Scientific Forecaster Discussion
fxus61 kbtv 231947
Area forecast discussion
National Weather Service Burlington Vermont
347 PM EDT Thu Mar 23 2017
clear skies will give way to increasing clouds and the threat
of light snows by tomorrow morning as a warm front pushes into
the area. Mixed precipitation or rain will be likely on and off
into the coming weekend as this front waffles south and north
across the region. Temperatures will moderate back toward more
seasonal late March values through the period.
Near term /through Friday night/...
as of 306 PM EDT Thursday...a nice rebound in temperatures
under full sun has occurred this afternoon as northwesterly flow
slowly diminishes with modifying Arctic high pressure sprawled
across the eastern Seaboard. Kbtv has hit 32f as of 230 PM. For
tonight clear skies will slowly give way to thickening and
lowering mid and upper level clouds as we progress after
midnight as winds trend light. An approaching warm frontal
system will be approaching from the south and west during this
time frame and the leading edge of its precipitation shield will
begin to encroach into our far western counties toward sunrise
Friday in the form of light snows. Temperatures will bottom out
early given the clear skies (5 to 15 above in the
mountains/teens to lower 20s valleys) but will trend steady or
slowly rise overnight as clouds arrive and light southerly
return flow develops.
A messy day then on tap for Friday as the warm front marches
into the region under strengthening southerly flow and
widespread mixed precipitation. Some channeling effects likely
in the Champlain Valley where gusts to near 30 mph look
plausible at this point. Boundary layer to mid level thermal
profiles will be critical in determining eventual p-type as
widespread light snows slowly transition to a mix of snow/sleet
and eventual rain from the Champlain Valley west. P-type should
hold more in the form of snow and/or a mix of snow/sleet across
much of east central and northeastern Vermont where mid level warming
will be less and colder near surface layers will be harder to
scour out. Mixed precipitation top down methodology using a
variety of model output continues to support the idea of little
in the way of freezing rain with this feature, which appears
reasonable seeing the primary mid-level warm layer generally
runs in the 0-3c range through 21z. Experience would suggest
however at least some patchy -fzra may occur here and there
through the morning hours. Front end snow totals should
generally run in the 0.5 to 2 inch range, with slightly higher
totals from 1.5 to 4 inches likely across east central and
northeastern Vermont. Given the front end light snows will inhibit
any pavement icing and only low probabilities of a few
hundredths of ice accumulation are suggested (if any) will hold
off on issuing any advisories at this point. Late day high
temperatures should range from the lower to mid 30s east and
north, and the upper 30s to lower 40s elsewhere.
By Friday night widespread light rains (or mixed precipitation
north and east) will gradually wane over time as best warm
thermal advection lessens. Later at night models continue to
suggest building high pressure to our north will push the front
back southward into the area with flow transitioning to a light
northerly regime by daybreak Saturday. This will tend to shunt
the precipitation shield southward as well as coverage/intensity
lessens. Some lingering light rains/mixed precipitation/light
snows will remain possible though settle generally into our
southern counties by morning. Lows a bit tricky though with
expected abundance of clouds upper 20s to lower 30s looks
reasonable for most spots.
Short term /Saturday through Saturday night/...
as of 338 PM EDT Thursday....for Saturday and Saturday night
frontal boundary will remain draped across our forecast area.
This means that threat for mixed precipitation will continue
through the short term period. Large area of high pressure will
push south out of Canada on Saturday and push frontal boundary
south of our region. Precipitation will also push south of the
area and we will be in the cold sector on the north side of the
front. During the second half of Saturday night frontal boundary
lifts back up over the area and will be situated across
northern New York and Vermont. Despite odd frontal boundary
drifting south of the area then back across our area the
temperatures Saturday and Saturday night will be very near to
seasonal normals. We will have a little bit of rain across our
southern zones on Saturday, then some mixed precipitation as the
boundary lifts back northward Saturday night with some snow,
sleet, and freezing rain.
Long term /Sunday through Thursday/...
as of 346 PM EDT Thursday...aforementioned frontal boundary
remains over northern New York from Sunday through Monday. More
mixed precipitation is expected as thermal boundary is stacked
up right over US. Upper level low pressure system and strong
upper level shortwave cross the region later Sunday into Sunday
night, and still pushing eastward across our County Warning Area on Monday.
Precipitation will finally end Monday night. But, will only be a
short break in the action with another low pressure system
approaching for Tuesday into Wednesday. Unfortunately with
freezing lines staying very close to our forecast area, we will
mostly have rain with these systems but need to also continue to
monitor potential for trouble with mixed precipitation as well,
freezing rain and sleet. Tough to find a dry period over the
next week with very active weather and borderline temperatures
causing lots of forecasting challenges.
Aviation /20z Thursday through Tuesday/...
through 18z Friday...VFR through 12z as high pressure gives way
to approaching warm front and associated precipitation. Sky clear
expected through 00z, then slowly thickening/lowering VFR overcast in
the 00z to 12z time frame. Winds light/modest northwesterly
through 00z, trending light overnight. After 12z Friday
widespread snow overspreads all terminals, likely transitioning
to a snow/sleet/rain mix from Champlain Valley terminals west
toward the end of this forecast cycle. Winds trending southerly
5 to 15 knots, most pronounced at kbtv/kpbg where valley
channeling effects may push gusts near 25 kts.
Outlook 18z Friday through Tuesday...
18z Friday through 18z Saturday...widespread light mixed
precipitationlikely, slowly settling southward and lessening in
coverage by Saturday afternoon affecting mainly southern
terminals at that point. Highest threat of mix to occur at
18z Saturday through 12z Sunday...trending mainly VFR
/precipitation-free as Canadian high pressure noses briefly
southward into the area.
12z Sunday through 12z Tuesday...widespread mixed precipitation
and/or rain return to the region.
12z Tuesday Onward...light and spotty mixed precipitation
transitions toward a period of steadier rains by Wednesday.