Area Forecast Discussion
Issued by NWS Boston, MA

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227 FXUS61 KBOX 221804 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 204 PM EDT Fri Jun 22 2018 .SYNOPSIS... High pressure builds across the area this afternoon allowing for dry conditions. Patchy fog may redevelop along south coastal areas tonight. Unsettled weather is expected at times this weekend, especially on Sunday, when the greatest risk for wet weather should be. Dry with seasonable summer temperatures should return by Monday or Monday night, depending on timing of a cold front. Seasonable warmth with dry weather expected both Tuesday and Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 2 PM Update... High pressure centered over northern New England continues to bring dry conditions to our region this afternoon. Cirrus and a bit of diurnal cumulus bringing partly to mostly sunny skies. Forecast high temps continue to look on track. Given position of surface high, an E/SE onshore wind continues thru this afternoon. So highs in the mid 70s to around 80 are forecast away from the E coast. Then for E/SE coastal locales including the Cape and Islands, the breeze off the ocean waters will limit highs to the mid 60s to low 70s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Tonight... The high across Maine into the Maritimes will hold in place through most of the night. Winds will shift to SE, which will keep low level moisture working in across coastal areas. May see patchy fog redevelop across S coastal areas overnight. With the ridge axis remaining across the region, some question as to whether any showers may move in after midnight. 00Z models have varying timing with the onset of the precip as low pressure shifts E into Ohio/W PA overnight. Have carried CHC POPs overnight tonight, but lower than average confidence due to widened model solution timing. Saturday... The E-W oriented ridge pushes eastward early Saturday. Most models signaling rain through the day. The ECMWF and Canadian GGEM trying to bring in some bands of heavier rainfall along with some instability, with K indices in the lower-mid 30s and SLIs lower to below zero mainly near and S of the Mass Pike Sat afternoon. However, a continued E-SE wind flow off the cooler ocean waters should be a stabilizing influence so did not mention thunder at this point. Temps will be around 10 degrees below seasonal normals, only reaching the mid 60s to lower 70s. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights... * Warmer with scattered showers/thunderstorms on Sunday * Mainly dry with seasonable summer warmth Tue and Wed * More showers possible towards the end of next week Details... Saturday night...Low pressure moving from the Great Lakes across northern New England should push a cold front through southern New England late. Scattered showers, with a few thunderstorms, remain possible. Sunday... The greatest risk for showers and thunderstorms remains Sunday, ahead of a secondary cold front. Amount of forecast instability does not appear to be substantial, but mid level lapse rates could be decent. Will need to monitor changes to thunderstorm potential Sunday. Monday... Impressive cold pool aloft/shortwave passes by our region. GFS is the most aggressive lingering lift and moisture behind a cold front. ECMWF and Canadian quite a bit drier, but consistent with prior runs. it`s still really a question of how quickly the drier air arrives behind a secondary cold front. Given the proximity of a cold pool aloft, will keep at least a mention of lingering showers early. Tuesday through Thursday... High pressure passing to our south will keep our weather mainly dry Tuesday and Wednesday. An approaching warm front could bring a few showers by Thursday. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...High confidence. This afternoon...VFR conditions hold for the remainder of this afternoon, with an E/SE wind. Tonight...Patchy fog may form in the vicinity of the Cape and Islands overnight, may produce a period of MVFR-IFR conditions. Otherwise, VFR. Scattered -SHRA develop towards 09Z-12Z. Saturday...Scattered -SHRA continue across the region with mainly VFR conditions. Isolated TSRA. MVFR/IFR to start along the south coast/Cape/Islands, spreading northward over the course of the day. KBOS Terminal...High confidence in TAF. VFR thru tonight, deteriorating to MVFR Sat morning then IFR towards 00Z Sat. KBDL Terminal...High confidence in TAF. VFR thru tonight, deteriorating to MVFR Sat morning then IFR towards 00Z Sat. Outlook /Saturday Night through Tuesday/...Moderate confidence. Saturday night...Mainly MVFR/IFR conditions in areas of showers and fog. Isolated TSRA. Sunday: Mainly VFR, with local IFR possible. Chance SHRA, isolated TSRA, patchy FG. Sunday Night: Mainly VFR, with local MVFR possible. Chance SHRA, isolated TSRA. Monday: Mainly VFR, with local MVFR possible. Breezy. Monday Night: VFR. Breezy. Tuesday: VFR. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...High confidence. This afternoon...E/SE winds during the afternoon, may see gusts up to 20 kt on the southern outer waters. Seas remain below 5 ft. Tonight and Saturday...E-SE winds in place. A few gusts up to 25 kt on the southern outer waters possible late tonight into early Sat. Visibility restriction in patchy fog along the southern waters late tonight, then in showers and patchy fog moving in from S-N during Sat. Outlook /Saturday Night through Tuesday/...Moderate confidence. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, with isolated thunderstorms. Patchy fog. Areas of visibility 1 nm or less. Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, with isolated thunderstorms. Patchy fog. Areas of visibility 1 nm or less. Sunday Night: Winds less than 25 kt. Local rough seas. Slight chance of rain showers, with isolated thunderstorms. Monday: Winds less than 25 kt. Seas up to 5 ft. Monday Night: Winds less than 25 kt. Areas of rough seas. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...Belk/EVT/NMB SHORT TERM...Belk/EVT LONG TERM...Belk AVIATION...Belk/EVT/NMB MARINE...Belk/EVT/NMB

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