Area Forecast Discussion
Issued by NWS Boston, MA

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129 FXUS61 KBOX 220732 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 332 AM EDT SUN MAY 22 2016 .SYNOPSIS...
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Coastal low pressure brings wet weather today as it passes well offshore of Nantucket. The low continues on to Nova Scotia tonight. We get a break in the wet weather tonight and Monday. A second low pressure then moves up the coast and brings more scattered showers Monday night and Tuesday. A warming trend begins Wednesday, with showers diminishing. A front lingers just to our north late next week.
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&& .NEAR TERM /THROUGH TODAY/...
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Low pressure was centered about 200 miles south of Providence overnight and moving northeast. Radar showed the rain shield from this weather system over Cape Cod and Islands and also trending northeast. Meanwhile showers were moving across Connecticut and Western/Central MA. These are tied in with the upper trough and cold pool which hangs back across New York and PA. The coastal low will pass about 125 miles southeast of Nantucket around midday. Expect light rain to continue over the Cape and Islands until this passage. Also potential for drizzle or sprinkles in Eastern MA through the morning. The potential then diminishes this afternoon as the low moves off. Showers from the NY trough will remain a concern in Western sections this morning. Lapse rates linger around 6.2C/KM this afternoon but stability parameters remain mediocre at best. So the chance of showers in the west should diminish this afternoon. Northeast surface flow off the water will slowly turn north this afternoon but should be enough to keep eastern areas in the 60s. Farther west the light flow and breaks of sun with 6-7C temps aloft supporting surface temps around 70.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
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Upper closed low settles in to place centered over Virginia with the closed circulation extending up the coast to New England. This circulation along with plently of moisture between 850 mb and 700 mb should maintain at least partly cloudy skies Sunday night and Monday. Dew points in the 40s should keep surface temps in the mid 40s to lower 50s. The sunshine that does occur on Monday should bring surface temps into the upper 60s and lower to mid 70s inland. A developing northeast wind will move ashore on the Cape and Islands and East Coastal Massachusetts and keep max surface temps in the upper 50s and 60s there. Upper jet moving around the closed low will move the associated surface low north on Monday. The favorable left exit region of this jet, which will support lift and shower development, will also move north. Current model information holds this feature south of New England through much of Monday. It may come close enough to bring a few showers to the South Coast late in the day. Most if not all of the showers should wait until Monday night.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Highlights... * Unstable and wet, but milder, Tuesday. * Warmer still, and drier Wednesday * Warmer still late week, but potentially unsettled. Overview and Model Preferences... Still looking at an amplified pattern, with our region beneath an anomalous cutoff through early next week. A strong downstream blocking ridge should shift east just enough mid week to permit this cutoff to eventually dissipate toward the end of next week. As it does, we get into more of a zonal mid level flow, which should stall a frontal boundary just to our north late next week. As usual with these patterns, models are in very good overall agreement with the trends and evolution. The portion of the forecast most likely to be an issue will be the timing. Will favor a consensus approach to smooth over some of these timing differences, which are more pronounced late next week. Details... Monday into Tuesday... Core of the upper level cold pool moves over southern New England Monday night into Tuesday. In addition, a second surface low pressure should move into our region Monday night into Tuesday. This will mean another period of clouds, along with some showers. Timing- wise, expecting most of these showers to continue Monday night, peak Tuesday morning, then gradually move away Tuesday evening. This timing could change with later forecasts. Isolated thunderstorms are possible, despite modest CAPE values less than 500 J/kg. This is just due to the strength of the cold pool aloft. Wednesday... Brief ridge of high pressure to our south takes over, leading to drier conditions and more summer-like temperatures. Will have to consider seabreeze potential some more. At this point, it appears the synoptic flow should be just strong enough to prevent lower temperatures along most of the east coast of MA. Cape Cod and the islands, as well as Cape Ann, will likely not share in as much warmth. Thursday through Saturday... Warm front shifts into Canada and northern New England with return flow and ridging, Thursday. This front looks like it will get stalled just to our north late next week, due to the nearly zonal flow aloft. Looks like a good warm sector setup, with potential destabilization possible. The question will be available moisture. Thinking diurnally-driven showers and thunderstorms are possible, and will feature rainfall chances as such, especially Friday into Saturday across the western half of southern New England. Summer-like temperatures should continue.
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&& .AVIATION /07Z 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 Monday/... Today... Moderate Confidence. Mixed MVFR/IFR cigs and light showers will move northeast today and bring improvement to VFR by afternoon. Gusty winds over Cape Cod and Islands may reach 25-30 knots for a time this afternoon/evening. Tonight... Moderate Confidence. Mainly VFR. Potential for MVFR from low ceilings on Cape Cod and Islands. Monday... Moderate Confidence. VFR with potential patches of MVFR in showers. North flow turns from the Northeast during the day especially along the East Massachusetts coast and across Cape Cod and Islands. This will bring a low chance of MVFR cigs/vsbys in light showers. A more substantial area of showers will move up from the south during the day, reaching the South Coast toward evening. KBOS TAF...Moderate confidence in TAF. KBDL TAF...High confidence in TAF. Outlook...Monday night into Wednesday. Monday night into Tuesday...Moderate Confidence. Although not a complete washout, periods of showers will continue across the area with northeasterly flow. This also suggests low clouds. Therefore, periods of MVFR/IFR are likely, but it`s possible occasional VFR, especially across the interior, will occur. Wednesday...High Confidence. Mainly VFR with high pressure. Thursday...Moderate Confidence. Mainly VFR. Scattered MVFR in showers possible, mainly west of KLWM-KORH-KIJD.
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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. Today... Moderate confidence. Low pressure passes about 125 miles southeast of Nantucket early afternoon. This will bring light rain to the southern waters this morning. Winds will increase from the northeast toward midday and afternoon with gusts 25 to 30 knots. Seas will build today with 5 to 9 feet on the outer waters and the RI waters. Small Craft advisory continues for most of our waters through the day. Tonight... Moderate confidence. Low pressure moves off across Nova Scotia. This will turn winds from the north with diminishing speeds. But seas will linger at 5 to 9 feet, mainly across the outer waters. Small Craft advisory continues on most waters due to seas. Monday... High confidence. North winds diminish in the morning. Lingering 5 to 7 foot seas on the Eastern Outer Waters. Low pressure moves up from the south during the late afternoon and spreads showers across the Southern waters with briefly low vsbys. This will also turn winds from the northeast, but speeds will remain at or below 20 knots. Small Craft Advisory will continue to be needed on the Eastern Outer Waters. Outlook /Monday Night through Thursday/... Tuesday...Moderate Confidence. Winds still remain below 25 kt, but a second approaching low pressure will allow for building southerly swell. Small craft advisories may need to continue for some waters. Wednesday into Thursday...High Confidence. High pres briefly builds over the waters, mainly quiet boating weather expected.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ232>234. Small Craft Advisory until 8 AM EDT Monday for ANZ231-250-251- 254. Small Craft Advisory until 5 AM EDT Monday for ANZ235-237. Small Craft Advisory until 8 AM EDT Monday for ANZ255-256.
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&& $$ SYNOPSIS...WTB/Belk NEAR TERM...WTB/Belk SHORT TERM...WTB LONG TERM...Belk AVIATION...WTB/Belk MARINE...WTB/Belk

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