textproduct: Burlington

WHAT HAS CHANGED

As of 301 PM EDT Friday...

No significant changes were made to the ongoing forecast.

KEY MESSAGES

As of 301 PM EDT Friday...

1. Another round of patchy frost will likely develop overnight, again mainly where the growing season has not yet begun.

2. A series of weak fronts will bring some showers through early next week.

3. Quiet conditions are expected for middle of next week with some showers possible for Thursday.

DISCUSSION

As of 301 PM EDT Friday...

KEY MESSAGE 1: A seasonably cool air mass continues to sit over the region, with the greatest temperature anomalies in the mid-levels. This cool air aloft has helped create a lot of cloud cover, and even some isolated light rain and higher elevation snow showers today, despite dry air near the ground. As this compact upper level low scoots to our east tonight, the forcing to generate clouds will leave with ridging supporting a mainly clear sky, allowing temperatures to fall back to the low to mid 30s with localized sub- freezing temperatures in much of the region. However, somewhat milder temperatures in the St. Lawrence and Champlain Valleys are expected where some southerly flow should stabilize temperatures overnight. Hence, again no freeze or frost products were issued due to the growing season climatology but actions to protect any sensitive plants are advised.

KEY MESSAGE 2: A messy upper air pattern with a couple of surface fronts sliding through the region remains on track to provide chances for rain. The first round of showers and associated cloudiness remains targeted to our southern areas during the daytime hours Saturday tied to a warm front, with light rain adding up to only around 0.1" or less of new rainfall for most locations that see rain in our region. There is uncertainty in terms of how far north rain will progress during this event. Run to run model guidance doesn't give much of a trend one way or another, with consensus generally showing at least some measurable rain across Orange and eastern Addison Counties and points south in Vermont and southern portions of Essex County, New York. The northwestern flank of the precipitation and cloud cover, associated with 700 millibar frontogenesis, will result in cooler daytime temperatures in these areas, mainly in the upper 40s to low 50s. Have tried to enhance the temperature differences here versus our northern/western most locations, where a combination of dry air, sunshine, and breezy southerly breezes will result in much warmer conditions in the 60s.

The next rainfall event follows quickly for Saturday night as a cold front approaches from the west. The dynamics are more favorable for relatively heavy precipitation, although neither the thermal nor pressure gradient is conducive for anything noteworthy with regards to precipitation rates and wind gusts. Rainfall will be on the scattered side as the primary front sweeps eastward, with pretty meager moisture supporting most areas again seeing under 0.1" of an inch of rain. Most of the showers will exit Sunday morning, with some potential redevelopment of showers during the daytime hours; greatest chances of rain during the day will be over southern and eastern portions of Vermont. As for winds, while not overly impactful we have bumped up higher elevation winds with an overnight low level jet near 40 to 45 knots. High stability will limit breeziness elsewhere. Winds will taper off during the day Sunday when mixing develops, but also with the weakness of the front there also won't be a lot of cold air advection to maximize momentum transfer. That being said, the westerly flow that develops Sunday afternoon could become hazardous for any early season marine interests as choppy waves could develop.

Finally, while the current forecast for Monday is mainly dry, another upper level trough and subtle surface boundary will likely combine to support limited shower chances. These showers would largely be diurnally-driven with increasing instability/steep lower level lapse rates, not too different from how today has unfolded. The greater PoPs right now during the afternoon look reasonable across the northernmost areas in the Adirondacks, but a spot shower probably could occur anywhere in northern New York and northern portions of Vermont per latest guidance. Temperatures should trend cooler, featuring high temperatures about 5 degrees below those on Sunday and around 10 degrees below normal.

KEY MESSAGE 3: Tuesday is favored to be the coolest day of the week with temperatures most likely ranging in the 50s for most location and around 60 degrees for southern Vermont. This will largely be due to moderate northwest flow under the upper level trough. This pattern favors some breezes in the northern Champlain Valley; gusts were increased to be generally in the 20-30 mph over Lake Champlain. A few showers will be possible under the trough, but migratory ridging will likely increase stability through the day limiting shower chances to more isolated coverage.

There is a stronger consensus that temperatures will warm through the remainder of the week with highs running around to slightly over seasonal averages in the mid/upper 60s for broader valleys. Guidance continues to point to a system to move through around Thursday, though some discrepancies on timing remain. Rain will be likely as it moves through, but forcing may be more limited with projections showing the low becoming increasingly barotropic as it tracks eastward.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Through 18Z Saturday...A few showers are occurring out there under cyclonic flow aloft and decently steep low level lapse rates. Given low level dry air, showers have remained VFR; chances continue into early this evening until surface instability wains. Conditions likely remain VFR for all terminals through 12Z Saturday before some showers shift northward with CIGs lowering at RUT. Some MVFR conditions are possible 14-18Z Saturday, but southeast winds at RUT will help delay IFR concerns until more persistent showers move into southern Vermont. Otherwise, westerly flow shifts southerly overnight and increases after 12Z Saturday. Channeling in the northern Champlain Valley will promote some gusts in excess of 20kts at BTV/PBG.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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