textproduct: Burlington

WHAT HAS CHANGED

As of 237 AM EDT Monday...

No significant changes associated with this forecast package.

KEY MESSAGES

As of 237 AM EDT Monday...

1. Light to moderate rainfall is expected to develop central and southern Vermont this afternoon, but the potential for any flooding is low.

2. An approaching cold front will bring a sharp increase in shower and thunderstorm chances for the end of the week with unsettled conditions continuing into the weekend.

DISCUSSION

As of 237 AM EDT Monday...

KEY MESSAGE 1: GOES-19 mid lvl water vapor imagery shows decaying convective induced vort and associated sfc low pres over the Ohio Valley moving toward the Mid Atlantic/NE CONUS. Sfc low pres is progged to track from the Ohio Valley into Southern New England by tonight, while our cwa stays on the cooler/stable side of this system. The lack of instability acrs our cwa, should minimize rainfall rates this aftn/evening and result in a low probability of any flooding. In addition, flow aloft is progressive west to east, which should keep precip moving. As southern stream s/w energy lifts toward southern NY this aftn, expect an expanding area of light to moderate rain to develop over the High Peaks into central/southern VT. The best 700-500mb lift and deep layer moisture (850-500mb) wl be located over Rutland/Windsor counties associated with northern side deformation zone. Expected a sharp north to south precip gradient acrs our cwa, which is similar to a winter-time unphased and progressive Ohio Valley low pres system.

HREF shows 60-90% prob of 24 hour rainfall >1.0" acrs Rutland/Windsor counties, while 30% or less for rainfall >2.0". The HREF total mean precip is in the 1.25" to 1.50" range mostly along and south of Route 4, which looks a little high given dynamics and available moisture with this system, as pw values approach 1.25". Thinking qpf around 1.0" south, to 0.10 to 0.30" along a SLK to BTV to 1V4 line and a tenth or less near the International Border. This highlights the sharp north to south precip gradient expected and have pops accordingly. Given recent rainfall hydro wl need to be watched, but feel pretty confident no issues in our cwa through tonight. Given expanding cloud cover and rain developing by this aftn, have trimmed 1 to 3 degrees off NBM with highs mostly in the upper 60s to mid 70s, warmest north and coolest south.

Tonight initial s/w energy quickly shifts off the New England Coast and subsidence aloft builds into our cwa as weak elongated low pres is located over SNE. Have continued with some lingering showers thru 06z, but feel decreasing moisture profiles should limit areal coverage of precip aft midnight. Some patchy fog is possible in areas that can decouple and clear out with lows in the upper 40s to upper 50s. On Tuesday, northern stream s/w energy approaches the International Border area btwn 21-00z, but moisture/instability parameters are weak. Thinking dynamics and northwest upslope flow, wl be enough to produce scattered showers, especially northern Dacks into the mtns of central/northern VT. Areal coverage should be mostly confined to the trrn and parts of the NEK on Tues. Did trim a degree or two from progged high temps with values mostly in the 70s to near 80 locally in the CPV.

Our next northern stream mid/upper lvl trof and associated height falls arrives late Thurs. Weak 1010mb sfc low pres is progged over the central Great Lakes, while a warm frnt/moisture surge is lifting acrs the Ohio Valley into the NE CONUS on Thurs aftn. The combination of warm frontal lift/moisture and s/w energy riding along gradient should produce a period of showers and embedded showers late Thurs/Thurs night. Crnt guidance indicates best instability wl stay south of our cwa thru Thurs, along with the highest pw values. We wl keep pops in the chc range for Thurs and increase them toward likely Thurs night. Highs wl be near normal both Weds and Thurs with values in the mid 70s to lower 80s with lows lower 50s to lower 60s.

KEY MESSAGE 2: Low pressure crossing the Great Lakes will advect in moisture and warmth to northern New York and Vermont ahead of a warm front Thursday night, with lows both Thursday and Friday nights will be mild in the 50s and lower 60s. Seasonable highs in the 70s and lower 80s are expected on Friday afternoon. Blended guidance has trended slightly in the direction of global deterministic solutions, therefore the main swath of steady rain and embedded thunderstorms is looking like it comes through Thursday night as low pressure grows closer to the forecast area while passing into Quebec. Precip chances 70-90% are forecast Thursday night, then on Friday, low pressure will speed across Quebec towards the Canadian maritimes, dragging both a warm front and a weak cold front through the forecast area, keeping the region showery with afternoon thunderstorms. Highest precip chances 55-95% are focused along the international border, closest to low pressure, as well as in the mountains with orographic assistance. A half an inch of rainfall in 24 hours Thursday night through Friday looks most likely across the Adirondacks and northern Vermont, though probabilities of 1 inch or more within a span of 24 hours are lower, around 15-45%. That being said, anywhere that we see convective showers and thunderstorms, especially training storms, could see localized higher amounts than expected. We'll be keeping an eye on this pattern through the week given recent saturation of soils and increased runoff potential. Then on Friday night we expect a dramatic decrease in shower chances and coverage as the low pressure rushes east into the Canadian maritimes and drier air filters into northern New York and Vermont. Cyclonic flow will likely linger behind the system, keeping some shower chances in place over at least a portion of the weekend depending on how fast ridging can build back in, with highs each afternoon in the 70s and lower 80s.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Through 12Z Tuesday...Fog and low clouds are quickly burning off and dissipating this morning with the exception of site MPV which remains socked in LIFR conditions. Hard to say exactly when conditions will improve there, but based off climatological data, forecast model projections, and recent observations at the site, thinking we should see VFR conditions arrive at MPV around 13Z Monday. From there, we anticipate winds to increase across all sites out of the south today 5-15 knots. Light to moderate rainfall is expected to develop across central and southern Vermont this afternoon, bringing likely visibilities to 3-6 miles. The arrival of precip will most likely be around 18Z-22Z Monday, lasting just a few hours with the exception of RUT, which should have more rain and for a longer duration. Following the rain, we expect ceilings to lower to MVFR levels 00Z-06Z Tuesday, with RUT potentially having earlier onset of MVFR cigs. RUT is also the most likely site to see IFR ceilings during this 00Z-06Z Tuesday period.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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