Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 141730 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1230 PM EST Wed Feb 14 2018 .SYNOPSIS... High pressure continues to slide east today, with warming in its wake. A few showers skirt the southern tier tonight. An approaching cold front will bring a period of rain to the region late Thursday night into Friday morning with mild temperatures. Dry but much colder weather returns Friday night into Saturday behind the front. A fast moving low pressure system may bring accumulating snow to portions of the region Saturday night into Sunday morning. Above normal temperatures will quickly return early next week along with the risk for some showers. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1230 PM Update... Clouds have been hanging tough early this afternoon, although we are starting to see large breaks in cloud cover across NE MA and moreso in western CT. Cross sections indicate clouds will slowly erode through late afternoon, so earlier trend of gradual clearing still looks good. Highs should top out in 40s, though can`t rule out a few locations making a run at 50.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Tonight... A second, slightly more vigorous shortwave will slide through the mean W-E jet during the late night. This is coincident with a moisture increase and PWATs near 0.75 (nearly 2 std deviations above normal). However, the core of this wave looks to remain to the S, and given confluent flow aloft, it should yield a tight gradient in SHRA risk from S-N between midnight and sunrise. In fact, some of the available WRF data keeps the bulk of the QPF completely offshore. POPs will range from likely offshore to slight chance up to about the Mass Pike. However, lift is weak and lower lvl convergence nearly non-existent, so will feature showery precip rather than stratiform. The increase in clouds during the evening will stall diurnal cooling, so will likely see mins remain generally above freezing, mainly in the mid-upper 30s. Thu... The continued slow shift of the warm front will lead to continued warm advection, but also moisture, likely in the form of more widespread low-mid stratus even as early AM showers dissipate. Therefore, highs will be a struggle between the continued warming as H92 temps increase to nearly +8C as an average, in spite of the H85 temps remaining near +5C, and the continued cloud cover through the day. Without breaks, mixing suggests highs should still reach the mid 50s, however a few breaks of sun could easily lead to upper 50s to near 60, which is just shy of records. Overall, mild weather continues, with a mainly dry day after any AM showers erode. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Highlights... * Mild with a period of rain late Thu night/Fri am * Dry but turning much colder Friday night into Saturday * Accumulating snow potential Sat night/Sun am but not a lock * Above normal temperatures return early next week Details... Thursday night and Friday... Wave of low pressure and associated cold front will approach the region Thursday night into Friday morning. Enough lift and forcing available for a period of rain late Thu night/Fri am...but the system is progressive so mainly dry weather by Friday afternoon. Unseasonably mild Thu night with low temps only dropping into the 40s in many locations. The colder air will also lag a bit behind the front. This should allow high temps Fri to reach well into the 40s across the high terrain...while some lower elevations may reach into the lower to middle 50s. Friday night and Saturday... Much colder air returns to the region Fri night/Sat as high pressure builds in from the west. Low temps Fri night will be mainly in the teens to middle 20s with highs on Sat in the 30s. Saturday night and Sunday... The potential for accumulating snow exists Saturday night into Sunday morning...but it is far from a lock and many options remain on the table. While the overall current pattern is rather hostile for winter weather...New England February climatology still allows for snowstorms in unfavorable pattern if timing/track is ideal. This set up features high pressure moving east and away from our region as southern stream energy lifts northeast. The timing and amplification of the shortwave approaching from the southwest remain quite uncertain and will have a large impact on the outcome. The operational 00z GGEM and especially the GFS are rather amplified and show a fast moving but impressive snowstorm impacting the region Sat night/Sun am. Meanwhile...the latest operational ECMWF and UKMET are much flatter and indicate just a glancing blow with most of the precipitation staying to our south. Given the time frame of this event...the individual ensemble members are much more significant. As one might expect they are showing a large amount of spread at this point. The solutions range from glancing blows, while others indicate 6+ inch snowfall potential for a good chunk of the region. There also are a few members that are so amplified that they confine the significant snow back into the interior while boundary layer/ptype issues become more of a concern on the coastal plain. We are still more than 100 hours out in the model world from this potential event...so we have to keep all options on the table at this point. Monday and Tuesday... Anomalous upper level ridge across the southeast will build northward resulting in abnormally high height fields/southwest flow aloft into southern New England. The result will be above normal temperatures along with the risk for some showers at times. It is possible that we see a day of well above normal temperatures...but that is uncertain since there may be shallow cool air that may try to slip south. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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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 Thursday/... 18Z Update...Moderate confidence. Lingering MVFR/IFR ceilings will slowly lift through late afternoon and expect VFR conditions throughout by 20-22Z with prevailing SW flow. Conditions quickly deteriorate to IFR/LIFR overnight (after 04Z) especially across CT, RI, and SE MA where an area of showers will move through until daybreak. Slow improvement Thu as ceilings lift to MVFR, but am optimistic for further improvement to VFR ceilings after 18z. KBOS Terminal...Moderate confidence in TAF. KBDL Terminal...Moderate confidence in TAF. Outlook /Thursday Night through Sunday/...Moderate Confidence. Thursday Night: MVFR with locally IFR conditions developing. Breezy. RA late. Friday: MVFR/IFR conditions possible early in the morning with improvement later. Windy with gusts to 30 kt. Chance SHRA in the morning. Friday Night: VFR. Windy with gusts to 30 kt. Saturday: Mainly VFR. Breezy. Saturday Night: Mainly IFR, with local MVFR possible. Breezy. SN likely. Sunday: Improving conditions by afternoon. Breezy. Chance SN in the morning.
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&& .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/...High confidence. Today and tonight... S-SW winds will gust to around 25 kt, first over the waters closest to the Gulf of Maine late this morning, then the southern waters this afternoon and evening. This suggests the need to expand small craft advisories this morning. Otherwise, some rain showers/fog will yield lowered vsbys. Thu... S-SW winds continue, but generally weaker than today and tonight. Therefore, expecting conditions below advisory criteria. Outlook /Thursday Night through Sunday/...Moderate to High Thursday Night: Winds less than 25 kt. Local rough seas. Rain. Local visibility 1 to 3 nm. Friday: Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Chance of rain showers. Friday Night: Risk for a period of gale force winds with gusts up to 35 kt. Rough seas up to 11 ft. Saturday: Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Local visibility 1 to 3 nm. Saturday Night: Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Snow, rain likely. Visibility 1 to 3 nm. Sunday: Risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Chance of snow, slight chance of rain. Areas of visibility 1 to 3 nm. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST Thursday for ANZ232>235- 237-255-256. Small Craft Advisory until 5 PM EST this afternoon for ANZ231- 250-251. Small Craft Advisory until 10 PM EST this evening for ANZ254.
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&& $$ SYNOPSIS...Frank/Doody NEAR TERM...Frank/Doody/NMB SHORT TERM...JWD LONG TERM...Frank AVIATION...JWD MARINE...Frank/Doody

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