textproduct: Burlington

WHAT HAS CHANGED

As of 223 PM EDT Saturday...

Have increased chances for precipitation slightly on Sunday on northern and western slopes of the Adirondacks as well as northern Vermont along the international border due to cold pool/upslope type rain showers and thunderstorms. Have also incorporated patchy fog in valley locations to the forecast tonight and Sunday night.

KEY MESSAGES

As of 223 PM EDT Saturday...

1. Intervals of showers and thunderstorms will continue this afternoon and evening. Warm and humid conditions will persist through much of the weekend.

2. Chances for heavier showers and thunderstorms continue to look likely Monday into Tuesday as a shortwave pushes through the region.

3. Unsettled weather continues Wednesday onward, and temperatures trend slightly below normal by the weekend.

DISCUSSION

As of 223 PM EDT Saturday...

KEY MESSAGE 1: A large, closed upper low over Hudson Bay in Canada will send a prefrontal trough shortwave through northern New York and Vermont this afternoon, arriving into a warm, humid air mass with temperatures in the upper 70s to mid 80s. This will result in likely showers and thunderstorms over the next several hours, most widespread across the Champlain Valley and northern Vermont. Severe weather is not expected from these storms with minimal shear available, though any shower or storm could produce heavy rainfall with precipitable water values 1.50-1.75 inches and slow storm motions. Locations that have received heavy rainfall already in the past 24 hours will be particularly at risk for flooding and ponding of water in low lying spots. Precipitation should wane overnight tonight, but chances remain across northern New York and northern Vermont for additional heavy showers and embedded rumbles of thunder as a cold front moves through the region (20-60% precip chances). Lows tonight will remain mild ahead of the front in the upper 50s and 60s. A brief break in the unsettled pattern is expected to develop throughout the day Sunday as a narrow axis of high pressure and drier air move over the region, though high temperatures will remain warm in the upper 70s to mid 80s and there is the chance of a shower or two with embedded rumbles of thunder (20-50% chance precip) on northern and western slopes of the Adirondacks as well as northern Vermont along the international border. Sunday night, temperatures should fall back towards seasonal normals in the 50s to mid 60s.

KEY MESSAGE 2: We remain in the cyclonic flow of the closed upper low over Hudson Bay in Canada early next week, and another shortwave is expected to drive through northern New York and Vermont Monday and Monday night. This will likely produce precipitation across northern New York Monday afternoon, expanding to Vermont during the evening/overnight hours (50-90% chance precip). Highs both Monday and Tuesday will be in the mid 70s to mid 80s, resulting in the potential for showers and thunderstorms. Once again, wind shear is looking unimpressive (limited severe threat), but moisture will advect back in from the Great Lakes with modeled Pwats 1.50-1.75" returning. We'll be monitoring this period for flooding potential, particularly Monday evening.

KEY MESSAGE 3: The unsettled weather pattern will continue for the second half of the week. In general, expect intervals of showers and thunderstorms interspersed with drier days and a trend towards slightly cooler temperatures towards the weekend.

The midweek timeframe will feature progressive zonal flow that will send a series of quick-moving systems through our area. Despite the numerous chances for rain, hydro concerns are low given the expected progressive movement of the systems. For Wednesday and Thursday, the best chances for showers (and possibly a few embedded thunderstorms) will be during the afternoon hours as marginal instability develops.

Looking towards the end of the week, the upper-level flow will amplify as ridging builds over the western US with downstream troughing over the eastern US/Canada. The cyclonic flow over the northeastern US will favor a continuation of scattered showers with slightly below normal temperatures for the weekend.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 18Z Sunday...Scattered showers with a few embedded thunderstorms will increase in coverage this afternoon, peaking between 18Z and 22Z. Any thunderstorms that do materialize will be pulse-like in nature, and are not expected to last long. Given the isolated coverage and brief duration of individual storms, have left mention of thunderstorms out of all TAFs at this point. However, will be watching radar closely and will amend to include tstorms if terminals are expected to be impacted. Any thunderstorms or showers that do go over a terminal may briefly bring MVFR/IFR visibilities and MVFR ceilings, but outside of precipitation conditions are expected to remain predominantly VFR.

Overnight tonight, expect ceilings and visibilities to lower as a mix of low stratus and mist/fog develops. Forecast soundings suggest fog is most likely in climatologically favoured valleys of central and eastern Vermont, where low-level winds will remain lighter than over northern New York. Meanwhile, an area of stratus looks likely to develop over northern New York, especially over the northern Adirondacks after 06Z. Just how expansive the stratus will get is lower confidence, and for now have just introduced a SCT003 layer at KMSS. However, there is the possibility that KMSS could also see a period of IFR or LIFR ceilings mainly between 06Z and 12Z. The overnight stratus and fog is unlikely to affect the Champlain Valley terminals, and have forecasted VFR conditions overnight for KBTV, KPBG, and KRUT.

Outlook...

Sunday Night: VFR. NO SIG WX. Monday: VFR. Slight chance SHRA, Slight chance TSRA. Monday Night: Mainly VFR, with local IFR possible. Likely SHRA, Slight chance TSRA. Tuesday: Mainly VFR, with local IFR possible. Slight chance SHRA, Slight chance TSRA. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Chance SHRA, Slight chance TSRA. Wednesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Thursday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance TSRA.

BTV WATCHES/WARNINGS/ADVISORIES

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