Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | 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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 280539 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1239 AM EST Mon Nov 28 2016 .SYNOPSIS... High pressure builds into the region tonight and Monday with generally dry weather. A warm front will bring widespread rain to the region Tuesday into Tuesday evening, then more rain is likely late Wednesday into Thursday as low pressure moves into New England. Cooler and drier weather will return for Friday and the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 10 pm update... Dissipation of the majority of the cloud cover across S New England has allowed for some radiational cooling and decoupling as winds begin to go light. Only caveat at the moment is the outer Cape, where ocean effect clouds will linger for another few hours until winds shift to the W and the fetch is lost. Despite this good setup for radiational cooling, noticing late day dwpts were not as well mixed as previously thought so they are starting higher this evening. Therefore may not see temps get quite as cool. Still expecting widespread mid-upper 20s, but maybe less in the way of low 20s as was initially thought. This will be the primary change with this late evening update. Previous discussion... High pressure over NY/PA builds east and reduces the pressure gradient over Southern New England. This will allow winds to slacken as the skies clear. This should allow radiational cooling by the latter part of the night. With dew points in the 20s, min temps should also reach the 20s, except around 30 or low 30s along the coast and islands. Min temps upstream also showed 20s with coldest spots 20-21. Sounds good. Ocean effect clouds off Eastern MA will linger into the evening, but should diminish overnight as Northwest winds also diminish. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... Monday... High pressure over the region with plenty of subsidence and a dry airmass. That will mean a sunny day with light wind. Some increasing cirrus-level moisture is expected late in the day, so expect some high thin clouds toward sunset. The subsidence inversion will limit the depth of the mixed layer, probably to 950 mb. Temps in that layer will reach 1-2C...equiv to -8C to -9C at 850 mb. Expect high temps once again in the 40s, mostly low to mid 40s. Monday night... High pressure shifts east. Moisture increases at high levels before midnight, then at lower levels late at night. Temperatures will chill in the evening, but as the clouds thicken we expect temps to stop falling around midnight and possibly rise a little overnight. Min temps would be mid 20s to mid 30s except near 40 on the Islands. Strong low level jet ahead of the next weather system with 40-50 knot southerlies at 925 mb and 60 knots at 850 mb. Through 12z most of this is directed up through PA and NY, and so that is where most of the pcpn should develop. But by 12Z Tuesday some of this jet is edging toward Western CT and Western MA, so there is a low-end chance of pcpn late at night in our area with the best chance along the east slopes of the Berkshires. Precip type will depend on timing...an earlier start would catch the departing cold air and could start as sleet/freezing rain. Best chance for this would be in Hampshire/Franklin Counties. Farther south the likelihood would be for rain. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Rain expected through Tue evening, low risk of icing early Tue morning * Rain again late Wednesday into Thursday morning * Dry, cool, and blustery Friday through the weekend There is increasing confidence in the model trends, particularly through the mid week period. A strong upper level low and its surface reflection rotate slowly through the Great Lakes, bringing a couple of periods of rain to southern New England. One with the warm front Tuesday and Tuesday evening, the second with a developing secondary low somewhere along the northeastern U.S. coast late Wednesday into Thursday. In addition to the rain, expect warmer than normal temperatures during this time with 50s to even near 60 degree high temperatures south of the Mass Pike possible. These systems move north and east of southern New England Thursday with drier and cooler weather filling in behind. Aside from more normal temperatures, winds will be rather blustery with a tight pressure gradient over southern New England. Tuesday...As the upper level trough and surface low get settled into the Great Lakes region, a warm front will move into southern New England bringing a round of overrunning precip and warming temperatures into the region. Plenty of moisture will be brought in by a strong southerly low level jet. With high pressure creeping out of the area early Tuesday morning, cannot rule out some freezing rain at the onset across northwestern MA. Temperatures appear to be rather marginal at this point, and the pattern is not ideal for cold air damming, so have low confidence in this occurring. Definitely still something to watch over the next few days. Wednesday and Thursday...The upper low remains in the Great Lakes region for much of this time, moving northeastward into Ontario and Quebec Thursday. A secondary low pressure system will form somewhere along the NE US coast Wednesday, bringing another period of heavy rain to the region late Wednesday into Thursday. There is some uncertainty in the models and the ensemble members with where exactly this low develops (ranging from S of Long Island to the Gulf of Maine). Timing is still a bit uncertain as it will depend on where this low pressure develops. Temperatures will remain warm, particularly south of the Mass Pike where temperatures could reach into the 50s to even around 60 Wednesday afternoon. These warmer temperatures look to be limited more to south and east of the I-95 corridor on Thursday as the low pressure system pulls away from the coast. Friday through Sunday...The upper level low and its surface reflections will move into the Maritimes, leaving southern New England in a tight pressure gradient between the departing low and a strong high pressure across the southeastern CONUS. This will result in rather blustery weather, in addition to temperatures returning to near normal or just below normal. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/... Today and tonight...High confidence. VFR. Generally light W-NW winds with some building high clouds starting late tonight. Tuesday...Moderate confidence. Early VFR conditions will gradually give way to MVFR, then finally IFR by late afternoon/evening due to a mix of low CIGS and vsbys in fog and mod rain. Will also have to watch for some light icing during the morning when the precip starts, this will be most likely in the CT Vally as well as the higher terrain of N MA. More details on this to follow. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday...High confidence. Heavy rain will result in MVFR/IFR conditions through Tuesday evening. Conditions may improve to VFR/MVFR briefly overnight. Wednesday and Thursday...High confidence in trends, lower in timing. Will start out dry with a mix of MVFR/VFR conditions, then deteriorating Wednesday afternoon as another round of heavy rain moves in. Conditions should improve again late Thursday as rain comes to an end and clouds lift. Friday...Moderate confidence. Mainly VFR. Blustery W winds expected.
-- 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 Tuesday/...High confidence. Tonight... Northwest winds gust around 25 knots during the evening, then diminish overnight. The persistent NW wind will maintain 5-7 foot seas on the outer waters much of the night. Small Craft Advisories continue through the night on the outer waters, but drop off piece-by-piece on the bays and sounds during the night. Monday... High pressure builds over the waters. Winds and seas will diminish through the day. Continue Small Crafts on the Eastern and Southeast outer waters through midday, mostly due to 5 foot seas. Monday night... Light winds and seas. Winds will increase a little from the south and southwest. Outlook /Tuesday Night through Friday/... Moderate confidence. Winds and seas build as low pressure approaches and then passes southern New England. Small craft advisories will likely be necessary for much of this time, for seas, if not for winds also. The strongest winds will likely occur on Friday. There is a low probability of gales on Friday.
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 5 AM EST early this morning for ANZ231-256. Small Craft Advisory until 1 PM EST this afternoon for ANZ250- 254-255. Small Craft Advisory until 9 AM EST this morning for ANZ251.
-- End Changed Discussion --
&& $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/Doody SHORT TERM...WTB LONG TERM...RLG AVIATION...Doody/RLG MARINE...WTB/RLG

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