Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170230 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1030 PM EDT Mon Apr 16 2018 .SYNOPSIS... Drier air will move into southern New Eng overnight as a cold front moves off the coast. An upper level system will keep unsettled conditions across the region through mid week. A low pressure area will produce a period of chilly rain during Thursday. Lingering rain showers Thursday night may mix with or change to wet snow across northern Massachusetts. The weekend looks to be dry but with more below normal temperatures. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 10 PM update... Low pressure near Albany NY is moving northeast and extrapolates to Western Maine by 12Z/8 AM. Cold front extending south from the low will swing across Southern New England overnight. Regional radar shows showers over NY moving northeast. These will affect Western Mass until just after midnight, but should move off through NH overnight. Winds have diminished to 15 knots or less. Meanwhile surface flow remains from the south. Fog has developed across northern Mass and may spread farther south. Expect this fog to linger until the cold front swings through, at which point the lower dew points should dry the air sufficiently to diminish the fog. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Tuesday... Mid level low moves over SNE with cyclonic flow aloft. Deep moisture in the column combined with steepening 925-700 mb lapse rates will result in a few showers developing, especially across the interior. Otherwise, any morning sunshine will quickly give way to mostly cloudy skies. Temps still about 10 degrees below normal for this time of year. W/SW flow with gusts to 20-25 mph at times. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Highlights... * Chilly rain appears likely for Thursday, possibly lingering into Thursday night * The coming weekend looks to be dry but cooler than normal Discussion... The large scale pattern across greater North America is dominated by large closed low centers, typical of early spring. A closed low about northern New England early in this period will drift across the Canadian maritimes later in the week. For the most part, temperatures are expected to remain somewhat below normal for most of this period. One precipitation event is expected on Thursday and possibly into Thursday night as a fairly vigorous short wave trough approaches from the west and eventually becomes absorbed into the Canadian Maritimes closed low. As far as the surface track, the GFS and Canadian models bring it across southern New England. The ECMWF, both the 00Z and 12Z operational runs and their respective ensembles, tracks the surface low just south of New England and then NE into the eastern Gulf of Maine. The UKMET and NAM also keep the low track south of New England. The track differences would be reflected in stratiform versus showery precipitation and temperatures. For now, we are leaning toward the ECMWF solution with temperatures in the 40s during most of the day Thursday and a period or two of stratiform rain along with drizzle. The thermal profile looks like wet snow could mix with the rain or even have the precipitation change to a period of snow across northern MA before ending Thursday night as the boundary layer cools a tad per model 925 mb temperature projections. No accumulation is expected other than perhaps a coating or so across the higher elevations of the Berkshires and Worcester hills. A model consensus would point toward a dry but cooler than normal weekend ahead. A closed upper low pressure center will move across the southern USA and produce an anomalous coastal storm off the SE USA coast by early next week, but any impacts on southern New England would be after this forecast period. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/... Tonight...Moderate confidence. MVFR/IFR stratus and patchy fog will gradually improve to MVFR/VFR overnight. There may be a few areas of dense fog with vsby less than 1/2 mile between 00Z and 03Z across some interior sections. Wind gusts 30+ KT over Cape Ann and Cape Cod near 00Z should diminish quickly after 00Z. Mainly dry with just a few rain/snow showers possible over over the Berkshires. Tuesday...Moderate confidence. Mix of MVFR/VFR cigs, lowest conditions in the west. A few rain showers possible, mixed with snow over higher elevations. SW gusts 20-25 kt Cape/Islands. KBOS Terminal...Moderate confidence in TAF. Rain and gusty winds should be passed by 00Z. Until about 06 or 07Z may have fog and stratus to contend with until wind veers more toward the SW and dewpoints begin to lower. Anticipate conditions becoming VFR in time for the morning push. KBDL Terminal...Moderate confidence in TAF. Risk of fog and stratus in moist air mass until around 03Z and then anticipate fairly steady improvement overnight. Outlook /Tuesday Night through Saturday/...Moderate confidence. Tuesday Night through Wednesday: Mainly VFR. Wednesday Night: Mainly VFR, with MVFR conditions possibly developing west to east. Chance of light rain and slight chance of light freezing rain NW MA. Thursday: Mainly MVFR ceilings and visibilities, with local IFR conditions possible in rain and fog. Thursday Night...MVFR ceilings and visibilities in rain and fog improving to VFR by morning. Chance of precipitation mixing with or changing to snow across northern MA. Friday...Mainly VFR. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/...High confidence. 9 pm update... Winds have sufficiently diminished for us to take down the remaining Gale Warnings east of Massachusetts. Winds are actually diminishing below 25 knots as well, but seas linger above 5 feet on most of the waters, and on at least the extreme north portion of Cape Cod Bay. Between winds and seas, expect periods of Small Craft winds and seas through Tuesday. Most waters will have SCA headlines through this time. Outlook /Tuesday Night through Saturday/...Moderate Confidence. Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas at or above 5 feet, especially outer coastal waters south of New England. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas near or a little above 5 across the outer south coastal waters. Wednesday Night: Winds less than 25 kt. Seas near 5 feet outer coastal waters. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain. Thursday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers. Friday: Winds less than 25 kt. Seas up to 5 ft over the outer coastal waters. && .CLIMATE... New record lowest max temperatures set for April 15 BOS 39 in 2018. Previous 40 in 1881. PVD 41 in 2018. Previous 42 in 1972. BDL 40 in 2018. Previous 41 in 1943. ORH 34 in 2018. Previous 39 in 1943. New record daily snowfall set for April 15 PVD trace in 2018. Previous trace in 2007. BDL 0.5 in 2018. Previous trace in 2014. ORH 0.4 in 2018. Previous 0.2 in 1988. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Coastal Flood Advisory until 11 PM EDT this evening for MAZ020. RI...Coastal Flood Advisory until 11 PM EDT this evening for RIZ002- 004>007. MARINE...Small Craft Advisory from 5 AM Tuesday to 5 AM EDT Wednesday for ANZ232>234. Small Craft Advisory until 11 AM EDT Tuesday for ANZ231. Small Craft Advisory from 5 AM to 6 PM EDT Tuesday for ANZ236. Small Craft Advisory until 5 AM EDT Wednesday for ANZ235-237- 250-251-254>256. && $$ SYNOPSIS...WTB/KJC/Thompson NEAR TERM...WTB/KJC/Thompson SHORT TERM...KJC LONG TERM...Thompson AVIATION...KJC/Thompson MARINE...WTB/KJC/Thompson CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.