Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 070920 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 420 AM EST Tue Feb 7 2023 .SYNOPSIS...
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Dry, seasonable conditions today give way to mixed precipitation overnight. Light freezing rain is possible across much of the area. A period of mainly rain is expected later Thursday into Thursday night as low pressure passes well to our northwest. Unseasonably mild temperatures follow on Friday and record highs may be challenged. Seasonable temperatures return this weekend. We also will have to watch an offshore low pressure system for a period of rain and/or snow this weekend...but this may remain south of the region.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Lingering clouds over the Cape will decrease as a maritime low continues to pull out to sea. Mostly sunny conditions this morning, thanks to high pressure overhead, will gradually give way to increasing clouds this afternoon ahead of our next precipitation maker. Northerly flow will keep temperatures near normal. Winds gradually shift to the south this afternoon.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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A complex but quick hitting mid/upper level shortwave will bring mixed precipitation to southern New England after 00Z this evening as its` parent low sweeps through southern Quebec. While progressive, this system looks to bring a headache, in terms of precipitation forecasting, to our area between 00Z and 06z from west to east. A significant layer of dry air aloft ahead of the system will allow for evaporational cooling at the surface as the column begins to saturate; dropping surface temperature to near or below the freezing mark. With a strong warm nose between 800-850mb, freezing rain and sleet are likely to fall across western portions of our CWA. As the system moves east, the entire column will gradually saturate, which will allow more of a rain/snow mix to develop. Locations south of the I-90 corridor, specifically across SE MA and southern RI, will stay above freezing through the column for the entire event, yielding light rain in these areas. The 00Z model suite was much more aggressive regarding the geographic distribution of freezing rain compared to earlier model runs, with the NAM, GFS, and ECWMF showing light accumulations of freezing rain across most of Massachusetts north of the I-90 corridor. Given confidence has grown in the potential for freezing rain, we elected to hoist a Winter Weather Advisory for all of Massachusetts north and west of the I-495 corridor. The day shift will be able to evaluate the need to expand this advisory into our metropolitan areas, like Hartford, Providence, and Boston as it is possible that these locations see light accumulations of FZRA, especially if current model trends continue. In any case, FZRA/Sleet/Snow accumulations are expected to be very minor, with less than an inch of snow/sleet possible. With that said, we are all too familiar with what a trace/glaze of ice can do to roadways, so drivers this evening should take extra precautions to avoid slick roadways. Fortunately, this progressive system will be out of our hair before sunrise on Wednesday, with some clouds lingering during the morning hours. The afternoon will bring abundant sunshine with high pressure overhead, and mild temperatures in the upper 40s to near 50 degrees! Breezy WSW winds will gradually shift to the NW and diminish through the day.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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Highlights... * A period of mainly rain later Thu into Thu night * Dry/Unseasonably mild Fri with near record high temps possible * Seasonable temps return this weekend * Period of unsettled weather possible this weekend or may stay south Details... Thursday & Thursday night... Low pressure over the midwest will lift northeast into the eastern Great Lakes and then Quebec Thu & Thu night. In response...a modest southwest LLJ will develop and increase the forcing for ascent. This will allow for a period of rain to overspread the region sometime later Thu into Thu night. Antecedent cold air will be lacking ahead of this system and with the low passing well to our northwest...Ptype will mainly be rain. It is possible that just enough cold air will be present in northwest MA for a bit of snow/ice at the onset. Friday... Southwest flow coupled with anomalous mid level warmth in place will set the stage for unseasonably mild temperatures to close out the work week. 850T on the order of +3C to +6C coupled with good mixing should yield highs well up into the 50s...to perhaps 60+ in a few spots. The potential exists for record highs depending on the amount of solar insolation. A modest LLJ will also allow for it to become quite breezy to windy across the region. This Weekend... A more seasonable airmass will return to the region this weekend behind as high pressure builds over Quebec and into northern New England...sending cooler air southward. We also will have to watch an offshore low pressure system for the potential for a period of rain and/or snow. However...the upper level pattern is not very amplified. This may allow the precipitation in association with this offshore system to remain to our south. A lot of spread in the ensembles...so will just have to keep things probabilistic until the models come into better agreement.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 09Z update... Tuesday... High confidence. VFR, but may see persistent MVFR cigs Cape/Islands in the morning as low pressure pulls out to sea. N wind gusts to 25 kt Cape/Islands diminishing by mid morning. Winds turn southerly in the afternoon, increasing late in the day. Tuesday Night...High Confidence in timing, Moderate Confidence in precipitation type. Mixed precipitation moves through the region between about 00Z and 06Z from west to east. P-Type will vary significantly, from the possibility of -SN and -FZRA at western terminals, to all rain at terminals in RI and across the Cape and Islands. Low confidence in P-Type along the I-90 corridor, as precipitation likely starts as -FZRA before transitioning to -IP/-RASN. Breezy southerly winds diminish as they turn WSW winds overnight. Wednesday... High Confidence. MVFR ceilings and reduced visibilities become VFR by 12Z Wednesday except across the high terrain where MVFR cigs will hang on through mid morning; meaning MVFR cigs possible at ORH for a period Wednesday am. Cigs become VFR at all terminals by about 16Z. Breezy conditions redevelop after sunrise; WSW winds, gusting to 20 kt, diminish to between 5-15kt as they gradually shift to the NW by Wednesday afternoon. KBOS Terminal...Moderate Confidence in TAF. VFR today as northerly winds shift to the south by this afternoon. Mixed precipitation likely between 03-06Z this evening, high confidence in the timing but low to moderate confidence in P-Type. Chance for IP to mix in closer to 03Z before precipitation becomes more of a RA/SN mix. Little to no accumulation expected. KBDL Terminal...Moderate Confidence in TAF. VFR today. Mixed precipitation moves in between 00-03Z this evening, likely as a rain/sleet mix. Little to no accumulation of frozen precipitation expected, but a glaze of freezing rain is not out of the realm of possibilities. Outlook /Wednesday Night through Saturday/... Wednesday Night: VFR. Breezy. Thursday: Mainly VFR, with local IFR possible. Breezy. RA likely, chance FZRA. Thursday Night: Mainly IFR, with local MVFR possible. Windy with gusts up to 35 kt. RA likely. Friday: VFR. Windy with gusts up to 35 kt. Friday Night: VFR. Breezy. Chance RA. Saturday: Mainly VFR, with local MVFR possible. Windy with gusts up to 30 kt. Chance RA.
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&& .MARINE...
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Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 09Z Update... Today through Wednesday ... All gale warnings have been converted to small craft advisories as winds have fallen below Gale criteria and are expected to remain below for the next 24-36 hours. North/northeast winds will shift to the south by late this afternoon. Winds gradually shift to the SW and eventually NW through Wednesday afternoon. as a cold front moves across the waters push through the region overnight tonight with scattered showers and 20 to 30 knot wind gusts out of the west. Seas will gradually diminish through the period from 7-10 feet to near or just below 5 feet but Wednesday afternoon. Outlook /Wednesday Night through Saturday/... Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain. Local visibility 1 to 3 nm. Thursday Night: Moderate risk for gale force winds with gusts up to 40 kt. Seas up to 5 ft. Rain likely. Visibility 1 to 3 nm. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Slight chance of rain. Friday Night: Winds less than 25 kt. Local rough seas. Chance of rain. Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Chance of rain.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...Winter Weather Advisory from 7 PM this evening to 2 AM EST Wednesday for MAZ002>012-014-026. RI...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ230- 236. Small Craft Advisory until 7 AM EST Wednesday for ANZ231>235- 237-251. Small Craft Advisory until 7 PM EST Wednesday for ANZ250- 254>256.
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&& $$ SYNOPSIS...Frank/KS NEAR TERM...KS SHORT TERM...KS LONG TERM...Frank AVIATION...Frank/KS MARINE...Frank/KS

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