Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220909 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 507 AM EDT MON AUG 22 2016 .SYNOPSIS...
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Last of the heavy showers will exit the southeast New England coast by early to mid morning. Otherwise, high pressure will bring beautiful late summer weather today and Tuesday with low humidity. Warmer and more humid weather is expected Wednesday through Friday along with the risk of showers and thunderstorms by weeks end. Dry weather may return next weekend.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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5 am update... Very busy early this morning as a low cape/high shear environment resulted in a localized area of significant tree damage/power outages in the Marlborough and especially Concord MA areas. KBOS and TBOS radar showed a strong gate to gate couplet for a time, so some of this damage may have been tornadic. A damage team will likely be headed out to the region later this morning. Fortunately, things are winding down rather quickly as cluster of heavy rain showers/isolated thunderstorms across parts of RI/SE MA will come to an end by 7 am. Activity may persist a tad longer across the Cape/Islands, but even in these locations showers should be gone by mid morning at the latest. Otherwise, a beautiful day on tap with skies quickly becoming mostly sunny this morning. Much drier air will also be working into the region, so a big relief from the humidity. High temps will only top out in the middle to upper 70s across the higher terrain, to the lower 80s in the coastal plain. Northwest winds may gust to around 25 mph at times.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Tonight... High pressure building in from the west will result in mainly clear skies and diminishing wind. Given the dry airmass behind this morning`s cold front, it will be an ideal setup for radiational cooling. Expect the normally coolest outlying locations to bottom out in the middle to upper 40s, while the urban heat island in Boston will be the warm spot only dropping to around 60. Tuesday... Another beautiful day for southern New England, but with less wind with high pressure in control. Mostly sunny skies will result in afternoon high temps in the upper 70s to the lower 80s, but with low humidity.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Highlights... * Warmer and more humid Wed thru Fri * Dry much of next week except a risk of T-storms Fri Overview and model preferences... A slight taste of fall early leads into gradual warming and more seasonal late August conditions by late in the week. The cooler/drier stretch is courtesy of a Hudson Bay vortex which will advect Canadian prairie air into New England Mon and Tue. After, thanks to better dynamic digging of a trof across the W CONUS, the resulting downstream ridge across the E and NE allows influence of the subtropical high to impact the region. This will bring about slightly more humid and summer-like conditions by the end of the week. One last forecast note is a weakening trof and upper lvl shortwave which may bring about some wet/unstable wx Fri. Models continue to show good agreement through much of the long term, so have no problems continuing to use a consensus blend that also includes persistence with this update. Details... Wed and Thu... Continued warming trend but under the influence of high pres which will be shifting E. The combination of moisture/heat advection will lead to slightly more humid/slightly warmer conditions each day. H85 temps reach near +15C Wed then +16C Thu. This translates with full mixing to mid-upper 80s with a few spots possibly touching 90F. Dwpts begin shifting back into the 60s by Thu afternoon. Fri... Weakening shortwave ejects from the developed longwave trof across the W CONUS. Models continue to align fairly well on timing of the attendance cold front across new England, bringing it through in the later hours of Fri/Fri evening. The issue is how much stability/moisture is left when this front arrives. ECENS/GEFs probabilities are rather low for the near 2.00 inch PWAT mark, and likewise QPF probabilities are low for numbers more than 0.50 inches. This is likely a result of the weakened wave interacting with the relatively anomalous high pres just offshore. Remnant subsidence will also limit moisture increases. In fact, noting that the operational ECMWF and even some ensemble members are now completely dry with this frontal passage. For now, will continue with afternoon/evening pops in the slight to chance range as there is still much time to better resolve these more mesoscale features. Next weekend... Another round of ridging and drier air moves in from the NW behind the exiting front. While a return to drier wx looks likely, it is not expected to be as cool or dry as the airmass moving in tomorrow. Looking at highs near normal with a return to more comfortable dwpts.
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&& .AVIATION /09Z MONDAY THROUGH FRIDAY/...
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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 Tuesday/... Today...High confidence. Lingering MVFR-IFR conditions in showers and low clouds along the coastal plain will improve to VFR by 12z. Perhaps an hour or so later across portions of the Cape and Islands. Otherwise, VFR conditions today with northwest wind gusts of 20 to 25 knots. Tonight and Tuesday...High confidence. Winds diminish this evening and VFR conditions persist through Tuesday. KBOS Terminal...High confidence in TAF. Improvement to VFR by 10 or 11z. KBDL Terminal...High confidence in TAF. Outlook /Tuesday Night through Friday/... High confidence in a stretch of mainly dry VFR weather. Sea breezes most likely mid-late week.
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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 Tuesday/... Today and tonight...High confidence. Near shore northwest wind gusts of 20 to perhaps close to 25 knots expected today. Opted to leave the near shore waters out of any headlines, but day shift will likely have to re-evaluate. We did hoist small craft headlines for our outer eastern MA waters, where northwest 25 knot wind gusts and 3 to 5 foot seas may develop for a time late this afternoon and evening. Tuesday...High confidence. High pressure building in from the west will keep winds and seas below small craft advisory thresholds along with excellent visibility. Outlook /Tuesday Night through Friday/...High confidence. Tuesday through Thursday ... High confidence. Quiet boating weather as slow moving high pressure builds over the waters. By Thu SSW winds will likely become gusty near shore. Friday...Moderate confidence. Increasing SSW flow and seas, may just touch small craft criteria. Otherwise, late day risk of showers and thunderstorms over the waters.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 2 PM this afternoon to 2 AM EDT Tuesday for ANZ250-254.
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&& $$ SYNOPSIS...Frank/Doody NEAR TERM...Frank SHORT TERM...Frank LONG TERM...Doody AVIATION...Frank/Doody MARINE...Frank/Doody

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