Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 141432 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1032 AM EDT Sat Oct 14 2017 .SYNOPSIS... A weak trough of low pressure offshore moves north today and brings periods of rain to CT, RI and southeast MA, possibly heavy at times along the south coast including Cape Cod and the Islands. A warm front then lifts northward tonight bringing spotty light rain, drizzle and fog to the region into Sunday morning. Very warm and humid conditions overspread the area Sunday afternoon along with gusty southwest winds. A cold front sweeps across the region Sunday night and is accompanied by scattered showers. Behind the front, cooler and less humid weather Monday and Tuesday followed by warming temperatures Wednesday through Friday. Dry weather prevails much of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1030 AM Update... Continue to watch area of showers as the move onto the south coast this morning. Went ahead and updated the forecast to reflect the latest radar. These showers are inline along the nose of the strengthen low level jet and in the higher theta-e plume. SPC meso analysis also indicated the development of the inverted trough/coastal front as 1000-925 mb frontogenesis is strengthening. Latest Hi- res guidance of the HRRR, RAP and now the 12z NAM are showing near or over 1 inch of QPF across the south coastal regions of MA and onto the Cape. This seems reasonable as PWAT values have increased to 1.8 inches, which is 2 STD above normal for this time of year. Will go ahead and update the SPS to account for where the heaviest rainfall will fall. Northerly flow across the CT river valley will continue to keep dry air in place thus limiting any rainfall in that region. This will lead to a very tight gradient of who will see rain and who will not in CT and portions of west/central MA. Light flow somewhat east at times east of the Worcester Hills has resulted in some light showers/drizzle, including the city of Boston. Expect this on/off showers to continue until the system passes around 21z. Even through strengthening LLJ at 925 mbs could reach 25-35 kts, BUFKIT soundings do show a very strong inversion in place. Thus will keep wind gusts around 20-25 MPH with the strongest winds over the Cape and the Islands. Aside from adjustments to the forecast to account for current conditions, the bulk of it still is on track for today. Just increase pop and qpf amounts per latest guidance.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... Tonight... Short range and high res models continue to signaling the trough and its moisture shifting E as mid level winds become W-SW during the night. Will see best shot for scattered showers during the evening, then should dry out across western areas around or after midnight. May see some light precip linger through the night across parts of E Mass and RI. With continued SW winds in place, will be a rather mild night. Readings forecast to bottom out in the upper 50s to lower 60s. May see lows close to record high mins at some of our four long term climate sites. See Climate section below for details. Sunday... Conditions should improve Sunday morning as the moisture dissipates, but clouds look to linger through most of the day. Might see some breaks from time to time. Noting increasing SW low level jet up to H85, on order of 40-50 kt, moving across the region. Good mixing working in ahead of the approaching front, so will see gusty winds across most areas. Have carried gusts up to 25-30 kt, highest across eastern areas and along the coast. Temps will be mild, with highs in the lower-mid 70s, though a bit cooler along the immediate S coast. Some showers may push into the E slopes of the Berkshires late in the day ahead of the front. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Cold front accompanied by showers & gusty winds Sunday night * Cooler than normal Mon ngt/Tue then warming Wed thru Fri * Mainly dry weather next week Sunday night... Surface low tracking across southeast Quebec Sunday evening with its trailing cold front sweeping across southern New England. Tight pressure gradient in the prefrontal environment results in gusty southwest winds Sunday evening. Core of low level jet is over Gulf of Maine Sunday evening but up to 45 kt at 925 mb extends back into eastern MA. Both NAM and GFS BUFKIT soundings suggest gusts up to 35 kt/40mph possible at times Sun evening. While these wind speeds are below wind advisory criteria, given trees remain fully leaved these speeds may result in isolated wind damage. Thus may need a wind advisory as the event nears. However models have been trending weaker/more sheared with short wave and attending surface low. Something to watch on later model runs. As for precip, fairly robust forcing for ascent associated with strong frontal convergence combined with 150 kt jet streak approaching the region. Limiting factor will be the lack of deep layer moisture and instability thru the column. This lack of moisture and instability will likely limit areal coverage of showers to scattered. It will be a warm and humid evening with dew pts in the 60s. However frontal passage overnight advects a post frontal airmass with dew pts crashing into the 40s western MA/CT, 50s RI/eastern MA. Monday and Tuesday... Showers possible early Mon across Cape Cod and the Islands before cold front exits by midday. Elsewhere, dry post frontal airmass overspreads the area with impressive low level CAA as 925 mb temps crashing from +17c at midnight to +7C by midday Mon! Highs Monday will be 55-60, a few degs cooler than normal. It will feel chilly given a brisk NNW wind. Trailing short wave moves across the area Mon evening. Not much moisture with this feature so just expecting a second surge of cooler air. In fact quite cool as 850 mb temps dip to about -3C 12z Tue. Thus chilly with lows in the 30s most locations, except low 40s in the urban areas. Highs Tue only recovering into the 50s, a few degs cooler than normal. Although light winds and mostly sunny conditions will help offset the cool temps. Wed/Thu/Fri... Rising heights will translate to a gradual warming trend and dry weather. Highs will warm into the 60s Wed, near 70 Thu and into the 70s Fri. Normal high this time of year is 59-64. && .AVIATION /14Z 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/...Moderate confidence. 1430z Update... Today...VFR for locations west of MHT to BDL. Otherwise MVFR- IFR CIGS for the rest of the region. Conditions will continue to lower or remain IFR across the south coast due to heavy rain and fog through the rest of the day. Improving conditions from west to east during the late afternoon. Tonight...MVFR-IFR CIGS mainly near and S of the Mass Pike, VFR CIGS across N Mass. CIGS may lower to MVFR-IFR across most areas after midnight. Spotty showers linger through the night, along with patchy fog, with areas of MVFR-IFR VSBYS mainly after midnight. Sunday...Showers end during the morning, but patchy fog lingers through midday with MVFR to local IFR conditions, lowest across coastal areas. CIGS/VSBYS improve across most areas during afternoon, but MVFR may linger along the S coast and across the higher inland terrain. SW winds gusting up to 25-30 kt Sunday afternoon, highest along E Mass, RI and along the coast. KBOS TAF...Moderate confidence in TAF. MVFR in lower clouds by mid morning. Sct -SHRA will continue into late this afternoon, with local MVFR VSBYS. KBDL TAF...Moderate confidence in TAF. MVFR to brief IFR VSBYS in patchy fog but conditions will improve later in the day. low probability for some -RA. MVFR-IFR conditions in low CIGS/fog by around midnight. Outlook /Sunday Night through Wednesday/...High confidence Sunday night...VFR to start then lowering to MVFR in scattered showers. SW winds 20-30 kt. Monday...VFR with some showers over Cape Cod and Islands early Mon. Otherwise dry with gusty NNW winds up to 20 kt. Tue & Wed...VFR and dry.
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&& .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... Today...Moderate to high confidence. Expect seas up to around 5 ft lingering across the southern outer waters through the day. With the persistent onshore wind flow, have included the open waters E and S of Cape Cod, as seas will build to around 5 ft again. May also see S-SE wind gusts up to 20 kt during the afternoon across the southern waters. Area of showers will develop S of New England early today, then push across the waters during the day. May see some heavier showers along the southern waters with reduced visibility. Patchy fog will also linger. Tonight...Moderate confidence. S-SW winds, which may gust up to 15-20 kt across the southern waters late tonight. Seas remain around 5 ft across the southern open waters. Scattered showers and patchy fog will continue with poor visibility, but should push offshore after midnight from W-E. Sunday...Moderate confidence. SW winds increase ahead of an approaching front during Sunday. Gusts up to 25-30 kt likely during Sunday afternoon, which will cause seas to build up to 5-7 ft. Have raised Small Crafts for the remaining waters. May see a few lingering showers Sunday morning, then will push offshore. However, patchy fog will linger into the afternoon, so will see reduced visibility. Outlook /Sunday Night through Wednesday/...High confidence Sunday night...SW winds 20-30 kt ahead of a cold front shifting to NW toward Mon morning. Scattered showers accompany the front. Monday...Cold front moves offshore by midday with NNW winds up to 20 kt. Good vsby behind the front. Tue & Wed...Ridge of high pres over New England Tue shifts south Wed. && .CLIMATE... Min temperatures Saturday night could be rather close the record maximum low temperatures for our four long term climate sites. October 15 Record maximum low temperatures Boston 64/1954 Worcester 64/1954 Hartford 63/2014 Providence 63/2014 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 1 PM Sunday to 6 AM EDT Monday for ANZ231>234. Small Craft Advisory from 2 PM Sunday to 6 AM EDT Monday for ANZ230-236-251. Small Craft Advisory from 11 AM Sunday to 6 AM EDT Monday for ANZ235-237-250. Small Craft Advisory until 6 AM EDT Monday for ANZ254>256. && $$ SYNOPSIS...Nocera/EVT NEAR TERM...Nocera/Dunten SHORT TERM...EVT LONG TERM...Nocera AVIATION...Nocera/EVT MARINE...Nocera/EVT CLIMATE...Staff

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