Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 251805 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 205 PM EDT MON JUL 25 2016 .SYNOPSIS... Summer heat will continue into much of the upcoming week. A weak front will bring an increased risk of showers and thunderstorms... some possibly severe...this afternoon and evening. Showers and thunderstorms are possible again late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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2 PM update... Heat indices are in the 95-100 degree range in the regions where a Heat Advisory is in effect...generally from the Connecticut valley northeastward to the Merrimack valley as well as interior southeast Massachusetts. Actual temperatures were in the mid 90s with dewpoints from 65 to 70. Convective update... Thunderstorms were approaching the Berkshires and western CT. Downdraft CAPE has increased to 1100-1200 in western sections. Any thunderstorms have the potential to produce strong to damaging wind gusts this afternoon and evening. A second line of strong to severe thunderstorms was moving through southern NY near the PA border. These were moving to the east and mesoscale models bring them across our region late this afternoon into the evening hours. Again, a few could be severe with damaging wind gusts. Locally heavy rain and dangerous cloud to ground lightning strikes will also accompany any of the storms. Winds have become rather gusty...to 20-25 mph at some interior locations. Easterly sea breezes at Boston and the north shore are expected to shift to the south/southwest late this afternoon. Temperatures could then rapidly shoot up from the lower 80s to above 90 in the Boston area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Tonight... With increasing mid lvl lapse as the core of the upper shortwave moves across the region, it may lead to lingering convection into the earlier overnight hours. This correlates to ML CAPEs near 1000j/kg lingering along with an increase in shear, closer to 35 kt. Timing of shortwave will be key, but eastern areas could see the remnant of this convection linger through 02-04Z (10-midnight local). Otherwise, dwpts will be slow to decrease even as winds shift toward the W-NW. Expect some localized ground fog especially where rainfall is observed. Indications suggest Cape/Islands see a mix of marine fog/stratus. Min temps mainly in the 60s. Tomorrow... Even with nose of high pres, NW flow and some cooling aloft. Temps will still approach the low to mid 90s thanks to some downsloping and H85 temps starting near +18C. Clearing skies after any stratus and or remnant high clouds dissipate. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Hot temperatures continue through the middle of this week, away from the coast * Should be a little less humid Tuesday and Wednesday * Showers and thunderstorms are possible again late this week Overview... 25/00z guidance is in decent overall agreement through mid week, then more significant differences in the details start to emerge. This is a bit of change from previous runs. Will favor a consensus approach for this forecast. That should smooth over the more minor differences through mid week, as well as account for the greater uncertainty late this week into next weekend. Details... Tuesday Night and Wednesday...Drier weather with high pressure in control. Still hot, especially away from the coasts. Sea breezes are more likely Thursday and Friday...Uncertainty increases with this portion of the forecast. Temperatures will cool a few degrees Thursday as clouds increase and a cold front starts to move through southern New England. This front is expected to stall somewhere near our region on Friday. The presence of this front, and likely increase in clouds, should lower max temperatures Friday. Scattered showers and thunderstorms will be possible with this frontal passage, particularly on Thursday when more instability is expected. They may linger into Friday, but as mentioned above, that will largely depend on how far off the south coast the front pushes. Regardless, Friday is likely to be cloudy and cooler, though more humid than previous days. Saturday and Sunday...Lots of uncertainty remains with this portion of the forecast, leading to a low confidence forecast. Latest runs of the models now keep a frontal boundary nearby. Will mention a chance of showers, for now. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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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 Tuesday/... Through today...Moderate confidence. Mainly VFR through the afternoon. Between 19Z and 03Z, there could be two rounds of thunderstorms. The first between 19Z and 22Z moving across southern MA and northern CT...and then eastward across RI and southeast MA. The next may move through from west to east between 22Z and 03Z. Damaging wind gusts are possible in any thunderstorms, along with locally heavy rain. IFR possible in thunderstorms. Later Tonight...moderate confidence. Most thunderstorms/showers end between 02Z and 04Z with VFR developing initially then late night fog especially at typically prone airports. Stratus also possible along the Cape/Islands especially. Mix of IFR/MVFR conditions. Tomorrow...high confidence. Mainly VFR after early morning fog/stratus dissipates. Winds mainly NW with gusts 15-20 kt. KBOS TAF...Moderate confidence in TAF. Sea breeze in place. VFR but chances of strong thunderstorms late this afternoon and evening. KBDL TAF...Moderate confidence in TAF. Chance of strong thunderstorms this afternoon. Outlook /Tuesday Night through Friday/...Moderate to high confidence. Quiet boating weather is expected through this time. The exception will be Thursday into Friday. While winds and seas will remain below small craft advisory criteria, low clouds, fog, and periodic showers and thunderstorms should limit visibilities.
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&& .MARINE...
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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 Tuesday/...High confidence. Seas remain below SCA. Winds from the W-SW, then shift to the NW tomorrow with some gusts 15-20 kt. Onshore sea breezes in Boston Harbor and off of Cape Ann should shift back to the southwest toward evening. There is a risk for strong thunderstorms late this afternoon and evening. Outlook /Tuesday Night through Friday/...Moderate to high confidence. Quiet boating weather is expected through this time. The exception will be Thursday and Friday when winds and seas will remain below SCA criteria, but low clouds, fog, and periodic showers and thunderstorms will limit visibilities.
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&& .CLIMATE... Here are the record high max and min temperatures for July 25: Boston - 96 (1882)/78 (2001) Hartford - 98 (2001)/75 (2001) Providence - 96 (2001)/75 (2001) Worcester - 93 (1941)/73 (2001) && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory until 6 PM EDT this evening for CTZ002>004. Air Quality Alert until 10 PM EDT this evening for CTZ002-003. MA...Air Quality Alert until 11 PM EDT this evening for MAZ004>016- 026. Heat Advisory until 6 PM EDT this evening for MAZ005-010>013- 017. RI...Heat Advisory until 6 PM EDT this evening for RIZ001. MARINE...None. && $$ SYNOPSIS...Belk/Doody/Field NEAR TERM...Field SHORT TERM...Doody LONG TERM...Belk AVIATION...Belk/Doody/Field MARINE...Belk/Doody/Field CLIMATE...Staff

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