textproduct: Burlington

WHAT HAS CHANGED

As of 226 AM EDT Friday...

No significant changes were made to the forecast.

KEY MESSAGES

As of 226 AM EDT Friday...

1. A cold front will pass through the region today with associated light showers. The front clears the area this afternoon/evening with clearing skies, as high pressure builds in for the weekend.

2. Brief high pressure will break down Monday night, and give way to rounds of rain.

DISCUSSION

As of 226 AM EDT Friday...

KEY MESSAGE 1: A cold front will move through the region today with some light associated rain showers. The front at the time of this forecast is just entering the St. Lawrence Valley. Southwesterly flow is driving some lake enhanced showers and clouds downstream of Lake Ontario into portions of southern St. Lawrence County in New York. The front will gradually shift east this morning through northern New York and into Vermont just after sunrise. A few isolated showers will be possible with the front, especially in the Northeast Kingdom, where some better convergence will be located. Moisture will be lacking with the front due to convection yesterday. As the front moves east towards the Connecticut River, some diurnally driven instability could be enough to generate some isolated rumbles of thunder, though chances for any stronger storms are low to none. High temperatures today will be tricky with the frontal passage in addition to normal diurnal heating. Though with cooling flow aloft, and winds turning northwest, highs in the raw model guidance show cooler trends with high only in the upper 60s to low 70s. Highs in south and eastern Vermont may remain on the warmer side into the mid to upper 70s, to near 80 with the front reaching them later in the day today. As the front clears the area by tomorrow afternoon/evening, much drier and cooler air will filter in overnight. Strong radiational cooling is anticipated tonight with temperature outside of Lake Champlain falling well into the low to mid 40s. Localized sub 40 temperatures may be possible in the coldest hollows of the Adirondacks. Friday night will see high probabilities for valley fog with many locations falling below crossover temperatures under clearing skies.

High pressure will build in on Saturday with mainly clear skies aside from fair weather cumulus in the higher terrain. Some light breezes from southwest channeled flow in the St. Lawrence Valley to 10 mph will be possible as well. Highs will be relatively seasonable in the mid 70s. High pressure will dip south on Sunday as a cold front will sink south from Quebec. Zonal flow ahead of a positively tilted shortwave will keep moisture fairly progressive, but some shower activity will be possible near the International Border by mid to late Sunday. Lifting along the front with cool temperatures aloft may lead to some weak instability on the southern periphery of the front in northern Vermont and near the US-11 corridor in northern New York. The front then stalls out across the region becoming oriented northwest to southeast Sunday night, setting the stage for a more active weather pattern heading into next week.

KEY MESSAGE 2: Over Monday night into Tuesday, surface high pressure centered north of Montreal will begin to shift east. A humid air mass will amble east in response to a 500mb high around 595 dam builds into the southeastern US. Various vorts picked up from the tropical Pacific will round the ridge axis while a compact upper low tracks east across Canada. Moisture will overrun the dry air left in the wake of surface high pressure along Sunday's front just to our south. The boundary appears likely to waffle around the region as surface high pressure redevelops across the Canadian maritimes and helps slow things up a bit. The weather system translating east across Canada will start to move east of our area after Wednesday, which will then drag a cold front southeast next Thursday. Secondary cyclogenesis appears likely across coastal Maine, and the slow moving nature of the system could allow some additional showers to linger into Friday until the backside of the longwave trough ambles east.

Some uncertainty remains on the exact placement of heavier swaths of rain along the waffling boundary. Ensemble means and probabilities suggest that the highest rainfall totals will have a greater probability south. Between Monday and Thursday, probabilities of 1 (30-40%) and 2" (~10%) over the 72 hour time frame are relatively unchanged from yesterday. Cluster analysis does show some spread in where the highest rainfall amounts could be, and so we'll continue to closely monitor how this pattern evolves.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

Through 06Z Saturday...Conditions are VFR at this moment, but there are pockets of clouds located around 2000-3000 ft agl across the region as well as hints of patchy fog evident near KSLK and on the FAA cam at KRUT. Showers have diminished, but a cold front is still positioned west of the St. Lawrence Valley and could produce a few showers or drizzle as warm, southwest flow gradually slows near the boundary and moisture gets trapped beneath a weak inversion layer around 800-1500 ft agl. High clouds cover eastern Vermont. Ceilings will fall to 1200-2500 ft agl as the front passes east with winds becoming variable along the boundary, and then northwest. Some fog is possible at KSLK and KMPV, but could also be hampered by the front. The most likely places for 600-900 ft agl ceilings appears to be KSLK and KRUT, but KEFK and KMPV could also be close around 1000-1300 ft agl. Only slow improvement is expect after 12z with MVFR lingering through about 16- 19z. As ceilings improve, wind speeds will increase to 5 to 10 knots with a few gusts 15 to 18 knots. Skies will trend clear and winds will decrease beyond 00z Saturday.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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