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Area forecast discussion
National Weather Service Burlington Vermont
402 PM EST Sat Feb 25 2017

Synopsis...
a strong cold front will continue move eastward across the
north country this afternoon and early evening. The leading edge
of the front will have strong gusty winds and heavy rain. Rain
will continue behind the front continuing the potential for ice
jams and river flooding through the weekend. Tonight, lingering
snow showers concentrated over the higher terrain will taper off
Sunday morning. More seasonable weather returns Sunday with
some light snow in the higher elevations before a quieter period
of weather to start the work week.

&&

Near term /through Sunday/...
as of 318 PM EST Saturday...strong cold front moving through
northern New York this afternoon has produced strong gusty
winds, heavy rain and isolated lightning/thunder. Gusty winds
out ahead of the front from strong 850mb jet...cxx vwp showing
50kts at 850mb has also helped with deeper mixing and strong
warm air advection, resulting in temperatures in the 60s to around 70. Expect
the leading edge of to reach the Champlain Valley around 22z,
continuing east into central Vermont around 00z and eastern Vermont
shortly thereafter. The very warm temperatures and the heavy
rain that is moving eastward across the area will continue the
flood threat. Already have some areas/rivers flooding (see
flw's) and expect the rain this afternoon and evening to result
in runoff reaching the rivers and rivers cresting on Sunday.
Observed 6-hourly rainfall amounts have generally ranged from
quarter inch to half inch. Rain will continue with still some
embedded areas of moderate to heavy rain possible into this
evening. Expect the back edge to move out of the slv around 03z,
cpv after midnight/05z. Lingering precipitation focused around
the higher terrain is expected through Sunday morning. Also
behind the front, the cold air advection surges in and we will
see 25-35 degree diurnal swings with lows in the mid-upper 20s
expected. Thus the precip lingering behind the anafront will
likely end as end as a period of rain/snow in the valleys and
heavy wet snow in the higher elevations where several inches of
accumulation are possible.

Sunday, some gusty winds of 30kts or less are possible in
lingering pgf before subsiding in the afternoon. Drier air will
move in with slight ridging at the surface. Max temperatures in
decreasing cloud cover will generally be in the 30s.

&&

Short term /Sunday night through Monday night/...
as of 318 PM EST Saturday...ridging at the surface continues
Sunday night, but a mid level shortwave will near the
international border Monday morning. Models disagree how far
south the shortwave will reach, but with limited moisture
available, have kept only slight chance pops throughout the
period, mainly for higher terrain near the international border.
With increased cloud cover possible from the shortwave and
generally moderating temperatures as low level flow becomes for
SW, expect min temperatures Sunday night to be in the 20s.
Increasing 500mb heights indicative of continued moderating
temperatures in SW flow on the northwest edge of surface ridge will
have Monday and Monday night dry with Max temperatures in the
40s and mins in the 20s.

&&

Long term /Tuesday through Saturday/...
as of 318 PM EST Saturday...Tuesday the area will remain under
slight ridging aloft, but moisture and weak vorticity attempt to
move in from the south. NAM and GFS in agreement bringing
precipitation into at least the southern half of the forecast
area Tuesday afternoon, while European model (ecmwf) wait for developing low to
bring precipitation Tuesday night-Wednesday. This system
associated with deepening 500mb trough over the northern plains
states. Details of track of developing surface low and strength
continue to be under debate. Overall 12z GFS and European model (ecmwf) show the
surface low to track near the international border, which could
start precip as rain through most of Thursday before the
associated cold front moves through. Lingering snow showers
possible late Thursday. Overall still time for models to focus
around a solution.

&&

Aviation /21z Saturday through Thursday/...
through 18z Sunday...active weather is descending on the area
this afternoon with a line of showers and isolated thunderstorms
moving from west to east across the area between 18z and 02z.
During this time expect MVFR/IFR conditions for both ceilings
and visibilities due to the showers and isolated storms. Gusty
south winds...in the 20 to 30 knot range...will exist in advance
of the precipitation...then shift to the southwest and west
after 02z through the remainder of the period. Winds will taper
down a bit...but still be gusting in the 15 to 25 knot range. As
precipitation ends after 02z...visibilities will improve into
the VFR category and in the MVFR/VFR categories for ceilings.

Outlook 18z Sunday through Wednesday...

18z Sunday - 12z Tuesday...mainly VFR under high pressure.

12z Tuesday - 00z Thursday...VFR with chance MVFR/IFR rain
showers.

&&

Hydrology...
as of 430 am EST Saturday...rivers seeing rises with snowmelt
and ice jams on northern rivers. Missisquoi river jams causing
high water at a few spots along that river and have issued a
Flood Warning for Franklin County along the river for the jams.
Great Chazy showing some ice impacts with locals reporting a jam
in place at Perry Mills but water finding a way through. East
Branch ausable at ausable Forks New York jam has moved downstream and
has come to rest near Chester New York with no effect according to
emergency management. Passumpsic River also at risk for ice jams
but no ice movement yet reported there. Ice jams possible
anywhere there is a constriction in the river such as a Bend or
bridge abutment to stop ice movement.

Thunderstorms and rain moving into area will combine with
ongoing snowmelt produced by record setting temperatures to
transition this to an open water minor flood event. Have already
issued flood warnings for flooding for East Branch ausable at
ausable Forks and Otter Creek at Center Rutland to exceed flood
stage later tonight. Both gages only a couple feet below flood
stage at issuance. Watching Winooski basin for rain/snowmelt
flooding as well but holding off on warnings at the moment until
we see the rainfall amounts. Missisquoi also at risk of open
water flooding possibly at North Troy Vermont where ice is not
present. LaMoille river less of a flood threat as it is starting
at lower levels, and forecast to see mainly within-bank rises.

Most river rises overnight with crests after midnight into mid
day Sunday.

&&

Climate...
several more record high temperatures are expected to be broken
tomorrow on February 25, 2017. Here are the current records for
our long standing sites:

Burlington, Vermont 55|1985
Montpelier, Vermont 59|1985
St. Johnsbury, Vermont 60|2016
Massena, New York 50|1956
Mount Mansfield, Vermont 49|1961

&&

Btv watches/warnings/advisories...
Vermont...Flood Watch through Sunday evening for vtz001>012-016>019.
New York...Flood Watch through Sunday evening for nyz026>031-034-035-087.

&&

$$
Synopsis...deal/kgm
near term...kgm
short term...kgm

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