Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 250616
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
216 AM EDT MON JUL 25 2016

.SYNOPSIS...
An upper level trough will slowly cross the region today producing
scattered showers and thunderstorms. A trailing cold front will
pass through our region this evening...followed by slightly
cooler and less humid weather Tuesday before temperatures and
eventually humidity levels trend upward again Wednesday and
Thursday. A weak area of low pressure will then cross the region
Friday and Saturday bringing the next chance of showers and
thunderstorms.

&&

.NEAR TERM /THROUGH TODAY/...
For the remainder of the night high pressure across New England
will continue to drift eastward into the Atlantic. Subsidence
behind a departing mid-level wave helped keep things dry
overnight, with even some breaks in the mid and high clouds during
the early morning hours. Following radar trends and a consensusof
model guidance expect the region to remain dry until around
daybreak when things get more interesting.

A weak mid level trough and pre-frontal surface trough will
approach the region around daybreak. Mesoscale model guidance
continues to struggle with the details of timing and placement for
convection. However, there is consensus that this trough and a
modest 30+ knot low level jet will provide the focus for this
activity. This suggests that for areas west of Rochester the best
chance for showers and thunderstorms will be this morning with
this mid level wave. Even so, radar trends show only a broken line
of convection upstream supporting chance POPS at this time.
Thunderstorms will produce `briefly` heavy rainfall which may
provide localized drought relief to some areas. The NAM forecasts
precipitable water values above 2 inches.

This afternoon, the pre-frontal trough will move across Central
and Eastern New York. Here, there will be a better opportunity for
heating ahead of this, which would enhance instability and thus
increase the severe weather potential. Winds aloft are forecast to
increase a bit with modest speed and directional shear providing
some opportunity for organized convection. The lake breeze
convergence zone will also provide a focus for this convection, in
addition to residual outflow boundaries and topography. The window
for severe weather will be narrow, with a consensus of guidance
quickly bringing drier air behind this trough, with convection
likely to exit into Central New York late afternoon. The actual
cold front will not reach the area until after this, but by then
the boundary layer should be too dry to support any storms.

Meanwhile, a breezy southwesterly winds will allow a lake shadow
to quickly develop northeast of Lake Erie which should keep
Buffalo mainly dry during the afternoon. Highs will reach 85-90
depending on how much sun develops in the afternoon.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Monday night through Wednesday night will feature dry and warm
conditions as high pressure builds across the region and lingers
through mid-week. An upper level trough will exit to our east Monday
night giving way to mainly zonal flow with some weak ridging Tuesday
into Wednesday. A surface high will build across the Ohio valley
Tuesday and remain stalled there through Wednesday. 850 mb
temperatures will take a small step back to around +16C on Tuesday
behind the departing wave, allowing high temperatures to run near
seasonal values, while drier northwesterly flow will cut dew points
back into the mid to upper 50s, making the warmth more comfortable.
By Wednesday, the modifying airmass under the surface high will push
850 mb temperatures to about +18C, resulting in afternoon
temperatures back into in the upper 80s. However, humidity will
remain low as the dry high pressure remains in control and dew
points again drop into the mid 50s for the afternoon. Overnight lows
will run in the mid to upper 60s near the lake plains. Mainly clear
skies and light winds allow radiational cooling to drop interior
valleys into the mid to upper 50s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
While drought busting rains are not anticipated during this
period...there is relatively high confidence that the pattern will
be more active...so many areas should pick up at least a little
rainfall. This will be due to a subtle shift in the dominant ridge
that has been in firm control of the country.

Unlike the past couple weeks when an expansive sub-tropical ridge
either flexed its muscles with anomalously high heights over the
nations mid section...or stretched from ocean to ocean across the
southern half of the Conus...this time frame will feature low
amplitude troughing over the Great Lakes region. Meanwhile...the
heart of the aforementioned ridge will have retrograded to the
Desert Southwest. This upper level transition will encourage a
little more baroclinicity across the Great Lakes region...which
should support a more active storm track.

At the surface...the period will open with a wavy frontal boundary
that will be stalled in the vcnty of the Mason Dixon Line. It is
interesting in that all of the real baroclinicity...lift and moisture
will be found a few hundred miles north of the sfc front. This
should initially keep the bulk of any showers and thunderstorms
north of the international border...but as push into Friday...a
fairly well organized wave will develop over the Mid West and slowly
track east along the front. The ensembles are all over the place
with the location...speed and track of this wave...but all are in
general agreement that the system will move close enough to our
region to help generate more widespread rainfall. The best
opportunity for some rain would be Friday and Friday evening with
basin average rainfall averaging under a quarter inch...but locally
up to three quarters of an inch.

Confidence drops off for the weekend as a second wave could bring
another round of beneficial showers and thunderstorms to the
forecast area. This will largely depend on the strength of the first
system though...so will only use relatively low pops to express this
potential.

In terms of temperatures...while mercury levels will generally be
lower than those of the past few weeks...there is high confidence
that they will remain close to...if not still a few degrees above
normal.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Largely dry VFR conditions should prevail underneath varying
amounts of mid and high cloud cover through around 10Z. There is a
limited potential for fog to briefly develop at JHW due to the
breaks in the cloud cover.

A trough will cross Western New York this morning and then move
into Central New York this afternoon. This should provide the main
focus for showers and thunderstorms, however coverage should be
scattered in nature so will maintain VCTS in the TAFS until
confidence in timing and location increases. Convection will end
from west to east this afternoon, with breezy and dry conditions
first developing at BUF due to lake shadowing.

Any lingering showers should be done by 00Z Tuesday with
widespreadVFR conditions expected tonight.

Outlook...
Tuesday and Wednesday...Mainly VFR.
Thursday...Mainly VFR with a chance of showers and thunderstorms.
Friday...VFR/MVFR with a chance of showers and thunderstorms.

&&

.MARINE...
A cold front will move east across the lower Great Lakes today.
Southwest winds will increase along and ahead of the cold front,
especially on Lake Erie where winds and waves may approach Small
Craft Advisory criteria this afternoon. Winds will diminish
tonight following the passage of the weak front, with winds and
waves then expected to remain below Small Craft Advisory levels
through midweek.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...CHURCH
LONG TERM...RSH
AVIATION...APFFEL
MARINE...HITCHCOCK/JJR



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