Scientific Forecaster Discussion
fxus61 kbtv 232038
Area forecast discussion
National Weather Service Burlington Vermont
338 PM EST Fri Feb 23 2018
an active period of weather is expected starting today
lasting through upcoming weekend with two systems providing the
north country with a wintry mix to rain type of scenario. First
system impacts our region on this afternoon with the second on
Sunday, as the trend of above normal temperatures continue.
Minor ice accumulation will be seen in eastern and central
Vermont this afternoon and could produce a few slick spots during
the evening commute. Gusty southeast downslope winds along the
western slopes are possible on Sunday.
Near term /through Saturday night/...
as of 338 PM EST Friday...overall forecast remains in good
shape for this evening and overnight as low pressure passing
northeast through the Great Lakes drags a warm front through
the region this evening, and the trailing cold front during the
overnight. Overrunning precipitation took a bit longer to move
into the region, which was a good thing as it allowed surface
temps across much of the area to warm above freezing. Still
seeing some pockets of freezing or slightly sub-freezing temps
across portions of the eastern Adirondacks and east of the Green
Mountain spine, where a mix of freezing rain, rain, and sleet
continues to be possible this evening, but as surface temps
continue to climb through the midnight hour we should see any
mix change to plain rain by the day's end. With this in mind,
will keep current advisories in place, except for northern
Franklin County in New York which we'll cancel based on surface temps
rising above freezing this hour.
After midnight, cold front tracks into the forecast area from
the northwest with precipitation generally diminishing but some
upslope rain/snow showers will likely continue until dawn across
the higher peaks with minimal snow accumulation expected. High
pressure builds into the region by Saturday morning with morning
clouds slowly decreasing to a partly sunny afternoon. Temps
overnight don't budge too much as cold air advection behind the
front isn't particularly strong so we're looking at lows only in
the low/mid 30s, which will set the stage for Saturday highs in
the upper 30s to low 40s. Temps do cool off Saturday night as
skies briefly clear under high pressure, but after midnight
clouds will increase again ahead of our next system for Sunday.
More on that below.
Short term /Sunday through Sunday night/...
as of 338 PM EST Friday...precipitation will move into the
north country Sunday morning as a warm front/occluded front
attempts to push into the northeastern US. Cold air at the
surface will be slow to erode out however and forecast
soundings show thermal profiles that support a transition from
snow to mixed precipitation to rain throughout Sunday morning.
Throughout the morning hours, southwesterly geostrophic flow
will increase between the parent low pressure system over the
Great Lakes and the ridge of high pressure over the western
Atlantic. This will advect in warmer temperatures along with
enough Gulf moisture to support over a third of an inch of
precipitation over the north country. Meanwhile at the surface,
an increasing pressure gradient will support strong
easterly/southeasterly surface/900 mb winds that will flow
perpendicular to The Spine of the Green Mountains. Forecast
soundings show an inversion setting up near/above mountain top,
which will support mountain waves that will create strong gusty
downsloping winds on the west side of the Green Mountains. Areas
of northern New York north and west of the Adirondack Mountains
will also see gusty winds Sunday morning. All said and done,
gusts in excess of 40 mph look possible during the late morning
and early afternoon. These winds will likely have an effect on
the precipitation type and distribution, with downsloping areas
warming and drying out faster than other places. In addition,
ongoing precipitation in other areas will prevent some of the
strongest winds from reaching the surface. All said and done,
the precipitation and winds observed will be highly variable
across the different topography of our forecast area.
By mid afternoon Sunday, winds will slacken as the pressure
gradient decreases. Rain will continue during the afternoon
hours and taper off Sunday night after a cold front pushes east
through the forecast area.
Long term /Monday through Friday/...
as of 338 PM EST Friday...by Monday, the persistent Bermuda
high will start to weaken and flow will become more zonal
through the week. We should see mostly quiet weather for the
start of the work week with a surface high setting up to our
south over the mid Atlantic coast. By midweek, we will see
chances of light precipitation return as a weak low pressure
system traverses through Ontario/Quebec to our north.
Temperatures will remain above normal through the week with
highs forecast generally in the 40s and lows in the upper 20s to
low 30s. Any waves that do track across the the forecast area
during this timeframe will likely bring a mix of rain and snow
as we remain in in a baroclinic transition zone with
temperatures hovering within 10 degrees or so of freezing.
Aviation /21z Friday through Wednesday/...
through 18z Saturday...VFR conditions across the region this
afternoon will trend to a mix of IFR and MVFR as ceilings lower
mainly after 00z for the overnight hours. A brief period of
mixed precipitation is possible this afternoon and early evening
before precipitation type changes to all rain and is scattered
through midnight, then isolated. Low clouds lift to VFR across
the area after 12z Saturday with northwest winds becoming gusty
Saturday night: VFR. Chance snow.
Sunday: mainly MVFR and IFR, with areas VFR possible. Windy with
gusts to 30 kt. Definite ra, definite pl, definite fzra, likely
Sunday night: mainly VFR, with local MVFR possible. Slight chance
Monday: mainly VFR, with local IFR possible. No sig weather.
Monday night: mainly VFR, with local MVFR possible. No sig weather.
Tuesday: VFR. No sig weather.
Tuesday night: VFR. No sig weather.
Wednesday: VFR. Chance shra, slight chance shsn.
Vermont...Winter Weather Advisory until 10 PM EST this evening for
New York...Winter Weather Advisory until 7 PM EST this evening for nyz026-