textproduct: Burlington

WHAT HAS CHANGED

As of 241 PM EDT Wednesday...

No significant changes, the severe threat for tomorrow remains relatively the same.

KEY MESSAGES

As of 241 PM EDT Wednesday...

1. A few showers continue through tonight.

2. Rounds of showers tomorrow with heightened thunderstorm chances across southern Vermont.

3. Rainy and windy weather expected for the latter half of the weekend as another frontal system impacts the region. Mountain snow possible late Sunday into Sunday night with a cold frontal passage.

4. Much colder but dry to start next week, though trending warmer with chances of rain by mid week.

DISCUSSION

As of 241 PM EDT Wednesday...

KEY MESSAGE 1: The stalled boundary will remain across the region through tonight, helping lead to a few rounds of showers. Another MCS will develop across the Great Lakes this evening and progress eastward tonight. The convective elements look to mostly stay to the south and they should be elevated by the time they approach. The stratiform precip on the northern extent looks to pass through, though a brief convective shower could reach far southern areas. Overall, a couple tenths of an inch of rain are expected for southern areas with decreasing amounts farther north. Areas north of the boundary like the Champlain and St. Lawrence Valleys will likely continue to see cool temperatures in the 50s and upper 40s and areas of mist and drizzle through tonight. Patchy fog formation is possible anywhere tonight due to light winds and abundant moisture.

KEY MESSAGE 2: A mostly dry period exists tomorrow morning after the overnight MCS moves out. An area of low pressure will ride along this stalled boundary during the afternoon and evening, bringing multiple rounds of showers. The front will become a warm front during the morning and push north. South of the front, there should be areas of clearing and temperatures should rise into the 70s to near 80. With dew points expected to rise to around 60 and with somewhat steep lapse rates, around or slightly over 1,000 J of CAPE looks to develop down there. However, the low looks to track south of the international border so the front does not look to pass all the way north of the region. North of the boundary, it will be a completely different story. There will be rounds of synoptically forced showers, some lower cloud cover, additional convective blowoff and notably cooler temperatures. Therefore, any instability that forms there looks to be minimal. All areas should see strong dynamics, with HREF mean 0-6 KM shear between 45-60 KTs, 0-1 km SRH between 75-150 m2/s2 and 0-3 KM SRH between 150-250 m2/s2. Due to the favorable ingredients, isolated to scattered severe storms are possible across southern Vermont. The main threat would be damaging winds, though large hail is possible as well. Due to the relatively fast motion of the storms, flash flooding is not expected. Compared to yesterday, the dynamics look slightly better and the warm sector looks to make its way a little farther north, but the exact details and placement of the front remain uncertain. The airmass on the backside of the low is warm so temperatures remain well above climatological normals heading into the weekend.

KEY MESSAGE 3: Low pressure will slide by well to our north Saturday and Saturday night, dragging a cold front along in its wake. Temperatures will warm on a 50+ kt 850 mb jet ahead of the front, allowing highs to rise into the 60s and 70s. Efficient mixing will bring windy conditions late Saturday afternoon into the evening as the core of the jet moves overhead. Gusts of 20 to 30 mph are likely, with locally higher gusts possible in the St Lawrence/Champlain Valleys due to channel and perhaps along the northern slopes of the Adirondacks due to downsloping.

The cold front moves through Saturday night into early Sunday, so expect we'll have yet another non-diurnal temperature range, with temperatures likely rising or holding steady overnight (especially from the Champlain Valley eastward), then falling or holding steady on Sunday under strong cold air advection (especially over northern NY). Winds will remain gusty, first from the S/SW, turning toward the W/NW after the frontal passage. Showers will come to a quick end from west to east Sunday evening/night as much drier air follows the front; PWATs will only drop to 0.25 or less. Hence, while we expect anticipate temperatures to fall below freezing Sunday night (20s to around 30F by daybreak Monday morning), little to no snow accumulation is expected, particularly below summit levels.

KEY MESSAGE 4: Canadian high pressure will settle over the region for the start of the work week. This will be a dry but colder airmass; highs on Monday could well struggle to get into the 40s in the higher terrain, with the wider valleys remaining in the low to mid 40s. Winds will be brisk out of the north/northwest, but we should see at least some sunshine, especially by afternoon. The ridge starts to shift east Monday night into Tuesday, so temperatures should warm 5-10 degrees. Model consensus deviates significantly from there onward, specifically with the strength/placement of an incoming upper trough. Still, do anticipate at least some increasing precipitation chances as moisture returns northward along the back side of the departing ridge, though the details are very uncertain at this point. Given the uncertainty, have not deviated from WPC's forecast from Monday onward.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Through 00Z Friday...Another night of changeable conditions is expected as winds trend light and variable with a stationary boundary just to our south. Low clouds are lifting north to the international border as the boundary is edging north as low pressure is moving northeast over the Great Lakes, just scattering at KPBG and KBTV just now. Convection is developing to our southwest tied to the area of low pressure. The system will skirt south of the region, but rain could impact KRUT about 03z-07z with visibility briefly dipping to 2-4SM and/or lowering ceilings. It's passage will likely bring the region of lower clouds and visibilities back southwards. So focused prevailing 300-800 ft ceilings over KEFK, KSLK, and KMSS, and then once the system starts to track closer and then away, gradually step IFR back into KPBG and KBTV. Fog will be likely again tonight, but visibility reductions are not expected to be quite as low. Still, intervals of visibilities less than 1-4SM could develop at each terminal through about 13-14z. Similar to today, south winds will develop in the morning resulting in improving aviation conditions. Another batch of showers and thunderstorms will progress east and approach the St. Lawrence Valley about 15-16z Thursday.

Outlook...

Thursday Night: MVFR/IFR conditions possible. Likely SHRA, Slight chance TSRA. Friday: MVFR/IFR conditions possible. Chance SHRA. Friday Night: VFR. NO SIG WX. Saturday: Mainly VFR, with local MVFR possible. Windy with gusts to 30 kt. NO SIG WX. Saturday Night: Mainly VFR, with areas MVFR possible. Likely SHRA. Sunday: Mainly MVFR, with local IFR possible. Likely SHRA. Sunday Night: VFR. Chance SHRA, Slight chance SHSN. Monday: VFR. Slight chance SHRA, Slight chance SHSN.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.