Lexington, Massachusetts, USA
000 FXUS61 KBOX 111112 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 612 AM EST Tue Feb 11 2025 .SYNOPSIS... Dry and cold conditions today with below normal temperatures. Low pressure will track well south of New England tonight and may bring some light snow to the immediate south coast and Islands followed by drying conditions Wednesday. Another system moves across southern New England Wednesday night through Thursday, with light snow to start, transitioning to wintry mix and then rain Thursday morning. There is potential for light snow accumulations. Drier weather returns for Friday into early on Saturday before another strong frontal system brings another period of mixed precipitation over the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... * Dry today with increasing clouds. Quiet weather today with high pressure in control. Skies will quickly become more overcast with high clouds moving in as moisture increases above 700 mb. SW winds will increase as the pressure gradient tightens just a bit thanks to a shortwave trough passing to our north. This may lead to some gusts of 20 to 25 mph but not expecting them to be widespread. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Key Messages... * System passing to our south may bring a dusting of snow to the immediate south coast with an inch or two possible on the islands. * Dry on Wednesday with a few stray flurries possible. Tonight a low pressure system passes well south of the 70/40 benchmark brushing SNE with the northern extent of its precipitation shield. Most guidance has remained on track for less than an inch of snow on the south coast including the newest 00z and 06z HRRR guidance which was leaned on heavily for this update. Best shot at seeing 1+ inches of snow is the islands where around 0.01" of QPF is possible. GEFS guidance indicates a 50-60% chance of an inch of snow while the EPS odds are nil. Regardless, any snow that falls isn't expected to be impactful with light snow in around midnight and out by 6 am. Lows dip into the teens (interior) and low to mid 20s. Wednesday high pressure centered to our north keeps the weather quiet ahead of an incoming shortwave/surface low Wednesday night. Winds will be generally light with onshore easterly flow. Can't rule out a few widely scattered showers/flurries with increasing low level moisture on those easterly winds later in the day but the appreciable precipitation doesn't move in until Wednesday night. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Key Messages: * Wed night into Thurs, system brings a wintry mix of snow, icing and eventually rain. * Uncertainty in snow amounts with Weds night system, but more likely minor accumulations. * A low-pressure system approaches Saturday, likely bringing another round of wintry precip to southern New England. Details: A mid-level shortwave trough moves across the Great Lakes region and across the northeast Wednesday night into Thursday. Coupled with an upper level jet and a plume of above normal moisture (PWATs 250-280% of normal), this will support another round of precipitation across southern New England. Models are in good agreement with a sufficiently cold antecedent airmass in place Wednesday night when the precipitation arrives. For most areas, this will support the precipitation type as snow at the onset Wednesday night. There is also good model agreement with a warm front pushing northward after midnight. As the warm air aloft works in from south to north, snow transitions to sleet/freezing rain and eventually to all rain. There may be a period at the onset of the warm front where the forcing may support mesoscale banding with moderate snow rates in spots. Areas on or hugging the east coast may transition sooner than surrounding locations with a little nudge from the easterly onshore flow. Models diverge when it comes to how the system develops as it tracks northward with some solutions showing development of a secondary low. The GFS/GEFS members have been a fan of this solution. In that case, shallow cool air may stick around in northern MA for a bit longer leading to a longer period of wintry precip before switching to all rain. Conditions dry out in the afternoon as the bulk of the system exits northeast. As far as amounts go, GEFS probabilities for > 3" of snow range from 30 to as 60% in far north MA and the Berkshires and less than 3" elsewhere. Compared to previous runs, the 00z run has trended downward. The ECMWF ens trends warmer quicker resulting in considerably lower probabilities, favoring a trace to 3". Light accumulations, if any, are looking more likely overall still. Can't rule out some minor impact to the AM commute mainly for northern MA. Strong cold air advection follows the system as a cold front pushes across Thursday night with high pressure moving in. Friday will be cooler and dry with highs below normal in the low 30s. After brief ridging aloft, another mid-level trough approaches southern New England for the weekend. This will support another system bringing precipitation in the Saturday-early Sunday timeframe. There is a notable amount of spread in models when it comes to the details still (track, timing). The track in particular has varied among guidance which will have implications on precipitation type. Details will be ironed out as we get closer. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...High confidence. VFR conditions. SW winds at 8-12 kts develop by the afternoon with a occasional gusts up to 18 kts. Winds decrease after 21z becoming light SW less than 8 kts. Tonight...Moderate confidence. Light snow approaches south coast tonight, around or after 06z. Uncertainty with northern extent of snow area. Best chance for a period of light snow with IFR vsbys and minor accumulations will be over the Islands with lower probability along the south coast. VFR northward of south coast and Cape/Islands. Wednesday...High confidence. VFR. NE winds 10-15 kts. KBOS TAF...High Confidence in TAF. KBDL TAF...High Confidence in TAF. Outlook /Wednesday Night through Saturday/... Wednesday Night: Mainly IFR, with areas MVFR possible. Breezy. PL, chance SN, FZRA. Thursday: Mainly IFR, with local MVFR possible. Breezy. Chance RA, FZRA, PL. Thursday Night through Friday: VFR. Windy with gusts up to 35 kt. Friday Night: VFR. Breezy. Saturday: Mainly VFR, with local IFR possible. Chance SN. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. W/NW winds to 10-15 kt shift to SW 10-20 kt today. Winds will then become N-NE 10- 20 kt late tonight as front slides south of the region. A low to our south will bring snow to the southern waters tonight with light winds. Winds turn out of the NE on Wednesday increasing to 10-15 kts with gusts to 20 kts. Outlook /Wednesday Night through Saturday/... Wednesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Rain, chance of snow. Areas of visibility 1 to 3 nm. Thursday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Rain. Thursday Night: Strong winds with gusts up to 30 kt. Rough seas up to 9 ft. Slight chance of rain. Friday: Strong winds with gusts up to 30 kt. Areas of rough seas. Friday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Saturday: Winds less than 25 kt. Chance of rain, chance of snow. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 7 PM Wednesday to 7 PM EST Thursday for ANZ231>235-237-250-251-254>256. && $$ SYNOPSIS...BW/Mensch NEAR TERM...BW SHORT TERM...BW LONG TERM...Mensch AVIATION...BW/Mensch MARINE...BW/Mensch
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