Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 252311 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 711 PM EDT Wed Apr 25 2018 .SYNOPSIS... Low pressure will push northeast from the mid Atlantic coast, crossing the region tonight. This will bring locally heavy downpours may result in some brief poor drainage street flooding and possibly an isolated thunderstorm or two. Seasonably mild temperatures will follow for the remainder of the week with mainly dry weather other than a period of showers Friday. A cool down will occur Saturday night and Sunday, but this will be short lived as unseasonably warm temperatures are in store for the region by the middle of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 7 PM Update... Convective showers with locally heavy rain continue to lift north across eastern half of New England. Activity is located along the nose of the low level jet. In addition, still can`t rule out an isold t-storm as elevated instability is present. As the axis of the low level jet shifts to the east main focus for heavy rain will gradually shift offshore after midnight. Main impact will be localized nuisance poor drainage street flooding in areas of heavy rain. Gusty southerly winds SE New Eng this evening will diminish late this evening. Other concern for tonight is dense fog as some mid level drying moves in tonight while low levels remain saturated. Low vsbys have developed over southern RI where we will issue a dense fog advisory through tonight. Plenty of low level moisture present and advisory may need to be expanded along the rest of the south coast. Previous discussion... Surface low still in the vicinity with digging upper level trough approaching from the west. The evening will start off with a dry weather trend as mid-level dry slot pushes through. Still quite saturated as the low levels so fog and drizzle may be an issue. As the upper level low rotates through, the mid and upper levels begin to saturated and there could be a redevelopment in strong showers moving through SNE. Best timing is between 3-9z as strong mid-level omega pushes through. The east coast of MA has the best shot of seeing the strong downpours. Still cannot rule out the thunder potential as RAP data has several hundred julep of MUCape and showalters dropping below 0C. Heavy rainfall will be the main threat as well as gusty winds, especially along the passing cold front. Ahead of the passage of the front, patchy dense fog is possible across the region. This is due to the saturated low level moisture as well as weak pressure gradient ahead of the FROPA. Both the HRRR- TL and the NARRE indicated high probs that visibilities will drop at or below a mile, with some potential for less than 1/4 mi. Locations along Long Island are starting to drop below 1/2 mile, but still see coastal above 1-2 miles. So confidence isn`t quite high to issue a dense fog adv at this time. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Thursday... Upper level low will begin to pivot out of the region during the day on Thursday. Still some lingering moisture in the mid-levels with steep lapse rates which will yield to sct showers in the morning. Deep layer moisture will push northward towards Maine resulting in low precip chances by the afternoon hours. Still expect sct to broken clouds but overall trend will be dry by sunset. Gusty WNW flow expected along as the mid level shortwave passes through. Steep lapse rates and downsloping flow will result in good mixing to near 850mb. Expect wind gusts to near 25-30 MPH by the afternoon as highs reach into the mid to upper 60s. Overall a pleasant Spring day. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Highlights... * A period of showers Fri afternoon/evening * Scattered showers Sat, mainly interior * Dry and cooler Sun then seasonably mild Mon * Dry with a significant warming trend Tue/Wed Friday... Southern stream shortwave will be lifting northward into SNE during the afternoon/evening. Shortwave is deamplifying but modest low level jet and PWAT plume will bring a period of showers to much of SNE, especially afternoon into early evening. There may be a focus for brief heavy showers and an isold t-storm across RI and SE MA where some elevated instability is present along the nose of the low level jet. Highs will range from the upper 50s to lower 60s. Saturday... Next mid level shortwave and cold front approaches from the west. This will lead to an increasing risk of sct showers, mainly across central/western MA and northern CT during the afternoon. Otherwise, expect pt-mosunny skies in the coastal plain with increasing afternoon clouds in western New Eng. There is a low risk a few showers could move into eastern New Eng Sat night as the front moves through. With pre-frontal SW flow, milder temps expected Sat, reaching mid 60s to near 70, except cooler along the south coast. Sunday... Cooler post-frontal airmass as deep trough settles over the northeast and 850 mb temps cool to around -4C. Temps will remain mostly in the 50s, with a few locations topping out near 60 in RI and eastern MA. Chilly night Sun night with lows in the 30s but close to 30 across the typical colder locations. Frost headlines may be needed where growing season has started, with greatest risk across northern CT. Monday through Wednesday... A pattern change will occur next week as deep trough lifts out Mon and is replaced by building heights and mid level ridging through the middle of the week. Monday will be the transition day with seasonably mild temps after a cold start to the day. Then warming mid level temps will result in temps reaching into the 70s Tue with potential for some lower 80s Wed. But SW flow will result in cooler temps along the south coast. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/...Moderate to High confidence. Tonight...IFR-LIFR conditions. Showers with locally heavy rain through this evening and can`t rule out an isold t-storm. Low CIGS and areas of fog will linger across the terminals much of the night. Thursday...Improving conditions to VFR with mix of MVFR north of the Pike during the day. Gusty westerly winds between 20-30 kts by the afternoon. KBOS Terminal...Moderate confidence in TAF. IFR conditions in rain and lower ceilings through the evening push. Low risk for TSRA from 21Z-04Z. KBDL Terminal...Moderate confidence in TAF. IFR conditions in rain and lower ceilings through the evening push. Dense fog is possible during the overnight. Outlook /Thursday Night through Monday/...Moderate to High Thursday Night: VFR. Breezy. Friday: MVFR/IFR conditions possible. Breezy. SHRA likely. Friday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA. Saturday: Mainly VFR, with local MVFR possible. Slight chance SHRA. Saturday Night: Mainly VFR, with local MVFR possible. Sunday through Sunday Night: VFR. Breezy. Monday: VFR. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/... Tonight...Moderate confidence. Small Craft Advisories for all waters except Boston Harbor. Expect E-SE winds gusting up to 30 kt. Low risk for a few 35 knot gusts early in the evening across the southeast waters. Rough seas up to 10 to 12 ft. Rain showers, heavy at times along with areas of fog and isolated thunderstorms. Visibility locally below 1 nm at times across the southern waters tonight. Thursday...Moderate to high confidence. Small craft conditions continue as winds shift to W, though winds diminish during the day. May see gusts up to 25-30 kt through midday. Seas remain at 5 feet or greater through the day across the open waters as well as the south bays and sounds. Outlook /Thursday Night through Monday/...Moderate to High Thursday Night: Winds less than 25 kt. Rough seas up to 9 ft. Friday: Winds less than 25 kt. Seas up to 5 ft. Rain showers likely. Friday Night: Winds less than 25 kt. Areas of rough seas. Chance of rain showers. Saturday through Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. && .EQUIPMENT... The NOAA Weather Radio transmitter serving Providence is out of service due to phone line problems. The phone company has prioritized the issues and is working to get the weather broadcast back on the air as soon as possible. The transmitter serving Hyannis is back in service. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...Dense Fog Advisory until 8 AM EDT Thursday for RIZ006>008. MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ232>234- 251. Small Craft Advisory until 3 AM EDT Thursday for ANZ231. Small Craft Advisory until 11 AM EDT Thursday for ANZ236. Small Craft Advisory until 8 AM EDT Friday for ANZ235-237-250- 254>256. && $$ SYNOPSIS...KJC/Dunten NEAR TERM...KJC/Dunten SHORT TERM...Dunten LONG TERM...KJC AVIATION...KJC/Dunten MARINE...KJC/Dunten EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.