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Area forecast discussion
National Weather Service Buffalo New York
456 PM EDT Tue Jul 23 2019

Synopsis...
high pressure centered over the upper Mississippi Valley will slowly
build east and provide US with generally fair weather through the
remainder of the week. The exception will be to the east of Lake
Ontario and near The Finger lakes this evening, then toward The
Finger lakes region again on Wednesday where more showers will
be possible. Otherwise the cool comfortable weather will give
way to warmer conditions as we head into the weekend.

&&

Near term /through Wednesday/...
a staunch high amplitude ridge centered over the western states will
keep general high pressure in place from the plains to the lower
Great Lakes during this period. While this will result in enough
subsidence to support fair dry weather over the majority of our
forecast area...there will be some subtleties that we will have to
keep an eye on.

Starting with late this afternoon...850 mb temps of 10c and strong
diurnal induced instability will keep some showers and thunderstorms
in place over The Finger lakes. These will be short lived with any
impacted areas receiving less than a quarter inch of rain. Another
area to watch will be across the north country...where a dew point
(secondary cold front) boundary will continue to slowly push south.
This feature will tend to wash out during the first half of
tonight...but in the meantime...there will be more scattered showers
and isolated storms for sites from the Tug Hill northward.
Otherwise...it should be a fine late afternoon and evening with
comfortable conditions.

Tonight...the diurnally induced instability will give way to the
large scale subsidence. This will support fair dry weather across
the region...although as we push into the wee hours of Wednesday
morning...lake driven instability (lake Delta T arnd 14) could
encourage a shower or near the lakes. There will be a slight
preference for shower activity near Lake Erie...as the axis of a
longwave trough will cross the region. As mentioned in earlier
discussions...a couple small disturbances seen in WV imagery over
lower Michigan will move across Lake Erie during this period... thus
the slight favoring for that area for lake induced shower activity.
Meanwhile...it will once again be a fairly comfortable night for
sleeping with mins generally ranging from the lower 50s across the
southern tier and Lewis County...to 55 to 60 elsewhere.

Wednesday should be a Carbon copy of today (tues). While high
pressure over the upper mid west will nose into the region...
diurnally driven instability within our relatively cool airmass will
support some shower activity inland from the lakes after 16z. Have
raised slgt chc pops to chc for this area. Temps will once again top
out in the mid to upper 70s across the lower elevations/lake plains.
These values are about five degrees below normal.

&&

Short term /Wednesday night through Friday night/...
any isolated showers will end Wednesday evening when a weak mid
level trough exits eastward into New England. This will leave mainly
clear to partly cloudy skies overnight. The airmass will still be
fairly cool, with lows in the upper 50s to lower 60s on the lake
plains and some lower 50s in the cooler southern tier valleys and
Lewis County.

A weak mid level trough axis embedded in northwest flow aloft will
move across the eastern Great Lakes. Weak forcing from this may
support a few isolated showers, with any showers focusing inland
away from the lakes in the afternoon as stable lake shadows develop.
There may be enough instability by afternoon to support an isolated
thunderstorm as well, but again the majority of the area will stay
dry. Warm advection will allow temperatures to move back to around
average, with lower 80s at lower elevations and mid to upper 70s for
higher terrain.

After this, high pressure centered near Ohio will gradually ridge
into the region Thursday night through Friday night. This will
result in dry weather and mainly clear skies during the period.
Temperatures on Friday will be a few degrees warmer with highs in the
mid 80s across lower terrain and around 80 across higher elevations.

&&

Long term /Saturday through Tuesday/...
within a zonal flow aloft and subtropical ridge gripping the eastern
coastline...fair weather is expected through much of this time
period.

A dampening shortwave advancing across southern Canada Saturday-
Sunday looks to bring nothing more than some clouds and an uptick in
humidity. Showers and thunderstorms will become possible towards
early next week as humidity builds, and a warming land mass may
bring lake breeze showers or thunderstorms Monday. By Tuesday a weak
cold front is forecast to be near, or crossing the area which would
bring the most widespread convection this period. Will insert a
chance for storms for now in the forecast.

As temperatures at 850 hpa warm from the low teens to mid teens
celsius through the period...day to day afternoon warming will go
from around the low-mid 80s early to mid-upper 80s by Monday. As
clouds increase Tuesday temperatures will likely be several degrees
cooler.

&&

Aviation /21z Tuesday through Sunday/...
while VFR conditions will be found across the region during the
remainder of the afternoon...there may still be a shower or two
across the north country, affecting kart.

Tonight...VFR conditions will persist across the bulk of the region.
The exception will be across parts of the southern tier and Finger
Lakes where some late night fog and or stratus will result in some
MVFR to IFR conditions.

On Wednesday...high pressure nosing to the east from the center of
the country will support VFR conditons for our region along with
light winds.

Outlook...

Wednesday through Sunday...mainly VFR.

&&

Marine...
while a weak surface pressure gradient will keep nearly ideal
conditions (generally light winds and negligible waves) in place for
recreational boating for the bulk of this week...there will be the
risk for waterspouts later tonight and early Wednesday morning.

The axis of a longwave trough will Cross Lake Erie during the second
half of tonight. Several of the WV channels depict subtle shortwaves
within the trough. These features will move from the upper Great
Lakes to Lake Erie tonight...with the focus being on the western
half of the lake. National Weather Service kcle is already highlighting the risk for
spouts on their end of the lake. The aforementioned synoptic pattern
will be accompanied by a favorable thermal profile...as 850 mb temps
in the vcnty of 10-11c and lake surface temps around 25c will
promote sufficient low level instability. As outlined by the
outstanding waterspout research from szilagyi (environ can)...
this instability combined with a convective depth of more than
15k ft is conducive for spout development. This will especially
be the case in a regime with light winds and possibly a land breeze
boundary for which to focus low level convergence. Will thus
maintain slight chc for spouts on Lake Erie from about 06 to 12z
Wednesday.

&&

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

&&

$$

Synopsis...jla/rsh
near term...rsh

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