Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170011 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 711 PM EST Fri Nov 16 2018 .SYNOPSIS... Dry and chilly weather continues into Sunday afternoon. Weak low pressure may bring patchy light rain and/or snow late Sunday into Monday. Another shot of colder air moves in by the middle of next week, though it should be mainly dry. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 7 PM Update... Showers have come to an end this evening as clouds begin to scatter out. Based on satellite initializing fairly well with the latest hi- res guidance have brought in clearing skies a bit earlier overnight, though enough moisture lingers to keep at least partly cloudy skies, mainly over northwest MA. Previous Discussion... A few left over light rain/snow showers will wind down early this evening. Temps mainly above freezing...so no problems expected on the roadways. Otherwise...dry weather with just an abundance of clouds this evening. We should see the clouds scatter out tonight...but guidance might be doing this too fast given a fair amount of low level moisture remaining. Enough westerly flow aloft and lack of cold advection will keep temperatures from bottoming out tonight. Lows should generally range from around 30 to the middle 30s...so many locations will not see temperatures drop too much from their current late afternoon readings. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Saturday... Westerly flow aloft and at the surface will result in a dry/tranquil Saturday. A mixture of clouds and sunshine with decent mixing will allow highs to reach the lower 40s in the higher terrain...to the middle and upper 40s elsewhere. It is not out of the question that a couple locations hit 50. While these temperatures are still below normal for mid November...quite a bit milder than what we have experienced the last few days. Saturday night... Large high pressure gradually builds in from the west Saturday night. This will result in a dry, but chilly night. While we may see an increase in some mid/high level cloudiness overnight...there should be enough of a window to allow most locations to bottom out in the 20s especially with early season snow cover in place. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Highlights... * Weak low pressure brings periods of rain and snow late Sun into Mon * Dry and colder mid week * Potential for warm up toward next weekend Overview... High pressure on Sunday will give way to a weak low pressure system which crosses SNE late Sunday bringing a mix of rain and snow showers to the region. There exists good model agreement that the broad upper trough extending from Canada sweeps it east by mid week. This ushers in a large surface high pressure and a drier, much colder air mass. This dry airmass sticks around through the end of the week while temperatures, after bottoming out on Wednesday, start to moderate back toward more seasonable warmth. There`s good support for this warmup, as both the EPS and GEFS ensemble models show anomolous warmth in the low levels. Details... Sunday... Sunday will be a quiet day under the influence of a large surface high centered over SNE. Winds are light under a dry zonal flow at the mid levels with PWATs <0.5". We`ll start out with partly sunny skies, but clouds are on the increase through the day from south to north as mid level moisture streams in ahead of the next system. Northwest to west winds initially will keep temps cool, topping out in the 30s and low 40s. Sunday night and Monday... Flow becomes more amplified late Sunday as a shortwave swings through the broad upper trough extending from a mid level low over Hudson Bay. This helps develop an inland surface low that tracks across our south coast overnight. A weak warm front lifts north overnight with an increased tap of moisture through the column (PWATS ~0.75") for widespread light precipitation. The airmass remains cold enough that we`ll see snow initially for areas away from the coast. Along the coast onshore winds will keep the column too warm. Mid and upper level flow then becomes southwesterly as we go into Monday, which will warm temperatures and change thing over to rain from south to north through early Monday. QPF amounts are minimal, though there is still ample disagreement. The GFS/EC want to bring in between a quarter and a half inch of liquid while the higher res NAM indicates much less, so went with a blend for now. Tuesday through Friday... Tuesday we remain under the broad upper trough but should remain mostly dry with clearing skies and our last "warmer" day with highs in the 30s-40s (it`s all relative). By Wednesday a large surface high moves in bringing good CAA and a very cold airmass. H85 temperatures dip around -10 to -14C, 2 to 3 SD below normal. Deterministic and ensemble models paint a similar picture with low temps in the teens to low 20s Wednesday morning and highs in the 20s to 30s. This CAA will also have potential to help mix down a decent H95 jet for some gusty winds, but confidence is low on this given ~24 hr timing difference between the GFS and EC. Thursday and Friday temperatures begin to moderate a bit each day as the lob of arctic air rotates out of the area. Details are uncertain but in general Thursday-Friday look dry as a weak ridge builds toward the east coast and temperatures moderate into the 40s. Ensemble solutions begin to show anomolous warmth in the low levels by next weekend and we could in store for a significant warm up. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/... Tonight...Moderate to high confidence. A mix of clear skies and VRF/MVFR CIGS this evening, expected to imporove through the night. CIGs mainly expected to linger over northwest MA.Westerly wind gusts diminish for most...but some 25 to 35 knot gusts will continue across portions of the outer Cape/ACK with good mixing over the relatively mild ocean. Saturday and Saturday night...High confidence. Mainly VFR but some marginal MVFR cigs are possible generally during the daylight hours across the interior. Westerly wind gusts around 20 knots are expected Saturday afternoon. KBOS Terminal...Moderate to high confidence in TAF. KBDL Terminal...Moderate to high confidence in TAF. Outlook /Sunday through Wednesday/... Sunday: VFR. Sunday Night: MVFR/IFR conditions possible. Chance SN, chance RA. Monday: Mainly VFR, with local IFR possible. Breezy. Chance SN, slight chance RA. Monday Night: VFR. Slight chance SN. Tuesday: VFR. Breezy. Slight chance SN. Tuesday Night: VFR. Windy with local gusts to 30 kt. Wednesday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/...High confidence. Tonight...Good mixing over the relatively mild ocean will yield westerly wind gusts of 30 to 35 knots over the open waters tonight. Opted to extend gales through the evening...as it appears there may be another surge of 35 knot wind gusts. Seas will gradually diminish but remain above 5 feet over the open waters. Saturday and Saturday night...Pressure gradient will continue to weaken...but enough mixing should still yield westerly wind gusts of 20 to 25 knots. We will likely need small craft headlines for at least seas into Saturday afternoon over the open waters. Outlook /Sunday through Wednesday/... Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday Night: Winds less than 25 kt. Chance of rain. Monday through Monday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain. Local visibility 1 to 3 nm. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Slight chance of snow. Areas of visibility 1 to 3 nm. Wednesday: Winds less than 25 kt. Local rough seas. Local visibility 1 to 3 nm. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Warning until 1 AM EST Saturday for ANZ231-232-250-251- 254>256. Gale Warning until 10 PM EST this evening for ANZ233>235-237. Small Craft Advisory until 7 PM EST this evening for ANZ230- 236. && $$ SYNOPSIS...Frank/BW NEAR TERM...Frank/BW SHORT TERM...Frank LONG TERM...BW AVIATION...Frank/BW MARINE...Frank/BW

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