000 FXUS61 KBOX 230803 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 403 AM EDT Thu Mar 23 2023 .SYNOPSIS... Scattered showers today ahead of a cold front which moves sooth across the region this evening, followed by dry and a bit cooler weather Friday. Active weather on Saturday into early Sunday with a wintry mix across the interior and higher terrain, with a cold rain elsewhere. Drier weather returns Sunday into Monday with near seasonable temperatures. Unsettled weather may return heading into the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Warm front remains hung up across NE MA with light northerly flow to the north, but the front will lift to the north this morning with warm sector airmass across SNE today. Mainly dry conditions are expected this morning, although can't rule out a spot shower in warm advection pattern. Then scattered showers this afternoon as a cold front approaches from the north and forcing for ascent increases. However, the column never fully saturates so not expecting a washout which is supported by hi-res CAMs which indicate scattered coverage of showers with dry periods. Another mild day today in warm sector airmass, but mixed layer is quite shallow and not much sunshine today which will limit full heating potential. Expect highs generally mid/upper 50s with some lower 60s possible in the CT valley and portions of NE MA. Cooler Cape/Islands where stratus and patchy fog may linger through the day. Becoming breezy this afternoon as low level winds increase which will result in 20-30 mph gusts at times. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Tonight... Cold front pushes south across SNE 00-06z with scattered showers accompanying the front, then good drying moves in from the north late this evening and overnight with rapid drop in PWATs. Areas of fog expected to impact the south coast and Cape/Islands this evening until the front moves through and dries things out overnight. Gusty pre-frontal SW winds this evening shift to NW behind the front with gustiness continuing in cold advection pattern. Lows will range from mid 30s to lower 40s. Friday... Cold front pushes well to the south with high pres building over the Gt Lakes with dry NW flow across New Eng. The column is quite dry but this will not translate to full sunshine as plenty of high clouds will be around leading to filtered sunshine. While it will be a bit cooler Fri, temps will remain above normal as colder air will lag to the north. Highs will range from mid/upper 40s higher terrain to low/mid 50s elsewhere. NW winds will average 10-20 mph. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Highlights... * Unsettled Sat into early Sun. Wintry mix changing to rain across the interior. Light accumulation expected across the higher terrain. Elsewhere will be a cold rain. Gusty winds at times. * Dry weather returns Sun/Mon with near to slightly warmer than seasonable temperatures. * Could see a return of unsettled weather in the Tue/Wed timeframe, but confidence is quite low at this point. Friday night into early Sunday... A ridge axis will initially be over the OH Valley/central Great Lakes late on Fri, while a trough is over the Southern Plains. The ridge builds into New England by early Sat and toward Nova Scotia/Newfoundland by late Sat. The trough will lift into the central/eastern Great Lakes by late Sat. The trough swings into northern New England by early Sun. High pressure will initially be nudging in from Quebec into early Sat, while low pressure lifts into the central Great Lakes. The warm front associated with this system lifts into and through much of our region on Sat. A secondary low develops along/over the south coast late on Sat and lifts into the Gulf of Maine by early Sun. Will have increasing cloud cover Fri into early Sat with it taking a bit to saturate given the low/mid level dry air in place. Winds will shift from a northerly direction to the east as the night progresses. This advects in 0 to -5 degree Celsius air at 925 hPa. The result will be lows heading into Sat in the 20s across the higher terrain and 30s elsewhere. The main concern during this period forecast is Sat into early Sun. Anticipating that the airmass across the interior will start off cold enough for a snow/sleet mix. As the day progresses will have warmer air advect in and gradually change ptype across the interior over to more of a sleet/freezing rain or rain mix. The best shot at this point for a sustained wintry mix is across the higher terrain where temps are in the low/mid 30s. Will really struggle to accumulate during the day Sat given the late March sun angle and relatively light precip rates. Better shot for accumulation comes heading into early Sun as the secondary low lifts across SE MA. This will also coincide with any wintry mix changing back over snow across the interior. Winds shift to the W, which will advect 0 to -2 degree Celsius air at 925 hPa across the higher terrain. The other potential crux to this is given the 700 hPa low being to our NW we could see precip ending a bit quicker as the dry slot punches in. There is still uncertainty in the thermal profiles will really need to hone in on exact ptypes to get idea on the specific impacts expected. Ensemble guidance continuing to trend downward with 24 hr 10-1 SLR snow accumulations. At this point the 3" total probs are around 10-30 percent chances and 20-70 percent for 1" totals. As was the case yesterday the risk is highest across the higher terrain and generally around Rte 2 north. Still thinking it is not out of the question we may need Winter Weather Advisories given there could be some freezing rain, but not certain on how widespread this risk will be. Also anticipating gusty winds as the system moves through. Should see 925 hPa jet of roughly 30-40+ kts out of the S/SE initially and shifting to the W late on Sat into early Sun as the secondary low lifts into the Gulf of Maine. Still think that the wind risk is greater late Sat/into early Sun as we get into the W flow. May be difficult to mix down the SE/S winds given the warmer air advecting in and inversion in place per GFS/NAM Bufkit soundings. Sunday through Monday... Shortwave ridge builds from the central Great Lakes/Ontario early on Sun before flattening out over Quebec by late on Sun. Another ridge builds from the Mid/Upper Mississippi River Valley late on Sun into the eastern Great Lakes by late Mon. High pressure nudges into the region from the OH Valley/central Great Lakes on Sun. The high continues to nudge in as it builds into Ontario/Quebec on Mon. Anticipating dry and quiet weather through this period with high pressure in control. Will have near to slightly warmer than seasonable temperatures. Highs in the 40s across the higher terrain and the low/mid 50s elsewhere. Tuesday and Wednesday... Next potential shot for impactful weather across southern New England as a trough lifts into/through the Mid Atlantic. There is considerable uncertainty in the timing, track and intensity of a system moving through. Given the significant differences amongst guidance have just stuck with the NBM for now. This features chances of precipitation with rain changing to snow. Confidence is quite low during this timeframe. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through 12z... VFR/MVFR cigs will lower to IFR near the south coast and Cape/Islands 10-12z with patchy fog. Today...Moderate confidence. Cigs should temporarily improve to VFR this morning before lowering back to MVFR with patchy IFR in the afternoon. However, IFR expected to persist through the day Cape/Islands. A few brief showers possible this morning, with scattered showers this afternoon. SW gusts to 20-25 kt developing this afternoon. Tonight...High confidence in trends, lower confidence in timing. MVFR/IFR in the evening will improve to VFR 04-06z, but lower cigs/vsbys may linger a few hours beyond 06z over Cape/Islands. SW winds shift to NW during the evening with gusts 20-25 kt. Friday...High confidence. VFR. NW winds 10-20 kt. KBOS Terminal...Moderate confidence. A period of MVFR cigs possible for the morning and late afternoon push but timing is uncertain. SW gusts 20-25 kt this afternoon. Improving to VFR after midnight with wind shift to NW. KBDL Terminal...Moderate confidence. Mainly MVFR cigs, but may see a period of VFR this morning. Improving to VFR by midnight with wind shift to NW. Outlook /Friday Night through Monday/... Friday Night: VFR. Chance FZRA. Saturday: Mainly VFR, with local IFR possible. Windy with gusts up to 30 kt. RA, PL, FZRA. Saturday Night: Mainly VFR, with areas IFR possible. Windy with gusts up to 35 kt. RA, FZRA. Sunday: VFR. Windy with local gusts up to 30 kt. Slight chance RA. Sunday Night through Monday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Friday...High confidence. Developing low level jet will lead to increasing SW winds this afternoon and evening with gusts 25-30 kt developing. SCA is in effect for all waters. Wind shift to NW around and after midnight with 25 kt gusts late tonight into Fri morning, mainly over eastern MA waters. Winds diminish Fri afternoon. Seas building to 5-7 ft over outer southern waters late today into tonight. Poor vsbys developing in areas of dense fog this morning over the south coastal waters should improve some this afternoon, then vsbys drop again late afternoon and evening. Vsbys will improve after the cold front passage after midnight. Scattered showers this afternoon into this evening. Outlook /Friday Night through Monday/... Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Saturday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Rain. Saturday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 8 ft. Rain. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 9 ft. Slight chance of rain. Sunday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Monday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this evening for ANZ230-236-251. Small Craft Advisory from 2 PM this afternoon to 11 AM EDT Friday for ANZ231. Small Craft Advisory from 11 AM this morning to 2 AM EDT Friday for ANZ232>235-237. Small Craft Advisory from 2 PM this afternoon to 2 PM EDT Friday for ANZ250. Small Craft Advisory from 2 PM this afternoon to 8 PM EDT Friday for ANZ254. Small Craft Advisory from 11 AM this morning to 8 PM EDT Friday for ANZ255-256. && $$ SYNOPSIS...KJC/BL NEAR TERM...KJC SHORT TERM...KJC LONG TERM...BL AVIATION...KJC/BL MARINE...KJC/BL