Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 150905 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 505 AM EDT Sun Oct 15 2017 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Have extended the dense fog advisory across the remainder of the region, which includes north central and western Mass. Starting to see patchy dense fog develop there, which will linger through mid morning. Dewpoint depressions across the entire region are 2 degrees or less, along with mainly calm winds as weak warm front sits S and W of the region at 08Z. With low sun angle, will take a couple of hours to burn the dense fog off especially along the coast where it may linger even if the warm front comes through due to the high dewpoints over the cooler waters. Noting a band of spotty light showers which started to develop from S of Long Island into the east entrance of LI sound on KBOX 88D radar around 07Z. The showers were moving NE, running from near Montauk and Block Island and Westerly NE across Newport and New Bedford, where -SHRA reported at 0808Z. May see a few showers across near Nantucket as well. Visibility briefly improved at both locations, likely due to the precip in the vicinity, but has lowered back to 1/2SM at Nantucket again. As for today, what is left of the warm front around NYC and Long Island will work NE across the region as low pressure across the central Great Lakes shifts E-NE into southern Ontario and Quebec. All the short range and high res models do signal some spotty precip moving across this morning, and could see some spotty drizzle as well. Once the front shifts across, will see some improving conditions though low clouds may linger into the afternoon especially near the coast. Still noting H85 temps rising up to +16C to +17C by around midday or into the afternoon. Noting low level jet pushing into the region this afternoon, with the H85 jet increasing to around 40 kt by midday across central and eastern areas, with the good mixing below at or below H9. Gusty SW winds will kick in, especially across eastern Mass into RI and across the coastal waters, where gusts up to 25-30 kt are possible. Once the light precip moves out, expect mainly dry conditions through the remainder of the day. Leading edge of precip ahead of the front looks to hold off until this evening. With the strong warm air advection across the region, should see temps reach to the 70s during the afternoon, mildest across the lower CT valley and N central and NE Mass. However, depending upon whether there are breaks in the clouds, temps may soar even higher. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... Tonight... Strengthening low pressure system over the Great Lakes crosses southern Quebec and northern New England. Associated cold front will push SE across the region through the overnight hours. Area of showers associated with the front tends to weaken as the front moves across as best lift and moisture shifts NE. Could still see some scattered showers mainly across central and western areas through midnight or so, becoming spotty as the front shifts across. Some question whether some wind gusts may push across portions of the interior, especially over the higher terrain, as the front passes as a secondary low level jet approaches. Noting some potential gusts up to 35 kt or so across the higher terrain of the Berkshires and possibly as far W as the Worcester hills around or after midnight. Good cold air advection as H925 temps drop quickly around or after 06Z. Readings in the lower- mid 60s this evening across the higher inland terrain may fall back to the upper 40s by 09Z-10Z. Will need to monitor potential for even higher gusts as the cold air wraps in behind the front. Expect lows by Mon morning ranging from the mid-upper 40s across the higher terrain to the lower 60s along the coastal plain. && .LONG TERM /MONDAY THROUGH SATURDAY/... * 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. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/... 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. && .MARINE... 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 to high 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 to high confidence. Warm front moves N of the waters this morning, then S-SW winds increase with gusts up to 25-30 kt this afternoon, highest across the near shore and eastern outer waters. Seas will also build. Small Crafts continue for all waters. Areas of dense fog with poor visibility through mid morning or so, then should improve with increasing wind and milder air. Tonight...Moderate confidence. SW wind gusts ahead of the cold front will continue to gust up to 25-30 kt through this evening, then will start to diminish on the near shore waters as the front approaches. Low probability of gale force gusts on the outer waters prior to frontal passage after 06Z. 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. && .BOX WATCHES/WARNINGS/ADVISORIES... 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. && $$ SYNOPSIS...Nocera/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...Nocera AVIATION...Nocera/EVT MARINE...Nocera/EVT is the U.S. government's official web portal to all federal, state and local government web resources and services.