Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
400 am EDT Sat Oct 10 2015
expansive high pressure stretching from eastern Canada and the
lower Great Lakes to the Southern Plains will gradually push east
during the next couple of days. This will ensure fair dry weather
across our region into start of the upcoming work week. While it
will be relatively cool across our region today...we will experience
a day to day warming trend to the point where the Mercury is
forecast to reach into the 70s on Monday. The next chance for rain
will come Monday night into Tuesday when the next cold front will
cross the area.
Near term /through tonight/...
high pressure centered over the Central Plains will nose northeast
across the lower Great Lakes today...and this will provide our
region with fair dry weather. The only fly in the ointment will be
some nuisance lake effect cloud cover this morning to the southeast
of Lake Ontario...but diurnal mixing should largely clear this out
It will be on the cool side of normal today...as a fresh Canadian
airmass with 850 mb temperatures around zero will not only support the above
mentioned lake effect cloud cover...but will keep afternoon
temperatures from climbing out of the 50s. The cooler airmass though
will be tempered by a fair amount of sun and light winds.
As the elongated surface high moves to our southeast tonight...a warm
advective pattern will become well established over the lower Great
Lakes. This will help to keep US from getting overly chilly tonight
while setting the stage for a warmer second half to the weekend. Low
temperatures tonight will generally be in the low to middle 40s...with
30s expected in the Black River and southern tier valleys.
Short term /Sunday through Monday night/...
Sunday into Monday broad low-amplitude ridging will push eastward
across the Great Lakes. With the surface high sliding off the middle-
Atlantic coast and pressure falls north of the forecast area... the
pressure gradient will favor a return to southwesterly flow across
the region. This will bring a resurgence of warmer air... with 850mb
temperatures rising to +12 to +14c on Sunday and to around +14/+15c by
Monday. A deepening surface low tracking into the northern Great
Lakes by Sunday night/Monday will tighten the pressure gradient
across the region... strengthening surface winds and bending them
more southerly ahead of the low on Monday.
On Sunday highs will largely run in the middle 60s... with some
readings around 70 in the downslope favored Genesee Valley /
northern Finger Lakes region. Strongest winds on Sunday will funnel
up Lake Erie across the Niagara Frontier... across Lake Ontario and
into the Saint Lawrence valley. This will promote high temperatures
near Buffalo/ Watertown/ Clayton to run in the low 60s with the flow
off the cooling lakes. Those strongest winds will be up around 20 to
25 miles per hour with some gusts up to 35 miles per hour... with winds dropping off
quickly away from the Lake Shores to about half that. However...
with this being the warmer day of the weekend and under mainly sunny
skies and dry conditions it will be an overall pleasant fall day.
Sunday night lows will be fairly slow to fall with continued breezy
southerly warm advective flow. Lows will largely run in the 50s...
with perhaps a few interior southern tier / north country valleys
touching the upper 40s. The downslope prone lake plains / northern
Finger Lakes region will likely remain in the middle 50s.
Monday will easily be the warmest day of the entire 7 day forecast.
Storm Prediction Center sounding climatology from kbuf suggests that the maximum 850mb
temperature observed this time of year is only around +16/+17c. The
naefs climatology also suggests the forecast 850mb temperatures of +14/+15c
are in the 90th percentile for this time of the year. We likely wont
be warm enough to break any records but Monday will certainly be
well above seasonal average. Given this information have pushed the
high temperature forecast to upper end of the guidance spectrum.
Have temperatures pushing easily into the low to middle 70s in the
robust southerly flow / compressional warming ahead of an
approaching cold front. With the help of downsloping in the Genesee
Valley... highs could push upper 70s from Dansville into Rochester.
Monday will be dry and mostly sunny outside of some late day
middle/high level cloud cover increasing from west to east ahead of an
Monday night a splitting trough and associated cold front will cross
the region from west to east. This will mark the beginning of a cooler
stretch of weather for the rest of the work week that will likely
last into the weekend (teaser for the long term discussion below). A
broken line of showers will accompany the cold frontal boundary
through wester New York early Monday night. However dont expect
coverage / intensity to be overly impressive given the splitting
upper-level trough and lack of dynamics supporting the frontal
passage. Dynamics look slightly better as the front crosses into the
north country later Monday night... thus have chance probability of precipitation trending
up to low-likely probability of precipitation as the line moves from west to east across the
area. Overall quantitative precipitation forecast amounts will be unimpressive with just a thin
ribbon of moisture along the weakly forced front.
Long term /Tuesday through Friday/...
by Tuesday our 850 hpa temperatures will have fallen from the low
teens degrees c down to the low single digits behind the cold
frontal passage. The upper level trough will remain situated over
the eastern US...and will likely bring a cloudy day to the region
Tuesday with scattered light rain showers. With the temperatures at
850 hpa dropping into the low single digits we may even have some
lake enhancement to the rain showers to the east and later southeast
of the lakes through Tuesday night.
The take home message from Wednesday through the weekend and even
looking ahead into the start of next week is the weather will be
turning cooler and more unsettled. Global models and their ensembles
are in unusually excellent agreement on the overall pattern right
through the weekend. Ridging building up the West Coast will open
the door to colder air escaping from the Canadian Arctic across the
northeast United States under broad troughing. While the details of
individual shortwaves / storm systems remain a bit blurry from this
lead time... expect temperatures at and even below normal for this
time of year by the weekend. While there will still be plenty of dry
time... expect an increase in clipper storm systems / overall
cloudiness and even some lake effect precipitation.
Aviation /08z Saturday through Wednesday/...
clearing from north to south in the wake of yesterdays cold front
has led to mainly clear skies across the far western counties...
while some nuisance lake induced cloud cover will be found between
roc and syr. In either case...VFR conditions will be in play.
For Saturday...high pressure will advance across our region from
the upper Great Lakes. This will keep VFR conditions with light
winds over the region through at least Saturday evening.
Saturday night through Monday...VFR.
Monday night and Tuesday...possible MVFR from a cold front with
high pressure centered over the Central Plains will nose northeast
across the lower Great Lakes today. This will result in a weak surface
pressure gradient so that only light winds and negligible waves
will be found across lakes Erie...Ontario and the adjoining
The elongated surface high will then drift southeast tonight and Sunday.
While this will keep fair weather in place for mariners...winds will
freshen...particularly over Lake Erie. The next round of small craft
advisories can thus be expected on Lake Erie and possible the
western portion of Lake Ontario for Sunday.
Looking ahead to Monday/Columbus day...moderate to fresh
southerlies are forecast for the lower Great Lakes as a cold front
will Michigan. Showers from this frontal system are expected Monday
night with a lesser chance for precipitation in the wake of the front on