501
FXUS61 KBTV 200231
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
931 PM EST Thu Dec 19 2024
.SYNOPSIS...
*Periods of light snow are expected for Friday and Saturday.
*Very cold conditions will occur over the weekend, with wind
chills bottoming out Sunday morning well below zero.
*Below normal temperatures will moderate into early next week,
ahead of the next chance for snow on Christmas Eve.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 927 PM EST Thursday...Fairly quiet evening continuing
across Vermont and the North Country. Mid/high clouds have now
overspread the entire region, which should help slow additional
cooling overnight. Current temperatures are generally in the mid
teen to mid 20s, and expect we could see another few degrees of
cooling through daybreak. Webcams still showing a few snowflakes
falling in portions of the Northeast Kingdom, so left isolated
flurries in the forecast through midnight or so. Have not seen
any evidence of a lake-enhanced band of snow off/near Lake
Champlain, but given continued north flow overnight, have left a
slight chance of snow in the vicinity of the lake for now. The
forecast is in good shape and just needed a few minor tweaks
with this update.
Previous discussion...A polar air mass has been settling
into our region, characterized by a shallow, seasonably cold and
dry air mass with temperatures in the teens and twenties.
Dwindling flurry activity is expected as further drying helps
scatter the low clouds responsible for this precipitation this
evening, but then we will see a rapid increase in mid-level
cloud cover through midnight overspread the region from the
west. Between these clouds and continued shallow mixing due to
continued cold air advection, we will not radiate out tonight.
So temperatures, while seasonably cold, will not drop much
relative to where there are now, maybe 10 degrees or so.
As a mid-level trough digs into the eastern Great Lakes, upper level
divergence overhead combined with some broad convergent flow and a
touch of Atlantic moisture on the northern periphery of coastal low
pressure will support light snow breaking out during the day. Latest
thinking is that this stratiform, light snow will blossom first in
our southern areas before expanding northward and become most
persistent in the late afternoon/evening hours. Some chances of snow
persist overnight with the approach of the upper level trough, with
precipitation then becoming more showery in nature under another
cold air advection regime. This push of colder air Friday night will
be from the north as Arctic air seeps into the region, rather than
northwest like the ongoing one. This setup will favor shallow
inversions with blustery conditions in the broad valleys, leading to
single digit wind chills.
Snow character will be dry, with snow-to-liquid ratios most likely
ranging from 15-20:1. The cross-hair signature of upward motion in a
saturated dendritic snow growth zone looks rather favorable for
fluffy snow through the period, with a fairly deep cloud layer in
the -10 to -20 degree Celsius range. Precipitation looks clearly
light, hence the emphasis on that word; hourly precipitation amounts
across model guidance are less than 0.04"/hour, and the most common
amounts over 6 hours are generally close to 0.02-0.04" range,
leading to "storm total" amounts of near 0.05-0.1". In combination
with the high snow ratios, we will see many locations pick up an
inch or two of fresh powder through overnight Friday.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 318 PM EST Thursday...Considerable cold and some dryness will
be the name of the game this weekend. Lingering snow showers will
gradually taper off by Saturday afternoon with a quick coating to an
inch possible under the passing showers. Temperatures will hover in
the teens in the mountains and the low-20s in the valleys. High
pressure builds into the region Saturday night with significantly
cooler air. Temperatures will plummet overnight to below zero
in the Adirondacks and low single digits east of the Greens and
Champlain Valley. Locations receiving snow on Saturday will see
lower temperatures than those with bare ground overnight.
Furthermore, winds will be near 10-15 kts in the Adirondacks and
Greens, making feel like temperatures fall below -15 to -25,
especially in the higher summits. Frostbite will occur quickly
for those outside. By Sunday, most places will struggle to reach
the mid- teens with some locations potentially not making it
above zero in the higher elevations. Clouds will mostly clear
out on Sunday, with more clearing in the Champlain Valley. This
clearing will make temperatures overnight fall even further as
compared to Saturday. The Adirondacks and Greens will easily
fall below zero, with locations in the Champlain Valley coming
within a few degrees of zero. Wind chills will once again be
near -20 for places in the Adirondacks and the higher elevations
of the Greens. Special caution should be exercised for those
outside Sunday night.
&&
.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 318 PM EST Thursday...Pre-Christmas travel will be best on
Monday ahead of a shortwave which will impact the area Tuesday.
Temperatures will slowly stabilize on Monday with highs in the
low-20s in the Champlain Valley, and mid-to-upper teens in the
mountains. High pressure will translate eastward on Monday with
mostly clear skies for most of the area. Overnight lows will dip
into the single digits to low teens overnight Monday.
A lot of uncertainty still remains regarding precipitation chances
Christmas Eve and Christmas Day. Three shortwaves from Quebec, to
the Great lakes, and in the lee of the Rockies will move eastward
and how these shortwaves interact will be important for those
wishing for a white Christmas. Regardless of phasing,
precipitation will overspread the area late Monday through
Tuesday evening. The GFS and Canadian models show a slower
overall system, due in part to a stronger high centered to the
Northeast. This allows for a more developed moisture conveyor to
form from the Northeast to the Gulf of Mexico, increasing the
precipitation chances across the entirety of the region.
However, with the increased precipitation comes warmer Atlantic
and Gulf air, which will increase the 925 and 850 mb in the
Champlain Valley. This would likely decrease the chances of an
all snow event on Christmas Eve and would yield more widespread
rain/snow across the area. More moderate precipitation is likely
under this model. The European model indicates a faster moving
Great Lakes clipper and a less pronounced high impeding its
eastward motion. The Gulf of Mexico moisture advection would
have less time to develop keeping precipitation chances on the
lower side and cooler air in place. This solution would yield
more flurry type precipitation in the area. While overall
confidence is still low on the length of precipitation, there is
growing confidence in cooler air being able to hold on.
For Christmas Day, the GFS keeps some lingering upslope snow showers
in the morning and afternoon, whereas the European clears out any
precipitation early morning on Christmas. Temperatures will be
mainly below freezing for the entirety of the area, with some mid-
30s across the Champlain Valley. Brief ridging will move in
Wednesday night through Thursday, however, the strength of the high
will impact the timing of the next trough that will move in by the
end of next week.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Through 00Z Saturday...Ceilings will hold relatively steady this
evening. The low cloud deck should eventually scatter out later
tonight and all terminals should see VFR ceilings by that point. A
lake cloud could influence PBG tomorrow morning and briefly bring
the terminal to MVFR. Light snow arrives tomorrow afternoon from
west to east. It will be steady and it should be able to bring most
terminals down to IFR, but likely not LIFR. EFK will see the
lightest precipitation and it may be more periodic IFR rather than
consistent IFR. Ceilings will also come down when the precipitation
arrives, but they look to mostly drop to MVFR and not IFR, though
periodic IFR ceilings cannot be ruled out at this point. Winds will
be relatively light and either terrain driven or out of the north.
Outlook...
Friday Night: Mainly MVFR, with local VFR possible. Chance SN,
Chance SHSN.
Saturday: Mainly VFR, with areas MVFR possible. Chance SHSN.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: Mainly VFR, with local MVFR possible. Chance SHSN.
Tuesday: MVFR. Chance SHSN.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Kutikoff
NEAR TERM...Hastings/Kutikoff
SHORT TERM...Danzig
LONG TERM...Danzig
AVIATION...Myskowski
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