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 300613 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 113 AM EST Wed Nov 30 2016 .SYNOPSIS...
-- Changed Discussion --
Dry and mild overnight into Wednesday morning along with areas of dense fog especially across valley locations. Another soaking rain affects the region late Wednesday afternoon and night. Near seasonable conditions with breezy NW flow follows for the late week period into the weekend. Early next week, another wet- weather disturbance is possible with a potential wintry-mix with onset changing over to all rain.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
-- Changed Discussion --
1 am update... *** Dense fog CT River Valley/I-91 corridor this morning *** Dense Fog... Winds have decoupled in the CT river valley and coupled with low level moisture /dew pts in the upper 40s to lower 50s/ has resulted in dense fog to form. Thus have issued a dense fog advisory for this region until 14z/9am...with slow improvement thereafter. Elsewhere areas of dense fog may form as winds drop off during the predawn hours. This coupled with low level moisture in the form of dew pts in the 50s across RI and eastern MA may be sufficient for additional areas of dense fog to develop later this morning. Will monitor as the morning progresses. Winds... low level jet moving offshore however pres rises approaching from the west yielding sw winds to gusts up to 25-30 kt across Cape Cod and the islands. However the trend will be for winds to continue to diminish during the predawn hours. Temps... Mild early this morning with post frontal airmass dew pts in the 40s and 50s.
-- End Changed Discussion --
&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... * Another soaking rain later Wednesday into Wednesday night Wednesday and Wednesday night... Areas of fog should burn off by mid morning on Wednesday. While it will start off dry, another shortwave will approach from the SW. Easterly winds at the surface coupled with moist SW flow aloft will increase the forcing for ascent. Light rain will develop later into the morning into the afternoon from west to east. The heavier rain will probably not arrive until late Wednesday afternoon/evening when another impressive low level jet of 45 to 55 knots joins with PWATS that remain 2+ standard deviations above normal. There will be pockets of impressive frontogenesis/omega that should lead to bands of locally heavy rainfall. We also can not rule out an isolated t-storm or two S of the MA Pike with some marginal elevated instability. High temps on Wednesday should be in the upper 40s to the middle 50s, with the mildest readings found south of the MA Turnpike. In a nutshell...rainfall amounts from this second system should average between 0.50 and 1.50 inches. The rain should come to an end toward daybreak on Thursday as shortwave energy moves east of the region. Low temps will be in the 40s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... */ Highlights... - Near seasonable, dry pattern with breezy NW winds late week into the weekend - Initial wintry mix changing over to all rain possible early next week */ Overview... Perhaps an over-running onset of mixed wintry precipitation events, but otherwise a warm-wetter pattern continues. La Nina is seemingly the dominant influence upon the N Hemisphere as all other atmospheric teleconnections are near-neutral, relatively flat. A more buckled pattern than idealized across N America, with strong C CONUS cyclo- genesis drawing down colder air W beneath a favorable region of troughing while latching into tropical maritime air S. Would appear with prevailing E CONUS downstream ridging, deepening and occluding storm centers out of the C CONUS are stretched N/W of S New England, inside-runners, placing S New England in the warmer and wetter region of outcomes. A progressive pattern of initial over-running followed by a sweeping cold front before high pressure and colder air settles back in. Can not rule out a continuation of mixed wintry precipitation events with the onset of storm systems noting the potential for cold air damming and triple point lows. Will note in the details below. Would appear Arctic air presently is locked up round the polar low. Indications though that as we go towards mid-December the polar low and associated energy becomes displaced. Associated jet stream round the maritimes becomes buckled and more amplified. Potentially thus we could see shots of Arctic air being introduced as we go deeper into Winter. No doubt if the pattern continues we would see such air slide S across the Rockies into the C CONUS before sliding E, likely moderating. It`s early but worth noting of potential trends down the road, something to watch. */ Details... Thursday through the Weekend... NW flow and cold air advection initially through which mid-level energy and moisture continue to rotate round a dying low pressure center over the N/E Great Lakes Region. A reinforcing cold front inbetween around Saturday morning. Usual pattern: colder NW flow over the Lakes invokes broken to overcast cloud decks along with showery precipitation, downsloping over the high terrain N/W of our region, only scattered to broken decks remain with a slight chance of a shower, the greatest chance being over the Berkshires. Well- mixed lapse rates with diurnal heating, will see the mix-down of drier air and faster winds, but nothing that would appear to reach advisory level criteria. Cooler air over warmer waters, ocean-effect processes proceed, and depending on the direction of the wind, will more than likely impact the Outer Cape and Islands, especially on Saturday behind the reinforcing cold front. Will go with chance of showers at times for the aforementioned locales. Conditions overall will feel cooler given the breezy NW winds, but in actuality remain near-seasonable for this time of year. High pressure across the region over the weekend from the SW, will see a return S flow. Early next week... Consensus indications of wet-weather though the exact evolution and timing remains uncertain. With onset it is possible to see wintry mixed precipitation associated with over-running ahead of an area of low pressure emerging out of the S CONUS, especially if high pressure sets up over E Canada as some of the solutions indicate. Leaning towards an inside runner solution occluding into the E Great Lakes as a secondary low develops at the triple point and rapidly deepening offshore. Going with ensemble means but advertising low confidence. Chance PoPs for now through the remainder of the week. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/... 115 am update... Thru 12z... Low confidence forecast. Trends for cigs and vsbys is upward as west winds mix out low level moisture. However as winds diminish toward sunrise ground fog may develop especially with dew pts in the 40s and 50s. This already taking place in the CT river valley where winds have diminished and dense fog as formed. Not expecting any improvement here until 14z/15z. Elsewhere trend upward to MVFR-VFR but have to watch ground fog to develop 09z-12z which may lower conditions back to IFR-MVFR. Worst conditions will likely be in the interior valleys and low lying locations near the coast. After 12z... MVFR-VFR however local LIFR-IFR in dense fog CT river valley and low lying sections elsewhere will improve to MVFR-VFR toward midday. Then conditions lower back to MVFR-IFR in rain 18z-21z with rain becoming steady and heavy at times from BDL-ORH-ASH and pts westward. Confidence is low on exact timing but higher on trends. Tonight... Widespread IFR with embedded LIFR in rain...heavy at times inland from BDL-ORH-ASH and points westward. LLWS possible south coast. vsbys and cigs may improve to MVFR-VFR beginning 09z-12z Wed along with a drying trend and a wind shift to the west. Thursday... Any early MVFR cigs quickly lift to VFR along with dry conditions. Diurnal clouds yield VFR cigs for the afternoon. West winds 15 to 25 kt along with dry runways. High forecast confidence. KBOS TAF...MVFR-VFR this morning lowers to MVFR-IFR 21Z-24Z today as rain overspreads the terminal. Not expecting any dense fog this morning at Logan. KBDL TAF...LIFR in dense fog this morning likely lingers until 14z-15z then slow improvement thereafter. Outlook /Thursday Night through Sunday/... SCT-BKN low-end VFR. NW winds, blustery at times, especially along the coast with gusts initially Thursday and Friday up to 30 kts, tapering downward with time. MVFR possible over the Outer Cape with chance -RA and a breezy N wind.
-- 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 Thursday/... 7 pm update... Tonight...Moderate to high confidence. S gusts up to 40 kts expected with moderate to heavy rain which will push E of the waters later tonight prior to midnight. With gales, will see waves build 7 to 10 feet as they have already at buoy 44097. With heavy rain, expect reductions to visibility. Expect winds to diminish while turning out of the W towards Wednesday morning. Wednesday and Wednesday night... Winds should not be much of a factor into early Wednesday afternoon. However, east winds of 25 to 30 knots shifting to the south should develop later Wed afternoon and night. Brief marginal gale force wind gusts may develop, but inversion will keep those short-lived if they do occur. Seas once again should build back to between 7 and 10 feet across our southern waters. Outlook /Thursday Night through Sunday/... NW winds possibly gusting as high as 30 kts initially with a low risk of gale force, Thursday and Friday. Winds building with the wave stress. Likely to see the development of ocean-effect showers. Both wind and shower chances diminish as we go into the weekend.
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Dense Fog Advisory until 9 AM EST this morning for CTZ002. MA...Dense Fog Advisory until 9 AM EST this morning for MAZ003-010- 011. RI...None. MARINE...Gale Warning until 1 AM EST early this morning for ANZ231>235- 237-250-254>256. Small Craft Advisory until 1 AM EST early this morning for ANZ230-236-251.
-- End Changed Discussion --
&& $$ SYNOPSIS...Frank/Sipprell NEAR TERM...Frank/Nocera/Sipprell SHORT TERM...Frank LONG TERM...Sipprell AVIATION...Nocera/Sipprell MARINE...Frank/Sipprell

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