Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 141741 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 141 PM EDT Mon Aug 14 2017 .SYNOPSIS... High pressure brings dry weather through today. Moisture well ahead of an approaching cold front will allow for the risk of some showers and thunderstorms Tuesday afternoon. Dry conditions follow for Wednesday. A warm front approaches Thursday and Friday, bringing increasing clouds, and scattered showers along with a few thunderstorms. Showers may linger into next weekend as another low may approach. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 10AM update... A day of mainly filtered sunshine through CI as jet streak sets up well in advance of the slowly shifting Gert. Forecast is on track for the most part, only real adjustments will be to the forecast temps/highs, which are now a little bit warmer than previous forecast as the CI will do little to inhibit mixing late this morning. Previous Discussion... High confidence. High pressure maintains dry weather across our region today. Light winds will permit the development of sea breezes along both coasts. Partly cloudy at worst, mainly from high level clouds. Some diurnal clouds, mainly across the higher terrain of central and western Mass. Near normal temperatures expected. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Moderate confidence. Southerly return flow will increase humidity tonight. A nearly stationary front south of New England may move close enough to trigger some showers after midnight as a mid level shortwave passes by. The greatest risk will be towards Nantucket. Clouds continue to increase. Early Tuesday should be dry across most of the region. Will need to monitor the northward progress of a stalled front. The closer this front gets to our region, the closer deeper moisture associated with Tropical Storm Gert may get. Will keep at least a slight risk of showers across Nantucket Tuesday morning. Another potent mid level shortwave arrives during the afternoon. Enough ingredients in place where thunderstorms would be a concern. However, the greatest risk appears to be north of our region at this time. With the timing being in the afternoon, the greatest risk for thunderstorms will be across the interior. Convection subsides around sunset. Near normal temperatures through this period. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Overview... Cutoff H5 low across Quebec late Tuesday will shift E to the Maritimes Tue night/Wed. The first H5 short wave shifts E late Tuesday. A second strong but dry short wave/cold front barrels southward on Wednesday as the cutoff mid level system moves E. High amplitude H5 ridge then builds E from the Great Lakes late Wednesday into Thursday night. Another strong short wave and associated surface warm front works across the Great Lakes which may approach late Thu night or Friday, but low confidence due to wide model solution spread. Details... Tuesday night and Wednesday...Moderate confidence. Drier air works E as PWATs drop. Any leftover convection should diminish by Tue evening across the interior. Dewpts remain in the lower-mid 60s and, with clearing skies and light winds, may see overnight patchy fog develop mainly along the immediate S coast and inland valleys. Expect winds to shift to W-NW as dry cold front works across the region during Wed. Gusts may reach 15-20 kt along the immediate coast Wed afternoon. Highs on Wed will be in the 80s across most locations, possibly touching 90 in a few of the normally warmer locations. Thursday through Friday...Low to moderate confidence. Should be dry early Thu, then clouds will increase from the W. Fast flow aloft lending to lower confidence on timing of approaching warm front and low pressure from the Great Lakes. Exact track of the best instability/lift also in question, though appears that there may be periods of moderate to heavy rain Thu night/Fri across northern areas, at least for now. Have carried chance POPs increasing from W-E Thu, then some low LKLY POPs across central and northern areas Thu night into early Fri. May see some marginal instability work into the region as the low passes, so have mentioned isolated thunderstorms as well Thu night/Fri. Saturday-Sunday...Low confidence. At this point, a lot of uncertainty continues due to widely varying model solutions. In general, though, noting periods of scattered showers, but timing is very much in question. Looks like a decent shot for light precip Sat/Sat night, then may be a bit drier on Sunday. && .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 night/... Tonight and tomorrow...Moderate confidence. Mainly VFR except extreme SE MA/RI terminals which could experience a period of IFR conditions in low CIGS with low vsby fog possible especially Cape/Islands. This burns off after sunrise. Some showers possible late tonight, mainly Islands. Otherwise, a few showers and isolated T-storms mainly W MA during the afternoon tomorrow. Tomorrow night...Moderate confidence. VFR gives way to another mix of IFR/MVFR mainly CT/RI and SE MA while the remainder stays mostly VFR, then as winds shift around to the W, transition back to VFR everywhere toward the morning. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday night through Wednesday night...Moderate confidence. Mainly VFR conditions. Areas of MVFR-IFR CIGS/VSBYS in late night/early morning fog likely developing Tue night/early Wed. Thursday through Friday...Low confidence. Scattered showers push from W-E starting around midday Thu, reaching E coastal areas Thu evening. E-SE winds may produce periods of MVFR- IFR CIGS/VSBYS in patchy fog. Isolated thunderstorms possible Thu night through Fri night.
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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 Tuesday/...High confidence. Winds and seas expected to remain below Small Craft Advisory levels through Tuesday. Seabreezes on both coasts from mid morning into this evening. Increasing south flow tonight into Tuesday. Some showers possible around Nantucket late tonight into Tuesday morning. Outlook /Tuesday Night through Friday/... Tuesday night-Wednesday...Moderate confidence. S-SW winds shift to W toward Wed morning, then back to SW again on the southern waters Wed afternoon. May see gusts up to 20 kt early Tue night across eastern waters. Swells up to 5-6 ft from Tropical Storm Gert may push across the southern waters. Chance of rip currents across south facing beaches. Wednesday night through Friday...Low confidence. Winds shift to N Wed night, with gusts 15-20 kt possible on the open waters, then become E-SE up to 10-15 kt late Thu through Fri. Timing and track of passing low pressure lends to lower confidence on winds speed/direction. Seas mainly 4 ft or less. Reduced visibility in patchy late night/early morning fog across most waters Wed and Thu. Scattered showers push across the waters Thu and continue into Fri. Isolated thunderstorms possible Thu night-Fri. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...Belk/Doody SHORT TERM...Belk LONG TERM...EVT AVIATION...Doody/EVT MARINE...Belk/EVT is the U.S. government's official web portal to all federal, state and local government web resources and services.