043
FXUS61 KBUF 091825
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
225 PM EDT Tue Jul 9 2024

.SYNOPSIS...
Our stretch of fair dry weather will come crashing to an end later
tonight and Wednesday...as the remnants of Beryl will make its way
out of the Mid West. A soaking one to two inches of rain can be
expected in many areas by Thursday morning...with higher amounts
possible east of Lake Ontario and even moreso across the Adirondacks.
Along with tropical downpours on Wednesday...there will be the risk for
strong to severe thunderstorms...mainly across the western Southern
Tier and for portions of the Finger Lakes.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
...Significant Rains AND increased severe weather threat continues
from the Remnants of Beryl on Wednesday...

While a wealth of high and mid level clouds will stream across the
region this afternoon in advance of the remnants of Beryl...weak high
pressure will largely keep fair dry weather in place. The exception
will be across parts of the western Southern Tier and Finger Lakes
regions where subtle terrain induced lift could be enough to initiate
some spotty showers or isolated thunderstorms. Otherwise it will be
quite warm and moderately humid this afternoon with highs mainly in the
mid to upper 80s.

Conditions will significantly deteriorate during the course of
tonight though...as the remnants of Beryl over the Lower Ohio valley
will push northeast. A tropically enhanced warm front extending to the
east across Pennsylvania will approach our region in the process. A
modest 25 to 30kt low level jet impinging upon this boundary will
combine with forcing under the nose of an 80kt UL jet to lift a
deepening tropical airmass to generate increasingly widespread rain as
we progress through the overnight/wee hours Wednesday morning. PWAT
values will surge to 2.25" by daybreak...so some heavy rain will be
possible...particularly within any embedded thunderstorms. The focus of
the rain late tonight will be over the western counties with sites west
of the Finger Lakes most likely to experience the heavier downpours.

Wednesday will most certainly be the most unsettled day of the week...
as the center of whats left of Beryl will track across the far west end
of Lake Erie to southernmost Ontario. Meanwhile...the aforementioned
eastward extending warm front will gradually advance across our
forecast area. The deep tropical moisture will focus near and north of
the advancing warm front where widespread moderate to heavy rain is
expected. Daytime rainfall amounts are forecast to range from a quarter
to a half inch across the western Southern Tier to an inch most
elsewhere. Embedded thunderstorm activity could locally double that
amount. The good news is that the threat for excessive rains has
diminished across the sloped terrain of the Southern Tier...but on the
flip side...the risk remains in place for the more populated areas from
Buffalo...Batavia and Rochester to the Eastern Lake Ontario region. Six
hour FFG guidance for this particular area is in the vcnty of 2.25"...
so the risk for widespread hydro concerns will be minimal. The forecast
rainfall should easily double the flow in most area tributaries (north
of the Southern Tier)...but this would only bring most rivers/streams
to half bankfull Any concern would be more directed at urban areas of
areas with terrain (sloped sfcs). The exception would be over the
Eastern Lake Ontario region where some creeks could climb to three
quarters bankfull. That being said...WPC has outlined our entire forecast
area within a slight risk area for excessive rain...which is defined as
a 15% chance for rainfall to exceed flash flood guidance within 25
miles of any given point.

As for the potential for severe weather...the Storm Prediction Center
has outlined much of western New York within a slight risk area. This
aligns with the progression of the tropically enhanced warm front where
a notably enhanced amount of shear will be present. Bulk shear values
of 40-50 kts and veering low level profiles will support supercells and
a non-zero threat of tornadoes...along with clusters that will include
tropical rain loaded downdrafts (ie localized straight line wind damage
risk).

Wednesday night will remain very unsettled...particularly over the
Eastern Lake Ontario region. The center of the tropical remnants will
drift across the far western counties...while the axis of deepest
tropical moisture and associated will be slowly exiting via the
Thousand Islands and St Lawrence valley. This could produce an
additional inch to an inch and a half rain for the Eastern Lake Ontario
region...bringing 24 hour amounts to nearly three inches. The highest
amounts are expected to be over Lewis county.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
The widespread tropical rains will wind down from west to east by
early Thursday...as the system`s center and trailing cold front
pass through our longitude. In their wake, there will be a lingering
chance of much more scattered/weaker showers and a few more isolated
storms on Thursday, before high pressure and drier air build in
Thursday night and usher in a return to quieter and drier weather
from west to east to close out this period. Otherwise, we can
expect temperatures to average out near to a bit below normal
Thursday, although it will remain quite muggy (though humidity
levels will not be as oppressive as what we`ll see during
Wednesday).

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Much quieter weather is expected during this period with our typical
summertime heat and humidity lasting through the period.

Surface high pressure over our area Friday will be wedged in between
a trough over the central Great Lakes and an area of low pressure
tracking up the Eastern Seaboard on Friday. This should provide
mainly dry weather to close out the work week with highs ranging
from the upper 70s to mid 80s.

The trough over the central Great Lakes will track toward and across
the forecast area through the first half of the weekend, weakening
in the process. This will result in the potential for a few showers
across the area, mainly across eastern portions of the region where
increased Atlantic moisture is expected. For the period through the
first half of the weekend, there is still plenty of model
uncertainty among all the guidance, especially with regards to the
timing of the trough crossing the region. Some guidance brings the
trough through quicker before moisture increases to the east,
resulting in less shower potential. Some other guidance is slower
with the trough allowing the moisture to expand north and west,
resulting in increased shower potential for eastern portions of the
area.

After a dry start, shower potential will again increase later Sunday
into the new work week as a few shortwave troughs track across the
area within a quasi-zonal flow over the region. A cold front
tracking southeast across the Great Lakes and into the forecast area
Monday afternoon into Tuesday morning will increase the potential
for showers and storms during this timeframe. Again though, there is
plenty of uncertainty among guidance for timing and shower coverage.

Daytime temperatures near normal to start the period will slowly
trend upward and will be some 5 to 10 degrees above normal for the
second half of the period.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Through the rest of the day expect continued VFR conditions along
with thickening high and mid level cloud cover. While it will mostly
be dry...a couple showers and thunderstorms will be possible across
interior sections of the Southern Tier...Finger Lakes...and North
Country.

Tonight and Wednesday the remnants of Beryl will approach from the
southwest. This will bring continued thickening and lowering cloud
cover...and eventually periods of moderate to possibly heavy rain
late tonight and Wednesday...along with some scattered thunder
storms. This will result in flight conditions lowering to MVFR/IFR.
Wednesday afternoon and evening...enough instability could develop
to bring a risk of some strong to severe thunderstorms...with this
risk greatest south of a rough KBUF-KROC-KFZY axis. The main threat
with any such storms would be strong wind gusts.

Outlook...

Wednesday night...MVFR/IFR with widespread rain diminishing.
Thursday...Improvement to MVFR/VFR with leftover scattered
showers.
Friday...Mainly VFR with a low chance of showers and thunderstorms
across the Southern Tier/Finger Lakes.
Saturday...Mainly VFR with a low chance of showers and
thunderstorms well inland from the lakes.
Sunday...Mainly VFR with a chance of showers and thunderstorms.

&&

.MARINE...
Gentle to occasionally moderate breezes and minimal waves today will
remain favorable for recreational boating. Despite conditions
staying below small craft advisory criteria to, there will be an
increasing risk for thunderstorms, especially on Lake Erie.

Wednesday will be quite unsettled, as the remnants of Beryl will
move through with times of heavy rain and possibly some gusty
thunderstorms. The active weather will be accompanied by moderate to
occasionally fresh northeasterlies.

&&

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

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...JM/JJR
LONG TERM...JM/SW
AVIATION...JJR
MARINE...RSH/TMA