textproduct: Burlington

WHAT HAS CHANGED

As of 252 PM EDT Monday...

No significant changes have been made at this time. Well above normal temperatures are expected Tuesday with the potential for strong to severe thunderstorms.

KEY MESSAGES

As of 252 PM EDT Monday...

1. Well above normal temperatures expected on Tuesday with much cooler weather expected on Wednesday and Thursday.

2. Strong to locally severe thunderstorms possible Tuesday afternoon and evening.

3. Cooler and drier conditions are favored Thursday and Friday before a transition back to seasonable temperatures and a wetter pattern.

DISCUSSION

As of 252 PM EDT Monday...

KEY MESSAGE 1: Continued warm air advection will set the stage for unseasonably warm temperatures on Tuesday. The latest NBM shows high potential for 90 degree weather, however, much of the other guidance and MOS is showing temperatures likely plateauing in the mid to upper 80s. Cloud cover and convection will be a huge factor in determining how warm we get as a lot of guidance suggests partly to mostly cloudy skies. Any convection would increase cloud cover and any precipitation would drop temperatures significantly. Still, there is overwhelmingly high confidence in high temperatures being 15 to 20 degrees above normal. On Wednesday, a cold front will likely push through the region during the morning hours which will limit daytime heading with strong cold advection expected to follow in the wake of the front. We could still warm into the 80s across eastern Vermont but will likely be in the 70s for most of Vermont and New York based on the timing of the frontal passage. Thursday will be 10-20 degrees colder than Wednesday as we will see temperatures struggle to climb into the mid 50s to lower 60s. North winds in the 10-20 mph range will help make it feel a bit blustery, especially after the recent warmth. Most clear skies should help it feel a little warmer given the late May sun angle.

KEY MESSAGE 2: The convective potential for Tuesday continues to remain very conditional. A lot of the machine learning and AI tools are showing modest probabilities (15-30%) for severe weather Tuesday afternoon and evening while the latest deterministic guidance shows rather lackluster instability. There is high confidence in around 50 knots of deep-layer shear as we have a strong 500 jet move overhead but the thermodynamic profiles keep fluctuating from model run to model run. Even though temperatures are expected to warm into the mid to upper 80s and dewpoints rising in the lower to mid 60s, the mid-level lapse rates between 850 mb and 500 mb aren't exactly what you want to see to maximize severe potential. In addition, no notable surface convergence outside of orographic lifting is expected with the cold front not expected to come through until Wednesday morning. There will be some weak height falls under anticyclonic flow aloft and a weak shortwave trough pushing through which will give up some deep layer support but getting storms to initially develop will be difficult. The main focus, initially, will be across the higher terrain and along lake breezes as this could create some surface convergence and the upper level support could take over from there.

There may be residual cloud cover from overnight convection across western New York which may stunt surface heating. Should this occur, instability values may underperform further and lead to little to no thunderstorm activity. Hence the condition potential. Largely unidirectional wind profiles with slight curvature in the Champlain Valley is expected which likely makes Tuesday a wind threat. High LCLs will strongly inhibit tornado potential with high freezing levels also making severe potential very difficult to come by. The main window for convection will be between 4 and 8 PM with instability waning rapidly following sunset.

KEY MESSAGE 3: Winds weaken Thursday night with skies clearing; this may be a period of concern for some frost outside the Champlain Valley with lows in the mid/upper 30s for many locations, and low 40s for the Champlain Valley. Temperatures begin to warm up on Friday with northwest flow weakening, high temperatures will reach the 60s areawide. A slow warming trend is then expected through the weekend into Monday.

Models begin to split on precipitation timing heading into the weekend. Consensus maintains some chances of showers increasing Saturday with more widespread rain Sunday. However, a number of models are beginning to hold onto the ridge longer delaying precipitation onset until the late weekend. Either way, a pattern shift to deep return flow from the Gulf Coast northeastward into the Northeast is appearing probable. This flow pattern would result in multiple days of rain potential once it sets up.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18Z Tuesday...A low level jet will sweep through this afternoon promoting some LLWS for MSS/SLK/PBG/EFK. Surface winds at PBG could gust 20-30kts at times with favorable off- lake, channeled flow while most other terminals see gusts around 20kts. Gusts drop by 00Z with clouds thickening early morning as a diffluent flow pattern moves over the region with some increasing elevated instability. A few showers will be possible after 06Z, but widespread LLWS will return as the next lljet moves into the region 00-12Z. Winds slacken overnight but pick up again Tuesday morning.

Outlook...

Tuesday Night: VFR. Slight chance SHRA, Slight chance TSRA. Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: VFR. NO SIG WX. Friday Night: VFR. Chance SHRA. Saturday: VFR. Chance SHRA.

MARINE

As of 300 AM EDT Monday...

A Lake Wind Advisory is in effect for the Broad Waters of Lake Champlain. Winds have been slow to materialize thus far after plenty of cloud cover and rainfall this morning stunted the winds on Lake Champlain. Winds have currently increased to 15 knots in the broad lake and will continue to increase to 25 knots between 8 and 10 PM this evening. These stronger winds will continue through 8 AM on Tuesday and will diminish to 15 knots or less on Tuesday. Waves are currently ranging between 1 and 2 feet and are expected to increase to 2-4 feet this evening with the highest waves expected across the broad lake.

BTV WATCHES/WARNINGS/ADVISORIES

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