textproduct: Burlington

WHAT HAS CHANGED

As of 222 PM EDT Tuesday...

No significant change have been made to the forecast.

KEY MESSAGES

As of 222 PM EDT Tuesday...

1. Cool and dry conditions continue this evening into tonight with increasing clouds and decreasing frost threats.

2. Conditions will trend wet by tomorrow morning with widespread, beneficial rainfall tomorrow through Thursday.

3. Showers with embedded thunderstorms are possible Saturday afternoon and evening, then temperatures warm above seasonal normals for the first half of next week with additional shower chances to start the work week.

DISCUSSION

As of 222 PM EDT Tuesday...

KEY MESSAGE 1: Cool and dry conditions will continue into this evening as high pressure quickly slides to the east. While temperatures will lower once again tonight, increasing clouds from west to east overnight, will limit the overall cooling that takes place. As such, no frost headlines are expected tonight in the areas where the growing season has started. However, there is still some potential frost in the Northeast Kingdom where clouds may arrive slightly later closer to tomorrow morning. Temperatures will still be chilly with lows in the mid to upper 30s in Vermont to around 40 across the St. Lawrence Valley.

KEY MESSAGE 2: There is little change in the overall synoptic pattern for tomorrow into Thursday as an upper trough will close into an upper low and slowly drift east. Model guidance has mostly settled in on our next systems arrival just after sunrise across the St. Lawrence Valley and reaching Vermont by the mid to late morning hours. There has been a slight trend towards a slower slight more west warm frontal lift however. The newest 12Z HRRR and NAM3K models have trended towards a drier eastern edge to the the warm front owing to a more west upper low centroid. HREF hourly rain rates also denote this trend with lower rate values across Vermont. Subsequently, strong diffluence aloft will also help shear the frontal zone which may further reduce the rainfall that falls. Regardless, there will be a period of light to perhaps some embedded moderate rain tomorrow morning into early afternoon areawide. The warm front lifts quickly north placing us into a messy warm sector with plenty of cloud cover and moisture advection as the warm sector becomes north to south oriented. Some clearing in the warm sector may allow for some instability as CAMS denote 150-250 J/kg of SBCAPE over northern New York embedded in a narrow strip of convection tomorrow afternoon. A rumble of thunder cannot be ruled out, mainly in St. Lawrence County and Franklin Counties of New York. Total precipitation from the initial round of rain will be between a quarter to around half an inch, with the higher amounts into the St. Lawrence Valley.

The system then begins to lose steam as it becomes subsidence dominated under closed off flow. The convective boundary Wednesday night will stall somewhere near the Champlain Valley into Thursday morning as flow aloft and moisture decreases. However, a baroclinic zone will favor cyclogenesis off the New England coast allowing a resurgence of a secondary low near Long Island in addition to yet another low near the 40 N, 70 W benchmark. The benchmark low will likely absorb the secondary low adding to the complexity of our weather into Thursday. Moisture resurgence will be focused along the washed out convective boundary around the Champlain Valley, of which the exact position is still somewhat uncertain. Along this boundary, however, an additional quarter to an inch from north to south is expected. Rain will slowly pivot out of the region by Friday morning. Total rainfall through Thursday night will range from half an inch near the International Border to an inch to inch and a quarter in southern Vermont and the Adirondacks. Locally in the higher terrain, up to 1.50" is possible in southern Vermont and the High Peaks of New York. Warm and more isolated to scattered showers are expected Friday as the system exits, though not a widespread rain by any means.

KEY MESSAGE 3: Friday night and Saturday morning will be a short-lived drier period as multi-level ridging crests over the forecast area. Surface high pressure will be displaced to the south, so it doesn't look like the most ideal radiational cooling night with lows near typical mid-May values in the 40s. Then, another shortwave is expected to move through northern New York and Vermont Saturday afternoon and evening, bringing with it some warm air advection. The probability of precipitation is around 25-45% during that period, highest along the international border, closer to the parent low pressure in Canada. Precipitation will likely be scattered showers with some embedded thunderstorms possible during the peak of the warmth Saturday afternoon as temperatures reach into the lower and mid 70s, several degrees above seasonal normals. We should still be in the warm sector Saturday night with lows in the mid 40s to lower 50s, then a weak frontal boundary will clip the Northeast Kingdom on Sunday with PoPs 15-25% for the odd shower. For the most part though, Sunday looks fairly dry. The frontal boundary should keep highs Sunday from getting higher than the mid 60s to mid 70s and keep lows seasonable in the 40s Sunday night. Upper ridging and surface pressure stemming from Quebec will continue the period of dry weather Sunday night before stronger warm air advection kicks in ahead of our next storm system. Temperatures could soar into the mid 70s to mid 80s the first two days of the work week while lows sit in the upper 40s and 50s. Precipitation from this system is looking most likely sometime Tuesday afternoon, but showers could begin as early as Monday or Monday night.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Through 18Z Wednesday...VFR conditions are expected to prevail this afternoon through around 12Z-16Z Wednesday with northwesterly winds decreasing this evening, becoming light and variable or calm overnight. Winds will then turn southeasterly early Wednesday morning as clouds increase ahead of our next storm system. Southeasterly flow will increase Wednesday as rain spreads across the region. Timing of precipitation arrival is a little tricky with a dry air mass in place ahead of the showers, resulting in a period of virga before rain arrives in earnest. Rain showers should be widespread and reaching the ground by around 12Z-16Z, bringing with them ceilings around 1000-3000 feet above ground level that should persist through 18Z Wednesday. Heavier showers could produce visibilities 3-6 miles throughout Wednesday morning. Some guidance suggests ceilings could reach IFR levels towards 18Z Wednesday, but model consensus on this is poor, and the probability of IFR ceilings is low over the next 24 hours. LLWS is anticipated at SLK and RUT around 14Z-18Z Wednesday as a low level jet moves overhead, spreading to the other sites after 18Z Wednesday.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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