Area Forecast Discussion

429 FXUS61 KBOX 220319 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1019 PM EST Tue Jan 21 2025 .SYNOPSIS... An arctic airmass will persist through Wednesday night with moderating temperatures Thursday into the weekend although still below normal temperatures. An ocean storm tracking well south of New England may bring light snow accumulations to the outer Cape and Islands tonight followed by clearing Wednesday. Generally dry conditions are expected during the end of the week and into next weekend, but we will have to watch another distant ocean storm Thursday night which could bring light snow to SE New England if it tracks further north and west. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 1015 PM update... Light snow has developed across the Cape/Islands but rather dry air in low levels not allowing this snow shield to push much further northward. May see a few flurries along the south coast of RI and MA, otherwise best chance of minor accum of an inch or 2 will be over the outer Cape and Nantucket, with a coating to an inch across the rest of Cape Cod. Snow will be moving offshore 07-10z. Otherwise, clearing has overspread western MA and the clearing line will advance eastward overnight with skies clearing from NW to SE. Temps have plummeted in western MA with the clearing and light winds, with readings already zero to -5F. Expect temps to fall sharply after midnight further E as skies clear. Lows will range from zero to -10F across interior MA but locally as cold as -10 to -15F in the Berkshires, with single numbers across much of the rest of the region. Previous discussion... Key Messages: * Frigid evening to early morning temperatures with apparent temps 5 to 10 below. Cold Weather Advisories for the Berkshires with apparent temperatures forecast near 15 to 20 below zero. * Minor (up to 2") snow accumulation for the Islands, with flurries or periods of light snow showers amounting to an inch or so for Cape Cod overnight. Main change with this update was to reduce PoP over Cape Cod some, which also naturally led to reductions in snow accumulations (which were already on the low side) for the Cape. Expansive shield of midlevel cloud cover on rather strong SWly 500 mb flow and midlevel moisture advection ahead of a shortwave disturbance coming out of the Alleghany Mtns in WV. Although the regional radar composite shows some echoes, this is all sampling midlevel cloud cover with current rather large temperature-dewpoint spreads some 15-20 degrees. As winds come around to WNW late this evening and overnight and allows for lower dewpoints to advect in, it`s not likely we`ll saturate enough to allow for much in the way of precip at least to Cape Cod. It could be enough to wring out some flurries in Barnstable County, but I`m not thinking conditions are enough to sustain persistent light snow. The best chance for minor accums look to be confined to MVY/ACK overnight, but that is also still a little unclear - it`s not likely to be any worse than a couple inches. But otherwise, the larger story for the rest of Southern New England is the frigid temps. Didn`t make many changes there with the coldest readings expected over northern/northwest MA. As was the case last night, a fresh snowpack at night really helped to bottom out temps and see no reason that shouldn`t again be the case. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Tomorrow and Tomorrow Night Key Messages * Bitter cold continues tomorrow and tomorrow night Any remaining snow over The Cape/Islands tapers off over The Atlantic shortly after sunrise. Bitter cold continues tomorrow with high temperatures once again suppressed to the upper teens/low 20s with a modest west/northwest breezing making it feel closer to single digit temperatures for most. Unlike today however, there will be abundant sunshine with a bone dry atmosphere characterized by PWATs around a tenth of an inch or less. A pattern change takes place tomorrow night as high pressure to the south slides off the east coast supporting south/southwesterly flow and WAA into southern New England. This will support increasing cloud cover tomorrow night and an uptick in 925 hPa temps to -10 to - 15C. While still cold, low temps tomorrow night aren`t expected to meet advisory criteria anywhere, but will still be in the single digits/low teens across the region. A few locations across the interior will see wind chills fall below 0while the rest of the region will feel like the low to high single digits. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Key Messages: * Other than passing snow showers Thurs night/Fri and possibly again on Sun/Sun night, dry weather is expected. * Recovery in temps closer to seasonable Thurs, then cooling off to below normal levels Fri and Sat before rebounding back to near/slightly above normal for Sunday. * Early next week outlook favors continued drier but cooler than normal weather. Details: Southern New England will be entrenched in what is climatologically the coldest portion of the calendar year during this forecast period. Overall this forecast period will be governed by the northern stream of a split-flow pattern at 500 mb, with mean troughing over the central and northeastern US and a trough/closed low feature over the southwest CONUS. Though we will have a couple of progressive Clipper type low pressure systems moving through during this period of time, one Thurs night/Fri and the other around Sun/Sun night, both of these features appear to be lacking in the moisture department. Other than passing snow showers with each, the main effect these Clippers would have is to offer briefly enhanced cloudiness with reinforcing shots of somewhat colder than normal temperatures in their wake. Significant impacts are not expected with either of these waves of low pressure, and much of the time should end up bring dry. Temperatures will start off "warming" up Thurs, which is really just a rebound out of the frigid early to midweek, and highs should be closer to seasonable levels with highs in the upper 20s to mid 30s and lows in the 20s. Passage of the first Clipper system then brings a period of colder than normal temperatures (e.g. highs mid 20s to around freezing with lows in the single digits Fri night). But this shot of cold air does not look to be nearly as stout as the colder airmass working its way over Southern New England today. Warmest day of this period then takes place on Sunday with highs in the low to mid 30s with some sunshine ahead of the 2nd clipper system, which then cools us off into early next week. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z TAF Update: Tonight...High Confidence VFR across the interior with winds becoming light out of the west/northwest. -SN expected over ACK with periods of MVFR ceilings and perhaps IFR vsbys, especially at ACK. Expect snow to taper off before 12Z. Tomorrow....High confidence. VFR. NW wind 5-15 kt. Tomorrow Night...High Confidence VFR. Winds becoming light out of the west/southwest. KBOS TAF...High Confidence in TAF. KBDL TAF...High Confidence in TAF. Outlook /Thursday through Sunday/... Thursday: VFR. Breezy. Thursday Night through Friday Night: VFR. Saturday through Sunday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High- greater than 60 percent. Tonight through Wednesday night... W winds 10-20 kt becoming NW-N later tonight into tomorrow. A few gusts over 20 kt possible late tonight and early Wed. Arctic airmass will result in areas of light freezing spray tonight into tomorrow morning. Expect periods of light snow over the south coastal waters tonight through tomorrow morning, especially southeast of Nantucket. Outlook /Thursday through Sunday/... Thursday: Winds less than 25 kt. Slight chance of rain. Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Friday through Saturday: Winds less than 25 kt. Saturday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Cold Weather Advisory until 10 AM EST Wednesday for MAZ002-008- 009. RI...None. MARINE...None. && $$ SYNOPSIS...Loconto/RM NEAR TERM...KJC/Loconto/RM SHORT TERM...RM LONG TERM...Loconto AVIATION...Loconto/RM MARINE...Loconto/RM NWS BOX Office Area Forecast Discussion