Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
1234 am EDT Wednesday Sep 24 2014
evening clouds will gradually give way to clearing skies overnight
as a large area of high pressure builds east into the region.
This high will provide outstanding early Fall weather to the
area...with dry weather and warm temperatures expected for the
remainder of the week and into next weekend. The next chance of
showers arrives Monday as a weak backdoor cold front sags through
the region...however precipitation looks to be light.
Near term /until 7 am this morning/...
as of 1231 am EDT Wednesday...infrared imagery indicates that stratus
clouds have dissipated across the region setting up mostly clear
and calm conditions for the pre-dawn hours. Main issue will be
fog...which will be locally dense in the favored river valleys
east of the Green Mountains...within the Adirondacks...and in the St.
Lawrence Valley. May also see some localized fog in the Champlain
Valley over the next few hours. Have updated the forecast to make
fog more widespread in the grids...and include locally dense
wording. Early am lows will generally be in the low-middle 40s.
Short term /7 am this morning through Thursday night/...
as of 323 PM EDT Tuesday...remainder of the short term (though next
weekend for that matter) will feature the development of huge deep
layer ridging across most of the nation east of The Rockies with
mainly warm and dry weather expected for our area. There does
remain some inconsistency among this morning's European model (ecmwf)/Gem and
GFS/NAM camps in regard to the inland push of a coastal trough of
low pressure during the Thursday time frame...with the non-
American Camp suggesting at least an outside shot of a light
shower across our southern counties. With such deep layer dry air
to the immediate north of this system however...will continue to
downplay this threat for now capping probability of precipitation in the 15-20 percent range
far south...and leaving remainder of forecast area dry with mainly
some middle and high level cloud cover expected. Highs tomorrow and
again on Thursday ranging from the middle 60s to lower 70s...with
overnight lows generally in the 40s...though mainly lower 50s in
milder spots of the Champlain and St Lawrence valleys. These
ranges are slightly greater than normal diurnal values...though
appear reasonable given deep layer subsidence and dry air across
the region. Late night/early morning patchy fog also a good bet in
favored locales as light winds and good radiative effects
Long term /Friday through Tuesday/...
as of 323 PM EDT Tuesday...the short version -- models still
showing a similar scenario. Big ridge so dry with above normal
temperatures Friday and through the weekend. Cool front slides
down from the north Monday with a spot shower or two and bringing
temperatures back closer to normal, then back to dry and
seasonable on Tuesday.
Want the longer version??
Friday: at this point discounting the more northward and slightly
slower trend of a coastal low, so with deep ridging in place,
should be lots of sun. Even if the Euro is correct, the lower
levels of the atmosphere are dry so some middle-level clouds first
thing Friday would be about it. With plenty of sun, we should be
able to mix to 925mb (about 2000ft) if not a bit higher. Thus the
12-14c temperatures should support surface highs into the lower 70s
for most of the area. Clear and calm overnight. Could be some
patchy fog I suppose, but mainly in the river valleys. Lows will be
near/slightly above normal -- 40s to 50s.
Saturday: strong ridging from surface to upper levels across the
region. So continued warming at Lower/Middle levels, with 925mb
temperatures up to 16-17c or so. This should readily support
temperatures about 80f (if not a bit higher) in the lower
elevations, middle/upper 70s for everyone else. MOS guidance still
looking to be on the cool side as it's probably being influenced by
climatology. Thus followed previous forecaster's thought of going
warmer. Saturday night, should be very much like Friday night.
Sunday: see Saturday.
Monday: axis of the upper ridge shifts farther west, allowing an
upper trough to dig into the northeast. At the surface, we'll see a
cold front swing through. Some timing differences between the
models, but they all indicate that moisture will be very limited. So
have only painted in 15-30% probability of precipitation at this point. Temperatures behind
the front do cool down, as depicted in 925mb temperature field with
values falling to 7-9c during the day -- meaning highs generally in
the 60s (warmest south). Could end up being a tricky temperature
forecast as timing of the front this far out is iffy at best. Also
of note, the Euro is a little more "amorphous" with this front, and
slowly oozes it down more like a backdoor front later Monday and
Tuesday: differences between GFS and Euro, though both suggest dry.
Euro has the backdoor front with residual clouds washing out over
the area. GFS is building in a surface high. Both show the upper
level ridge continuing to build to our west. Stuck with model
guidance blend, so highs near normal in the 60s.
Aviation /06z Wednesday through Sunday/...
through 00z Thursday...primarily VFR expected for the
period...aside from overnight and early morning fog/br. Broken-overcast
deck of stratus remains across the area this evening...and will
gradually thin and scatter out overnight. This eventual partial
clearing in combination with light winds and lingering low level
and surface moisture will create favorable conditions for fog/br
development at slk/mss/mpv where periods of IFR-vlifr fog/br
likely...especially slk. Btv/pbg/rut anticipated to remain VFR for
entire night. Any fog/br lifts by 1330z Wednesday morning giving
way to just a scattered cumulus deck of clouds with VFR ensuing.
Light and variable winds tonight turn generally southerly on
Wednesday from 5 to 8 knots.
Outlook 00z Thursday through Sunday...
VFR the entire period. Exceptions will be patchy late night fog
producing IFR or lower conditions...primarily mpv and slk.