Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 202302 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 702 PM EDT Thu Oct 20 2016 .SYNOPSIS... A warm front approaches from the south late tonight and will be accompanied by a few showers and/or drizzle along with areas of fog. Rain may become more widespread and heavy at times Friday and Friday night across eastern Massachusetts and Rhode Island as low pressure tracks across the region. Wrap-around showers are possible Saturday, otherwise becoming blustery, cooler and mainly dry by Saturday afternoon. Dry but cool and blustery into early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 7 PM Update...The forecast is generally on track at this point. Made a few edits to the sky cover forecast to increase cloud cover, particularly across eastern MA. 4 pm update... Low pressure tracks across western PA/NY tonight with accompanying warm front approaching from the south. Column remains dry in the mid levels, however low level moisture increases below 5 kft. Good signal for areas of drizzle/fog and perhaps a few low topped showers. The fog could locally become dense but not expecting widespread dense fog. Thus no statements or headlines at the moment. Dewpoints in the 50s now will increase overnight into the 60s. Thus not as cool as previous nights along with temps rising overnight given the strong low level moisture and thermal advection. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Friday... Still a low confidence forecast as models differ on the spacing and interaction of northern stream energy and subtropical low offshore. This is apparent in model wind fields with the NAM and RGEM much farther west with its low level jet. While the GFS and ECMWF farther east and weaker. Thus how far west does deep layer tropical moisture and lift track? Model consensus suggest into eastern MA and perhaps RI by afternoon or late day. Hence greatest risk for a period of heavy rain will be over this region. Will have to watch this closely as heavy rain threat could shift just offshore or farther west into RI, eastern CT, and the Worcester Hills. Meanwhile dry slot overspreads much of CT and western-central MA. Although showers ahead of approaching frontal boundary from the west may impact the Berkshires and Litchfield Hills and eventually the CT River Valley/I-91 corridor. Thus could be two areas of rain tomorrow, one across eastern MA and another across western portions of MA/CT, with not much in between. Expecting entire region to get into the warm sector tomorrow with dew pts in the 60s and temps in the upper 60s and low 70s. So definitely not feeling like late Oct. Given warm sector will have to watch for the risk of a few robust showers or isolated thunder western CT/MA given a few hundred joules of CAPE coupled with deep layer shear across this area. Friday Night... Much of the same, risk of showers across eastern MA associated with tropical plume of moisture and also western CT/MA as frontal boundary approaches. Still uncertainty here on how quick streams phase. Looks like low pres develops over the region and then bombs north of our latitude. Impressive mid level trough with negative tilt toward Sat morning. Despite dry slot approaching could have widespread low top showers toward morning. Warm start Fri evening with slow cooling toward Sat morning as cyclogenesis occurs across the region. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Highlights... * Wet weather may continue into Saturday * Temperatures drop below normal Saturday and continue dropping through Tuesday/Wednesday time frame * Mainly dry weather through this time with a few areas of showers possible on several days Models are in good agreement through much of the long term, particularly on the synoptic scale pattern. There are some discrepancies, but these are largely on the smaller scale details as well as timing. Looking at more seasonable or even cooler than seasonable weather through much of the long term. Saturday...There are still some placement/timing discrepancies with the surface low with models placing the low anywhere from south of southern New England to northern New England to start the day. All models have it then tracking north into Quebec, but the starting position will make some difference in wind direction and perhaps duration of the rain. We do lose the deep layer moisture that we had on Friday fairly quickly so expect rain to taper down fairly quickly Saturday. The larger concern Saturday will be the strong pressure gradient and decent cold air advection that will result in breezy conditions. Much of the day should remain below wind advisory criteria, but there are indications that winds will pick up towards the end of the day. Will continue to watch to see if wind advisories may be needed for a portion of Saturday. In addition, temperatures will drop back to near or just below normal levels Saturday, with highs in the mid 50s to around 60 degrees most locations. Sunday and Monday...The upper level trough slowly moves offshore and low pressure moves into the Maritimes while a few shortwaves move through southern New England. Temperatures will be a bit cooler than normal and gusty winds will likely continue through at least a portion of Sunday. Sunny skies will counter the cooler, breezy conditions somewhat but it will definitely feel like a more typical October out there. The shortwaves moving through may bring a few showers to the area as well. Tuesday and Wednesday...High pressure starts building into southern New England bringing cooler, dry weather. Temperatures will be 5-10 degrees below normal both days, cool enough to possibly induce some ocean effect clouds and showers on the Cape and Islands. Thursday...Shortwave ridging becomes more dominant across southern New England, allowing temperatures to rebound a bit, though they stay below normal. Dry weather is expected. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/... Tonight...High confidence on trends but lower confidence on exact timing and details. Widespread MVFR to start and then lowering to IFR/LIFR after 02z/03z in drizzle/fog and scattered showers. Localized LLWS possible with light easterly winds at the surface and southerly winds 20-30 kt developing at 2K ft. Friday...High confidence on trends but lower confidence on exact timing and details. Widespread IFR/LIFR conditions persisting in the morning...possibly lifting to MVFR at times in the afternoon with rain becoming more widespread. Isold t-storm possible. Friday night...High confidence on trends but lower confidence on exact timing and details. IFR/LIFR likely in periods of rain/drizzle and fog. Isold t-storm possible. KBOS TAF...High confidence in trends. KBDL TAF...High confidence in trends. Outlook /Saturday through Tuesday/... Saturday...Moderate confidence. A mix of conditions in scattered showers. Westerly winds increase, gusting to 25 to 30 kts. Higher gusts are possible towards evening particularly on the Cape and Islands. Sunday...High confidence. VFR. Gusty NW winds continue but will diminish slowly. Monday and Tuesday...Moderate confidence. Mainly VFR. Low confidence in MVFR/IFR conditions developing on the Cape and Islands in ocean effect clouds and rain showers. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...Moderate confidence. Tonight...warm front approaches from the south with areas of drizzle and fog lowering vsby to less than a mile at times. ENE winds 15 to 20 kt becoming southeast with gusts up to 25 kt at times. Friday...warm front lifts north with low vsby due to drizzle and fog improving somewhat toward midday. Periods of heavy rain possible in the afternoon across the eastern waters as subtropical low lifts north of the Bahamas tonight. Friday night...low consolidates over southern New England and then becomes a Gale Center over central-northern New England Sat. Winds variable as low tracks over the area. Vsby reduced at times in areas of rain and fog. Outlook /Saturday through Tuesday/... Saturday and Sunday...High confidence. Small craft advisory conditions will continue with a tight pressure gradient between the departing low pressure system and building high pressure in the Great Lakes. Westerly winds will shift to the northwest on Sunday. Have enough confidence in gale force winds occurring to issue a gale watch for all southern New England coastal waters for Saturday. This likely will need to be extended into a portion of Sunday at a later point. Monday and Tuesday...Moderate confidence. Marginal small craft advisory conditions continue though both winds and seas will diminish gradually through the period as the pressure gradient slackens. && .TIDES/COASTAL FLOODING... Astronomical high tides are subsiding with each tidal cycle. There may still be a small risk of minor splashover at the more vulnerable spots on the coastline during the Fri evening high tide cycle, but the general trend is now moving away from that. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Watch from Saturday morning through Saturday evening for ANZ230>237-250-251-254>256. Small Craft Advisory until 8 PM EDT Friday for ANZ250-254>256. && $$ SYNOPSIS...Nocera/RLG NEAR TERM...Nocera/RLG SHORT TERM...Nocera LONG TERM...RLG AVIATION...Nocera/RLG MARINE...Nocera/RLG TIDES/COASTAL FLOODING...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.