Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
343 am EST Friday Dec 19 2014
high pressure builds across the north country through the
weekend...bringing generally dry weather conditions...though skies
will remain variably cloudy due to low stratus. The next
significant storm system arrives for Christmas evening with very windy
and mild conditions...with periods of moderate to briefly heavy
rain. Brisk and somewhat colder conditions are expected for
Christmas day...with a transition to snow showers
possible...especially over the higher terrain.
Near term /until 7 PM this evening/...
as of 300 am EST Friday...blocked moist northwesterly flow
continues across the area today...though surface high pressure
will also build over the north country. Light snow showers will be
ending this morning as ridge builds into the area. Maximum
temperatures today will be colder than normal...topping out in the
middle to upper 20s due to dense cloud cover.
Short term /7 PM this evening through Sunday/...
as of 300 am EST Friday...more of the same for the rest of the
short term forecast. Main forecast challenge is extent of stratus
and impact on temperatures. Surface ridge builds over the area and
remains through the weekend. Will have light winds through the
period. Models are indicating high low level relative humidity and blocked flow
will keep region socked under stratus. Low level inversion sets up
and think any partial clearing will be limited. Fairly high bust
potential though...tough to say when inversion will break. If
inversion breaks will see warmer daytime temperatures and colder night
time temperatures. For now have stuck close to guidance on daytime temperatures
and higher than guidance for overnight min temperatures. Best chance at a
little bit of sun will be Saturday...as Sunday features shortwave
energy moving just south of our area and reinforcing cloud cover.
Long term /Sunday night through Thursday/...
as of 228 PM EST Thursday...rather tranquil weather early in the
period will be followed by much more active and stormy weather
heading into Christmas evening.
Surface high pressure remains over the north country Sunday night
then slowly retreats to the Canadian Maritimes on Monday.
Meanwhile...flow aloft gradually becomes more southwest while weak
shortwave moves through on Monday. The result will be mostly
cloudy skies but mainly dry conditions. A warming trend begins
with highs Monday in the lower to middle 30s. Another disturbance in
the flow aloft combined with increased moisture will bring a
chance for snow or rain showers on Tuesday with highs in the 30s.
Precipitation chances increase further Tuesday night and especially
on Wednesday into Wednesday night. Deep upper trough develops over
the Midwest and evolves into vertically stacked low over the central
Great Lakes Wednesday. Significant piece of energy rounding base of
this trough Tuesday night will result in development of second
surface low over Middle Atlantic States. This low expected to deepen
and bring widespread rain to the north country Wednesday into
Wednesday night. Forecast area expected to be in warm sector with
temperatures reaching into the 40s on Christmas evening day. With upper
trough taking on negative tilt...good influx of moisture expected
into region...driven by increasing 850 mb jet which may reach
60-80 kts later Wednesday. Potential for strong winds over the
higher terrain and especially along the western slopes due
downsloping. These strong winds will also result in significant
shadowing...so rainfall amounts likely to vary considerably. As
system lifts north of the area Wednesday night...colder air
wrapping around the storm will return on southwest winds...with
rain possibly changing to snow showers. Blustery and seasonably
cold temperatures on Christmas day with some snow showers...mainly over
the higher terrain.
Aviation /09z Friday through Tuesday/...
through 06z Saturday...persistent stratus deck will bring
predominantly MVFR conditions to the region through the period.
Periods of IFR also expected at mpv/slk tonight and continuing at
slk on Friday. Pbg is the only exception where some local
downsloping has allowed ceilings to lift to VFR and that is also
expected to continue through Friday. Some light snow showers
remain at btv/slk/mpv...and will likely continue through at least
12z...possibly lasting to 15z at mpv/slk. However any snow showers
will be light with only minor visibility reductions expected...if
any at all. Could also be a few brief periods of freezing drizzle
at same sites overnight.
Northwest winds from 5 to 10 knots will continue overnight and
Friday...except locally west/southwest at mss/slk.
Outlook 06z Saturday through Tuesday...
06z Sat-00z sun...improving conditions...but chance of lingering
stratus in some areas bringing periods of MVFR.
00z sun-00z Tuesday...VFR under high pressure.
00z Tuesday-00z Wednesday...periods of MVFR in light mixed precipitation.