textproduct: Burlington

WHAT HAS CHANGED

As of 722 AM EDT Tuesday...

Updated shower and thunderstorm potential for the morning hours across northern New York and northern Vermont. Chances have increased with a trough moving through.

KEY MESSAGES

As of 727 AM EDT Tuesday...

1. Unusually warm temperatures continue today into Wednesday before a cold front moves through the region bringing much cooler conditions by Thursday and Friday.

2. Strong to locally severe thunderstorms possible this afternoon and evening with more widespread showers possible overnight into Wednesday.

3. Breezy to gusty winds are expected today through Wednesday.

4. Seasonable temperatures and increasing chances of precipitation expected for the weekend into early next week.

DISCUSSION

As of 727 AM EDT Tuesday...

KEY MESSAGE 1: Heat will continue today with 925mb temperatures favored to warm into the 20-24C range. This is down from yesterday, but the warmer start this morning will continue to promote hot conditions. Maximum temperatures are favored back into the mid and upper 80s with 90 within reach for a few select locations. Flow will be swinging southwesterly, so Burlington may get a marginal reprieve as air moves across the colder surface of Lake Champlain; upper 80s are favored here. Conversely, eastern slopes will have an increase in temperatures from this wind direction that will promote increased compressional warming off the terrain of the Adirondacks and Greens. 90-93 degrees is more probable for eastern Essex County, NY and for the Springfield, VT area. Around 90 is possible for portions of Rutland/Addison Counties as well. Temperatures are expected to drop by 10-15 degrees for Wednesday, but remain 5-10 degrees above seasonal averages. Warmest spots will be in southern Vermont where there will be potential for more heating ahead of the boundary. Highs in the 70s are forecast with low 80s for southern Vermont locations. Northwest flow will dominate behind the front bringing sharply cooler temperatures for Thursday and Friday with highs likely in the mid/upper 50s, then 60s respectively. This will be around 10 degrees below seasonal averages and around a 30 degree departure from yesterday and today's high.

KEY MESSAGE 2: A conditional threat for strong to severe thunderstorms remains as heat continues while dew points rise. Highs in the mid/upper 80s to 90s coupled with dew points in the upper 50s to mid 60s would support a few stronger variety storms. Should any storms fire off, it's probable that outflows would be sufficient to ignite other cells, especially if they interact with lake breeze or move into convent flow around terrain. The biggest issue will be a trigger. Models are showing a subtle 500mb trough moving through late this morning and early afternoon which is what some of the CAMs are highlighting as a trigger. There should be ample cloud breaks to allow for heating which will put the focus on shower/cell initiation over higher terrain. Have increased chances of showers over the Adirondacks coincident with trough timing and as temps on the slopes rise to near 80 degrees which aligns with about noon. The biggest concern will be winds (15%) with a stout low level jet and deep layer of 40+kts extending from 2500-15000ft. There will be about a 5% chance of any storm developing hail this afternoon. The continued absence of strong low level shear means the tornadic threat is very low. Finally, can't rule heavy rain completely out with PWATs in excess of 1.5". If storms fire and a persistent boundary can set up, training cells could occur resulting in localized heavy rainfall. The threat for stronger storms will end around sunset with loss of heating and decrease further behind the prefrontal trough overnight Tuesday.

More synoptically induced precipitation is expected as the front begins to moves through tonight along a prefrontal trough and Wednesday as the surface front moves through.

KEY MESSAGE 3: Winds will be breezy through Wednesday given periods of low level jet passages and a moderately strong thermal/pressure gradient along and behind Wednesday's front. Gusts 20-35 mph are likely with highest gusts in the northern Champlain Valley and along the Highway 11 corridor in the vicinity of Malone/Ellenburg, NY. Gusts to 40 mph are possible should mixing be more pronounced; model soundings show robust southwest flow aloft with a deep 35-45kt layer 2500-15000+ft. Some model guidance is suggesting a narrow potential at gusts to 40 mph for portions of northern New York tonight, but this will be highly dependent on convection which is less certain. These winds will result in rough lake conditions on Lake Champlain. Lighter winds return Thursday as high pressure moves across the region.

KEY MESSAGE 4: There continues to be considerable differences in both ensembles and deterministic models in how shower chances play out for the upcoming holiday weekend. Ensemble members of both the GEFS and ECMWF are roughly split equally on whether waves of precipitation will cross the area Saturday into Sunday. The deterministic ECMWF also favors a wetter solution. Meanwhile, the remaining ensemble members along with the GFS and CMC keep ridging more firmly in place, with the axis running just to our east. This would keep rain shunted to our south and west through the day Saturday and most of Sunday, then trending rainy for Memorial Day. With this much uncertainty, have stayed with the NBM solution for now. Either way, temperatures will be seasonable with highs mainly in the 60s and lows in the 40s.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through 12Z Wednesday...This morning, some showers are moving into northern New York with a focus on MSS and SLK through 16Z. More nebulous are chances as the area of showers track into the Champlain Valley - have about 30% chance of showers 15-21Z. After 18Z, isolated to scattered showers/thunderstorms are possible, some of which may be strong to perhaps severe. Coverage/timing is too uncertain at this point to include any mention in the TAF, but MVFR/IFR conditions will be possible in any thunderstorms. Surface winds become light and variable around 5 kt this evening. However, a LLJ moving overhead will allow for periods of LLWS at all terminals overnight. Surface winds increase out of the S/SW after 14z Tue, gradually shifting toward the W/SW with gusts of 18-25 kt expected. LLWS will become pervasive overnight as LLjet spread across northern New York and much of Vermont ahead of an approaching cold front. Showers will begin at MSS after 09Z.

Outlook...

Wednesday: VFR. 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 236 AM EDT Tuesday...

A Lake Wind Advisory remains in effect for the Broad Waters of Lake Champlain. Winds are expected to increase this morning out of the south with sustained speeds 15 to 20kts and gusts around 25kts. These stronger winds will continue through 8 AM and will diminish to 15 knots or less until the early afternoon; winds then increase again as faster winds aloft mix to the surface. Gusts in excess of 20kts are probable before flow turns more southwesterly. South winds return tonight with stronger gusts possible. A front will pass through the region Wednesday resulting in a wind shift out of the north with gusts up to 30kts.

BTV WATCHES/WARNINGS/ADVISORIES

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