843 FXUS61 KBOX 172053 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 353 PM EST Tue Jan 17 2023 .SYNOPSIS... A weak disturbance may bring a few showers tonight, followed by mainly dry and mild weather Wednesday. A frontal system will bring mixed wintry precipitation Thursday afternoon into Friday, especially across northern Massachusetts with mainly rain near the coast. Drier conditions for the upcoming weekend along with near seasonable temperatures. Unsettled pattern returns late Sunday night into early next week as another storm likely impacts the region. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Fast moving shortwave moves through this evening and will be accompanied by a few brief showers. Still plenty of dry air in the low levels to overcome as dewpoints in the teens and 20s which will limit areal extent of precip, but some spotty light precip possible through this evening. Will also to watch for patchy freezing rain over the higher terrain in northern MA as temps aloft are warm and wet bulb cooling could bring temps down to near 32 with the precip. Any freezing rain would be spotty and limited in areal coverage. Shortwave moves to the east overnight so expect mainly dry conditions with partial clearing, although some upslope rain/snow showers to the west could spill into the east slopes of the Berkshires within WNW flow aloft. Lows will be mainly low/mid 30s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday... Another mid level trough passage with cold pool aloft and lingering low level moisture will yield lots of cloud cover, especially in the morning, with more sunshine developing in the afternoon. Not expecting much if any precip, although can't rule out a spot rain/snow shower in the morning over the higher terrain. Low level temps are cooling but somewhat deeper mixing and WNW flow will allow highs to reach well into 40s, to near 50 in the coastal plain. It will be a bit blustery with WNW gusts to 20-25 mph. Wednesday night... Upper trough moves to the east with shortwave ridging and surface high pres building in from the west. This will lead to clearing skies and diminishing wind, although high clouds ahead of next system will begin moving in overnight. A period of decent radiational cooling will allow low temps to drop to the mid 20s to lower 30s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Thursday afternoon a frontal system brings a wintry mix and cold rain before changing over to accumulating snow across the interior late Thursday night into Friday morning, increasing the threat for a potentially slick morning commute. * Drier weather expected for the upcoming weekend along with near normal temperatures Saturday and slightly above normal Sunday. * Unsettled weather potentially late Sunday night through Monday. Thursday through Friday night... Dry for much of the first half of Thursday, trending wet, as a frontal boundary lifts north during the afternoon. As previously mentioned in the prior forecast discussion, the concern Thursday evening revolves around a winter mix of sleet/freezing rain for those locations along the northern border of Vermont/New Hampshire. While temperatures aloft are above freezing, producing rain, the temperatures at the surface are likely to be 30F to 33F for areas generally at or greater than 1,000 feet. Overnight into Friday a surface low associated with the system moves out of western New York, pulling colder air down as it moves east. The big question remains, how much cold air will rush in and how quickly. Ensembles show a tight gradient for the probability of greater or equal to 3". The GFS ensemble gives us a probability between 40 and 60 percent along the northern border of Massachusetts with Vermont/New Hampshire. Then nothing south of the Mass Pike. The Euro ensemble a little more robust, with a greater than 80 percent chance along the northern border with Vermont/New Hampshire. With the cut off, with less than 10 percent chance for areas south of the southern border with Connecticut/Rhode Island. For areas south of the Mass Pike, a cold soaking rain is in store. PWATs reach around 1.0" to 1.3". Not out of the question areas along the southern coast of Rhode Island and Massachusetts receive an inch of rain. There still remains a fair amount of uncertainty with precipitation types. At this time we have held off on issuing any NWS headlines. But, a Winter Weather Advisory could be needed for northern Massachusetts if confidence in snow and ice continues to increase. Saturday through Sunday... A quieter period of weather with a 1025mb high building over the northeast. During this time expect more clouds, likely lower stratus as forecast soundings depict leftover low level moisture trapped below a surface inversion. As for temperatures, Saturday is pretty seasonable for mid-January, with 925mb temperatures between -4C/-6C. This will result in afternoon temperatures generally in the middle to upper-30s. A slightly warmer day for Sunday as WAA occurs aloft, 925mb temperatures ranging between +1C and -2C, resulting in afternoon temperatures in the upper-30s to low-40s. Sunday Night through early next week... Our next widespread weather system arrives sometime early Sunday evening or early Monday morning. While this part of the forecast is between 6 & 7 days out, did not spent too much time on it. As of now, global guidance shows a surface low pressure passing to our northwest and giving southern New England another drink of water and potential snow for interior New England. Once this system clears our Monday night, surface high pressures settles in for Tuesday. As for temperatures, next week looks to have slightly above normal temperatures in the upper-30s to low-40s. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through 00z... VFR with gradually lowering cigs. A few showers possible toward evening. Tonight...High confidence. VFR cigs with spotty MVFR cigs developing over the higher terrain. A few brief rain showers this evening. Wednesday...Moderate confidence. Cigs lowering to MVFR during the morning with spotty light rain/snow showers possible in the interior, then partial clearing and VFR developing in the afternoon. WNW wind gusts to 20-25 kt developing. Wednesday night...High confidence. Mainly VFR with diminishing wind. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Thursday through Sunday/... Thursday: Mainly VFR, with local IFR possible. RA, slight chance FZRA. Thursday Night: Mainly IFR, with areas MVFR possible. Breezy. RA, chance SN, slight chance FZRA. Friday: MVFR/IFR conditions possible. Breezy. SN likely, chance RA. Friday Night: Mainly VFR, with areas IFR possible. Breezy. Slight chance RA, slight chance SN. Saturday: Mainly VFR, with areas MVFR possible. Saturday Night: Mainly VFR, with local MVFR possible. Sunday: Mainly VFR, with local MVFR possible. Breezy. Slight chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Wednesday night...High confidence. Tonight...SW wind gusts to 20 kt this evening will veer to the W overnight. Leftover easterly swell will result in 5 ft seas over outer waters where SCA will continue. Wednesday...Wind shift to WNW 15-20 kt, with occasional gusts to 25kt at times. Mainly dry weather and good vsby. Wednesday night...NW gusts increasing to 20-30 kt in the evening, then diminishing late as high pres builds in from the west. SCA conditions persist over open waters. Outlook /Thursday through Sunday/... Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain. Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of seas approaching 5 ft. Rain. Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain. Friday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain. Saturday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain. Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Slight chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 AM EST Thursday for ANZ250- 254>256. Small Craft Advisory until 4 PM EST this afternoon for ANZ251. && $$ SYNOPSIS...KJC/Gaucher NEAR TERM...KJC SHORT TERM...KJC LONG TERM...Gaucher AVIATION...KJC/Gaucher MARINE...KJC/Gaucher