield cooler temps. Farther inland, not out of the question a few towns make a run at 80 degs! This combined with abundant sunshine, low dew pts/low RH likely results in Tue being the pick of the week. Not as warm Wed, Thu and Fri with frontal boundary getting hung up over or near SNE, along with possible waves of low pressure tracking south of the region. Highs likely in the 60s, except 50s along the coast, including Cape Cod and the Islands. Precipitation... Height falls and associated cold front will combine with good moisture advection (PWATs +2 sigma) to yield widespread showers Sunday afternoon thru Monday morning across southeast MA. High probability for 0.10 to 0.25 inches of rainfall during this time, with low probs up to 0.50 inches. Clearing develops NW to SE during Monday afternoon (last across SE MA) as the dry slot overspreads the region. With diurnal heating, weak cyclonic flow aloft and surface front lingering over the region, low probability of a few showers and/or an isolated thunderstorm late in the day across the interior, where duration of heating/sunshine will be greatest. Dry weather Tuesday with PWATs only about 60% of normal. Then becoming unsettled Wed, Thu and possibly Fri, along with a low confidence forecast. Negative height anomaly downstream over Newfoundland keeps a ridge axis with above normal heights from the Mid Atlantic into New England. Meanwhile, a positive tilt trough over the high plains ejects multiple plumes of moisture towards New England. Models struggling with the large scale flow, specifically how much of this moisture advects east into SNE, or dampens out running into the ridge or is shunted southeast of New England? Nonetheless, chance of showers both Wed, Thu and Fri. Although, there will also be periods of dry weather during this time period. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06Z TAF Update: Through 12Z: High confidence. VFR conditions persist through 12Z with light and variable winds becoming more steady out of the east/northeast by sunrise. Today...Moderate confidence MVFR level cloud bases move onshore this morning from the east, but there is a bit of uncertainty with respect to sky cover. Humidity in the low levels is choppy, so coverage may range from SCT to BKN at times. So expect intermittent periods of MVFR ceilings for the first half of the day until the skies fill into BKN/OVC buy mid-afternoon/evening. Steady east/northeast winds from 5 to 10 knots. Tonight...High Confidence MVFR/IFR ceilings return overnight with continued light easterly winds. Winds becoming more east/southeasterly by 12Z Sunday. Tomorrow...High Confidence MVFR borderline IFR ceilings for most of the day tomorrow with -RA spreading from west to east during the day. Southeast winds becoming more southerly by the afternoon. KBOS TAF...Moderate Confidence High confidence in MVFR cloud bases, but less confidence in coverage. There may be intermittent periods of SCT/BKN VFR/MVFR ceilings. KBDL TAF...High confidence in TAF. Outlook /Sunday Night through Wednesday/... Sunday Night: MVFR/IFR conditions possible. SHRA likely. Monday: Mainly VFR, with local IFR possible. Chance SHRA. Monday Night through Tuesday: VFR. Slight chance SHRA. Tuesday Night: VFR. Chance SHRA. Wednesday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Marine Today through Tomorrow Conditions remain on the calm and quiet side across the coastal waters through the weekend with high pressure largely in control. Easterly winds today become more southeasterly overnight and eventually southerly by Sunday. Seas generally in the 1 to 3 foot range. Outlook /Sunday Night through Wednesday/... Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Rain showers likely. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Tuesday: Winds less than 25 kt. Slight chance of rain showers. Tuesday Night through Wednesday: Winds less than 25 kt. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Nocera/RM NEAR TERM...RM SHORT TERM...RM LONG TERM...Nocera AVIATION...Nocera/RM MARINE...Nocera/RM