Area Forecast Discussion
Issued by NWS Boston, MA

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294 FXUS61 KBOX 270817 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 317 AM EST Mon Feb 27 2017 .SYNOPSIS...
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High pressure centererd south of New England today moves out to sea Tuesday. This brings back a mild flow of air with above normal temperatures. A couple of weather systems will bring periods of wet weather later Tuesday into Wednesday night. Colder air returns late this week into next weekend.
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&& .NEAR TERM /THROUGH TODAY/...
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High pressure centered south of New England. Flow around the high has brought west-southwest winds to our area, which will continue through the day. Dry airmass will mean mostly sunny skies, possibly some thin cirrus. Vertical profile shows potential for mixing up to 850 mb. Winds aloft in this mixed layer are 25-30 knots. So this means potential surface wind gusts reaching 25-30 knots. The mixing will tap temps aloft of -3C to -4C, which would support max sfc temps in the low to mid 50s. Given past behavior of model temperatures and the potential for mixing higher than model forecast, we added 2-3F to the max temps.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
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Tonight...Moderate-High confidence. West-southwest flow diminishes near the surface. But high pressure offshore maintains dry weather for much of the night. Weak cold front is indicated moving south from Canada into Northern New England. A weak airflow makes it difficult to determine how far south the front makes it, but pressure pattern suggests it gets no farther south than the Massachusetts border. Shortwave ejecting from a trough over the Pacific Southwest reaches the Great Lakes by Tuesday morning. Models do show a broad cloud area moving across New England, and the GFS is aggressive with measureable pcpn while the ECMWF is generally dry. We agree with increasing clouds, but tend more toward the drier ECMWF solution for pcpn. Most of the dynamics and low level inflow remain well to our west. Temperatures should cool off early, but warm advection remains weak through the night so at most temps would level off overnight with a range in the mid 20s NW to mid 30s coast. Tuesday...Moderate-High confidence. Increasing southwest flow, especially during the afternoon. This will bring an increasing potential for lift over us and so a chance of pcpn especially in the afternoon/evening. The airmass looks similar to today but with a few more clouds in place. So we expect another mild day with temperatures near 50 or in the low to mid 50s.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Highlights... * Above average temperatures for most of this week * Widespread showers possible Tuesday night through late Wednesday night * More seasonable conditions return Friday into Saturday Overview... 26/12z guidance continues to show rather good agreement on the overall pattern through Friday. That said, there are the typical discrepancies in the timing and amplitude of shorter wavelength features toward the end of this week. Since these sorts of details are usually less predictable at this time range, still prefer a consensus approach. Details... Wednesday into Thursday...Moderate confidence. Main weather producer will occur Wednesday into Thursday. Still some uncertainty on the timing and location of the surface low. Our region should remain in the warm sector of a low pressure moving through the Great Lakes. Strong southwest winds aloft are likely to bring an unseasonable amount of moisture our way. This expecting plenty of clouds. Rainfall amounts however are generally expected to be less than one half inch for most of our region. Convective instability will be the wildcard. Most convective indices are rather marginal. However, if we could get some low level instability to go along with the wind shear, then a few thunderstorms may develop. This has been consistent, weak signal the past couple of days. By no means is this a lock, but will keep the mention of isolated thunderstorms in the forecast. Still have high confidence that at least some precipitation will fall, and temperatures will be above average Wednesday into Wednesday night. Cold front will sweep through early Thursday morning, resulting in drying conditions with falling temperatures falling through the day. Strong cold air advection likely to mean gusty west to northwest winds. Friday and beyond...Moderate confidence. 26/12Z GFS remains the model with the strongest hint of a clipper-like low pressure passing by to our south Friday morning. The other models are neither as aggressive, nor as humid. Favored the drier consensus solution for now. This will be something to watch over the course of this week. High pressure remains to our south next weekend. After a period of more seasonable temperatures Friday and Saturday, it appears we get back into more of a warmup next Sunday. Good mixing and cold air over the ocean may result in ocean effect snow showers next weekend, before another clipper system possibly approaches towards late Sunday.
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&& .AVIATION /08Z 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. VFR. Increasing high clouds especially in the afternoon/evening. W-SW winds start the day light near the surface and at 25-30 knots in the lowest 5000 feet AGL. Expect some of this wind to mix to the surface in gusts during late morning and afternoon, then diminish toward evening. Tonight... High confidence. VFR. Increasing high clouds before midnight. Cloud bases lower to around 4500 feet overnight. Tuesday...Moderate confidence. VFR most of the day. Chance of MVFR cigs developing during the afternoon, but this could hold off until evening. There is a chance of reduced vsbys in showers in the afternoon but the better chances will hold off until night. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday night into Wednesday...Moderate confidence. Periods of -RA through the period will result in MVFR/IFR conditions. Cannot rule out LIFR in fog during the overnight hours. Thursday...Moderate confidence. VFR conditions from west to east during the morning. Blustery westerly winds are possible. Friday...Moderate confidence. Mainly VFR, with MVFR possible toward the south coast, including the Cape and islands.
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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/...High confidence. Today... High pressure offshore moves east tonight and Tuesday. West southwest flow actually increases for a time late morning and afternoon, bringing a chance of 25-30 knot winds during that time. Winds then diminish this evening. A Small Craft Advisory will be in effect on all waters for this wind. Meanwhile 5 foot seas will linger on the outer waters. Tonight and Tuesday... Winds and seas remain below Small Craft Advisory levels. Clouds do move in from the west later tonight. Vsbys may lower below 3 miles in showers along the southern waters, mostly Tuesday afternoon/evening. Outlook /Tuesday Night through Friday/... Tuesday night...Moderate confidence. Warm frontal passage Tuesday night could drop vsbys in rain and fog. Wednesday into Thursday...Moderate confidence. Approaching system from the west will push a cold front through on Thursday, increasing both seas and winds during this period. Heavy rain and a few thunderstorms are possible, lowering vsbys. There is the potential for southerly gales across the waters Wed night, and northwesterly gales on Thursday behind a cold front. Friday...Moderate confidence. Gusty west winds continue. Small Craft Advisories likely will be needed for some of the coastal waters.
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&& .FIRE WEATHER...
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Dry and blustery conditions will persist today pushing minimum relative humidity values at or below 30 percent for a good portion of interior Southern New England as southwesterly flow gusts 25 to 30 mph. Over the weekend much of Western and Central MA and CT saw around 0.50-0.75" of liquid, with around 0.10-0.25" to the east, there`s some concern of potential fire weather conditions over Northeast CT, RI and Eastern MA as temperatures warm into the mid and possibly upper 50s.
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&& .HYDROLOGY... Rising water levels, partly from weekend rain but also from snowmelt in Northern New England. There is still plenty of water moving downriver from the snowpack. We will need to monitor water levels across southern New England for a while this week. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST Tuesday for ANZ250-254. Small Craft Advisory until 10 PM EST this evening for ANZ255- 256.
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&& $$ SYNOPSIS...WTB/Belk NEAR TERM...WTB SHORT TERM...WTB LONG TERM...Belk AVIATION...WTB/Belk MARINE...WTB/Belk FIRE WEATHER... HYDROLOGY...

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