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Area forecast discussion
National Weather Service Buffalo New York
132 am EDT sun Oct 20 2019

Synopsis...
pleasant Fall weather will continue through Monday...as our region
will find itself between the remnants of tropical storm Nestor to
southeast and a weak disturbance over the upper Great Lakes. The
pleasant weather will be accompanied by day to day warming with
temperatures climbing into the 70s for parts of western New York
Monday afternoon. In the wake of a rainy frontal passage on
Tuesday...a distinct change back to more seasonable Fall weather
will then take place for the remainder of the week.

&&

Near term /through today/...
it will be a fair chilly night across the region...although our
starlit skies will be blurred by some cirrus debris from the distant
remnants of tropical storm Nestor. Despite the high clouds...the
Mercury will drop toward or below freezing in many areas...basically
from Oswego County north and east...but given that the growing
season was ended this morning...all mention of frost has been pulled
from the forecast.

While dry and generally pleasant weather will continue on Sunday...
the passage of a relatively flat mid level trough will introduce a
little more cloud cover. As the far flung cirrus from the tropical
remnants move out of our region during the morning...some broken
Alto-cu associated with the mid level trough will arrive. The most
dense portion of the mid level cloud cover should split our region
to the north and south though...so most areas should still be able
to experience partial sunshine.

In regards to temperatures...Sunday should be a few degrees milder
than yesterday (sat). While 850 mb temps will be similar (near 8c)...
the day will start off a few degrees higher. As has been the case...
there will still be a staunch 4 deg subsidence inversion near 850 mb...
so we will not be able to fully tap into this mild airmass. We
should be able to mix to h925 though...and since the airmass at that
level is forecast to warm to arnd 13c over the western counties...we
can expect afternoon temps to climb into the low to mid 60s. It will
be a few degrees cooler east of Lake Ontario.

Anyway you slice it though...the upcoming day should once again
offer fine viewing conditions of the fall foliage...which is nearing
its peak in most areas.

&&

Short term /tonight through Wednesday/...
Sunday night, our region will remain under the influence of the
surface high extending from James Bay south and east across New York
state. Meanwhile, our next weather maker will be in the process of
exiting the Rocky Mountains and beginning to track east across the
upper Midwest. Otherwise, with the surface high influencing our
weather expect generally clear skies and light wind flow overnight.
This will also allow for good radiational cooling to take place with
some River Valley fog formation. Look for lows in the lower 40s
inland away from the lakes with mid to upper 40s along the lake
plains.

Low pressure will then track out of the upper Midwest and arrive
across Lake Superior by late in the day on Monday. As this feature
tracks into the upper Great Lakes warm advection processes and
southerly flow will pick up across the forecast area. This will aid
in sending our temperatures up well above normal with upper 60s to
the lower 70s across the lake plains. Overall, it should be a fine
fall day across the area with plentiful sunshine expected for a good
portion of the day. It will make for a perfect day to get out and go
see the fall foliage, especially to go see Letchworth State Park
which is near or at peak.

The surface low over Lake Superior will slowly drift northward into
southeast Ontario Canada and mature Monday night. As it does so, it
will slowly pivot its trailing front into and then slowly east
across New York state. As the front crosses the forecast area it
will bring an area of widespread rainfall to the area for a good
portion of the day Tuesday. In regards to rainfall amounts, most
locations should expect to see rainfall totals come in just under an
inch. Behind the front, widespread rainfall will taper off along
with winds veering around to southwest. Also, over the course of the
day h850t will cool and are forecast to drop per European model (ecmwf)/GFS/NAM from
+12c to ~+2/3c by Tuesday evening.

The steadier precipitation should all be in the process of winding
down for our forecast area by early Tuesday night. Behind the front,
the atmospheric column will continue to cool. This in combination
with the broad mid level trough wrapping additional moisture in
across the lower lakes will support lake effect showers northeast of
both lakes. However, it will only be a brief window for lake driven
rain showers given the fact that synoptic moisture gets quickly
stripped away and equilibrium levels drop by Wednesday. With that
said, this event or setup will be somewhat similar to last
Wednesday. In that event some lightning and graupel was observed
within the stronger rain showers. Current BUFKIT forecast profiles
do show lake induced equilibrium levels climbing to near 21k for
this next event. Additionally, the depth from the surface to -10c
will be nearing 10k, which is another key ingredient. So it's not
out of the realm of possibility that some of the stronger showers
will again be able to produce lightning and graupel. Stay tuned!

Behind the front it will be markedly cooler with highs by Wednesday
expected to only top out in the 50s.

&&

Long term /Wednesday night through Saturday/...
the pressure gradient between low pressure across Hudson Bay and
high pressure across the mid-Atlantic states will result in a
general southwesterly flow across the region Wednesday night and
Thursday. Initially it will be cool enough aloft to support some
lake effect rain showers Wednesday night, then these may be followed
by more showers with a subtle shortwave embedded in the flow aloft
on Thursday. This said, showers will be scattered in nature and the
majority of the time will be cool and dry.

After this, 12z model guidance continues to differ with the GFS/Gem
slowly moving a shortwave across the region while the European model (ecmwf) has a
cut-off low developing across the southern states. If the former
verifies, there will be a period of rain Friday into Saturday as low
pressure develops in response to the shortwave. It also would result
in cooler conditions on Saturday when there would be a northwesterly
flow behind the system. The European model (ecmwf) solution would lead to a mainly
dry and slightly warmer pattern. Given the resulting forecast
uncertainty, have kept pops in the chance range until model guidance
comes to a better consensus. Temperatures will not stray too far
from normal for late October with daytime highs mainly in the 50s.

&&

Aviation /06z Sunday through Thursday/...
while there will be some mid and high level cloud cover through most
of the upcoming day...we can expect nearly ideal flying weather with
VFR conditions and light winds.

Any high VFR cigs will then give way to mainly clear skies for
Sunday night.

Outlook...
Monday...VFR.
Tuesday...MVFR with areas of rain and fog.
Wednesday...MVFR to VFR with scattered lake effect rain showers
northeast of lakes Erie and Ontario.
Thursday...VFR.

&&

Marine...
as surface high moves across New England through Sunday...a weak
pressure gradient will remain in place across the lower Great Lakes.
This will maintain light winds and negligible waves through the
remainder of the weekend.

East to southeast winds will begin to freshen on Monday...well ahead
of a slow moving cold front that will be crossing the mid-western
states.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

Synopsis...rsh
near term...rsh

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