Scientific Forecaster Discussion
fxus61 kbtv 211807
Area forecast discussion
National Weather Service Burlington Vermont
207 PM EDT Fri Jul 21 2017
a weak cold front moving southward from Quebec may bring an
isolated shower or thunderstorm near the international border
through this evening. Otherwise, looking for dry conditions
overnight and through much of the weekend. Northwest winds
Saturday and Sunday will bring slightly cooler temperatures,
with afternoon highs in the upper 70s to lower 80s. An upper
level disturbance approaching from the Great Lakes will bring
our next chance for widespread precipitation, with periods of
showers expected Sunday night into Monday across the north
Near term /through Saturday/...
as of 141 PM EDT Friday...relatively quiet near-term forecast
with a west-northwesterly mid-upper level flow regime in place
across nrn New York and New England. Winds across the region have been
SW-west this afternoon, and downslope warming allowing temps to
climb into the mid 80s across much of the Champlain Valley and
Connecticut valley this afternoon. There is a weak trough/cold
front across srn Quebec which will settle southward near the
Intl. Border this evening. This sfc feature may provide just
enough low-level convergence/ascent to yield a shower or
thunderstorm (sbcape around 1000 j/kg), and have maintained 20%
pops across the far nrn counties thru 01z this eve. Thereafter,
should be a relatively quiet night with weak NW wind shift and
just some patchy nocturnal fog possible in the favored spots
within the nrn Adirondack region and deeper river valleys of
central/ern Vermont. Overnight lows generally 60-63f, except upr 50s
in the nrn Adirondacks and far nern Vermont.
Pleasant conditions Saturday with nwly winds 5-10 mph yielding
slightly cooler high temps (upr 70s - lower 80s). Weak sfc high
pressure builds swd from srn Quebec, keeping conditions quiet
Saturday night with lows mainly in the 50s. Light wind
conditions may yield some additional valley fog 06-12z Sunday in
the favored valley locations.
Short term /Saturday night through Sunday/...
as of 358 am EDT Friday...trend in the latest nwp guidance for
the latter half of the weekend is trending drier, though I will
note that could easily change. The forecast largely depends on
how low pressure evolves out of convection expected to fire up
over the Wisconsin/Minnesota area this afternoon and night, and
where the mid-level thermal packing sets up downstream. There's
a general consensus that the boundary will set up south of the
btv forecast area, with a comparison of the 00z NAM/ECMWF/GFS
showing the GFS as the outlier with the most northern track and
deeper low. Don't want to totally discount it, so i've offered a
blended forecast for pops, trending towards the drier
NAM/ECMWF. This results in low chance pops across our southern
zones Saturday night, with only a slight chance north. Anything
that does affect the area overnight will dissipate by Sunday
morning with a mainly dry day expected, though chances for more
widespread showers increases from the southwest in the afternoon
as our next system approaches.
Long term /Sunday night through Thursday/...
as of 358 am EDT Friday...Sunday night through Tuesday
continues to look like the main active period of the next 7 days
as medium range guidance is in good agreement highlighting an
upper trough digging through the Great Lakes Sunday night and
across the northeast through Tuesday with a series of embedded
shortwave troughs bringing periods of precipitation to the north
country. Best dynamical forcing shifts over the County Warning Area Sunday
night into Monday morning with a decent plume of pwats around
1.5" skirting southern areas and modest mid-level lapse rates
around 6 c/km supporting the idea of some thunder, but overall
convective threat is rather low. Additional showers continue
Monday afternoon right through Tuesday as the trough shifts over
and east of the region by 00z Wednesday. By Tuesday night
surface high pressure and ridging aloft build into the area with
sunny/clear conditions expected for Wednesday and Wednesday
night. A weak cold front approaches for Thursday renewing
chances for showers along our northern border.
Aviation /18z Friday through Wednesday/...
through 18z Saturday...mainly VFR through the period, except IFR
nocturnal fog slk/mpv roughly 06-13z Saturday. May also see an
isold shra/tsra near the Intl border thru 01z Saturday. Will
monitor radar trends, but likelihood of impact at any taf
location <20%. Light SW winds trend light west this evening and
generally northwest 5-10kts during the daylight hrs Sat.
Saturday night: VFR. Slight chance rain showers.
Sunday: VFR. Chance rain showers.
Sunday night: VFR/MVFR. Likely rain showers...chance thunderstorms and rain.
Monday: VFR/MVFR. Likely rain showers...chance thunderstorms and rain.
Monday night: VFR. Chance rain showers.
Tuesday: VFR/MVFR. Chance rain showers.
Tuesday night: VFR. Slight chance rain showers.
Wednesday: VFR. No sig weather.