Area Forecast Discussion
Issued by NWS Boston, MA

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373 FXUS61 KBOX 281802 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 202 PM EDT Sun May 28 2017 .SYNOPSIS... Mainly dry and pleasant weather dominates into tonight, but a few brief spot showers are possible this afternoon. Low pressure in the Great Lakes generates a coastal low late Monday that passes off Nantucket Tuesday. This will bring wet weather for Memorial Day. Upper low and cold pool linger nearby most of next week, while surface high pressure builds in. Expect daytime clouds and scattered showers will pop up each day Tuesday through Friday. Otherwise fair weather with near seasonable temperatures. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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155 pm update... Considerable cloudiness at mid afternoon, but there were some peeks of sunshine at times especially along the south coast. Temps will hold mainly in the upper 60s to the lower 70s for the remainder of the afternoon, except the upper 50s to middle 60s along the immediate coast with sea breezes. Dry weather will dominate through early evening, but a few brief spot showers are possible. The highest risk for this will be across interior MA, but even in these locations dry weather will dominate.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Showers should diminish this evening. Then more widespread showers start to approach from the west after midnight. Still appears rainfall is most likely from mid morning into early afternoon. While an occluded front will not quite make it into our region, a secondary low pressure should develop and pass south of New England Monday. Convective parameters still show a destabilizing airmass at most layers. Mid level lapse rates remain sufficient to keep a mention of isolated thunderstorms in the forecast Monday. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights... * Unsettled weather pattern with hit or miss showers. * Seasonable temperatures through the period with slightly below average for the end of the week. * Hints of a drying trend for the weekend, but confidence is low. Pattern Details... The model guidance remains relatively agreeable in showing persistent upper troughing across the northeast with high amplitude ridging in the west and northern Plains. The ridge does diffuse on Friday into Saturday as troughing develops in Pacific NW which could relax the mass fields/drying trend over the NE. Still a lot of uncertainty with this outcome. Temperatures... Broad upper level trough over the region will keep any summer- like heat at bay through the period. Generally seasonable conditions on Tuesday and Wednesday thanks to southwest flow aloft and thermal ridge. This will result in high temps in the 70s. Depending on how much sun we can generate, cannot rule out a spot 80 temp on Wednesday due to strong mixing. Mid-level wave and associated front on Thursday drop temps aloft to well below average for late May. GEFS indicate this is close to 2 STD below normal. This will result in cooler than normal temperatures for Thursday and into Friday. There is the potential that next Saturday may trend a bit warmer as upper level trough begins to exit the region. However, the low could linger a bit longer into next weekend as the EC indicates. Thus low confidence on the weekend temperatures. Overnight lows will linger in the 50s through the period. Precipitation... Spot shower or two on Monday night as coastal low south of the region moves eastward. Dry weather for the first half of Tuesday before another shortwave move through the area during the later half of the day resulting in showers. Southwest flow aloft combined with building LLJ ans some elevated instability, could see some heavy rain and/or thunderstorms during the evening lasting into the overnight hours. Multiple disturbances will move through the mean trough as it settles in across the region through the rest of the work week: Wednesday through Friday. Very difficult to time disturbances and resulting precipitation chances. So will mention higher chances for showers during the more diurnally favored daylight hours, with slightly lower pops at night. Only day where a Drying trend could occur is on Thursday thanks to northwest flow aloft bring in drier air. Still large spread in the guidance for the weekend so a low confidence. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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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 Monday/... Mid to late afternoon...High confidence. Mainly VFR despite a broken deck of mid level cloudiness although some brief marginal MVFR cigs are possible. A brief spot shower or two is possible. Tonight...Low confidence. We kept things mainly VFR, but some of the guidance brings in a lot of MVFR-IFR conditions. Certainly possible, but just did not have enough confidence to go that pessimistic right now. Later shifts will have to monitor trends closely this evening. Monday and Monday night...Moderate to high confidence. MVFR to IFR conditions overspread the region through the morning and into the early afternoon in widespread rain. There also is a low risk for an embedded t-storm or two, mainly near the south coast on Mon. Easterly wind gusts around 20 knots are expected on the coast, with up to 25 knots across portions of the outer- cape Nantucket. The rain will taper off to light showers/drizzle from west to east late Monday afternoon/early evening. However, MVFR- IFR conditions may persist for much of Mon night with the lowest conditions most likely on the coast. KBOS TAF...Moderate confidence in TAF. KBDL TAF...Moderate confidence in TAF. Outlook /Tuesday through Thursday/...Moderate confidence. Tuesday... Potential for brief MVFR vsbys in scattered showers in the afternoon especially over Western/Central MA. South winds remain less than 20 knots. Isolated thunder possible. Wednesday-Thursday... VFR. Scattered afternoon showers. Westerly winds with gusts less than 20 knots.
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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 Monday/... Today and Tonight...High confidence. Weak ridge of high pressure will keep winds/seas below Small Craft Advisory thresholds. Monday...High confidence. An approaching low pressure south of New England will increase the pressure gradient toward daybreak. Enough southeast fetch may develop across our southwest outermost waters for some marginal 5 foot seas starting around 12z Monday. It is still too early to hoist any marine headlines for a marginal 3rd period event. Outlook /Monday Night through Thursday/...Moderate confidence. Monday night into Tuesday... Seas relaxing below 5 feet through the timeframe as NE winds back to the south. Gusts remain below 20 kts. Vsbys lowered in showers and iso thunder. Wednesday through Thursday... Winds less than 25 knots and seas less than 5 feet through the period. Scattered afternoon showers possible. && .TIDES/COASTAL FLOODING... Latest observations show a lingering surge about 0.7-0.9 feet above normal tides. We did have a few minor coastal flood reports very early this morning along the eastern MA coast. The higher of the two high tides today will be around midnight Monday. As we are even further removed from the highest of the recent high tides, will let the next shift reevaluate the need for another Coastal Flood Advisory or Statement. Any coastal flooding should be minimal. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/Belk/Dunten NEAR TERM...Frank SHORT TERM...Belk LONG TERM...Dunten AVIATION...Frank/Dunten MARINE...Belk/Dunten TIDES/COASTAL FLOODING...Belk

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