Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
340 PM EST Sat Dec 20 2014
high pressure will remain in place through the end of the weekend
with dry weather lasting into Monday. Increasing southerly winds
will bring a significant warming trend towards the middle of next
week with temperatures soaring to well above average. A strong area
of low pressure will then move through the central Great Lakes and
produce rain and gusty winds on Wednesday followed by gusty winds
and a few light rain or wet snow showers for Christmas day.
Near term /through Sunday/...
visible satellite imagery this afternoon showing extensive stratus
hanging very tough in most areas from Lake Ontario southward to the
PA state line. A few holes continue around the buf metropolitan area and
Niagara County as somewhat drier air advects in from the Niagara
peninsula. Otherwise expect stratus to remain in place with little
movement from the western southern tier across the Genesee Valley to
central New York. Clear skies will continue across the north country into
this evening where weak northeast flow continues to advect in drier
low level air from Quebec...holding the stratus at Bay.
Tonight through Sunday surface high pressure will remain in place
from Quebec into the lower Great Lakes. A weak middle level trough will
cross the region...but there is little moisture to work with above
the shallow low level stratus layer so expect this feature to cross
the area dry. Surface high pressure and very little advective push
will do little to help clean out low level moisture which will
remain trapped beneath a strong subsidence inversion. With this in
mind expect most areas to keep the stratus and gray skies tonight
through much of Sunday. The north country will start off clear this
evening but a light southerly flow may push stratus northward later
tonight and Sunday especially across the higher terrain.
Expect lows tonight to be similar to last night with middle 20s on the
lake plains of western New York and lower 20s across the interior...with
teens across the north country where good radiational cooling will
occur through at least the evening before stratus increases there.
Highs on Sunday will reach the lower 30s again across western New York
with still some upper 20s across the higher terrain east of Lake
Short term /Sunday night through Tuesday night/...
a ridge of high pressure surface and aloft will lie across the
northeast states Sunday night into Tuesday as an amplifying longwave
trough digs across the central states. This trough will eventually
contribute to the development of the much talked about Christmas
storm by midweek. Until then the ridging will keep fair but cloudy
skies through Monday and keep western and north-central New York
shielded from any precipitation. Monday night through Tuesday night
strengthening southerly flow will advect increasing moisture
northward across our region which will contribute to the cloudy
Tuesday and Tuesday night isentropic lift ahead of the developing
surface low over the lower Mississippi River valley will bring low
chances of a shower across upstate New York. Moisture profiles do
not become saturated until Christmas evening morning so plenty of dry
air aloft for any light showers ahead of time to evaporate on their
way to the ground. Best chances will be across the southern tier.
Anything that does make it to the ground early Tuesday morning
across the higher terrain may initially be consist of a wintery mix
with warm air over riding still near freezing temperatures.
The strengthening southerly flow will keep our temperatures climbing
ahead of the developing surface low. Temperatures Sunday night will slip
below freezing then warm into the middle 30s to around 40 on Monday.
Monday night through Tuesday we will continue to see 850mb temperatures
increase to around +10c. Most areas will remain above freezing
Monday night except for the higher elevations then temperatures push well
into the 40s on Tuesday and will likely continue to rise Tuesday
night. The strengthening pressure gradient will bring gusty winds on
Tuesday afternoon with highest gusts to near 40 miles per hour along the Lake
Long term /Wednesday through Saturday/...
the forecast for Christmas evening and Christmas day continues to be
focused on a storm expected to develop over the northern Gulf states
and shift north across the Great Lakes. Plenty of uncertainty remains
with respect to the strength and speed of this storm. Latest 12z
runs generally follow the same track with the surface low but the
12z European model (ecmwf) is a bit faster and deeper with the storm than the GFS and
On Christmas evening warm moist air will be transported north ahead
of this storm bringing rain and very mild temperatures to western
and north-central New York. Naefs precipitable waters are forecast to rise to near
one inch which is near the 99th percentile in a 30 year precipitable water climatology.
This moisture combined with the strong synoptic forcing associated
with the low and temperatures warming into the 50s Christmas evening
should yield some moderate to occasionally heavy rain showers. These
showers may help to drag down some gusty winds associated with a 50
knot 850mb jet streaking overhead.
A cold/occluded front will shift across western and north-central
New York Wednesday night as the surface low tracks across the
central Great Lakes. Exact timing of the frontal passage still needs
to be fine tuned as the European model (ecmwf) is about 6 hours faster than the GFS.
This front will be the leading edge to cooler temperatures. It is important
to mention that without a steep ridge over the western states the
source region of this cold air will be Pacific based and not Arctic
based so this lack of an Arctic airmass will bring a reduced threat
of any significant snow through Christmas day. 850mb temperatures are
warmer with todays runs only drop to between -5c and -8c. Surface
temperatures will only fall into the middle 30s on Christmas day and low 30s
across the higher terrain. The latest forecast now reflects a
rain/snow mix across the Lake Shores and lower terrain with some
limited snow across the higher terrain. Some weak lake enhancement
is also possible pending available Post-frontal moisture.
A higher concern still lies with a period of strong gusty winds on
Christmas day within the colder airmass behind the front. Cold air
advection will steepen low level lapse rates helping to mix 850mb
winds of 40-50kts down to the surface.
Beyond Christmas...models show a brief period of fair weather
possible on Friday as shortwave ridging quickly shifts across the
lower Great Lakes. Further out we will be watching next weekend for
another possible Great Lakes cutter storm which could bring another
round of strong winds and more rain showers.
Aviation /21z Saturday through Thursday/...
persistent stratus will continue to be the main story through the
18z taf cycle. Weak surface high pressure will remain in place this
afternoon through Sunday with abundant low level moisture trapped
beneath a subsidence inversion. This will continue to produce
widespread low stratus from Lake Ontario southward to the PA state
line. Some clearing will try to work into kbuf-kiag for a few hours
during the late afternoon and early evening...but this should fill
in again later this evening. Ceilings will be mainly MVFR in the stratus
with a few areas of IFR across the higher terrain of the western
southern tier. IFR may be more favored across the higher terrain
later tonight into Sunday morning.
The one exception will be across the north country...where clear
skies will dominate today. Weak southerly flow may allow low stratus
to spread north across the Tug Hill region tonight and towards kart
on Sunday with MVFR ceilings becoming more common.
Wednesday...MVFR with rain and gusty winds.
Thursday...MVFR with snow showers and gusty winds.
high pressure will remain in place through Sunday with very light
winds and flat wave action. Southeast winds will begin to increase
some on Monday but conditions will remain below Small Craft Advisory
levels until at least later Tuesday when south to southeast winds
A deep area of low pressure is then forecast to lift through the
central Great Lakes Wednesday through Thursday. This may produce a
period of gale force winds on both lakes...especially on Thursday as
cooler air pushes back into the lower lakes.