Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 221428 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1028 AM EDT Sun Oct 22 2017 .SYNOPSIS... High pressure south of New England will result in unseasonably mild and dry weather into Monday. Sea breezes along both coasts today will make it a little cooler there. A slow moving cold front will bring rounds of heavy rain showers Tuesday into Wednesday with a period of strong to damaging wind gusts possible. A few lingering showers are possible Thursday, but the trend towards drier and more seasonable temperatures are expected Thursday into Friday. Above normal temperatures may return by next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1005 AM Update... Good visibility reported from all observation sites at 14Z, as patchy fog has burned off. Still noting bands of high clouds crossing the region from the NW as seen on both GOES-13 and GOES-16 (prelim, non operational) visible satellite imagery after sunrise through 14Z. Tough to see if any low ocean clouds are trying to develop/push toward E coastal areas as some short range high resolution models continue to suggest. Still believe, as previous forecaster mentioned, that this is still too fast and overdone, so kept the low clouds out for now. Will continue to monitor. Bubble high pressure noted across E Mass at 14Z as main center sits across New Brunswick. Light/variable or calm winds continue for most locations, with light W-SW winds along the S coast. Noting some N-NE light winds across Cape Ann into Boston, and believe that the light E-NE winds will continue to work across most if not the entire region during this afternoon with very light pressure gradient in place. Other than adjustments on near term conditions to bring current, forecast pretty much on track. Have incorporated near term trends into the updated forecast. Previous Discussion... Only potential problem is the continued forecasted low clouds moving in off the ocean across E coastal areas during this afternoon as depicted by some high resolution model guidance. Believe this aspect is overdone and too fast, so did not bite at this point. High pressure will remain in control of our weather today, but will be centered more to our northeast today. The resulting light winds will set the stage for a seabreezes along both coasts, which in turn will mean lower max temperatures today. Highs across the eastern MA coast will reach between 65 and 70, while portions of the Connecticut River valley will see highs reach into the upper 70s to near 80. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Seabreezes diminish early this evening, to be replaced with a light south synoptic flow. Another mild night in store, with slowly increasing dew points. Dry weather continues. Still some concern for low clouds and patchy fog across portions of southeast MA, as dew points may get close to the water temperatures just offshore. Just don`t have much confidence in that outcome, yet. Monday is still expected to be mostly dry. Overrunning lift should get underway by the afternoon. The main limitation for rainfall will by the abundant relatively dry air near the ground. Many members of the 22/00Z guidance suite bring light rainfall into southern New England during the daytime Monday. Thinking this is likely a bit overdone, especially across the eastern half of southern New England. Will continue to have a chance of showers during the afternoon into evening hours across the western half of southern New England, owing to the proximity to the approaching cold front. There should be better low level moisture convergence to help overcome the drier air a little quicker. Temperatures should be a little lower with increasing clouds, but still well above normal. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights... * Period of strong to damaging wind gusts possible Tue into Wed am * Heavy rain will result in an urban/street flooding threat Tue-Wed * More seasonable late October temps finally return Thu/Fri Details... Monday night... Upper level ridging will gradually lose its grip on our region as low level jet increases ahead of low pressure lifting northeast towards the Great Lakes. While just a few spot showers are possible Monday evening, the threat for scattered showers will increase after midnight across the interior. Increasing low level moisture/lower clouds will hold overnight low temps in the upper 50s to lower 60s which may actually rise a bit toward daybreak. Tuesday and Wednesday... The two main concerns will be revolve around the potential for heavy rain and an urban/street flooding threat along with a period of strong to damaging winds. Deep trough to our west will continue to dig into the southeast states inducing meridional upper level flow into southern New England. The result will be a southerly low level jet/Pwats both increasing to 2-3+ standard deviations above normal. Timing of the cold front still uncertain, but strong LLJ/high Pwats coupled with strong forcing will bring periods of showers with heavy rainfall Tue into Wed. The front will be slow moving and both the GEFS/EPS showing decent probabilities of 2+ inches of rain with even some low probs of 4+ inches. Therefore, an urban/street flooding threat will exist Tue afternoon into Wed especially if the higher rainfall amounts are realized. The other concern will be the potential for a period of strong to damaging wind gusts Tue into Wed morning. Most of the guidance indicates a 925 mb southerly LLJ on the order of 45 to 60 knots. While some of this wind will remain aloft given an inversion in place, surface temps well up into the 60s to the lower 70s are expected Tue into Wed. This may allow some more of the wind to mix down than we normally might expect. In addition, the potential exists for a fine line with embedded thunder given we may see up to 500 J/KG of Cape with dewpoints in the 60s coupled with strong forcing. The potential exists for a period of southerly wind gusts of 40 to 50 mph especially along the coastal plain. If a fine line or any convection develops ahead of the front, a low risk for a few gusts up to 60 mph would be possible. Given most trees are fully leafed, these potential wind gusts will bring an enhanced risk for tree damage/isolated to scattered power outages. There is a pretty good bet that some wind headlines will likely be needed Tue afternoon into Wed am with the highest risk along the coastal plain. Thu/Fri/Sat... The cold front will probably cross the region by Thursday morning, but some lingering showers will remain possible Thu afternoon with the upper level shortwave. Dry weather likely arrives Thu night into Fri. Temps finally return to more seasonable levels Thu/Fri behind the cold front, but readings may be back above normal by next weekend. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/.... Through this afternoon...Moderate to high confidence. Sea breezes develop by midday along both coasts. Some high resolution guidance continues to have IFR CIGS moving onto the eastern MA coast during the afternoon. No evidence seen on both GOES-13 and GOES-16, though tough to see with bands of high clouds moving across. Continue to feel the low clouds are too fast and overdone, but can not rule out a low risk for development. Will continue to monitor Tonight...Moderate confidence. Uncertainty on how quickly MVFR-IFR conditions overspread the area from the south. Mainly dry conditions prevail along with light south winds. Monday...High confidence. Mainly VFR, although with a low risk for early AM fog and lower clouds with isolated IFR conditions possible. KBOS Terminal...Moderate to high confidence in TAF. We think northeast winds develop at the terminal by around 15Z or so. Low risk of IFR CIGS moving in off the ocean sometime this afternoon. Still feel this is too fast and overdone, but will continue to monitor. KBDL Terminal...High confidence in TAF. Outlook /Monday Night through Thursday/... Monday Night: Mainly MVFR, with local IFR possible. Breezy. Chance SHRA. Tuesday: Mainly MVFR, with local IFR possible. Strong winds with local gusts to 40 kt. SHRA likely. Tuesday Night: Mainly MVFR, with areas IFR possible. Strong winds with gusts to 40 kt. SHRA, isolated TSRA. Wednesday: MVFR/IFR conditions possible. Strong winds with local gusts to 40 kt. SHRA, isolated TSRA. Wednesday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA. Thursday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/...High confidence. Very tranquil boating weather for late Oct continues this period with light winds, dry weather and good vsby. Local seabreezes develop by midday today. Seas down to around 2 ft on the open waters, with some 3 foot seas E of Cape Ann which should subside by this evening. Light south winds tonight into Monday. Outlook /Monday Night through Thursday/...Moderate confidence. Monday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain showers. Tuesday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 11 ft. Chance of rain showers. Tuesday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 12 ft. Rain showers, isolated thunderstorms. Wednesday: Low risk for gale force winds with gusts up to 40 kt. Rough seas up to 16 ft. Rain showers, isolated thunderstorms. Areas of visibility 1 to 3 nm. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 14 ft. Rain showers. Visibility 1 to 3 nm. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 11 ft. Chance of rain showers. && .FIRE WEATHER... Dry weather continues through at least tonight with minimum RH values 25 to 35 percent today, lowest values over CT and western MA. However, with high pressure nearby winds will be very light. Thus fire weather parameters remaining below Red Flag Warning criteria. && .CLIMATE... All the record max temperatures for October 22 were set in 1979. While being well above normal today, most of these records appear to be safe. Here are the records for today Hartford 85 in 1979 Boston 83 in 1979 Worcester 82 in 1979 Providence 86 in 1979 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Frank NEAR TERM...Frank/EVT SHORT TERM...Belk LONG TERM...Frank AVIATION...Belk/Frank/EVT MARINE...Belk/Frank/EVT 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.