Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 260803 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 403 AM EDT Wed Apr 26 2017 .SYNOPSIS...
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Low pressure will slowly track up the east coast this morning bringing periods of rain. Low clouds along with some drizzle and fog are expected to linger tonight into Thursday especially along the coast. Very mild to warm afternoons should return Friday and Saturday with the low risk for a few showers/thunderstorms. Much cooler weather follows Sunday especially on the coast. Another cold front will likely bring more showers to the region sometime Monday into Tuesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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400 AM Update.... Overall trend in the forecast remains on track for early this morning. Next batch of precip is beginning to make its way onto the south coast as of 330 AM. This bulk of precip could drop near a half of an inch of QPF. Many areas across RI have already seen over 1.5 inches of rain so this will just continue to add. Will have to closely watch for nuisance flooding in the typically prone regions of Cranston/Warwick and eventually Fall River and New Bedford. Cannot rule out a rumble of thunder with the rain as models continue to show elevated instability with showalters dropping to below 0. However haven`t seen a bolt on the lightning tracker for quite some time, so confidence is low in a rumble of thunder. If convection does develop early this morning, then this will enhance the rainfall amounts for the morning commute. Today... Stacked surface low pressure system near the Mid-Atlantic will move towards southern New England today. Continuous southerly flow aloft will continue to pump moisture into the region through the day. Appears that surface warm front will try to move in, or may just stall across the area. This will result in difference in temperatures. For now continued with a blend in the guidance. The main bulk of precip will lift this morning. However, still some weak lift and with a very saturated moisture profile, anticipate on and off showers late this morning and into the afternoon hours. Increasing dewpoints across the south coast could lead to patchy fog development. Low confidence on how low vsbys will go, but something to watch through the day.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
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Wednesday night... Stacked low pressure system will begin to move south and east of the region. 850 mb becomes more of a open wave resulting in a more weaken system. Upper levels appear to begin to dry out as the low begins to move, however, at the surface and mid-levels, the profile is quite saturated. Anticipate a soupy mess with low clouds and fog. Will have to watch for vsbys dropping below a quarter of a mile which would result in a dense fog advisory. Confidence is low at this time, but something to watch. Continuous easterly flow overnight combined with some weak lift will result in areas of drizzle especially across eastern locations.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Low clouds/spotty drizzle Wed night+Thu with cool temps on coast * Mild to warm afternoons Fri/Sat with a low risk for a few t-storms * Backdoor cold front brings much cooler temps by Sun * Period of showers which may be briefly heavy sometime Mon/Tue Details... Wednesday night and Thursday... Closed upper level low will linger off the southern New England coast Wed night into Thu. Model cross sections indicate a fair amount of low level moisture lingering below the subsidence inversion. Given overall setup and time of year, feel low clouds will linger Wed night into Thu afternoon even across much of the interior. There also should be areas of fog and drizzle, especially on the coast Wed night and Thu am along with the risk for a spot shower or two. With that said, guidance is probably too warm with forecasted high temps on Thu given expected low cloud cover. High probably remain in the 60s for most of the region and perhaps stuck in the mid to upper 50s along the coast. Now if more sun is realized than expected it still would be possible for portions of the interior to break 70, but hedging cooler for now. Friday and Saturday... Upper level ridge of high pressure building off the southeast coast will be pumping higher height fields into southern New England. Decent shot for high temps to reach the 70s to lower 80s away from any marine influence along the coastline, especially the south coast with south to southwest flow. Most of this time should feature dry weather, but a few shortwaves will result in the low risk for a couple of showers/t-storms. Greater chance of development would occur if energy moves through closer to the time of peak heating on Fri and Sat. Saturday night and Sunday... Despite abnormally high height fields, strong high pressure will be building across eastern Canada. This will likely send a backdoor cold front south of the region late Sat or Sat night. Much cooler temps are likely for Sunday especially along the coast where they should remain in the 50s. Perhaps a few spot showers, but high pressure may suppress most of the activity to our southwest. Monday and Tuesday... Timing uncertain, but an approaching cold front will likely bring a period of showers. GEFS anomalies signaling decent low level jet coupled with fairly high Pwats so the showers may be heavy for a brief period of time. Again, timing uncertain and not expecting both days to be total washouts. Temperatures also uncertain given timing/wind direction. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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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 Tonight/... Before 12z...High confidence. Mainly IFR conditions persist in widespread rain showers. Heaviest rain and greatest risk for isolated t-storms will be now through 12z Wednesday. LLWS will be a concern especially across the Cape and Islands. Today...Moderate confidence. MVFR-IFR CIGS continue with areas of - RA/RA and patchy fog, especially across the eastern half of southern New England. Reduced VSBYS likely, down to IFR in spots. May see areas of LIFR CIGS across the higher inland terrain and along the coast. SE winds gusting up to around 25 kt across Cape Cod and the islands. LLWS impacts for the Cape and islands, and possibly as far north as BOS, during the morning hours. Tonight...Moderate confidence. MVFR-IFR conditions continue in areas of fog and drizzle. A few showers are possible. KBOS TAF...High confidence in TAF, moderate confidence on trends. KBDL TAF...High confidence in TAF, moderate confidence on trends. Outlook /Thursday through Sunday/... Wednesday night into Thursday...Moderate to high confidence. IFR to even LIFR conditions likely Wed night into part of Thu am along with some fog, drizzle and a spot shower. Lower conditions most likely on the coast. Conditions may improve to mainly MVFR by late Thu morning and afternoon. Thursday night and Friday...Moderate confidence. MVFR/IFR conditions likely in areas of low clouds and fog patches Thu night into early Fri am. Improvement to VFR likely by Fri afternoon with the low risk for a few showers and perhaps a t-storm. Saturday and Sunday...Moderate confidence. VFR conditions probably dominate.
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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 Tonight/...High confidence. Small Craft Advisories are in effect for all waters expect Boston Harbor and Narragansett Bay. Seas will remain above 5 feet with winds gusts near 20-25 kts into the afternoon. As the coastal low begins to move eastward, winds gusts will begin to subside and seas will relax. SCA will still be needed for ocean waters, but overall trend will be improvement. Could see vsbys restrictions across the waters tonight in dense fog. Outlook /Thursday through Sunday/... Wednesday night through Friday...Moderate to high confidence. Despite wind gusts mainly 20 knots or less, left over southeast swell will result in small craft seas persisting through Friday across many of our outer and southern waters. In addition, areas of fog may result in poor vsbys for mariners especially during the overnight and early morning hours. Saturday and Sunday...Moderate to high confidence. West to southwest wind gusts to 20 knots Saturday will shift to the northeast by late Sat or Sat night behind a backdoor cold front. Overall, expect winds and seas to remain below small craft advisory thresholds.
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&& .TIDES/COASTAL FLOODING...
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* Isolated minor coastal flooding impacts during astronomically high tides through tonight along the east and south coasts We are entering a spring tide cycle with high tides that are astronomically high. This combined with an anticipated storm surge of around 1 foot may set the stage for isolated pockets of minor coastal flooding along both south and east coasts around the time of high tide this morning and again tonight. Went ahead an issued a new coastal flood statement for potential for splashover. There is also the combination of runoff from heavy rain and elevated water levels near high tide this morning which could exacerbate drainage of fresh water in some coastal urban areas and near the mouths of streams and small rivers. We will need to continue to monitor the tides through at least Wednesday night as there is not a significant offshore flow or pressure rises to help evacuate a lingering surge. The astronomical high tides remain very elevated through the end of the week. Due to the breadth of the fetch, we may encounter enough wave action with lengthening periods on top of an elevated tide to cause pockets of erosion tonight through tonight along the Martha`s Vineyard south coast, Nantucket south and east coasts, and the outer Cape ocean side from Truro to Chatham. Boston High Tides (flood stage at Boston 12.5 feet)... 11.47 feet / Tuesday 11:20 pm 11.15 feet / Wednesday 11:50 am 11.92 feet / Thursday 12:07 am Providence High Tides (flood stage at Providence 7 feet)... 5.98 feet / Tuesday 8:11 pm 5.53 feet / Wednesday 8:41 am 6.21 feet / Wednesday 9:00 pm
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 3 PM EDT this afternoon for ANZ231>234. Small Craft Advisory until 9 AM EDT Thursday for ANZ235-237- 250-251-254>256.
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&& $$ SYNOPSIS...Belk/Dunten NEAR TERM...Dunten SHORT TERM...Dunten LONG TERM...Belk AVIATION...Belk/Dunten MARINE...Belk/Dunten TIDES/COASTAL FLOODING...staff

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