Area Forecast Discussion
Issued by NWS Boston, MA

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553 FXUS61 KBOX 250903 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 403 AM EST Sat Feb 25 2017 .SYNOPSIS...
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Mild air remains over the region today. A strong cold front will cross the region tonight, bringing showers and a low chance for thunderstorms as this front passes. Blustery conditions with temperatures close to seasonal normals expected for Sunday and Monday. A couple of weather systems will bring periods of wet weather Monday night into Thursday. Colder air looks to return late next week.
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&& .NEAR TERM /THROUGH TODAY/...
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Low clouds and fog over the region will diminish during the morning. After the cloudy start, expect partial clearing later this morning and for part of the afternoon. Digging shortwave over the Great Lakes will eject northeast into Canada. The digging turns the upper flow more northerly. A cold front over the eastern Great Lakes will sweep east across NY and PA during the day. Precipitation along the front will mostly move north/northeast into Canada and only slowly shift east. Best chance of showers from this front will be late afternoon and in Western MA/Western CT. Model guidance has been consistantly cool compared with verification the past couple of days. Temps at 925 mb support max sfc temps in the mid to upper 60s. The warmer guidance members also aim at this range.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/...
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The cold front arrives in the Hudson Valley around 6-7 pm and crosses into western New England around 8-9 pm...Central sections 9-10 pm...and eastern New England 10 pm to midnight. This front will be supported by the sharp upper shortwave. Airmass stability will decrease through the evening...for example, Totals will climb into the lower 50s. This supports the concept of sufficiently unstable conditions for a few thunderstorms as the cold front approaches and moves through. The greatest risk for tstms would be in Western MA and Western CT where the low level inflow is least maritime. Low level southerly winds will increase during the afternoon, so that by evening we expect a 50-knot jet at or below 5000 feet. Confidence is not high as to how much of that wind may be brought to the surface in gusts during showers/tstms, but its presence suggest a chance of strong wind gusts this evening...possibly isolated damaging wind. Greatest risk would again be in western areas early tonight. Precipitable water fields continue to advertise values a little over an inch, which is 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 behind a 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 late at night. Wind gusts at that time will have a potential of reaching 30-35 knots. Sunday...High confidence. The shortwave trough moves offshore Sunday morning. The last of any pcpn should end by that time. So Sunday shapes up to be a dry day as high pressure builds in from the west. Cold advection continues during the day. Mixing due to this advection will tap winds aloft of 25-35 knots and possibly a few areas of 40 knots. These winds will diminish during the afternoon as the high pressure area approaches. Temps aloft chill behind the front, but hover on Sunday at levels that support sfc max temps around 40 or the lower 40s. Given the morning temps starting in the 30s, we have forecast max temps in the upper 30s to mid 40s.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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Highlights... * Blustery and more seasonable temperatures Sun and Mon * Low pressure will bring scattered rain and/or snow showers Tue * Another low passes N of New England with rain showers possible Mon night through Wed night * A cold front may cause rain showers to mix or changing to snow showers Thursday Overview... Noting rather good agreement with the 12Z model suite on development and movement of weather features across the region into Tuesday. Beyond this, model solutions diverge, mainly due to continued progressive upper level steering flow across the lower 48, causing timing and track issues amongst the individual models. Appears the 12Z GFS is on the fast side of the guidance in moving systems along in the fast flow. Overall, looks like temps will continue to run warmer than seasonal normal, with the mildest temps around the Mon-Wed timeframe at this point. Signals beyond this appears to see a return to near or below normal temps by late next week. However, timing and track of the systems during that timeframe remain in question due to the fast steering flow aloft. Details... Monday...Moderate to high confidence. High pressure ridge builds offshore as center of the associated high will push off the mid Atlantic coast. Winds back to SW during the day on the backside of the high. Another dry day with some gusty winds, up to 20-30 mph possible around midday or during the afternoon, highest along the S coast, Cape Cod and the islands. Mid and upper level moisture will start to work in aloft, so clouds will be increasing during the afternoon. Highs will range from the mid 40s across the higher inland terrain to around 50 across the coastal plain. Monday night through Wednesday...Moderate confidence. As mentioned above, model solutions begin to diverge during this timeframe. Noting high pressure settling off the SE U.S. coast. Mid level steering currents shift to a more SW direction with broad ridging over eastern Canada into the western Atlc. Noting weak short waves in this flow, with a wide variety of tracks for each individual wave. At the surface, will see low pressure wave shift NE in the mid level flow late Mon night and Tue. Most of the energy remains just offshore, but will see slug of moisture cross the region. have carried slight chance to chance POPs, with the best chance for showers during Tuesday. Looks like models signal mainly rain, but could see some mixed rain/snow showers at the onset of precip overnight Mon night. QPF values on order of 0.1 to 0.2 inches during Tuesday. Mild air remains in place on Tuesday, so highs will be in the mid 40s to around 50. Precip will linger Tue night as first wave moves off the Mass coast into the Gulf of Maine. However, another low looks to cross out of the Great Lakes into southern Quebec late Tue night into Wed bringing another slug of precip to the region. SW winds remain in place, so temps will not fall much Tue night. Lows will be mainly in the 30s. Could see a brief period of mixed rain/snow showers along the Mass/NH border overnight. On Wednesday, the low shifts E-NE, but another trailing front will keep the chance for precip across the region into Wed night, but timing is in question. Another question is whether a secondary low will form along this front as it pushes toward the mid Atlantic coast or even a bit further north. This could delay the exit of the precip. Expect highs in the upper 40s to mid 50s, so expect rain showers to continue. Thursday...Low confidence. Low pressure looks to push into eastern Canada, with trailing cold front passing offshore. May see lingering rain and/or snow showers before ending. Timing of front`s exact track exiting the region still very much in question. 12Z model suite and ensembles signaling colder air working across the region by Thu night. Temps will be cooler than earlier in the week, but will be close to seasonal normals. Friday...Low confidence. For now, should see mainly dry but cold and blustery conditions. Highs may run about 5 degrees below seasonal normals.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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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 Sunday/... Today...Moderate confidence. Stratus lingers across all areas early this morning, with cigs between 500 and 1500 feet. Lowest cigs are along the south coast. Vsbys, after taking a dramatic dip at 10 pm, improved overnight to either MVFR or better. Expect the low cigs to continue through sunrise and then break. While low vsbys will be spotty, their potential will linger until sunrise as well. Most areas will have unrestricted vsbys by morning. VFR continues through most of the day. Increasing south winds at 2000-4000 feet through the day, with 50 knots possible over the CT Valley by 5-6 pm. This may bring low level wind shear to that area. Showers and scattered thunder will approach western areas after 21Z/4 pm, with IFR conditions possible in some showers. Some of the heavier showers/storms could bring strong wind gusts to the surface. Tonight...Moderate confidence. A cold front sweeps west to east across the region between 6 pm and midnight. Showers and widely scattered thunderstorms are possible. This means condtions may briefly lower to IFR in any showers or thunderstorms. We continue to expect low level wind shear as well as a chance of strong wind gusts with showers/storms as that 50 knot low level jet sweeps across ahead of the cold front. The best chance for this will continue to be in Western MA and CT early in the night. Behind the cold front, winds will shift from the west and west- northwest. Colder air moving in behind the front will allow strong WNW gusts to work in by late night, with speeds of 30 to 35 knots possible. The colder air may also bring a brief change from rain to snow at the western edge of the precipitation. Sunday...High confidence. VFR. West-Northwest winds will continue to gust 25-35 knots. There are pockets of 40 knots shown in our forecat guidance, so a few of these stronger winds are possible. Winds will diminish by mid to late afternoon. KBOS TAF...Moderate confidence in TAF through 12Z then High confidence in TAF through 25/22Z. Moderate confidence after 22Z. KBDL TAF...Moderate confidence in TAF through 12Z then High confidence in TAF through 25/22Z. Moderate confidence after 22Z. Outlook /Sunday Night through Wednesday/... Monday...High confidence. VFR. W-SW winds gusting to 20-25 kt, highest along the coast and over the higher terrain, diminishing Mon night. Monday night-Wednesday...Moderate confidence. Areas of MVFR conditions possible in -SHRA and/or -SHSN.
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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 Sunday/...High confidence. Today...High confidence. Increasing southerly winds through the day, with gusts to 25 knots mid to late afternoon. Seas will increase through the day with 5 to 6 foot heights on the southern waters by mid to late afternoon. Tonight...Moderate confidence. A cold front sweeps across the waters the first part of the night. This will bring showers and a widely scattered thunderstorm. The showers may tap strong winds at 2000 to 4000 feet above the surface and bring them to the surface in strong southerly wind gusts. Seas build to 5-8 feet on the exposed waters of the south and the outer waters of the east. Behind the front, winds shift from the West or West-Northwest and bring cooler air. Winds late tonight should gust 30 to 35 knots. Seas will continue at 5 to 8 feet. Sunday...High confidence. West-Northwest winds continue to gust 30 to 35 knots during the morning and early afternoon. Winds may slowly diminish during the later afternoon. Seas will linger at 5 to 8 feet on the exposed waters. Outlook /Sunday Night through Wednesday/... Monday...High confidence. Winds back to SW gusting up to 25-30 kt highest on the eastern outer waters. Seas remain around 5 ft. Will likely hold on to small craft conditions through Mon night over the outer waters. Good visibilities. Tuesday through Wednesday...Low to moderate confidence. Expect E-SE winds gusting to 20 kt on Tue, then shifting to SW on Wednesday. Gusts will increase to around 25 kt late Wed/Wed night, along with seas building to at or above 5 ft over the open waters. With approaching system to the west could see lower vsbys in rain and fog.
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&& .HYDROLOGY... We will need to monitor rising water levels across southern New England into early next week. Much, if not all, of our snowpack has, or will have, melted. There is still much more snowpack upstream, over northern new England, that will push into the headwaters and head downstream. Some river levels could approach action stage. && .CLIMATE...
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RECORD HIGH TEMPS FOR YESTERDAY BOS 73/2017 - previous record 70/1985 PVD 72/1985 - topped off at 71 degrees (no record) BDL 73/1985 - topped off at 72 degrees (no record) ORH 69/2017 - previous record 67/1985 RECORD HIGH MIN TEMPS FOR YESTERDAY BOS 49/1930 - bottomed out at 46 (no record) PVD 45/2017 - ties previous record of 45/1984 BDL 43/1981 - bottomed out at 42 (no record) ORH 48/1985 - previous record 46/1985 RECORD HIGH TEMPS FOR TODAY BOS 65/1930 PVD 69/1976 BDL 70/1976 ORH 64/1976 RECORD HIGH MIN TEMPS FOR TODAY BOS 46/1891 PVD 45/1930 BDL 45/1930 ORH 37/1996, 1984, 1976 DEW POINTS OF NOTE FOR YESTERDAY BOS Max Dew Point 54 ties highest for date set in 1985 PVD Max Dew Point 53 is highest for date. Previous high 50/1990 BDL Max Dew Point 54 is highest for date. Previous high 49/1990 ORH Max Dew Point 53 is highest for date. Previous high 48/1985
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...Dense Fog Advisory until 7 AM EST this morning for MAZ020>024. RI...Dense Fog Advisory until 7 AM EST this morning for RIZ002>008. MARINE...Gale Watch from late tonight through Sunday evening for ANZ230>237-250-251-254>256.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT HYDROLOGY... CLIMATE...

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