textproduct: Burlington

WHAT HAS CHANGED

As of 251 PM EDT Thursday...

No significant changes with this forecast. We are still anticipating scattered showers and thunderstorms this afternoon into the evening hours. A few strong to severe thunderstorms will possible, mainly along/south of a Newcomb, NY to Middlebury to Fairlee, VT line. Gusty winds and hail will be the primary threats.

KEY MESSAGES

As of 251 PM EDT Thursday...

1. Showers and thunderstorms will increase in coverage late this afternoon and continue into the evening. Some storms may be strong to severe, mainly over southern Vermont. Quieter weather follows for Friday and Friday night.

2. Warm and breezy weather on Saturday will give way to much cooler and rainy conditions on Sunday. Brief mountain snow will be possible as temperatures drop well below normal by Sunday night.

3. Cooler temperatures and drier weather expected next week.

DISCUSSION

As of 251 PM EDT Thursday...

KEY MESSAGE 1: We are watching thunderstorms bubble up along/south of Lake Ontario this afternoon. This activity should continue to develop over the next couple of hours, quickly moving east/northeast. The warm front has lifted north and now lies south of the international border. Temperatures in the low/mid 70s combined with dewpoints in the low 60s have allowed SB CAPE values of 1000+ J/kg over the southern Adirondacks into southern VT. Meanwhile, strong southwest flow aloft is contributing to 40-50 kt of 0-6km bulk shear. With this in mind, we still anticipate storms to develop near Lake Ontario (perhaps along a lake breeze) and propagate eastward. The hi-res CAM guidance continues to be fairly persistent showing isolated to perhaps scattered thunderstorms making it into central/southern VT, with more widespread showers with embedded thunder along and north of the warm front. Given the above parameters, a few mini supercells will be possible, capable of producing strong winds, hail, and briefly heavy rainfall. Storm motions will be fast, so flash flooding is not anticipated, outside of perhaps some urban, poor-drainage flooding if a storm happens to move directly over one of our more urban areas (ie Rutland, Barre, Burlington). A weak tornado can't be ruled out, but chances are very low and not the main concern, by far. Areas in far southern Essex County, NY and southern Addison/Orange Counties southward have the best chances of seeing any strong to severe thunderstorms, with timing roughly 4 to 8 pm. See the latest Mesoscale Discussion from SPC for additional details. Please stay tuned for any watches or warnings, especially if you have outdoor plans. Storms should wane after 8 pm, though showers will likely linger through midnight or so.

Ridging builds in on Friday as the upper trough exits to the east. A few showers can't be ruled out, especially over central/southern VT, but overall expect it'll be a dry day with skies becoming partly to mostly sunny. Highs will be in the 60s to near 70F, followed by overnight lows in the 40s Friday night.

KEY MESSAGE 2: Low pressure will slide by well to our north Saturday and Saturday night, dragging a cold front along in its wake. South/southwest flow will increase ahead of the front, allowing temperatures to warm into the 60s and 70s. Winds may have just enough easterly component across eastern VT that could keep areas east of the Greens from achieving full warming potential, perhaps just in the low to mid 60s. Still, expect it should be a fairly pleasant day. Winds will become breezy due to a 50+kt 850mb jet moving overhead, especially in the St Lawrence and northern Champlain Valleys where gusts of 25-35 mph will be possible.

The cold front approaches from the west late in the day and then crosses the forecast area Saturday night into early Sunday. As such, expect we'll have yet another period of non-diurnal temperatures, with temperatures rising or holding steady overnight, then falling or holding steady on Sunday under strong cold air advection. Widespread showers will likewise spread from west to east along/ahead of the front, with the bulk occurring overnight Saturday night and through Sunday morning. Moisture will be ample ahead of the front with PWATs approaching 1.50 inch, or near/above the 99th percentile. This So while instability will be lacking to poor frontal passage timing and a warm layer around 850mb, still expect there could be some briefly heavy rain as the front moves through. Much drier air will follow the front, ending the bulk of the showers by early Sunday afternoon. However, some isolated to scattered activity may linger into the evening hours as a secondary front crosses the region. As mentioned above, expect temperatures to be much colder than the previous day (topping out in the 40s and 50s), and likely dropping in the afternoon, especially on the higher summits. Therefore, any lingering showers could mix with and/or change over to snow by late in the day, though any daytime accumulation would be limited to 2500 ft or higher. Total rainfall will range from around 0.50 inch to around 1 inch in most areas. Winds will become blustery out of the W/NW, only adding to the chilly, raw feel of the day.

KEY MESSAGE 3: Following the passage of a cold front, temperatures are expected to plummet for the start of the upcoming work week. By Monday morning, temperatures are expected to fall below freezing across all of Vermont and northern New York with temperatures only rebounding into the mid 30s to lower 40s Monday afternoon. It'll be a start contrast compared to the above normal temperatures that we are currently experiencing. Temperatures are expected to slowly moderate throughout the week with temperatures warming back into the low to mid 50s by Thursday while lows remain within a few degrees plus or minus of freezing each morning.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Through 18Z Friday...Low clouds across the region will slowly improve this morning back to MVFR and eventually VFR for most terminals by midday. Low clouds will remain until 14-16Z based on satellite and model soundings, as well as persistence from yesterday. Beyond the morning low clouds, a weak surface low will bring additional chances for rain and rumbles of thunder into this afternoon/evening with winds becoming south/southwest. A broken line of showers appears likely between 18-23Z across much of northern New York, and between 22-02Z for the Champlain Valley and much of Vermont. Within this line, a couple scattered thunderstorms will be possible, mainly impacting RUT/MPV with lower confidence at BTV/PBG/SLK. The main threats will be strong gusts and some isolated large hail. Winds outside of any thunderstorms should remain light (< 10 knots) today, with a few breezes (10-15 knots) within the line of showers. Showers will taper off beyond 02-03Z tonight with a return of fog and mist as the stationary boundary lingers over the region. A return to MVFR/IFR conditions areawide, with better confidence in terminals receiving heavy rain, is expected.

Outlook...

Friday Night: VFR. NO SIG WX. Saturday: VFR. NO SIG WX. Saturday Night: Mainly MVFR, with areas VFR possible. Likely SHRA. Sunday: Mainly MVFR, with areas VFR possible. Likely SHRA. Sunday Night: Mainly VFR, with local MVFR possible. Chance SHSN, Chance SHRA. Monday: Mainly VFR, with local MVFR possible. Slight chance SHSN. Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX.

BTV WATCHES/WARNINGS/ADVISORIES

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