876 FXUS61 KBOX 082358 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 658 PM EST Tue Dec 8 2020 .SYNOPSIS... Weak ridging overnight, then a shot of light snow showers Wednesday as a short wave trough moves across southern New England. Dry weather with moderating temperatures Thursday and Friday. A round or two of mainly rain showers are expected this weekend, but a a period of frozen precipitation can not be ruled out across interior Massachusetts Saturday night into Sunday. It remains uncertain if a coastal storm will impact the region early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 7 PM Update... Skies have become mostly clear early this evening across eastern MA, but an abundance of clouds still covered interior MA/CT and RI. A weak ridge of high pressure building in from the west will allow at least partial clearing to take place across the rest of the region over the next few hours. This coupled with light winds will allow for decent radiational cooling conditions overnight. Low temps should drop into the middle teens to lower 20s in most locales toward daybreak. We also should another batch of clouds also begin to make their way into the region toward daybreak from the west ahead of an approaching shortwave. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... A weak surface trough will swing south out of the eastern Great Lakes around 12z Wednesday and will exit the southern New England coastal waters as a weak surface low come early Thursday. Latest ECMWF guidance suggests the short wave could be a bit more robust than previously thought, not by much, but enough to increase POPs. 925mb forecast humidity values are ranging between 70 and 90 percent with a -4C temperature. At the coast any shower activity will more than likely remain all rain with periods of light snow inland. Snow will be most prevalent in the area of the northern Berkshires with accumulations of 1 to 2 inches. Minor accumulation is also possible throughout the rest of southern New England. Wednesday night ridging sets up to out southwest and will aid in the clearing of clouds and any lingering moisture. A south and southwest flow will help to keep us slightly warmer overnight with lows in the low to middle 30s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Dry Thu & Fri with moderating temperatures * Period or two of showers this weekend with at least a low risk for a period of frozen Ptype across interior MA Sat night into Sun * Uncertainty if a coastal storm forms early next week Details... Thursday and Friday... Large high pressure builds in from the west on Thu and then moves offshore on Fri. The result will be dry/tranquil weather with moderating temps, especially by Fri with rising height fields. Highs on Thu should range from the upper 30s in the high terrain with low to mid 40s elsewhere. High temps on Fri should recover well into the 40s and portions of the coastal plain may take a run at 50. This Weekend... Amplifying shortwave over the Great Lakes will result in developing southwest flow aloft across our region. Timing of shortwave energy remains uncertain...but this will bring the likelihood for a period or two of rain showers sometime during the weekend. Saturday should be a mild day, probably with high temps between 45 and 55 degrees. However, temps Sat night into Sun are a lot more uncertain. While the upper level flow aloft and above normal height fields would suggest rather mild temperatures, there is one fly in the ointment. Both the ECWMF/UKMET indicate a 1040+ MB high pressure system over eastern Canada. This may allow for some shallow cold air to ooze down and perhaps result in at least the low risk for a wintry mix across parts of interior MA Sat night into Sun. Climo/Pattern recognition would favor the colder solutions which is the way we leaned the forecast. That being said; it is still 5 days out so the warmer GFS/CMC solutions are certainly possible. Early Next Week... High uncertainty exists early next week. Many of the EPS members indicate the potential for a coastal storm sometime Mon into Tue. Most of the GEFS solutions are flatter and would indicate generally dry/seasonable weather. Certainly will need time to sort this all out especially with timing of any potential coastal storm. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight...High confidence. Any lingering MVFR ceilings should improve to VFR by 02z-03z with perhaps the exception being the outer-Cape/Nantucket. Otherwise, VFR with diminishing WNW winds. Wednesday...High confidence. VFR early, then lowering to MVFR conditions for some locations in a few snow showers perhaps in the form of rain near the southeast New England coast. Minor snow accums possible in the Berks and possibly the northern Worcester Hills...where brief IFR conditions are possible. SW winds 5 to 15 knots. KBOS TAF...High confidence in the TAF. KBDL TAF...High confidence in the TAF. Outlook /Thursday through Sunday/... Thursday through Friday Night: VFR. Breezy. Saturday: Mainly MVFR, with local IFR possible. Chance SHRA, slight chance FZRA. Saturday Night through Sunday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA, chance FZRA. && .MARINE... Tonight... Winds diminish and become NW. Dry weather and good vsby. Wednesday... A trough of low pressure moves across New England, with winds becoming SW and increasing 20-25 kt. SCA continue through the evening and may need to be expanded to cover some of the sounds. Outlook /Thursday through Sunday/... Thursday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Friday through Friday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers. Sunday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 6 PM EST Wednesday for ANZ250-254- 255. && $$ SYNOPSIS...Gaucher/Frank NEAR TERM...Frank SHORT TERM...Gaucher LONG TERM...Frank AVIATION...Gaucher/Frank MARINE...Gaucher/Frank