ILN issues Area Forecast Discussion (AFD) at Aug 17, 2:30 PM EDT269
FXUS61 KILN 171830
AFDILN
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
230 PM EDT Sat Aug 17 2024
.SYNOPSIS...
Occasional periods of showers and thunderstorms will continue
through the weekend as a low pressure system moves through the
Great Lakes region. High pressure and a drier airmass will then
build into the Ohio Valley through the workweek. Below normal
temperatures and abundant sunshine are expected for the first
half of the workweek.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Several clusters have storms have developed near/SE of I-71 as
expected, with disorganized more cellular SHRA activity
pivoting into parts of WC OH. Given the favorable deep-layer and
LL thermodynamic environment entrenched across far srn OH and N
KY, the primary severe threat is likely to be focused in these
areas through late afternoon. As we progress into early evening,
the initial clusters of storms currently in the local area
should progress to the S/E and out of the ILN FA, likely
signaling an end to the main severe threat locally, or at the
very least a substantial downtick in the overall potential as
these areas will have difficulty rebounding thermodynamically
through the remainder of the day (even in the prospect of
additional redevelopment).
Given the tremendously-favorable DCAPE environment coinciding
with strong deep-layer instby and decent/sufficient deep-layer
shear, the strongest storms will pose a damaging wind threat,
especially if some of the cells can organize into clusters,
which has occurred somewhat already. But the threat should be
rather short-lived, potentially decreasing quite a bit
toward/beyond 21z as the area becomes convectively-contaminated
and the LL lapse rates suffer.
Further to the N/NW from WC through central OH, wraparound
moisture pivoting back in from the NW coinciding with better
forcing and slightly cooler temps aloft will promote numerous
disorganized SHRA and a few rumbles of thunder from time to
time. Although the downburst potential in these areas is quite a
bit lower than for locales further to the SE, some brief gusty
winds will still be possible given the steep LL lapse rates. The
main limiting factor for this activity is going to be updraft
strength/persistence.
SHRA/TSRA activity should wane as we progress past sunset, with
perhaps an ISO/spotty SHRA persisting across the region through
the nighttime hours. But would expect that most areas will
remain dry tonight as skies generally trend cloudier through the
predawn hours.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
The lumbering mid/upper level low/trof deepens/digs into the
ern Great Lakes/OH Vly region on Sunday, yielding broad/deep-
layer cyclonic flow in the region and fairly impressive negative
height anomalies to go along with it. This will translate to a
rather unsettled pattern locally Sunday as the combination of
typical diurnally-driven summertime heating and LL moisture
coinciding with cooler temps aloft will generate numerous
cellular/disorganized SHRA, with perhaps a rumble of thunder,
during the afternoon into early evening Sunday.
Daytime highs will be quite a bit cooler on Sunday, owing to
extensive/expansive cloud cover and numerous afternoon SHRA
pinwheeling around the low center just to the NE of the ILN FA.
Temps should top out in the mid 70s to around 80 degrees, with
likely to categorical PoPs from SW to NE, respectively, across the
local area for the afternoon time period. Sunday will likely be one
of those days where it rains on-and-off several times in any one
location over the course of the daytime, but perhaps not amounting
to more than a third to half of an inch in total. Drier and
cooler conditions evolve Sunday night as temps dip into the
lower/mid 60s as slightly drier air begins to slowly filter into
the region.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Deep trough along the Appalachians at the start of the period will
weaken and lift out mid to late week allowing mid level pattern to
deamplify. Thereafter, high pressure centered over the southern
Plains will be able to sprawl east northeast across the region and
to the Atlantic seaboard by the end of the period.
Surface high pressure will predominate through the week leading to
dry conditions. Temperatures will be below normal, especially at
night, through mid week. A warming trend will ensue as upper heights
rise and readings will be back above normal by Friday and
Saturday.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Several clusters of TSRA are already ongoing across the region,
with an expectation for additional more widespread, but loosely
organized, storms expected through the first part of the TAF
period. Coverage of activity should be fairly widespread,
although there may be a relative "minimum" near KCVG/KLUK/KILN
through the heart of the afternoon, with greater coverage
focused further to the N, S, and E. As such, have only included
a tempo TSRA at KDAY/KCMH/KLCK, but storms will be possible
just about anywhere at any time through 00z. Sudden reductions
in VSBYs and gusty winds will be possible with the activity but
will be handled with amendments as needed.
CIGs should be mainly VFR through this evening before trending
MVFR, or even IFR, past 06z, persisting through most of the
remainder of the morning Sunday. IFR CIGs will be favored for
nrn sites, but will be possible just about anywhere.
SW winds of 12-15kts, with gusts 20-25kts, are expected through
the afternoon before going more westerly and subsiding past 00z.
Winds will gradually go more out of the WNW toward the end of
the period at about 10-12kts. Winds may become light enough
during the overnight hours to promote the development of some
BR and MVFR VSBYs, but there are some uncertainties regarding
how widespread this may be, especially with some MVFR/IFR CIGs
filtering in during the predawn hours as well.
Diurnally-driven/enhanced SHRA, with a few rumbles of thunder,
will sprout about again toward the end of the period.
OUTLOOK...Thunderstorms possible on Sunday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...KC
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...
AVIATION...KC
Source:
ILN issues Area Forecast Discussion (AFD) at Aug 17, 2:30 PM EDT---------------
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