Lexington, Massachusetts, USA
000 FXUS61 KBOX 131203 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 703 AM EST Thu Feb 13 2025 .SYNOPSIS... The mix of wintry weather exits this morning then dry, but windy and colder weather follows tonight into Friday. Another system brings a round of wintry precipitation Saturday night and Sunday, starting as snow before changing to rain near the coast and a wintry mix inland. A shot of arctic air follows Monday and Tuesday along with gusty winds for Monday. && .NEAR TERM /THROUGH TONIGHT/... Key Messages... * A exiting storm system will continue to bring snow changing to a mix of sleet and freezing rain then rain this morning. * Drier and windy in the afternoon, increasingly gusty overnight. As expected the lackluster DGZ really did a number on our snowfall accumulations making for smaller crystals rather than large dendrites. As of 4AM the 850 mb warm nose has already made its way well into SNE, with snow remaining just north of a Worcester to Beverly line and a mix of sleet/freezing rain and plain rain elsewhere. Temperatures at the surface are in the 33-37F range south and east of the I-95 corridor and areas further north will slowly continue to flip to rain as the warm nose advances further. A Winter Weather Advisory continues for the interior where it will be a slick and icy commute. Dry slot moves in by mid afternoon as the low exits into the maritimes and winds swing around to the NW. This will allow the remaining shallow cold air to be scoured out leading to highs in the upper 30s (high terrain) to upper 40s (south coast). Mid level cold advection will create a well mixed boundary layer going into the afternoon and overnight hours just as a 45 to 55 kt westerly LLJ moves over SNE. This will make for breezy conditions in the afternoon over the southeast coast, expanding to the rest of the region in the late evening and overnight. Model soundings show mixing up to 850 mb, tapping into that LLJ and mixing down gusts as strong as 50 mph. The highest confidence in these gusts materializing is over western and central MA where a Wind Advisory is in effect. Cold NW winds lead to lows in the teens and 20s, but it will feel more like single digits and teens thanks to the wind. && .SHORT TERM /FRIDAY/... Key Messages... * Period of strong winds lingers into Friday morning, diminishing in the afternoon and evening. After a cold night temperatures rebound into the upper 20s and low 30s but the wind sticks around, making it colder. The windiest part of the day will be the morning, as the LLJ moves offshore by afternoon and the pressure gradient relaxes. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Key Messages: * Next system arrives Saturday afternoon bringing snow to start followed by a transition to ice and rain by mid-morning Sunday. * Exact snow amounts uncertain. At least minor accumulations (1-3") for northern CT and much of MA. * Windy conditions Monday. Below normal temperatures early next week. Details: Friday Night: High pressure remains in place Friday night with increasing cloud cover toward sunrise. The cold airmass in place will support a chillier night with low temperatures dropping into the teens with some single digits possible for the higher elevation areas across the MA interior. Weekend: The pattern becomes active again for the weekend as a southern stream shortwave trough ejects northward ahead of a deep upper level trough. Ensemble means track a surface low lifting NE across the region by the end of the weekend. Plenty of support for widespread precipitation with this system with a plume of above normal moisture with precipitable water values 300% of normal paired with synoptic ascent. With model guidance still struggling to pin down the track of the storm, precipitation type will be the main forecast challenge. There is good agreement among model guidance with a cool airmass in place ahead of the system Saturday. This will help prime the environment for snowfall with the arrival of the precipitation Saturday afternoon. Snow likely continues through the evening with pockets of moderate snow possible in the evening as mid-level warm front pushes northward. As mentioned earlier, the main complication will be precip-type. As warm air moves in aloft Saturday night, it will slowly warm the vertical column. This will bring us the classic change-over to a wintry mix. As a result of track/timing differences among guidance, the timing of the warm air is still uncertain which will factor into snow amounts. Despite disparities between guidance, there is a high chance for minor accumulations (1-3") for northern CT and most of MA. There are solutions that favor potent probability for higher amounts for > 6" that have been reflected in the ensemble probabilities ranging from 30-60% north of the Mass Pike. Some locally higher probs confined to the north border and higher terrain across the interior. What we can take from this right now is that areas north of the MA Pike have the highest potential for Advisory level amounts while others it is less certain due to the timing of the warm air and transition to mixed precip. So for now, 1-5" is a realistic range. By mid-morning Sunday, warm air will be in full force changing things to rain. Higher elevation areas across the interior such as the Berkshires and Worcester hills may lag in the change-over to rain Sunday morning with shallow cool air slower to erode out. A cold front with strong CAA behind it pushes through on the backside of the system Sunday evening accompanied by gusty west winds. Model guidance hints at wrap around moisture with the exiting system. This may support lingering rain/snow showers Sunday evening. Early Next Week: The ECMWF EFI highlights another period of anomalously high winds for Monday. With strong CAA advection and a moderate LLJ overhead, the potential for stronger gusts should be supported. This will support a windy day with potential for Advisory/near Advisory winds for the Berkshires and Worcester Hills (45 mph+). Otherwise looking at gusts 25-40 mph across other spots. Ensemble 850mb temperature anomalies show a well below normal airmass overhead early next week. This will set the stage for below normal temperatures with highs in the 20s by Tuesday. By Wednesday there are some signs of upper level heights becoming more zonal which should help moderate temperatures back into the low 30s. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 12z TAF Update... Today...High Confidence. IFR-LIFR ceilings in ice/rain. All terminals eventually change to plain rain by mid-late morning although can't rule out some light icing persisting in the highest terrain until lunch time (northern Worcester Hills/Berkshires). Bulk of the steady precipitation will be over by early afternoon. E wind gusts of 25 to 35 knots developing toward daybreak along the immediate coast and between 15 and 25 knots across the interior. The winds will then shift to the SW late afternoon with gusts of 25-35 knots towards the Cape/Islands...but much weaker across the interior. We do expect gusty southwest winds to develop across the interior though by early evening. Could see a period of wind shear in the afternoon to early evening period mainly for the Cape and Island, but can't rule out BOS/PVD. Tonight...High Confidence Gradually improvements in ceilings early evening with VFR conditions by 03z. Gusty west winds with gusts 25-35 kts and localized up to 40 kts for ORH and further west across the Berkshires. KBOS TAF...High Confidence. KBDL TAF...Moderate confidence in timing. The light freezing rain should change to plain rain in the 12z to 14z time range. Outlook /Friday Night through Monday/... Friday Night: VFR. Windy with local gusts up to 30 kt. Saturday: Mainly VFR, with local IFR possible. Chance SN. Saturday Night: Mainly IFR, with local MVFR possible. Breezy. SN, RA, PL, FZRA. Sunday: Mainly IFR, with areas MVFR possible. Windy with local gusts up to 30 kt. RA, FZRA. Sunday Night: Mainly VFR, with local MVFR possible. Windy with gusts up to 35 kt. RA likely, chance SN. Washingtons Birthday: VFR. Strong winds with local gusts up to 40 kt. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Friday...High Confidence. Areas of rain will reduce vsbys for mariners at times this morning as a low passes over the northern waters. This system will bring increasingly gusty S then SW and W winds through the day, gusting to 30 kts by this afternoon with seas 6-8 ft. Overnight winds and seas increase further with gusts as high as 40 kts and seas 8-10 ft. Friday winds and seas remain elevated by will slowly decrease throughout the day as high pressure approaches. Outlook /Friday Night through Monday/... 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 snow. Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Rain, snow. Local visibility 1 nm or less. Sunday: Strong winds with gusts up to 30 kt. Rough seas up to 14 ft. Rain. Areas of visibility 1 to 3 nm. Sunday Night: Strong winds with gusts up to 35 kt. Rough seas up to 14 ft. Chance of rain. Washingtons Birthday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 13 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory until 10 AM EST this morning for CTZ002>004. MA...Winter Weather Advisory until 10 AM EST this morning for MAZ002>006-008>012-026. Wind Advisory from 7 PM this evening to 1 PM EST Friday for MAZ002>004-008>012-026. RI...Winter Weather Advisory until 10 AM EST this morning for RIZ001. MARINE...Gale Warning from 10 PM this evening to 1 PM EST Friday for ANZ230. Gale Warning from 7 PM this evening to 7 PM EST Friday for ANZ231-251. Gale Warning from 7 PM this evening to 1 PM EST Friday for ANZ232>235-237-255-256. Gale Warning from 10 PM this evening to 7 AM EST Friday for ANZ236. Gale Warning from 7 PM this evening to 10 PM EST Friday for ANZ250-254. && $$ SYNOPSIS...BW/Mensch NEAR TERM...BW SHORT TERM...BW LONG TERM...Mensch AVIATION...BW/Mensch MARINE...BW/Mensch
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