Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 131944 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 344 PM EDT Sun Aug 13 2017 .SYNOPSIS...
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High pressure brings dry weather into Monday. Moisture well ahead of an approaching cold front will allow for the chance for showers and thunderstorms Tuesday afternoon. Dry conditions follow for Wednesday. A warm front approaches Thursday and Friday, bringing increasing clouds, and scattered showers along with a few thunderstorms. Showers may linger into Saturday as low pressure approaches.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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400 PM Update...High confidence. Increasing pressure gradient as high pressure from the west approaches and cold front continues to move out east. This has resulted in a few gusts to near 15-20 MPH this afternoon. Otherwise diurnal cu continues to stream across the region as temperatures continue to warm into the 80s. A great day to be outdoors as dewpoints continue to fall into the 50s. While the cold front is offshore, radar is picking up on some sort of boundary near the canal. Appears to be a weak sea breeze per meso sites. However this should give way over the next hour as winds aloft pick up a bit. Tonight...High confidence. Surface high will move across the region tonight. With nearly clear skies and light winds, radiational cooling will take place. Many locations look to drop into the mid to upper 50s. Location near the waters and metro regions will stay slightly warmer. Anticipate another round of patchy fog to develop across the low lying regions. BUFKIT profiles suggest it will be rather shallow and should burn off with sunrise Monday. One thing to note is that with skies remain clear, should be a good night to view the Perseid meteor shower.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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Monday and Monday night... High confidence. Despite longwave trough pattern over the region, a mid-level ridge will move across southern New England on Monday. This will lead to dry weather and light winds. Surface high pressure will begin to move offshore during the later half of the day resulting in light winds/sea breezes for the coastlines. Otherwise, another pleasant day will be on tap as temperatures will be similar to todays as 850mb temps remain around 13-14C. Humidity will be low during the first half of the day, but return southerly flow will begin to inch dewpoints back into the 60s by the evening hours. Cloud cover will also be on the increase by the later afternoon/evening as approaching shortwave moves through the upper level flow. Return southerly flow will continue to increase the low level moisture across the region. Stalled boundary well south of Long Island will turn into a warm front and begin to move northward towards the region. This will increase the fog and stratus potential once again in the WAA pattern. Overnight lows will remain mild leading to lows in the mid 60s. Lower confidence on the shower potential for Monday night/Tuesday morning across the Cape and Islands. As this front gets closer, combined with the approaching surface trough from the west, there could be enough to bring some showers to the region if the front lifts north enough. The GFS/RGEM keep the front farther south compared to the EC/NAM. Thus went down the middle until models can sort out there differences.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/...
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Details... Tuesday...Moderate confidence. Early in the day should be dry, however models show a sharp moisture gradient to the south of Long Island and Nantucket. Precipitable water increases to 2 inches offshore with moisture pooling along a front well to the north of what as of today is TD8. If this gradient were to nudge further north there could be some rain over the Islands and possibly Cape Cod. Otherwise, dry across the area Tuesday morning. Continue to anticipate a potent short wave moving thru the area later in the day. Timing of the short wave, preceded by diurnal heating, should allow for scattered showers and thunderstorms. Precipitable water ranges from 1 to 1.5 inches, not very high. However continue to note LIs around 0 to -1 ,along with steep low level lapse rates. SPC places interior southern New England in a marginal risk for severe weather. Will go with chance pops within the area denoted by a marginal risk for severe. Tuesday afternoon should remain dry closer to the shoreline. Convection subsides around sunset. Wednesday...Moderate confidence. Cold front sinking out of Canada pushes southward thru southern New England during Wednesday, bringing a dry airmass into the region. Moisture is quite limited even to start off the day, so anticipating this frontal passage to be dry. High pressure prevails Wednesday night, may see increasing clouds late. There is also a chance for rip currents Wed-Thu along south coastal MA/RI as well due to swell from TD8 and its projected forecast. Thursday thru Friday...Low to moderate confidence. Expect increasing clouds Thursday as low pressure approaches. However there is considerable model differences with respect to the timing of this system`s approach and subsequent timing on chances for rainfall. 12Z ECWMF is quicker with the surface low, tracking it over New England during Thu. Hence the ECWMF brings a soaking rainfall to our area Thu-Thu night. 12Z GFS and the 12Z GFS ensemble mean are much slower with the low`s approach, with high pressure to the east delaying deeper moisture and precip arrival until Thu night/Fri. Plan to go with chance pops for Thu into Fri with this forecast package, with highest pops Thu night. As low pressure nears, PWATs increase to near 2 inches and low instability brings the potential for isolated thunderstorms. Saturday-Sunday...Low confidence. Much uncertainty for next weekend regarding timing of possible showers, but do not anticipate the weekend will be a washout. Model consensus brings the better chance for showers on Saturday, drier for Sunday.
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&& .AVIATION /20Z 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 Night/... Before 00z...High confidence. VFR with a few gusts to near 15 kts this afternoon. Tonight...High confidence. VFR. Patchy MVFR fog possible in low lying terminals. Monday...High confidence. VFR. Seabreeze along the coasts from mid morning through the afternoon. Monday night...Moderate confidence. Mainly VFR with some MVFR/IFR cigs developing across the southern terminals as low level moisture streams in from the south. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Tuesday through Friday/...Moderate confidence. Tue-Thu...Moderate confidence. Mainly VFR conditions Tue-Thu. May see areas of MVFR-IFR CIGS/VSBYS in late night/early morning fog each night. Brief MVFR CIGS/VSBYS across the interior Tuesday afternoon/evening. Scattered showers with local MVFR conditions from W-E during Thursday. Thu night-Fri...Low confidence. A period of rain/showers is possible within this timeframe. East winds could produce a period of MVFR/IFR clouds/vsbys with patchy fog.
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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. Short Term /through Monday Night/...High confidence. Building high pressure across the waters tonight and tomorrow will relax seas to below 5 feet. Thus good boating weather is expected for Monday. Increasing low level moisture may lower vsbys across the southern waters late Monday night in fog. Outlook /Tuesday through Friday/...Moderate confidence. Winds expected to remain below small craft criteria through Thursday. Seas 4 ft or less Tuesday, and probably remain at 4 ft or less Wed-Thu. However, there is a chance for increasing swells along south coastal MA/RI Wed-Thu, with TD8 forecast to become a Tropical Storm and remain well south of the area. There is also a chance for rip currents Wed-Thu along south coastal MA/RI as well. Return of patchy late night/early morning fog across most waters Tue and Wed nights. Scattered showers are possible Thu-Thu night. During Fri an approaching low pressure system may allow for seas and E/NE winds to increase to SCA thresholds. Reduced visibility possible in scattered showers.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ254-255. Small Craft Advisory until 8 PM EDT this evening for ANZ235- 237. Small Craft Advisory until 11 PM EDT this evening for ANZ256. && $$ SYNOPSIS...Dunten/NMB NEAR TERM...Dunten SHORT TERM...Dunten LONG TERM...NMB AVIATION...Dunten/NMB MARINE...Dunten/NMB

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