textproduct: Burlington

WHAT HAS CHANGED

As of 303 PM EDT Monday...

Removed wind advisory and made minor tweaks to temperatures and timing of precip through midweek.

KEY MESSAGES

As of 254 AM EDT Tuesday...

1. Showers with embedded thunderstorms are expected on Tuesday with a couple of stronger storms possible, mainly south of Route 4.

2. Additional rounds of showers and thunderstorms are expected Wednesday and Thursday as boundary remains draped across our forecast area.

3. A more amplified weather pattern and shortwave will lead to unseasonably warm conditions and scattered rain showers at the end of the week.

4. A round of widespread showers Saturday night and Sunday will usher in a sharply cooler period early next week.

DISCUSSION

As of 254 AM EDT Tuesday...

KEY MESSAGE 1: The forecast challenge is amount of clearing and associated sfc heating/instability that can develop on Tues. GOES-19 water vapor imagery shows compact s/w energy moving along the International Border this aftn, while large area of subsidence/dry air aloft is located over the central Great Lake and approaching the SLV. As this moves overhead tonight, expect lowering cloud levels with some patchy fog possible over the northern Dack Valleys. Lows generally in the mid 40s to mid 50s tonight.

For Tuesday our s/w energy of interest is currently located over central IA with developing lightning over northern IL/WI. This energy wl quickly move eastward in the fast 700-500mb flow aloft and being located over the eastern Great Lakes by 12z Tues. Upstream satl imagery shows a rather messy warm sector in regards to plenty of clouds and feel this could influence our sfc heating/instability acrs our cwa on Tues. Weak sfc low pres is expected to travel along boundary draped near the International Border on Tues with very warm 925mb to 850mb thermal profiles, but soundings low clouds stuck under the inversion in the morning and mid/upper lvl convective debris clouds developing by early aftn, which wl probably limit sfc heating. HREF shows the greatest potential for sfc based CAPE profiles >500 J/kg south of a SLK to LEB line of 40 to 60%, with highest potential mainly south of Route 4. Meanwhile, the probability of 0 to 6 km shear >50 knots is 80 to 100% near the International Border, indicating strongest winds are north and best deep layer instability is south. NAM 12KM/NAM 3KM solutions are the most aggressive with sfc/mu CAPE values of 1000-1500 J/kg into our central/southern cwa, while HRRR/WRF NSSL and RAP are <500 J/kg. This wl become a nowcasting scenario on Tuesday, watching if clouds can dissipate and timing of boundary crossing our cwa for determining how robust convection can develop. For now a few stronger storms are possible mainly Rutland/Windsor counties, but feel greatest action wl be south of our cwa. The latest SPC day2 outlook continues to place part of our cwa in a Marginal Risk (1 out of 5). Temps are very challenging on Tues as 925mb temps would suggest highs well into the mid 70s to lower 80s, but clouds and precip with sharpening boundary wl have significant impacts on highs. Have mid 60s SLV to near 80F VSF.

KEY MESSAGE 2: An active pattern is expected for Weds and Thurs as boundary remains draped acrs our cwa with multiple s/w's riding in the westerly flow aloft producing additional chcs for precip. Boundary position and clouds wl have significant impact on temps and sfc instability for both Weds/Thurs. Latest trends indicate additional s/w energy arriving acrs our western cwa by 15z with some instability possible acrs our central/southern fa. Clouds and precip wl impact thermal profiles and associated thermal dynamics. Any stronger/deeper convection wl have the potential to produce localized heavy downpours, especially with pw values approaching 1.5" or 2 to 3 std above normal on Weds. Similar type temp profile as Tuesday with greatest probability of mid 70s acrs Rutland/Windsor counties, with coolest air over the northern SLV/CPV and parts of the NEK. Little change in the large scale synoptic pattern is anticipated on Thursday, as additional s/w dynamics and moisture in the westerly 700 to 500mb flow impacts our cwa. Additional showers with embedded storms are expected, with some localized heavy downpours possible. As always, the instability wl be driving factor on how strong storms can become, but progged 925mb temps are very warm again with values in the 14-18C range. If sun develops highs easily in the 70s, but if clouds prevail with occasional showers, temps mostly hold in the upper 50s to mid 60s.

KEY MESSAGE 3: A quick-hitting shortwave will bring some rain showers and potential embedded thunderstorms, mainly in southern Vermont, on Friday as guidance indicates 925mb temperatures could reach 13-17 C Friday afternoon. Due to this and decreasing clouds, forecast surface temps are as high as the 60s and lower 70s, with non-zero instability values projected. Probability of measurable precipitation runs about 30-60% Friday afternoon, likely realized as spotty showers everywhere and a few rumbles of thunder in central/southern Vermont. Lows Friday night should remain mild in the 40s and lower 50s, with only a brief period of high pressure between systems late Friday night and Saturday morning. The next chance for precipitation arrives late Saturday afternoon and evening as a larger frontal system approaches. Despite increasing clouds, temperatures are expected to again rise above seasonable normals Saturday, reaching into the 60s in strong southerly flow and modest warm air advection.

KEY MESSAGE 4: A large frontal system, centered over Ontario and the Hudson Bay Saturday night, will drag a cold frontal boundary through the forecast area into Sunday. Lows Saturday night in the 40s and lower 50s will fall into the upper 20s to mid 30s on Sunday night, and highs Sunday in the mid 50s to lower 60s become upper 30s to mid 40s Monday as cooler air spills into the region on northwesterly flow behind a secondary cold front. Probabilities of measurable precipitation in six hours are about 50-65% by Sunday afternoon, though probabilities of rainfall 0.50" within 24 hours during this period is around 10-30%. Thunderstorms are most likely Sunday afternoon in northern New York when warmth lingers, but the timing of instability, warmth, and forcing do not align favorably for widespread t-storms in this system as the best forcing occurs at night. Sunday night and Monday, as temperatures fall, there is the potential for some snow showers, mainly at higher elevations, before the arrival of drier air behind a secondary front tapers off precip. High pressure keeps weather quieter and cool toward the middle of next week.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

Through 06Z Wednesday...Showers with embedded thunderstorms are expected on Tuesday with a couple of stronger storms possible. Winds tonight are generally westerly to northwesterly with a few gusts observed in southern Vermont 10-20 knots. In areas seeing a lighter wind and breaks in clouds, some patchy fog may develop over the next few hours. Around 12Z-15Z Tuesday, a southerly wind will develop, except at MSS, which should see more northeasterly to northerly winds. Ceilings throughout the day will likely hover around 2500-3500 feet above ground level, potentially lower in showers crossing west to east across northern New York and Vermont 15Z Tuesday through 00Z Wednesday. Embedded thunderstorms are possible starting at 18Z Tuesday, but when and where t-storms occur is not clear at this time, so TAFs have only SHRA. Also with these showers and t-storms, gusts 30-35 knots are not out of the question. However, like the t- storms, the timing and location of such gusts is of higher uncertainty, so gusts closer to 15-25 knots are in the TAFs. Some LLWS is also expected as southwest to west winds at 2000 ft agl increase along the showers/storms, around 20Z Tuesday onwards. With the passage of the showers/associated frontal boundary, surface winds should turn out of the west-northwest again (except MSS) by around 00Z Wednesday, and ceilings are expected to fall into widespread IFR levels into the evening.

Outlook...

Wednesday: Mainly VFR, with local IFR possible. Likely SHRA, Slight chance TSRA. Wednesday Night: MVFR/IFR conditions possible. Chance SHRA, Slight chance TSRA. Thursday: Mainly MVFR, with areas IFR possible. Likely SHRA, Slight chance TSRA. Thursday Night: MVFR/IFR conditions possible. Chance SHRA. Friday: MVFR/IFR conditions possible. Chance SHRA. Friday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Saturday: MVFR. Slight chance SHRA.

EQUIPMENT

The Colchester Reef meteorological station is out of service. This site is not serviced by the NWS. An estimated return to service is May 1st. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES

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