Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
920 am EST Thursday Dec 25 2014
a cold front sweeping eastward through the region will usher in
strong and gusty southwesterly winds this morning...with wind
gusts in excess of 50 miles per hour at times across northern New York.
Associated rain showers will generally exit with the front by middle-
morning...but a few lingering sprinkles or mountain snow showers
are possible during the afternoon hours. It will be a mild
Christmas day with most valley sections remaining in the 40s this
afternoon with partly sunny skies expected. High pressure builds
into the region tonight through Saturday bringing drier and less
windy conditions. Temperatures will remain well above seasonal
levels with colder temperatures arriving during the early to
middle part of next week.
Near term /until 7 PM this evening/...
as of 920 am EST Thursday...current surface analysis shows 974mb low
pressure just east of Hudson Bay with surface cold front pushing across
eastern Vermont at this time. Expecting rain showers associated with this
boundary to be east of our County Warning Area by 10 am this morning...with gusty
southwest winds developing. Have updated pop grids to capture this
trend of precipitation rapidly exiting our County Warning Area this morning. Also...have
continued to mention chance probability of precipitation associated with southwest upslope
follow and weak low level cold air advection across the dacks today...with a few light
rain/snow showers anticipated. Expecting temperatures to jump a few
degrees across the lower CT River Valley associated with southwest
downslope follow...especially near vsf. Elsewhere...weak low level cold air advection will
result in temperatures slowly falling back into the 20s mountain summits to
30s midslopes and l/M 40s warmer valley locations for today. Still
looking at gusty winds between 35 and 45 knots...but strongest 850 to
925mb core of 45 to 60 knots is quickly lifting northeast of our
County Warning Area...with latest ktyx VAD at 925mb only showing 35 knots. As
depth of low level mixing increases...still thinking we have a chance
of seeing a few gusts in the 45 to 50 knot range across the
slv...where southwest channeling will help to enhance velocities.
All is covered well in current forecast. We will reevaluate current headlines
around noon for potential adjustments.
Hydro wise...we are seeing rises on many streams and rivers this
morning...with ausable and Otter Creek above action stage. The
combination of melting snow pack and quantitative precipitation forecast between 0.25 and 0.75 is
resulting in these rises. Not anticipating many problems...as quantitative precipitation forecast
was slightly less than expected...with higher values passing to
our south and east. Will continue Flood Watch for now...but this also
maybe taken down around noon.
Previous forecast below: cold front is currently pushing eastward across
the Champlain Valley...and also Marks the back edge of associated
rain showers per composite reflectivity at 1148z. We/ve seen wind
gusts to 44 kts at Potsdam (kptd) and Massena (kmss). May see
slightly stronger winds with better mixing after sunrise...but
have capped the peak gusts right at 50 kts with this update with
best low- level jet core passing through now and not quite lining up
with the better mixing expected later. Other than this slight
adjustment...no significant changes have been made to the
Previous discussion...deep (979mb) surface low continues to push
northeastward across southwestern Quebec at 08z with southward trailing cold front making
its way into central New York and the St. Lawrence Valley. Winds behind
the front are strong and gusty as expected...and have seen gusts
around 50kt across western New York and portions of southeastern Ontario during the
past 1-3 hours. High Wind Warning in our St. Lawrence Valley zones
and Wind Advisory for the remainder of northern New York continues to look on
track with winds gradually ramping up with frontal passage 10-13z
time frame. Strongest winds should be this morning...but steep
lapse rates and continued moderately strong p-gradient south of
the low pressure center will maintain 35-50 miles per hour gusts through
afternoon in New York...with gusts 30-40 miles per hour across portions of central
and northern Vermont.
Temperatures are briefly spiking into the low-middle 50s in areas
seeing low-level mixing ahead of the cold front. Meanwhile...in
stable areas east of the Green Mountains...temperatures are still in the
34-36f range...but will actually jump into the 40s with frontal
passage and with mixed planetary boundary layer conditions. Overall looking for
temperatures to hold in the 40s for most sections through the
afternoon hours...except middle-upper 30s across the Adirondacks. Low-
level moisture flux from Lake Ontario and orographic ascent on
southwesterly flow will maintain clouds and scattered rain/snow showers
across the Adirondacks. Elsewhere...anticipate some partial
clearing to develop with strong middle-level drying this afternoon.
Can/T rule out a brief sprinkle or two...but it appears main
threat for any Post-frontal showers will be within the northern
The lack of significant rainfall with this system has limited the
flood threat. Still some snowmelt through today so left Flood Watch
in place at this point. Further details on the Hydro aspects can
be found in Hydro section below.
Short term /7 PM this evening through Saturday/...
as of 323 am EST Thursday...quieter weather returns through the
short-term period with temperatures remaining around 15deg above
late December normals. As surface low departs...high pressure centered
across the Ohio Valley region builds eastward into the northestern Continental U.S.
Tonight...and remains through Saturday. This anticyclone will bring
dry conditions and lighter winds. Skies will be partly to mostly
sunny for Friday. On Saturday...a quick moving shortwave and
associated surface low moves from the northern Great Lakes across southeastern
Ontario into Quebec and may bring some additional clouds to
northern portions of the forecast area...especially Saturday
afteroon. Could see a sprinkle or isolated rain shower across the St.
Lawrence Valley with this feature.
Temperatures tonight generally in the upper 20s to lower 30s...with
high temperatures in the 40-44f range both Friday and Saturday for most
Long term /Saturday night through Wednesday/...
as of 322 am EST Thursday...windy conditions Saturday night,
mainly at higher elevations as low level jet moves through the
base of trough aloft. A weak surface low will traverse to our
northwest...bringing a chance for rain and snow showers Saturday
night into early Sunday as an associated cold front moves through
the region from west to east. Northwest flow will settle in late
Sunday into early Monday with some residual moisture, could see
some upslope snow showers. A few weak upper level disturbances
will keep slight to low chance for snow showers, mainly for the
higher terrain through the rest of the period.
Temperatures will trend cooler, as maxes start at 5-10 degrees
warmer than normal on Sunday and cool to about 5 degrees below
normal Tuesday and Wednesday. Min temperatures will be near the
normal maximum Saturday night and quickly cool behind the
aforementioned front to near normal in the teens and single digits
Sunday night through the rest of the period.
Aviation /14z Thursday through Monday/...
through 12z Friday...generally VFR conditions with very strong gusty
winds will prevail today. With rain showers continuing to slide
eastward this morning...tempo MVFR possible, but generally areal
coverage of these showers will diminish throughout the day.
Otherwise, gusts of 30-45kts in northern New York and 25-35kts across
Vermont expected through at least Sundown. Gusts expected to subside
during the evening...leaving west to southwest winds at 10-15kts.
Some MVFR ceilings may develop after 05z at kslk.
Outlook 12z Friday through Monday...
12z Friday-12z Saturday...surface high pressure builds into the region.
12z Saturday-06z Monday...a chance of mainly rain showers along with
MVFR ceilings possible at slk/mss/mpv.
06z Monday Onward...VFR with MVFR possible in light scattered
cold frontal passage will bring isolated 0.1-0.25" rainfall amounts
early this morning...and that should bring an end to any
significant quantitative precipitation forecast with this event. Overall rainfall amounts were
less than forecast...which is limiting the flood threat. Only active
Flood Warning is for the ausable river at ausable Forks
(asfn6)...but even that site has leveled off for now a bit below
the flood stage. We will continue to monitor trends. Have left
the Flood Watch in place for now with some additional snowmelt
with temperatures low-middle 50s...but if current trends hold we may be able
to drop the watch later this morning.
a lake Wind Advisory remains in effect through today, Christmas day,
with winds shifting into the southwest with frontal passage this
morning. Will see sustained winds of 20-30 kts...and can/T rule
out a few gusts upward of 40 knots through the remainder of this
morning. Wind speeds should trend downward toward 15-25 kts late
afternoon and then below advisory thresholds by late evening.
Vermont...Flood Watch through Friday morning for vtz001>012-016>019.
New York...High Wind Warning until 6 PM EST this evening for nyz026-027-
Flood Watch through Friday morning for nyz026>031-034-035-087.
Wind Advisory until 6 PM EST this evening for nyz028>030-034-