Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250756 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 356 AM EDT SAT JUN 25 2016 .SYNOPSIS...
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Large high pressure remains over the northeast U.S. into early next week keeping warm and dry conditions across the region. Warmest days will be Sunday afternoon into Monday with highest temperatures inland. An approaching cold front brings showers and psoobly some thunder later Monday night through Wednesday. High pressure then brings dry seasonable weather for the end of next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1045 PM Update... Mainly clear skies across the region at 02Z. Noting a few mid level clouds moving across near the E slopes of the Berkshires of NW Mass, along with some mid and high clouds scrapping across the islands from the northern fringe of scattered showers and a few thunderstorms moving E at around 40N southward. With high pressure across the region and winds dropping off to near calm, temps will continue to fall back especially in the normally cooler valley. Seeing temps down to the mid 50s across interior E Mass and even at Martha`s Vineyard with calm winds. Could see patchy radiation fog developing in those areas after 1 or 2 AM through around sunrise. Otherwise, expect clear conditions overnight for most of the area. Near term forecast pretty much on track. Have updated to bring conditions current and incorporated into the overnight trends. Previous discussion... With the ideal radiational cooling conditions followed the cooler MET and MAV guidance as 2m temps too warm in this pattern for overnight mins. Could be a few hours of patchy fog toward daybreak in the typically prone locations. Could be some mid to high cloudiness on the southern horizon across the Islands and Cape Cod as shortwave energy in the WNW flow aloft induces a weak frontal wave off the mid-Atlantic coast and tracks eastward, south of 40N. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... Saturday... High pressure overhead providing light winds and promoting afternoon sea breezes. However, with mean mid-level trough axis just offshore, cold temps aloft linger across southern New England with H5 temps about -14C. This provides modest mid level lapse rates, however should be enough deep layer dry air within the column to offset any shower potential. NAM offers a risk of isolated afternoon showers in the high terrain however this is a result of its dew pts climbing into the 60s. Not happening with surface ridge over the area and other model guidance limiting dew pts to the 50s. Thus have discounted the NAM and will continue with a dry forecast. Very similar day tomorrow to today with comfortable humidity and warm temps with afternoon highs in the 80s inland away from the cooling afternoon sea breezes. Highs in the 70s along the coast. Given the recent dry weather /dry soil, etc/ temps have been overachieving. Thus have added a few degs to a model blend. Sat night... High pressure remains over the area providing dry weather. Another comfortable cool night with low dew pts, light winds and mostly clear skies. Followed a blend of the MOS guid which yielded lows in the 50s to near 60 in the city of Boston. Could be a few hours of patchy fog toward daybreak in the typical prone locations. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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Big Picture... A shortwave originating over the Pacific Northwest moves east across Canada and then digs over New England Tuesday and Wednesday. Above normal heights Monday diminish to near normal the rest of the week. This suggests above normal temps Monday trending to normal during mid to late week. Model forecast mass fields are similar much of the period. There are differences between GFS and ECMWF with timing on the midweek cold front. Confidence is limited as to exact timing, but potential for convection should exist for both days. Details... Sunday night through Monday... High pressure offshore moves farther away, and the surface flow turns more from the south and southwest. Expect dry weather during this time. 850 mb temps of 14-16C would support max sfc temps in the mid 80s. Monday night through Wednesday... Northern shortwave approaches from the Great Lakes. At this time the upper shortwave digs southeast toward New England and turns the upper flow more from the southwest and parallel to the cold front. With flow moving along the cold front rather than pushing it, we should see the forward progress slow until the trough axis swings overhead. Meanwhile the surface flow will bring a warm humid airmass across New England with dew points climbing into the 60s. Stability parameters will favor convection. The cold front will be the eventual focussing mechanism on Wednesday, but a pre-frontal trough may concentrate convection on Tuesday. Thursday-Friday... High pressure builds in behind the cold front but with upper contours and 850 temps near seasonal normals.
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&& .AVIATION /08Z 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/...High Confidence. Overnight...VFR. Low risk for patchy fog/MVFR after 06Z-07Z for a few hours in the typically prone locations. Saturday and Saturday night...VFR with light and variable winds inland, then sea breezes along the coast by midday or earlier Saturday. Low risk again for patchy MVFR conditions in fog late Sat night in normally prone locations. KBOS TAF...High confidence. VFR. Light SE winds will become light/variable overnight. Winds then shift back to SE Sat morning. KBDL TAF...High confidence. VFR. Low chance for MVFR-IFR conditions in patchy fog 07Z-11Z tonight and again Sat night. Outlook /Sunday night through Wednesday/... Sunday night and Monday... High confidence. VFR. Light winds. Areas of IFR/LIFR possible in late night/early morning fog. Monday night through Wednesday... Moderate confidence. Mostly VFR. Areas of IFR/LIFR in late night/early mornign fog. Also brief MVFR cigs/vsbys in scattered showers/thunderstorms.
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&& .MARINE...
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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/...High confidence. Ridge of high pres over southern New England thru Sat night yielding light and variable winds. Weak low pres will track southeast of 40N/70W Saturday. Outlook /Sunday night through Wednesday/... Moderate confidence. Winds and seas remain below Small Craft Advisory thresholds through the period. Potential for low vsbys in fog, especially Tuesday and Wednesday early mornings. Scattered showers and thunderstorms with brief poor vsbys Tuesday and Wednesday.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...WTB AVIATION...WTB/EVT MARINE...WTB/EVT

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