Lexington, Massachusetts, USA
000 FXUS61 KBOX 112315 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 615 PM EST Tue Feb 11 2025 .SYNOPSIS... Low pressure passes well south of New England tonight and will bring a coating to an inch or two of light snow to the South Coast, Cape Cod, and the Islands. Another system moves across southern New England Wednesday night through Thursday, with light snow to start, transitioning to a wintry mix and then to rain Thursday morning. Dry weather returns Friday into early Saturday before yet another system brings a round of wintry precipitation this weekend, probably starting as snow before changing to rain near the coast and a wintry mix inland. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 615 PM Update Key Messages: * Light snow near South Coast with minimal impact. Coating for most but 1-2" in spots especially along the immediate South Coast and Islands. * Cloudy and cold elsewhere. Latest high-res model guidance supports going forecast and is in line with satellite and radar trends. We'll see a sharp northern edge to the precip shield as low pressure tracks well south of New England overnight and fights drier air to the north. We may see some flurries make it close to Hartford (but probably staying south of the city) and more likely into Providence and Plymouth, while accumulating snow stays right near South Coast, Cape Cod, and Islands. Most places should just get a fresh coating of snow overnight while Islands stand best chance at 1" or 2" in spots. Everything is done by 5-6 am Wed at latest. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... 245 PM update... Wednesday... Key Messages: Mainly dry & seasonably cold weather Frontal wave south of 40N/70W 12z Wed, zips out to sea with weak subsidence over SNE. This will support mainly dry weather along with a few breaks of sunshine (more clouds than sun). Although, cold NE onshore flow streaming across the relatively mild ocean, will yield more ocean effect strato-cu over eastern MA, with scattered flurries possible from time to time, per hi res simulated reflectivity fields. Seasonably cold with highs in the 30s, although it will feel colder across eastern MA with blustery NE winds 10-15 mph with gusts up to 20 mph at times. Wednesday night and Thursday... Key Messages: wintry mix of snow to sleet to freezing rain Wed night into Thu AM, will yield slippery travel, esp NW of I-95 1035 mb high over the maritimes provides low cold air damming (CAD) over SNE, while WAA rides up and over the cold surface dome. Precip overspreads the region between 06z-12z Thu initially in the form of snow as the cold air is deep. However, model soundings indicate warm air aloft eventually wins out and changes ptype from snow to sleet and then freezing rain. Not expecting freezing rain in the coastal plain, just a period of snow and sleet before changing over to all rain, as model soundings indicate rapidly warming boundary layer. However, farther inland, with secondary surface wave traversing somewhere near the I-95 corridor, this locks in shallow cold air across the interior during the morning, specifically northern CT into western-central MA, possibly as far east as the I-495 corridor. Thus, given the duration of mixed precip, including a period of freezing rain, decided to issue a winter weather advisory Wed night into Thu morning for the area mentioned above, mainly northwest of I- 95. Shallow cold air may linger long enough to impact the Thu AM commute in this region. Then by afternoon, dry slot overspreads the region with precip ending from west to east. As the surface low exits into the Gulf of Maine, winds turn to the west and become gusty and temps rise into the 40s late in the day, perhaps only upper 30s across northwest MA, where shallow cold air may be more difficult to scour out. Nonetheless, above normal along with some breaks of sunshine possible late across western MA/CT. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... 245 PM update... Key Messages: * Travel impacts likely this weekend, especially across interior where snow probably changes to a mix or even rain for a time. Less of an impact near coast where change to all rain is more likely. * Minor snow accumulation possible late Sunday night into Monday morning. * Dry and cold weather follows early next week. After a brief respite Fri, active weather pattern continues this weekend as southern stream short wave over southern Plains rounds broad upper trough in place across Northeast. This setup is fairly complex as front stalls somewhere near South Coast and a wave of low pressure rides NE along it, so timing is questionable this far out but ensemble probabilities favor best chance of precipitation from sometime Sat afternoon into Sun. We do know that this system will have a lot of moisture available and ensembles show wind and moisture fields running 2 to 3 standard deviations above normal. Ensemble probabilities reflect that with fairly high odds of at least 0.50" of precipitation and even decent odds of 1" or a little more. That said, this does not have the look of a significant snowfall for SNE as the overall pattern has a "warm" look to it with track of 500 mb, 700 mb, and 850 mb lows all to the north of our region. It's the lowest levels that will ultimately determine precipitation type which is highly dependent upon track of surface low. Right now model/ensemble consensus favors a track right over SNE but we'll see wobbles north and south over next couple of days. Cold air in place means snow for much of SNE at start Sat afternoon and Sat night, with minor accumulations before coastal areas probably see a change to a mix and eventually rain either late Sat night or Sun morning. Farther inland, change will be slower to occur, if it occurs at all, but best chances of accumulating snow or a mix should be in higher elevations of western/central MA and perhaps northern CT and northwest RI. However, if we see a low track end up farther inland, then even these higher elevation areas would see a change to rain as milder air floods in. Based upon ensemble snow probabilities (which use 10:1 ratio) this favors an Advisory- level event for locations near and north of Mass Pike, perhaps for other areas should we end up with more in way of mixed precipitation. Colder air returns behind departing low Sun night into Mon morning, which is when we could see a change back to light snow for much of SNE and perhaps minor accumulations. Dry and cold weather prevails early next week as yet another high pressure system coming out of Canada heads to the Ohio Valley and East Coast. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z TAF Update: High confidence. VFR cigs for most of SNE overnight. Light snow grazes South Coast with IFR vsbys along immediate coast, Cape Cod, and Islands mainly 05-09z Wed with less of a chance into KPVD where we may see some flurries. MVFR cigs prevail Wed with E/NE winds, gusting to 25kt along coast. We should also see scattered flurries, mainly near coast, but not confident enough in timing to include in TAFs. Next round of precipitation arrives as we approach end of TAF period (03-06z) and should bring MVFR cigs/vsbys in light snow to CT and western MA with less of a chance farther east. Looking ahead to Thu, IFR/LIFR with rain likely along the coast, wintry mix inland, then all precip ending as rain by afternoon. Improvement to MVFR/VFR toward 00z Fri. KBOS TAF...High confidence. May see flurries (P6SM -SHSN) during day Wed but not confident enough in timing to include. Looking ahead to Wed night/Thu, light snow probably starts after midnight (06z) and quickly changes to rain around 09z with less than one inch of snow accumulation before the changeover. KBDL TAF...High confidence. Flurries expected to remain to the south tonight. Looking ahead to Wed night/Thu, light snow begins around 04z and changes to a FZRAPL mix 07z-10z, before changing to rain closer to 13-14z. Snow accumulation around one inch with less than 0.10" of icing before the change to rain. Outlook /Thursday Night through Sunday/... Thursday Night: VFR. Windy with gusts up to 35 kt. Slight chance FZRA. Friday: VFR. Windy with gusts up to 30 kt. Friday Night: VFR. Breezy. Saturday: Mainly VFR, with local IFR possible. Chance SN, chance RA. Saturday Night: MVFR/IFR conditions possible. SN, RA. Sunday: Breezy. RA, SN. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 245 PM update... Key Messages: * Light snow may reduce vsby southern waters of MA/RI tonight * NE winds 15-20G30 kt late Wed night/Thu AM * Wind shift to WNW late Thu, 20-25 kt Weak wave of low pressure tracks well south of New England tonight, bringing a period of snow to the southern waters of MA/RI. Wave tracks south of 40N/70W 12z Wed, then zips east out to sea. Tranquil conditions Wed, with NE wind 10-15 kt. Then Wed night, low pres approaches from the SW, with NE winds 15-20G30KT across the MA/RI waters late Wed night into Thu AM. Low moves up the I95 corridor early Thu, then into the Gulf of ME Thu afternoon, with wind shift from NE to WNW late. Outlook /Thursday Night through Sunday/... Thursday Night: Strong winds with gusts up to 35 kt. Rough seas up to 10 ft. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Friday Night: Winds less than 25 kt. Local rough seas. Saturday: Winds less than 25 kt. Chance of rain, chance of snow. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 12 ft. Rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory from 10 PM Wednesday to 10 AM EST Thursday for CTZ002>004. MA...Winter Weather Advisory from 10 PM Wednesday to 10 AM EST Thursday for MAZ002>006-008>012-026. RI...Winter Weather Advisory from 10 PM Wednesday to 10 AM EST Thursday for RIZ001. MARINE...Small Craft Advisory from 7 PM Wednesday to 7 PM EST Thursday for ANZ231>235-237-250-251-254>256. && $$ SYNOPSIS...JWD/Nocera NEAR TERM...JWD SHORT TERM...Nocera LONG TERM...JWD AVIATION...JWD MARINE...JWD/Nocera
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