Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 191835 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 235 PM EDT Sat May 19 2018 .SYNOPSIS...
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A warm front will bring a steady widespread light rainfall today, becoming more showery late this afternoon into tonight. Chilly conditions today transition to warm and humid later tonight into Sunday with hit or miss showers/thunderstorms. Dry on Monday with passing showers during the mid-week. Cooler, drier air follows for Thursday into Friday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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230 PM Update... WAA advection rains continue across the region this afternoon. Cool ENE flow ahead of warm front keeping temps in the 50s. Steady light rain becomes more spotty early this evening and overnight as best WAA lifts into northern New England. However areas of drizzle and fog will maintain damp conditions. Not much change from previous forecast.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... Tonight...Warm front lifts north across our region this evening. Increasing low level jet will advect higher precipitable water values and some elevated instability. Expecting at least a risk for showers, with a thunderstorm or two not out of the question. Temperatures should slowly rise overnight behind the warm front. As temperatures rise, so will dewpoints. This should lead to patchy fog formation. Sunday...A cold front should cross our region by evening. Given the modest instability and forcing, not expecting severe weather at this time, just scattered showers with a few thunderstorms. More summer-like temperatures and humidity, with highs in the 70s away from the south coast Cape and islands. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Dry weather returns by Monday * Passing showers Tuesday and Wednesday * Potential for dry weather but below avg temps for the end of the week Details... Sunday night into Monday...High confidence. Conditions should be improving as upper level trough pushes cold front through the region Sunday night/early Monday. Surface high pressure from Canada will move into the region resulting in dry weather. Westerly flow aloft will result in downslope flow allowing temps to remain in the mid to upper 70s away from the coast. Tuesday into Wednesday...Moderate confidence. Increasing chances for showers on Tuesday as weak disturbances moves through the flow and south of the region. Still some spread on timing and location of where precip will fall. Highest confidence is south of the Pike. Behind this disturbance, an approaching cold front will move in from the northwest. Could see some showers along this front but moisture is a bit marginal. Temperatures will be more seasonable with highs in the low to mid 70s. Thursday and Beyond...Moderate confidence. Drier but breezy conditions looks to be in store for the end of the week due to a northwest flow pattern. Will have to watch for a possible disturbance or two passing through the flow. For now trended the temperatures below avg and kept with a dry forecast. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. 18z update... Widespread IFR/LIFR late this afternoon into tonight in rain transitioning to spotty light rain/drizzle and patchy fog. LLWS marginal across RI and eastern MA tonight as low level SW jet increases. Sunday... IFR/LIFR lifts to MVFR by midday, slightly longer south coast. Drizzle and areas of morning fog erode by midday but give way to a broken line of showers along and ahead of approaching front. Very low prob of isolated T-storm but showers will contain locally heavy rain from about 17z-21z from west to east. Breezy southwest winds 15 to 20 kt with a few gusts up to 25 kt possible. Sunday night... Any leftover IFR/MVFR early evening over Cape Cod improves rapidly to VFR. Otherwise VFR and dry weather. KBOS Terminal...a broke line of showers with heavy rain Sunday 17z-20z. Very low risk of brief isolated T-storm. KBDL Terminal...moderate to heavy confidence in the TAF. Outlook /Monday through Wednesday/...Moderate confidence. Monday through Tuesday: VFR. Slight chance SHRA. Tuesday Night: VFR. Chance SHRA. Wednesday: VFR. Slight chance SHRA.
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&& .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...Moderate confidence. E flow gradually becomes SE this evening as a warm front crosses the waters from S to N. Steady rainfall likely. Increasing S winds tonight, shifting SW Sunday. Building seas across the outer coastal waters tonight into Sunday. Vsbys reduced in rain and fog today, with areas of dense fog developing tonight. Risk for scattered showers and isolated thunderstorms Sunday. Outlook /Sunday Night through Wednesday/...Moderate confidence. Sunday Night: Winds less than 25 kt. Local rough seas. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday Night through Tuesday: Winds less than 25 kt. Slight chance of rain showers. Tuesday Night: Winds less than 25 kt. Chance of rain showers. Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from midnight tonight to 6 PM EDT Sunday for ANZ231>235-237-250-254-255. Small Craft Advisory from 4 AM to noon EDT Sunday for ANZ230. Small Craft Advisory from midnight tonight to 3 PM EDT Sunday for ANZ236. Small Craft Advisory from midnight tonight to noon EDT Sunday for ANZ251. Small Craft Advisory until 2 PM EDT this afternoon for ANZ256. && $$ SYNOPSIS...Belk/Dunten NEAR TERM...Belk/Nocera/Dunten SHORT TERM...Belk LONG TERM...Dunten AVIATION...Belk/Nocera/Dunten MARINE...Belk/Dunten

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