Area Forecast Discussion
Issued by NWS Boston, MA

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743 FXUS61 KBOX 182056 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 456 PM EDT Tue Oct 18 2016 .SYNOPSIS... A warm front will lift north of the region this evening. This will bring unseasonable warm temperatures through Wednesday. A cold front will move also across the region Wednesday but with little weather associated with it. Unsettled weather is likely at times Thursday and Friday. Not as warm late week but still mild for mid Oct. A drying and cooling trend likely next weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 345 PM Update...Made minor adjustments to the temperature and wind gust forecasts based on the current trends and the placement of the front. This continues cooler temperatures north of the front and warmer temperatures and stronger winds south of the front. Otherwise, the forecast is on track. This evening... Stratus and fog north of the warm front have lingered over Central and Northeast MA. But with the passage of the warm front and a shift to south winds, expect clearing skies all areas. Tonight... Expect fair skies for much of the night. A cold front approaches from the Great Lakes later at night and will bring some increasing clouds from the west. Meanwhile fair skies and diminishing wind along with above normal dew points will generate fog in some spots before the clouds move in. Low confidence on how much of the fog will linger after clouds increase. With dew points in the upper 50s and lower 60s, min temps should no lower than that. The resulting small temp-dewpt differences will also contribute to overnight fog. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... The cold front slips through Southern New England during Wednesday. Limited moisture, all of it below 700 mb, but enough to generate 1.5 inch PW values. Cross sections show weak lift. The upper jet remains across the St Lawrence Valley along with its supporting dynamics. A few showers are possible, but widely scattered at best. Temperatures Wednesday will depend on the speed of clearing as the front moves south of us. If clouds linger, then we may barely climb into the lower 70s. If skies clear fast enough, we have potential to reach 80 or the low 80s. At this time we will stay consistent with the previous forecast. At night,the front will stall to our south. High pressure moves across Northern New England. This will keep us dry through the night. Clouds may increase later in the night as the next system approaches. Low level inflow ahead of the Ohio Valley system will be focused on Eastern/Central PA. The right entrance region of the upper jet will be even farther west over the Great Lakes. For that reason we have eliminated pops from the forecast for Wed. night. Dew points 45-55 and light north winds will define the min temperature. The light flow may allow some fog to form, but the speed of return of clouds ahead of the next system may interfere with fog formation. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Unsettled weather expected Thursday and Friday * Cooler but still seasonable weather expected through Friday * Temperatures fall a bit below normal this weekend into early next week On a broad scale, the models are in good agreement for the most part. There are some discrepancies, particularly Thursday and Friday, that extend from potential tropical development in the Bahamas and surface low developing in the Ohio Valley and how and where they develop, strengthen, and interact. The UKMET is one of the faster solutions, while the Canadian is one of the slowest and strongest. The GFS and the ECMWF fall in the middle of these solutions both speed and strength wise. These solutions indicate some interaction between the extra-tropical and tropical systems but keep the bulk of the moisture offshore of southern New England. Both show a brief period of heavier rain over some portion of the region, but differ on where exactly this area of heavier rain develops. This will be something to watch in the coming days. Bulk of the guidance indicates a widespread half to one inch of rainfall, with a relatively small area possibly getting up to two to three inches. Welcome rain once again, but not drought busting. Beyond the end of the work week, models are in decent agreement with the general pattern and we will see a return to more normal autumn weather. Thursday and Friday...High pressure will move into the maritimes Thursday as low pressure and a cold front approach from the Ohio Valley. This low pressure will strengthen over southern New England, possibly interacting with the above-mentioned tropical low moving up the coast. Late on Friday the low pressure will move northward into Maine and then Quebec. This will bring showers to the region both Thursday and Friday. Models are showing the higher PWAT values (tropical moisture) mainly over the eastern half of southern New England on Friday. Thus, believe the heavier rain will occur on Friday. There is some indication of some marginal instability, so a few claps of thunder are possible, but for the most part expect only showers. After the cold front Wednesday, expect temperatures to fall back to near normal for mid October through the end of the week. Saturday and Sunday...This will be a bit of a transition period as the upper level trough slowly moves offshore and low pressure moves into the Maritimes. A decent pressure gradient and a strong low level jet will make this a somewhat breezy time as well as a bit cooler than normal. Sunny skies will counter the cooler, breezy conditions somewhat but it will definitely feel like typical October out there. Monday and Tuesday...High pressure starts building into southern New England. There is some uncertainty in the models with possibly a shortwave or cold front moving through Monday bringing a period of showers. Otherwise, expect continued quiet, normal to below normal temperatures. && .AVIATION /21Z TUESDAY THROUGH SUNDAY/...
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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 Wednesday Night/... This evening...Lingering LIFR cigs in Eastern MA will lift and break by evening. Winds shift out of the south with the clearing. Tonight...Moderate confidence. Mainly VFR with 4-8K FT cigs developing. Low risk of a brief shower late tonight, especially Northern MA. Low confidence on potential for IFR fog. Diminishing wind. Wednesday...Moderate confidence. Mainly VFR cigs with clearing moving north to south across the region during the afternoon. Low risk of a brief shower south of the Pike in the morning. Wednesday night... Moderate confidence. Generally VFR. Low confidence on fog formation after midnight. This will depend a lot on how fast clouds move back in from the southwest overnight. KBOS TAF...low confidence in near term and then high confidence. Challenging period for BOS TAF right during the afternoon/evening push with fog bank coming onshore from harbor at same time clearing within 5 to 10 mi of airfield from south. MQE and GHG have both shifted to south, and models depict increasing low level SW jet in very near term. Have decided to delay BOS breaking out but think it really should do so sometime between 2130 and 2200 UTC, but experience has shown these situations to be very challenging. Once BOS finally breaks out early this evening, conditions should remain VFR. KBDL TAF...High confidence in TAF. Outlook /Thursday through Sunday/... Thursday and Friday...Moderate confidence. A mix of conditions, potentially all MVFR/IFR in low clouds, rain, and fog at times. Some improvement is possible late Friday and Friday night. Saturday and Sunday...High confidence. Improving conditions to VFR quickly on Saturday. Westerly to northwesterly winds increasing, gusting to 25 to 30 kts.
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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 Wednesday Night/...Moderate-High confidence. Tonight...Increasing SW winds with gusts of 25-30 kt developing, best chance on the southern waters. These will diminish overnight. Seas building to 5-7 ft over the outer waters and exposed southern nearshore waters. Wednesday...A weak cold front moves across the waters during the day. Expect SW winds to shift out of the NW. Winds will be less than 20 kt. Diminishing seas. Wednesday night...Winds below 15 knots and seas less than 4 feet through the night. Outlook /Thursday through Sunday/... Thursday...High confidence. Mainly quiet boating weather is expected with occasional 5 foot seas on the outermost waters. Friday...Moderate confidence. Seas and winds increase as low pressure moves across southern New England and approaches the waters. In addition, a potential tropical or sub-tropical low may move up the coast and work in tandem with the low over southern New England. This potential interaction is what keeps our confidence in the moderate range. Especially with wind direction. Small craft advisories will likely be necessary for most of the waters. Saturday and Sunday...High confidence. Small craft advisory conditions will continue with a tight pressure gradient between the departing low pressure system and building high pressure in the Great Lakes. Westerly winds will shift to the northwest on Sunday. && .TIDES/COASTAL FLOODING... Winds from the south tonight will shift out of the northwest during Wednesday. With an offshore wind, we do not anticipate any coastal flood issues beyond perhaps very spotty minor flooding at the times of the highest tides through Thursday. Friday could be another story, but much uncertainty remains. Depending upon the interaction of a fairly high amplitude short wave trof and a possible low center with subtropical origins off the coast, there could be a significant east to southeast low level flow toward our coastline, possibly building a surge over a foot or two. The range of possibilities are wide, but there remains a low risk of at least some coastal flooding during the Friday PM high tides. We will need to monitor trends with later computer model operational and ensemble runs. && .CLIMATE... Record High Temperatures: Tuesday October 18th Wednesday October 19th Boston 82 in 1947 Boston 84 in 1945 Worcester 85 in 1908 Worcester 81 in 1963 Providence 85 in 1908 Providence 81 in 1945 Hartford 80 in 1968 Hartford 82 in 1963 && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ232>235- 237-250-254>256. Small Craft Advisory until 11 PM EDT this evening for ANZ230. Small Craft Advisory until 2 AM EDT Wednesday for ANZ231-236- 251.
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&& $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/RLG SHORT TERM...WTB LONG TERM...RLG AVIATION...WTB/RLG/Thompson MARINE...WTB/RLG TIDES/COASTAL FLOODING... CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.