Area Forecast Discussion
Issued by NWS Boston, MA

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695 FXUS61 KBOX 201420 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1020 AM EDT Fri Oct 20 2017 .SYNOPSIS... High pressure will move from the Appalachians today to a position east of New England on Sunday. It will provide dry and much warmer than normal temperatures through the weekend. The risk of showers will increase by the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 10 AM update... SPS mesoanalysis indicates mean mid level trough axis east of New England and with upstream mean ridge axis across the Great Lakes. This will provide deep layer anticyclonic flow and associated subsidence into New England today. The 12z observed sounding from ALY reveals this well underway with a sharp mid level subsidence inversion just below 700 mb. This will provide the region with abundant sunshine and mild temps with highs 65-70, still warmer than normal. Northwest winds 10-20 mph will provide some downslope into the coastal plain, drying out the blyr with dew pts in the 30s mixing down to the surface from aloft. Overall, ideal weather for late Oct and certainly a top 10 day. Previous discussion below. ================================================================ Satellite imagery shows that the upper level trough axis has shifted east of the region. A band of thick cirrus clouds over southern New England was beginning to pull out to the east. It should be mainly off the coast by daybreak, leaving mostly sunny skies across our area. At the surface, a weak, dry cold front will move through as a wind shift, with winds shifting to west toward daybreak and then to the northwest during the day today. Wind gusts to 20 mph are expected for a time late this morning and into the mid afternoon hours. Mixing during the day will reach 925 mb or a little higher, similar to yesterday, with temperatures at that level supporting max sfc temps around 70, except mid 60s in the slopes of the Berkshires and on Nantucket. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Tonight... Skies will be clear and winds will be light. It will be on the chilly side with lows in the upper 30s to mid 40s, except mid 40s to lower 50s Cape Cod and the islands. Saturday... * Very warm weather, but may fall short of record highs High pressure will become centered just south of southern New England. An upper level ridge along the east coast will build into the region. 925 mb temperatures will reach +17C during the afternoon. With full sunshine, am expecting highs in the mid to upper 70s, but cannot rule out a high near 80 in Hartford County. Should be the 60s to lower 70s...along the south coast, Cape Cod, and the islands with southwest flow. Record highs are 80 at Worcester, 81 at Providence, and 82 at Hartford and Boston...all set back in 1920. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights... * Warm and dry weather lasting into Monday * Unsettled weather pattern with showers at times Tue into Thu 20/00Z guidance coming into better agreement on the upcoming pattern change later next week. Still some detail differences, with the CMC remaining the odd model out after Tuesday. Will continue to favor a consensus blend approach to smooth over the less predictable details. Have high confidence in the forecast through Monday, dropping to low confidence in the details after Tuesday. Strong mid level ridge along the Eastern Seaboard will finally be replaced by a deep trough during the middle of next week. Still expecting temperatures to be above normal for late October, but the trend will be downward after Monday. Our prolonged dry spell also appears it will come to an end during the middle of next week. Depending upon how quickly a cold front can move east, which is not a given with a strong high pressure over the North Atlantic, we could see periods of showers lingering from Monday night through the end of next week. This would be a greater possibility if a low pressure develops along this front by Wednesday. Still thinking the greatest risk for widespread showers will be ahead of a cold front Tuesday into Wednesday. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...Generally high confidence. 10 AM update... Not much change from previous 12z TAFs. VFR, dry runways and NW winds 10-20 kt. Earlier discussion below. ================================================================= VFR conditions through Saturday. Just an isolated fog patch or two late tonight in the normally colder spots. Northwest winds will pick up a little, with late morning and afternoon gusts near 20 knots today. Winds then diminish with sunset and will be light through Saturday. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Saturday Night through Tuesday/... Saturday Night through Sunday Night: VFR. Monday: VFR. Slight chance SHRA. Monday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Tuesday: Mainly MVFR, with local IFR possible. Breezy. SHRA. Any isolated fog patches, especially in the CT River Valley, will dissipate first thing after sunrise. Otherwise && .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. 10 AM update... Very tranquil boating weather for late Oct with NW winds 10-20 kt, highest near shore. Good vsby and dry weather. Enjoy! Earlier discussion below. ================================================================ Today...Northwest winds will gust to around 20 knots during the day. Seas will be near 5 ft early this morning on the southern outer waters but seas will subside to 3 to 4 ft throughout all outer waters during the day. Have kept a Small Craft Advisory posted for the southern outer waters through 10 AM this morning. Tonight and Saturday...Ideal boating weather. Winds remain 15 knots or less, and seas mainly 2 ft or less. Wind direction will shift from the north tonight to the southwest on Saturday. Outlook /Saturday Night through Tuesday/...High confidence. Saturday Night through Sunday Night: Winds less than 25 kt. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Chance of rain showers. && .FIRE WEATHER... Will reissue the Special Weather Statement highlighting a risk of only marginally elevated fire weather potential for today. Northwest winds may gust up to 20 mph at times late this morning through the mid-afternoon hours. We are not expecting 25 mph or higher gusts. Minimum RH values will reach 30-35 percent across much of the region. These values, combined with the lack of recent rainfall will lead to a marginally elevated fire weather potential for today. && .CLIMATE... Record high temperatures for Saturday, October 21: BOS 82 in 1920 BDL 82 in 1920 PVD 81 in 1920 ORH 80 in 1920 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ255- 256. && $$ SYNOPSIS...Belk/GAF NEAR TERM...Nocera/GAF SHORT TERM...GAF LONG TERM...Belk AVIATION...Belk/Nocera/GAF MARINE...Belk/GAF FIRE WEATHER...staff CLIMATE...staff is the U.S. government's official web portal to all federal, state and local government web resources and services.