Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271005 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 605 AM EDT Thu Oct 27 2016 .SYNOPSIS... High pressure will push offshore this morning. As low pressure approaches from the west, a wintry mix of precipitation will develop across western and north central areas by late morning. The mixture will change to all rain as temperatures rise by late today. Low pressure will intensify as it moves across the region tonight and early Friday, bringing periods of heavy rain, patchy fog and scattered thunderstorms, along with strong winds along the coast. Drying trend Friday but becoming breezy behind departing low. A cold front may bring a few showers to the region Saturday afternoon and evening. Low pressure may form on this front and bring the risk for a period of rain to the area Sunday. Dry much of next week with temperatures cool Monday but becoming mild Tue and Wed. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Conditions remain dry across the region at 09Z, except for lingering scattered ocean effect rain showers over the outer Cape and Nantucket early this morning. Expect the showers to end by late morning as winds shift to NE and diminish. Elsewhere, high clouds remain across the region. High pressure ridge moves offshore this morning. Strong overrunning shifts E as low pressure shifts across NY state today, with a warm front trailing ahead. Mid and high clouds will continue to thicken during the day. Enough lift and increasing low level moisture as winds shift to E-NE during the day will cause precipitation to push into the region. May take some time to reach to reach the ground, with temp/dewpt spreads from 5 to 10 degrees. Dewpts will slowly rise during the morning across central and western areas, so precip should develop there. Temps at 09Z mainly in the 20s across central and western areas, and will be slow to rise this morning. Will see mixed rain/snow as precip starts especially across N central and W Mass into N central CT. AS the winds veer during the day, precip will eventually change over to all rain except across the higher terrain, generally the E slopes of the Berkshires. Could see some light snow accumulations AOA 1000-1500 feet through most of the day. With the high dewpoint depressions, will see evaporative cooling as the precip commences. Temps will remain chilly through the day, ranging from the mid and upper 30s across the E slopes of the Berkshires to around 50 along the immediate E coast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Will see rapidly changing conditions as a secondary low develops along the triple point of the frontal system as it pushes into the region this evening. Strong low level jet develops as it wraps around the low and approaches the region, on the order of 50 kt at 4-6Kft. 00Z short range models remain in very good agreement in bringing this low across overnight, as well as rapidly increasing SE winds mainly across E Mass into south coastal RI. Wind advisories have been issued from E coastal and SE Mass into SE RI and Block Island. The low will move steadily across the region, so will see about 6-9 hour window of strong winds. Could see gusts up to 45-55 mph, highest across E coastal Mass. Expect the strongest winds between 05Z and 11Z, though could linger a bit longer across the Cape Ann region. Winds will quickly shift to SW as the low pushes E, but when the shift occurs still in question. Excellent inflow of low level moisture along with the deepening of the low across the region will bring periods of heavy rain onshore. QPF amounts on order of 0.5 to 0.8 inches with some locally higher amounts are forecast. May see some brief localized flooding in any heavier rainfall, generally urban and poor drainage. Will also see good elevated instability in place, so have also mentioned the low risk for a band of scattered thunderstorms rotating across central and eastern areas overnight. With the overall E-SE wind flow in place through the night, temps will bottom out early tonight before holding steady or slowly rising after midnight. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... 4 am update... Highlights... * Temps more seasonable this period * Risk of a few showers late Sat, a more widespread rain Sunday? * Mainly dry and seasonable much of next week Friday... At 12z triple pt low somewhere along northeast MA coastline and continuing to deepen/strengthen as mid level low approaches from NY state. Dry slot thru the region so drying trend develops with just some leftover showers across northern-northeast MA early Fri morning. However system becomes vertically stacked by afternoon as mid level low captures surface reflection off the NH/ME coast. This may result in comma head showers rotating back into northeast MA and clipping the outer Cape Fri aftn. Elsewhere dry weather should prevail along with increasing northwest winds as low continues to deepen off NH/ME coast. Probably more clouds than sunshine given cyclonic flow aloft persisting across the region. High temps will likely be observed in the morning especially across RI and eastern MA where leftover warm sector will yield morning highs of 55-60. Low to mid 50s elsewhere with upper 40s higher terrain. Weekend... Uncertainty as models continue to struggle with amplitude of lead (Saturday) and trailing (Sunday) northern stream short wave energy. As of now models bring low pressure across northern New England Sat with attending cold front entering southern New England late Sat and Sat night. This may be accompanied by a few showers but much of the day and night will remain dry. Then on Sunday both GFS and EC suggest trailing northern stream short wave energy will be robust enough to spawn a weak frontal wave on the front before boundary exits southern New England. This would yield a risk of rain overspreading the region Sunday from west to east. 00z GEFS ensembles have shifted in this direction as well. Given time range and uncertainty will follow a model blend and trend the forecast toward Sunday having the higher probability of rain of the two weekend days. Temps will be more seasonable than recent days with highs both Sat and Sun 55-60. Although if frontal wave verifies Sunday could be the cooler day given precip potential Monday thru Wednesday... Brief cool down Sunday night and Mon behind departing northern stream short wave. However temps rebound nicely Tue and Wed as subtropical ridge over the southeast states builds northward up the Eastern Seaboard. Mainly dry this period with a low risk of showers sometime around Wed as northern stream energy and attending cold front move into New England and begin to erode the northern portion of this subtropical ridge. && .AVIATION /10Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Through 12Z...High confidence. Mainly VFR. Low end VFR to MVFR CIGS across outer Cape Cod and Nantucket with scattered ocean effect rain showers. N winds will diminish, then will begin to shift to NE toward daybreak. Today...High confidence in trends, lower on timing. Area of light snow and rain moves into central and western areas by mid morning. Mixed precip should change to rain as winds shift to E-SE and temperatures rise. Mixed -RA/-SN may lingers across the E slopes of the Berkshires with MVFR CIGS/VSBYS mainly around or after 16Z- 18Z. Should not see snow accumulations on runways, but a light coating is possible across the higher terrain of the Berkshires (mainly AOA 1000-1500 feet). Should remain mainly VFR through midday, then CIGS/VSBYS lower to MVFR to local IFR from W-E during the afternoon. Should remain mainly VFR across E Mass until evening. Tonight...Moderate confidence in trends, lower for timing. Expect mainly MVFR conditions with areas of IFR in rain and fog. May see leftover mix of snow along the E slopes of the Berkshires early, but temps will slowly rise overnight so should end. Rain will be heavy at times, along with brief period of scattered thunderstorms mainly across central and eastern areas around or after midnight. E-SE winds increase across RI/E Mass, with gusts up to 30-40 kt mainly around or after midnight. LLWS likely, especially between 05Z and 12Z when winds shift from SE to SW-W as low pressure moves E. KBOS TAF...High confidence in trends, lower confidence in timing. KBDL TAF...High confidence in trends, lower confidence in timing. Outlook /Friday through Monday/... 4 am update... Friday...Moderate confidence. Areas of MVFR cigs/vsbys in showers early, but trending VFR during the day. Northwest winds increase with gust potential 30 to 40 knots. Saturday-Sunday...Low confidence. VFR likely Sat with perhaps a period of marginal MVFR in scattered showers late Sat/Sat night. Possible MVFR-IFR Sunday across CT/RI and southeast in periods of rain. Monday-Tuesday...Moderate to high confidence. VFR and mainly dry weather. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...High confidence. Through 12Z...N winds less than 15 kt will shift to NE toward daybreak. Seas 4 ft or less. Scattered ocean effect rain showers will continue across outer Cape Cod and Nantucket as well as Cape Cod Bay and the nearby coastal waters. Some brief visibility restrictions at times. Today...Winds shift to E-SE during the day as low pressure approaches. Wind gusts may approach small craft criteria on the waters S of Block Island by evening. Seas will remain below 5 ft. Visibility restrictions move in during the afternoon in developing light rain and patchy fog. Tonight...SE winds will rapidly increase, gusting to gale force by late this evening. Gale warnings have been issued. Seas will build up to 6-8 ft by around midnight across the open waters, then will push toward south facing near shore waters as they continue to build overnight. Visibility restrictions in rain and patchy fog. Low chance for thunderstorms. Outlook /Friday through Monday/... 4 am update... Friday...Moderate confidence. Gale center near Cape Ann early Fri moves slowly into Gulf of ME Fri afternoon. WNW gales all waters. Saturday-Sunday...Low confidence. Southwest winds 20-30 kt Sat ahead of approaching cold front. Wind shift Sunday morning to north behind departing front. However boundary is slow to depart as low pres may form on the front over NJ and then tracks south of Long Island Sun aftn and then across Georges Bank Sunday night. Monday-Tuesday...Moderate confidence. Modest north winds Mon behind departing low pressure. Light winds Tue as high pres crest over the area. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Frost Advisory until 9 AM EDT this morning for MAZ007-015-016- 019-022. Wind Advisory from 1 AM to 10 AM EDT Friday for MAZ007-014>024. Freeze Warning until 9 AM EDT this morning for MAZ014-018-020. RI...Wind Advisory from 11 PM this evening to 5 AM EDT Friday for RIZ007-008. Frost Advisory until 9 AM EDT this morning for RIZ005-007. Freeze Warning until 9 AM EDT this morning for RIZ001>004-006. MARINE...Gale Warning from 11 PM this evening to 11 AM EDT Friday for ANZ231>234. Gale Warning from 1 AM to 9 AM EDT Friday for ANZ230. Gale Warning from 10 PM this evening to 5 AM EDT Friday for ANZ236. Gale Warning from 9 PM this evening to 9 AM EDT Friday for ANZ235-237. Gale Warning from 1 AM to 6 PM EDT Friday for ANZ250-251. Gale Warning from 11 PM this evening to 6 PM EDT Friday for ANZ254-255. Gale Warning from 9 PM this evening to 2 PM EDT Friday for ANZ256. && $$ SYNOPSIS...Nocera/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...Nocera AVIATION...Nocera/EVT MARINE...Nocera/EVT is the U.S. government's official web portal to all federal, state and local government web resources and services.