Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 241737 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 137 PM EDT WED AUG 24 2016 .SYNOPSIS... High pressure will remain in control with higher temperatures today, but continued low humidity. More warm, humid conditions will return late this week. There is a risk for showers and thunderstorms Thursday night and Friday as a weak front passes. Another high will bring dry and somewhat less humid weather this weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 930 AM Update... 12z soundings at CHH/OKX/ALY are quite dry through the column and dry air forecast to persist. Abundant sunshine will prevail with just a few developing cu in the interior. 850 mb temps increase to 16C later today supporting highs in the mid/upper 80s, cooler south coast with sw flow. Still can`t rule out a weak seabreeze developing along the east coast given light boundary layer flow, but most of the hi-res guidance keeps the seabreeze offshore. Mixing of dry boundary layer will result in dewpoints in the 50s for most places this afternoon so comfortable humidity levels, but sw flow will likely keep dewpoints above 60 along the south coast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... High pressure continues to move farther offshore. South to southwest winds continue to increase ever so slightly through this period. Expecting near to above normal temperatures through Thursday. Latest guidance continues to show the slow approach of a prefrontal trough toward western New England late Thursday. Given weak forcing, and relatively lower humidity, decided to keep the forecast dry through Thursday. There is a possibility for a few isolated showers across western MA, but not enough of a risk to put showers in the forecast at this time. This timing may change. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Highlights... * Scattered showers/thunderstorms Thursday night and Friday * Drier weather this weekend * Another front may bring shot of wet weather Sunday night and Monday Overview and model preferences... Overall summer pattern remains in place across North America during most if not all of this timeframe as high pressure remains across the south central and SE U.S., keeping a rather fast mid level W-SW wind flow in place late this week across the northern tier states. Noting the overall H5 pattern begins to shift S Thu night/Fri as a surface front works SE out of central Ontario/Quebec. This will push off the south coast of New England by early this weekend, with high pressure bringing more dry and somewhat less humid conditions. 00Z operational models are in lower agreement in bringing an H5 short wave and its associated weak low pressure/front in the fast flow aloft, with the ECMWF a bit more bullish with its precip field vs. the GGEM and GFS for Sunday night and Monday. Less confidence with the timing of this feature. Have lower confidence with evolution of the upper level pattern early next week. Big questions as to the development and track of a tropical wave /99L/ near or east of the Bahamas. At this point, does not appear to affect the region, but may influence the overall upper level pattern, potentially somewhere across the southern Gulf states, but could be further into next week before any possible effects are felt. Details... Thursday night-Friday...High pressure remains along the eastern seaboard with SW wind flow in place. H5 heights lower somewhat, with surface low pressure and associated cold front moving slowly across during this timeframe. PWATs increase to 1.8 to 1.9 inches, so should see some rainfall with this front. However, noting rather limited instability but best near and with the passing front. Have mentioned scattered showers/thunderstorms in the forecast, with best shot across central and northern areas Thu night through midday Friday. Will remain warm/humid Thu night with lows only in the mid 60s to around 70. As the front passes, winds will shift to W-NW during the day Friday. However, somewhat drier air will be delayed until Friday night so will still feel rather humid. Highs will be in the mid-upper 80s. Saturday-Sunday...Large high pressure will cross the northeast U.S. with somewhat cooler and drier conditions. Dewpts will only fall back to the lower-mid 60s, with some upper 50s Saturday night across the inland valleys. N-NW wind to start off Saturday, then will veer to E-NE during later Saturday and E-SE on Sunday. With the warm sea surface temps on place, not much cooling air off the ocean. Expect highs both days in the lower-mid 80s, except in the mid- upper 70s along the immediate S coast. Another front may begin to approach Sunday night, which push a few widely scattered showers around the Route 2 area of N Mass. However, timing is in question with the large high across the mid Atlantic/SE U.S. states. Monday-Tuesday...Low confidence on timing of the approaching front during Monday, which is somewhat faster on the GFS vs. the ECMWF. Went along with ensemble guidance for this timeframe, with chance POPs going for most of Monday into Monday night. Still quite a few questions on Tuesday, as the front may stall near or just off the southern New England coast. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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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 Thursday night/... Thought tonight...High confidence. VFR, but low risk for patchy MVFR/IFR late tonight in the fog prone location in the CT valley. Thursday...High confidence. VFR with cigs 5-10k ft developing in western New Eng in the afternoon. SW gusts to 20-25 kt near the coast in the afternoon. Thursday night...Moderate confidence. Mainly VFR cigs, but areas of MVFR cigs possible. A few showers and isold t-storms possible. KBOS Terminal...Weak seabreeze may develop this afternoon but left it out of TAF as confidence is not high. KBDL Terminal...High confidence in the TAF. Outlook /Friday through Sunday/... Thursday night...Moderate to high Confidence. Mainly VFR. S-SW winds gusting to 20 kt along the S coast Thu evening. Scattered showers/isolated thunderstorms push into N and W areas overnight along with patchy late night fog in normally prone valley locations. Local MVFR-IFR conditions. Friday...Moderate Confidence. Scattered SHRA/TSRA as cold front moves across the region. Mainly VFR with local TEMPO MVFR-IFR CIGS/VSBYS possible with any storms. Conditions improve from NW-SE Friday night, though may see brief patchy fog across portions of CT valley after 07Z-08Z. Saturday and Sunday...High Confidence. VFR. Light winds. Likely sea breezes on Saturday. Winds becoming E-SE Sunday.
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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 Thursday/...High confidence. Tranquil boating conditions through the period as high pressure remains in control of our weather.. Mainly SW winds 15 kt or less with light seas and good visibility. A few gusts up to 20 kt possible Thursday, especially during the afternoon. Outlook /Thursday Night through Sunday/... Thursday night...High Confidence. S-SW winds gusting to around 20 kt Thursday evening along the southern near shore waters. May see local MVFR-IFR VSBYs in patchy fog mainly after 06Z along the southern near shore waters. Seas may briefly reach 5 ft on the outer waters east of Cape Ann early. Friday...Moderate Confidence. S-SW winds gusting up to 25 kt on the southern waters to east of Cape Cod with seas building to around 5 ft. Winds will diminish as they shift to W-NW Friday night. Seas subside below 5 ft. Patchy fog may develop overnight on the southern outer waters. Saturday and Sunday...High Confidence. Expect N winds shifting to E-NE during Saturday, then E-SE on Sunday. Winds and seas remain below small craft criteria. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...KJC SHORT TERM...Belk LONG TERM...EVT AVIATION...KJC/EVT MARINE...Belk/EVT

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