textproduct: Burlington

WHAT HAS CHANGED

As of 228 PM EDT Sunday...

Frost Advisory has been issued from 2 AM to 9 AM tonight for southwestern St. Lawrence County in New York, and in Vermont, Lamoille, Washington, Rutland, Orange, eastern Franklin, western Windsor, eastern Chittenden, and eastern Addison Counties.

KEY MESSAGES

As of 228 PM EDT Sunday...

1. Trending cooler and drier for early this week, with frost potential overnight tonight through Tuesday for portions of the region.

2. A gradually warming and wetter pattern is expected to begin midweek with widespread rain showers Wednesday through Thursday, then temperatures trend near or above normal into the weekend.

DISCUSSION

As of 228 PM EDT Sunday...

KEY MESSAGE 1: A cold front has moved through the region this morning with winds turning to the west. Diurnally driven temperatures will prevail today with temperatures this afternoon near 60 to the low to mid 60s. Skies should be able to become partly to mostly clear tonight, with most of the cloud cover observed upstream into Ontario waining as diurnal heating ceases. HREF and Hi-res guidance depict this well with a band of clearing across the central St. Lawrence Valley into central and southern Vermont. There is a chance that some scattered low clouds may hang on near the International Border, but regardless, some radiational cooling is expected across the region which will lower temperatures towards 33 to 36 F. With the Frost program beginning across the St. Lawrence Valley and eastern and southern Vermont (outside the NEK) Tonight, temperatures will be conducive for patchy frost development. A Frost Advisory has been issued for portions of the St. Lawrence Valley and portions of central and southern Vermont. Warmer air due to proximity to Lake Champlain should reduce the frost potential across the Champlain Valley.

Troughing will continue tomorrow with weak embedded shortwaves and highs in the 50s. Steepening lapse rates and cooling aloft from synoptically driven northwest flow will lead to some isolated to scattered showers with the potential for some summit level snow across the Adirondacks. Given the expectation for these showers to be low topped, cold, and instability driven (around 100-150J/kg of SBCAPE) some isolated graupel and perhaps small hail is possible, but well below any severe thresholds. The best chance for any shower will be across northern New York, with precipitation amounts limited. Showers will taper off as daytime heating wains into the evening. High pressure will begin to nose in Monday Night with better chances for clearing skies, frost potential will be nearly areawide tomorrow night with additional frost advisories, and perhaps freeze warnings needed. Cool conditions continue Tuesday under the high with temperatures in the 50s, and continued frost potential Tuesday night, mainly east of the Greens. High pressure will shift east Tuesday night ahead of our next weather system and pattern change for the mid to late week period.

KEY MESSAGE 2: A mid to upper level trough and preceding surface low pressure system is expected to roll through the Great Lakes and Northeast Wednesday through Thursday, bringing increased potential for measurable precipitation during the mid to late week period. There will be two main periods of precipitation, the first being lighter showers associated with initial warm air advection on Wednesday, when temperatures will be in the lower to mid 50s. Then early Thursday, more potent forcing will likely produce additional rain showers and embedded thunderstorms as a cold frontal boundary meets Thursday afternoon temperatures in the mid 50s to lower 60s and the upper low arrives just west of the forecast area. Rain is anticipated to taper off Thursday night and Friday as high pressure tries to nose in from the Ohio Valley late in the week, bringing highs into the mid 50s mid 60s and lows in the upper 30s and 40s. Deterministic global models then try to show another upper wave riding the ridging next weekend, but surface high pressure may limit how much precipitation actually reaches the forecast area. At the moment, have PoPs 15-35% for most of the weekend. Temperatures over the weekend will be largely dependent on how the systems and moisture evolve, but at the moment trends point towards highs warming into the 60s to mid 70s and lows upper 30s to lower 50s.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday...As a cold frontal boundary that brought rain to the region shifts south and east, getting farther from northern New York and Vermont this afternoon, there is a very high likelihood of VFR conditions through 18Z Monday with cloud bases expected to stay 3500+ feet above ground level. Main focus of this 24 hour TAF period will be winds. As rain is clearing the area, we see winds picking up again out of the southwest, at times gusting 15-25 knots. These gusty winds will continue for the remainder of the afternoon out of the west-southwest, decreasing around 00Z-03Z Monday and becoming light and variable overnight with some spots keeping a light west- southwest wind and others becoming more terrain-influenced, like at RUT with a light southeasterly flow. Additional rain showers are possible on Monday, but these would be widely scattered and very light due to dry air, and would largely occur after 18Z.

Outlook...

Monday Night: VFR. Isolated SHRA, Patchy frost. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. NO SIG WX. Wednesday: Mainly VFR, with local MVFR possible. Definite SHRA. Wednesday Night: Mainly MVFR, with areas VFR possible. Likely SHRA. Thursday: Mainly MVFR, with areas IFR possible. Definite SHRA, Slight chance TSRA. Thursday Night: Mainly IFR, with areas MVFR possible. Chance SHRA. Friday: MVFR/IFR conditions possible. Slight chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

VT...Frost Advisory from 2 AM to 9 AM EDT Monday for VTZ006-008-010- 011-016>020. NY...Frost Advisory from 2 AM to 9 AM EDT Monday for NYZ087.