Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 150813 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 413 AM EDT Sun Oct 15 2017 .SYNOPSIS...
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Areas of dense fog this morning across the region associated with an approaching warm front. The front lifts north of the area later this morning giving way to a very warm and humid afternoon. A sharp cold front sweeps across the region tonight and will be accompanied by scattered showers into Monday morning. Behind the front it turns sharply cooler and brisk Monday afternoon with temperatures dropping down close to freezing into Tuesday morning. Gradual warm-up Wednesday followed by highs in the 70s Thursday into next weekend along with dry weather.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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140 AM Update... Dense fog has extended further inland, into portions of the interior Merrimack valley and central Mass, NE CT, with some patchy dense fog in portions of the CT valley at 05Z. Pushed the Dense Fog Advisory to include all of E coastal Mass westward to most of Middlesex and southern Worcester counties into NE CT. Rather low T/Td spreads which, along with low sun angle, will prolong the fog until around mid morning. Some fog may linger longer still, mainly along coastal areas into midday with increasing SW winds. Temps running in the mid 50s to lower 60s Previous Discussion... With the light/variable or calm winds and high dewpoints, expect conditions to continue to lower, so extended the Dense Fog Advisory further inland to include all of RI, N central and NE CT and S central and E Mass through 9 AM.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM MONDAY/... Today... Showers and drizzle will slowly come to an end after daybreak on Sunday as surface warm front push through the area. Behind the front, 850 mb temps warm to 17C and 925 mb LLJ strengthens to near 30-40 kts. If clouds break during the afternoon, and mixing increases up to 850 mb, then temperatures could warm into the low 80s. Aside from warm temperatures, we could see gusts to near 25 MPH or higher if true mixing occurs. Highest gusts will be across the eastern half of the region, which is closer to the strengthen LLJ. Sunday will continue to trend dry, but still cannot rule out a few isolated showers developing across the south coast. Tonight... Strengthening low pressure system over the Great Lakes will move eastwards towards northern New England by Monday morning. This surface low will drag a cold front through upstate NY and southern New England during the overnight hours. The main story however is the secondary shortwave rounding the trough late Sunday pushing this front through the region during the predawn hours of Monday morning. Ahead of this front, cannot rule out a few isolated showers across the south coast with continue low level moisture and dewpoints near the mid to upper 60s. Overnight lows will remain warm as WAA continues to stream into the region. Some showers will develop along the front, but mid-levels are still on the dry side so do not expect much in the way of heavy rainfall. After midnight, the cold front will begin to approach the region resulting in a surge of southerly winds with gusts near 25 MPH. The front appears to quickly push through around 2-6 AM. Stout CAA behind the front will result in a quick drop in temperatures and a surge of wind. Temperatures could from 60F to 45F within a 3 hour span. BUKFIT soundings show good mixing behind the front with 850 mb LLJ increasing to 50-55 kts. This could result in a quick 35-40 MPH gusts with some higher gusts across the higher elevations right behind the front. This could result in down tree and wires during the overnight hours. There is the potential for wind headlines but will let later shifts take another look. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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* Highlights... - Chilly Monday and Tuesday - Gradual warming begins Wed then 70s Thu into next weekend - Extended dry stretch of weather Mon afternoon into next weekend * Synoptic Overview... Ensembles from both the GFS and EC in good agreement that a series of northern stream short waves will temporarily erode the subtropical ridge over currently over the southeast states. The core of the coldest air arrives Mon night into Tue associated with trailing/secondary short wave energy. Then a gradual warming trend starts mid week as heights begin to rise behind departing northern stream short wave. By Thu the subtropical ridge reemerges over the southeast states and peaks at 591 dam into the weekend. This pattern will support a prolong period of dry weather across southern New England along with temps warming into the 70s Thu into next weekend! * Daily Details... Monday and Tuesday... Could be some leftover showers over southeast MA Monday morning associated with departing cold front, otherwise deep layer dry air invades the area from the northwest. Model time sections reveal post frontal strato-cu likely to develop so a mix of sun and clouds for the afternoon. Noticeable cool down behind the front with 925 mb temps falling to about +7C 18z Mon, supporting afternoon temps in the upper 50s, few degs cooler than normal. Although it will feel cool with NW winds up to 25 mph at times. Strong short wave trough moves across the area late in the day/evening. However not much moisture with this feature so not expecting much fanfare other than a reinforcing surge of cool air. This CAA (-4C at 850 mb, -1 SD) combined with light low level NNW drainage flow temps will tumble into the 30s regionwide, except low 40s downtown Boston. Given this setup leaned toward the coldest MOS guidance. Will likely eventually need frost/freeze headlines. Tuesday, temps only recover into the mid and upper 50s, a few degs cooler than normal with avg highs for mid Oct 59-64 degs. Although light winds and mostly sunny conditions will help offset the cool temps. Wednesday... Will be our transition day toward milder weather as the high shifts south of New England and low level WAA commences with 925 mb temps jumping from +4C Tue afternoon to +12C Wed afternoon. Blyr will be shallow given 1024 mb surface pressure but full sun and WSW winds will support highs 65-70, about 5 degs warmer than normal. Thu/Fri/Sat... 00z ECENS and GEFS both suggest warming trend continues Thu ahead of an approaching northern stream short wave. Then brief cool down Fri before warming trend returns next weekend as subtropical ridge reemerges over the southeast states into the Mid Atlc region. Not expecting any precip in this pattern.
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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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 Tonight/...Moderate confidence. Through 12Z... Areas of IFR-VLIFR mainly across most of S central and E Mass into RI and NE CT through around 12Z. Expect 1/4SM FG across most areas, especially from KOWD-KPVD-KWST and S/E as well as portions of interior NE Mass, NE CT and the CT valley. Elsewhere, may see patchy IFR conditions at times through 12Z. Today... Gradual improvement S/E during the day. IFR-LIFR may hold long over S/SE coast through at least midday, possible all day. VFR elsewhere, increasing S-SW winds with gusts near 25 kts. Tonight... IFR-LIFR CIGs along the S coast. Lesser VSBY impact with continued S/SW breezy winds. Improving NW to SE as winds shift W/NW, immediately gusty, potentially up to 40 kts, becoming VFR. SCT -SHRA associated with the wind shift. KBOS TAF...Moderate confidence in TAF. Going to have to watch closely during the overnight into morning push for IFR-LIFR VSBYs. Will hold to 1SM BR with this latest issuance given a more S rather than E flow. KBDL TAF...Moderate confidence in TAF. Terminal may remain out of IFR-LIFR VSBYs, however can not rule out IFR-LIFR CIGs and the possibility of MVFR BR and DZ. Outlook /Monday through Thursday/...Moderate confidence. Monday...high confidence. Possible MVFR-IFR in morning showers over southeast MA including Cape Cod and Islands. Then improving to VFR by mid morning. Elsewhere VFR in the morning then marginal MVFR-VFR in afternoon post frontal strato-cu. NNW winds gusting up to 25 kt. Tuesday through Thursday...high confidence. VFR, dry weather and light to modest winds.
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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 Tonight/... Through 12Z...Moderate confidence. Areas of dense fog across the near shore waters, and likely further offshore. May see patchy drizzle as well. Light S-SW winds. Seas remain at around 5 ft on the southern outer waters. Today...Moderate confidence. Passing warm front will allow southerly winds to increase to 25-30 kts by the afternoon. Seas will being to strengthen, SCA will continue for all waters. Tonight...Moderate confidence. Increasing southerly LLJ will aid in wind gusts to near 30 kts. Stout cold front will approach the waters switching the winds to a more westerly direction. Low prob for gale force winds for just an hour or two behind the front. Outlook /Monday through Thursday/...Moderate confidence. Monday... Cold front sweeps across the waters during the morning hours and may be accompanied by scattered showers and patchy fog. Behind the front (by mid morning) NNW winds 15-20 kt with gusts possibly up to 25 kt. Tuesday thru Thursday... High pressure shifts south of New England with winds becoming WSW. Dry weather and good vsby expected.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...Dense Fog Advisory until 10 AM EDT this morning for CTZ002>004. MA...Dense Fog Advisory until 10 AM EDT this morning for MAZ002>024- 026. RI...Dense Fog Advisory until 10 AM EDT this morning for RIZ001>008. MARINE...Small Craft Advisory from 3 PM this afternoon to 8 AM EDT Monday for ANZ231>234. Small Craft Advisory from 2 PM this afternoon to 5 AM EDT Monday for ANZ230-236. Small Craft Advisory from 2 PM this afternoon to 8 AM EDT Monday for ANZ235-237. Small Craft Advisory from 11 AM this morning to 9 AM EDT Monday for ANZ250. Small Craft Advisory from 2 PM this afternoon to 6 AM EDT Monday for ANZ251. Small Craft Advisory until 6 AM EDT Monday for ANZ254>256.
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&& $$ SYNOPSIS...Nocera NEAR TERM...EVT SHORT TERM...Dunten LONG TERM...Nocera/Sipprell AVIATION...Nocera/Sipprell/EVT MARINE...Nocera/Dunten/Sipprell/EVT

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