Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
196 FXUS61 KBOX 240847 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 347 AM EST Fri Feb 24 2017 .SYNOPSIS...
-- Changed Discussion --
High pressure over the Atlantic Ocean will maintain dry and unseasonably warm conditions through Saturday. A warm front near northern Massachusetts may bring a few showers across that area this morning before moving off to the north. A strong cold front will cross the region Saturday night, bringing showers and areas of fog. There will be a low chance for isolated thunderstorms as the front passes. Dry but blustery conditions return on Sunday into Monday with normally cool temperatures. A couple of fast moving low pressure areas may bring unsettled conditions to the region around the middle of next week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
Light flow makes it difficult to pinpoint the stalling cold front/eventual warm front. But a rough estimate from weak wind speeds would place it across Srn VT and Srn NH. In any case, it will start the day either in Northern Mass or close by to the north. A couple of showers moved up through NW CT into Central MA overnight, but otherwise the early morning features partly cloudy skies and areas of fog. A 40-50 knot southwest low level jet is riding up and over the top of the stalled front...out over the Eastern Great Lakes. This has generated an area of showers which is sliding northeast up the front. Meanwhile an upper ridge builds through the day over New England with a southwest upper flow in place. This should nudge the stalled front farther north and steer most of the showers across VT and NH. Northern MA could get clipped during the mid to late morning, but even this chance should slide north with the departing warm front. Forecasting sky cover in New England in a wintertime southwest flow is always dangerous. Most of the sky cover in place over our area is either fog or convection moving with the front. Satellite shows many clear spots over us, and partly to mostly clear skies upstream to the southwest. Expect morning clouds to diminish with partly to mostly sunny skies in the afternoon. Mixing yesterday overachieved, reaching 700 mb on the evening Albany sounding while other sites showed mixing to between 800 and 850 mb. Mixing to 850 mb would support max temps today in the mid 70s! Meanwhile mixing to 900 and 925 mb would support max temps in the mid to upper 60s. This is still several degrees warmer than model guidance. With sunshine and an eye to yesterday, we will favor max temps in the mid and upper 60s...values of 62 to 68 inland and 50s along the south coast. Winds in the mixed layer show a max potential of 30 knots, but mixed values more favor 25 knots. We will again bump guidance up a bit to the favored values. Records for max temp and high min temp are listed in the climate section at the end of this discussion.
-- End Changed Discussion --
&& .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
Tonight... With Southern New England deep into the warm sector, we expect another mild dry night with areas of fog. Dew points in the warm sector remain in the 40s, which should keep temperatures no lower than that. Saturday and Saturday night... Shortwave ejecting into the Central Plains this morning is digging a surface low along the stalled front. This low is moving northeast into the Midwest. Models are consistant in moving this low northeast into Canada Saturday, eventually swinging a cold front through New England Saturday night. Low clouds and fog linger first thing Saturday morning, but should break and allow higher clouds to take over. There could be some breaks of sun with all of this, which would allow for a period of mixing especially around midday. Three forecasting concerns will be temps, winds, and precip. Even with modest mixing, temps aloft should again allow temps to climb to at least 60. With a period of dry weather and some sun late morning/midday, we opted to again forecast higher than guidance by several degrees. Temps in the mixed layer do support max sfc temps in the low to mid 60s. A south-southeast wind may take shape, which could hold down temps below these values in the coastal plain. Winds in the mixed layer show gust potential of 25 to 30 knots, and so we bumped gust values up a little from guidance. The cold front crosses NY and PA during the day, with the best upper dynamics in that area through the day. This suggests much of the daytime will be rain-free with increasing chance of showers later in the day. A strong primary low level jet is indicated just ahead of the cold front, with 40-50 knot winds. Also, appreciable instability is noted. for example there is a zone of Totals at 50-52 just ahead of the front. Finally, as the front sweeps through early Saturday night it will be accompanied by the right entrance region of the upper jet. We will continue to mention slight chance of thunder. Potential for strong wind gusts with any convection. Precipitable water values continue to show just over an inch, well above normal. But this is a narrow and fast-moving zone, so while showers may be briefly strong, total amounts should be 0.50 inches or less. Colder air rushes in late Saturday night following the cold front. It will be a race between the cold air and the departing showers, but a brief changeover to snow is possible at the end. Any accumulations should be limited, generally less than an inch and mainly over the higher terrain of the Berkshires and Worcester Hills. Finally, the colder air advection behind the front will bring mixing of strong WNW winds aloft to the surface. Wind gusts will have a potential late Saturday night of reaching 30-40 knots. One other aspect after this system passes will be rising water levels across the watershed into early next week. Much if not all the snowpack has or will have melted across this region, but still much more upstream that will push into the headwaters and head downstream. Will need to monitor in case some river levels approach action stage.
-- End Changed Discussion --
&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
Highlights... * Blustery and seasonably cool Sunday and Monday * Progressive steering pattern around the middle of next week may bring a few weather systems and unsettled conditions Overview... 12Z model suite remains in pretty good agreement through Sunday, then model solutions diverge greatly after this timeframe thanks to a redeveloping broad upper level steering pattern across the lower 48 through the middle of next week. Have low confidence in timing and track of individual systems from Mon through Thu due to the fast flow aloft. Strong H5 short wave moves quickly across the region late Sat and Sat night, with its associated cold front. Will see normally cool but blustery conditions move in for Sunday and Monday as high pressure moves across. Beyond this, really tough resolving sensible weather with low continuity amongst the model suite through the middle of next week. Monday is a good example, with the GFS continuing to develop a wave of low pres in the developing SW flow aloft, while the Canadian GGEM and ECMWF keep dry conditions. Do note some model to model consistency with a couple of systems during the Tue night to Thu timeframe, but timing is still in question. Used a blend of available guidance through Sunday with rather good confidence. Into next week, transitioned to the model ensembles which showed a bit better continuity than individual model solutions. Details... Sunday through Tuesday... Saturday...Moderate confidence. MVFR-IFR conditions in areas of fog and low clouds. May see spotty drizzle along the S coast Sat morning. Isolated TSTMS approach the E slopes of the Berkshires around 21Z-22Z, then shift steadily E Sat evening. Brief heavy rain possible across W Mass with any thunder. Precip mixing with or changes to -SN around midnight or so across the higher inland terrain ending after 06Z. May see local IFR-LIFR conditions in any -SN. Conditions improve rapidly toward daybreak across central and western areas. W winds gusting to 20-25 kt after midnight. High pressure builds to the mid Atlantic coast Sunday, keeping good shot of cold air advection working across in the W-NW wind flow at the surface and aloft. H85 temps drop from -4C (east) to -10C (west) at 12Z Sunday down to -9C to -11C at 18Z. Excellent low level mixing also works in, with a 50 kt jet at H85 moving across Sunday, and 30-35 kt jet at both H9 and H95. So, will likely see wind gusts up to 30-35 mph during the day Sunday, highest gusts across the higher terrain and along the coast. At least skies will be mainly sunny. Remains seasonably cool and blustery on Monday, but some big model differences especially on the 12Z GFS. This model continues to signal a fast moving weak system working NE around the backside of the departing high pres off the mid Atlantic coast Mon night and Tue. Low confidence continues. Most models showing a bit better continuity with another system in the Tuesday timeframe. Looks like good lift ahead of another warm front as low pressure moves across the Great Lakes. Again, looks like the GGEM and ECMWF are in better agreement with the GFS the outlier. Went with chance POPs with this system, though low confidence remains. Wednesday-Thursday... Upper level pattern remains progressive, with H5 trough migrating across the central U.S. during this timeframe. Timing of the associated low pres and cold front still in question, but looks like another decent shot of precip with it some time late Wednesday into Thursday. Lower than average confidence during this timeframe.
-- End Changed Discussion --
&& .AVIATION /07Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/... Today...Moderate confidence. Generally VFR. Areas of IFR/LIFR in fog through mid morning with improvement by mid morning. Scattered showers this morning may briefly produce 3 to 5 mile vsbys, with best chance over northern MA. Tonight...Moderate confidence. VFR with areas of IFR/LIFR developing in areas of fog. Saturday...Moderate confidence. Lingering IFR in morning fog, otherwise VFR. Showers approach from the west and are most likely between 21Z and 03Z in the west, and between 00Z and 06Z in the east. Conditions may briefly lower to IFR in any rain showers. Isolated thunderstorms are possible as this band of showers moves through. Rain may chance to snow in the higher terrain as it tapers off. Low level wind shear is possible in the evening with S-SW winds at 40-50 knots at 2000-3000 feet AGL. Winds shift from the west during the early night as a cold front sweeps through from west to east. WNW winds will become gusty overnight with gusts to 30 to 35 knots possible. KBOS TAF...Moderate confidence in TAF due to variable cigs in fog areas. Confidence improves after 14Z. KBDL TAF...Moderate confidence in TAF due to variable cigs in fog areas. Confidence improves after 14Z. Outlook /Sunday through Tuesday/... Sunday...Moderate confidence. VFR conditions. NW winds gusting to 25-30 kt, highest along the immediate coast and across the higher terrain. Monday...Low confidence. Mainly VFR conditions. SW winds gusting to around 25 kt, highest along S coast. May see local MVFR in isold -SHRA mainly S of the Mass Pike Mon afternoon/night. Tuesday...Low confidence due to timing of weather features. May see scattered -SHRA with local MVFR conditions. May mix with or change to -SHSN during the nighttime hours mainly across the higher terrain.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/...High confidence. South-Southwest winds today with brief gusts near 25 knots possible. Areas of poor vsbys in fog through mid morning. Winds diminish tonight. Seas remain below 5 feet through tonight. Saturday...Moderate confidence. Winds shift a little from the south-southeast and increase with gusts of 25-30 knots possible. Seas also build with heights 5-7 feet on the southern waters in the afternoon/evening. A cold front sweeps across the waters Saturday evening and early night with showers and isolated thunderstorms. Strong winds aloft may produce a couple of strong wind gusts in showers and storms. Winds shift behind the cold front. Winds from the west after midnight will have potential gusts of 30 to 35 knots. This would be borderline conditions for gales toward Sunday morning. A Gale Watch may be needed. Outlook /Sunday through Tuesday/... Sunday...High confidence. W-NW winds gusting to 25-30 kt across the open waters. Low chance for gale force gusts on the eastern outer waters. Seas up to 6-9 ft, though will slowly subside as winds diminish Sun night. Good visibilities. Monday-Tuesday...Low confidence due to timing of weather features. SW winds may gust to around 25 kt at times on the outer waters Mon and Mon night, then diminish Tue. Local visibility restrictions possible in scattered showers Mon night-Tue, though timing in question.
-- End Changed Discussion --
&& .CLIMATE...
-- Changed Discussion --
RECORD HIGH TEMPS FOR TODAY BOS 70/1985 PVD 72/1985 BDL 73/1985 ORH 67/1985 RECORD HIGH MIN TEMPS FOR TODAY BOS 49/1930 PVD 45/1984 BDL 43/1981 ORH 46/1985 RECORD HIGH TEMPS FOR SATURDAY BOS 65/1930 PVD 69/1976 BDL 70/1976 ORH 64/1976 RECORD HIGH MIN TEMPS FOR SATURDAY BOS 46/1891 PVD 45/1930 BDL 45/1930 ORH 37/1996, 1984, 1976
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT CLIMATE...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.