####018009057#### FXUS61 KBOX 041300 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 900 AM EDT Sat May 4 2024 .SYNOPSIS... High pressure brings dry weather with cooler onshore breezes Saturday. A slow-moving frontal boundary brings widespread showers Sunday into early Monday. Then gradual clearing Monday afternoon along with warming temperatures. Tuesday looks to be the pick of the week, with abundant sunshine and highs in the 70s to near 80, although significantly cooler near the coast with afternoon seabreezes. Then lots of clouds Wed, Thu and Fri along with periodic showers possible. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 9 AM Update * Partly Sunny with some increasing clouds into the afternoon * Highs lower 50s coast, 60+ inland and near 70 lower CT Rvr Previous forecast is on track. High pressure across the Canadian Maritimes will continue to generate a low level easterly flow of air across southern New England. Therefore...we will have a large range in temperatures across the region. Highs should range from the lower 50s along the immediate coast...but 60+ not too far inland and near 70 in the lower CT River Valley. Dry weather with partly sunny skies are anticipated through the afternoon with upper level ridging in control. We do expect some lower clouds to invade areas near the coast and some higher clouds to overspread the region from the west through the afternoon. && .SHORT TERM /6 PM THIS EVENING 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 /13Z SATURDAY THROUGH WEDNESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 12z TAF Update: Through 12Z: High confidence, only low confidence for the immediate eastern MA coast, as low clouds come onshore this morning. Thining marginal IFR/MVFR clouds will be confined to the immediate coast, then lift to VFR cloud bases farther inland away from the coast. Earlier discussion below. ----------------------------------------------------------------- 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...Frank SHORT TERM...RM LONG TERM...Nocera AVIATION...Nocera/RM MARINE...Nocera/RM ####018004182#### FXUS66 KEKA 041300 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 412 AM PDT Sat May 4 2024 .SYNOPSIS...A passing cold front will continue to bring periods of heavy rain early this morning, with snow above 2500 feet. A much colder airmass will then settle in behind the front to bring near freezing to freezing temperatures for some interior valleys. && .DISCUSSION...A late season cold front brought widespread heavy rainfall rates up to 0.5 inches per hour overnight, with activity continuing this morning as it moves southward. Soils, creeks, rivers, and gutter systems have handled the water well with non- advisory level issues observed so far. Interior snowfall continues as snow levels are quickly dropping. The Winter Weather Advisory remains for elevations above 2500 feet. A seasonably anomalous, cold upper low will work its way over N CA throughout the day. Associated instability and 700mb temperatures as cold as -13C will bring showers and possibly a thunderstorm, some which could contain small hail through this evening. Colder to much colder than average tempertures will remain in place through the weekend and into next week. Near freezing to freezing temperatures for some interior valleys are forecast, but expected fog and lingering cloud cover will hold the temperature up for some valleys over the next couple of nights. Zonal flow followed by a weak shortwave on Monday will bring more unsettled weather and drizzle to light rain. A pronounced ridge of high pressure will then begin building in mid to late next week, and there is growing probability for the warmest interior valleys to exceed 85 degrees through that period. /JJW && .AVIATION...Biggest problem to deal with to start the forecast will be ceilings in the IFR to MVFR range behind a cold front as wind has shifted to the west. Cold front aloft will play a part in some thunderstorm potential this afternoon and evening, although chances are quite small. Ensembles indicate the chance of MVFR or worse ceilings dips below 50% along the coast by about 21-22Z, and toward 17Z for KUKI. For visibility, the overall trend is for improvement in visibility for all TAF sites, except for some potential that some slight worsening of visibility will occur within the first couple of hours of the forecast. Can't rule out the potential for small hail accumulation for the coast this afternoon and early evening. We may not completely lose our light rain or drizzle potential through the night tonight and into early Sunday morning. && .MARINE...After strong winds occurred directly behind a passing cold front earlier this morning, gusty northwest winds will become confined to the southern waters by late this morning, with the potential for thunderstorm development. Steep wind wave response expected late today through Sunday as lingering showers dissipate. Combined seas today are forecast to be 5-7 feet with 7-9 second periods through the weekend before a long period northwest swell fills in early next week. Strong northerlies combined with another steep northwest swell by Tuesday night or Wednesday may produce combined seas exceeding 10 feet. A few persistent northwest swells for the next several days will play a factor in combined wave height increasing by mid-week. Small craft advisories are all ending by mid-evening tonight. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Winter Weather Advisory until 11 AM PDT this morning for CAZ102-105>108-111. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 AM PDT this morning for PZZ470. Small Craft Advisory until 9 PM PDT this evening for PZZ475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png