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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 161320
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
920 AM EDT Mon May 16 2022

.SYNOPSIS...
Showers with some embedded thunder continue to move through
early Monday morning before pushing eastward. High pressure
builds in late Monday, offering dry and pleasant conditions
through Tuesday. The pattern quickly becomes more active by
Wednesday, with periods of showers and storms expected through
the end of the work week and into the start of the next weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
Sharp mid level trof over the area to shift east with northwest
flow developing. Widespread showers and thunderstorms have
shifted off to the east with the trof, leaving just a few
residual post frontal showers over the far northeast.

Northwesterly flow aloft will allow for cooler and drier air to
filter in. Latest visible satellite imagery shows lingering
clouds, which will break apart from the west as we head into the
afternoon.

Colder air aloft will result in steep low level lapse rates
which will allow for some cu development. Forcing is limited but
with this low level instby there may be a few stray showers
over the far north. Therefore, have kept a slight chance mention
in the far north.

Highs are expected to be in the low to mid-70s.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Weak surface high pressure builds in from the west as the Ohio
Valley becomes positioned downstream of an H5 ridge. As drier
air advects in, clouds will dissolve Monday evening and leave us
with mostly clear skies overnight. Combined with weakening
westerly surface winds, lows will be able to bottom out in the
low to mid-50s.

Tuesday will be very pleasant as we remain downstream of an H5
ridge. Limited moisture availability will allow skies to remain
mostly sunny throughout the day. Additionally, dewpoints in the
mid 40s to near 50 will keep outdoor humidity levels in the
comfortable range.

Tuesday night continues to remain quiet, but we will begin to
observe a breakdown in the H5 ridge, with flow aloft becoming
more quasi-zonal. Cloud coverage will begin to increase from
west to east overnight, but the forecast remains dry during this
period as of now.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
An active weather pattern is expected for the start of the long term
period as several quickly-moving S/Ws track E across the OH Vly
within the quasi-zonal/NW flow atop a quasi-stationary WNW-ESE
oriented LL frontal boundary.

The first of several midlevel disturbances will track E through the
OH Vly late Tuesday night into the day on Wednesday. This will
promote the development of some convection toward daybreak Wednesday
and beyond, which will be primarily elevated in nature until better
LL destabilization can occur later into the day on Wednesday
from the SW. This initial batch of SHRA, with perhaps a rumble
of thunder or two, is likely to move quickly through the ILN FA
through the first half of the day Wednesday. It will leave in
its wake a trailing WNW- ESE oriented baroclinic zone draped
across the southern OH Vly, potentially very close to the OH
Rvr. As the initial S/W pulls E, better sfc theta-e advection
will become established by late Wednesday afternoon through the
evening hours, with LL destabilization efforts underway,
initially for SW parts of the local area during this time frame.


There remain quite a few of uncertainties in the fcst at these time
ranges, but the setup for active weather locally does seem to carry
with it some degree of concern for episodic SHRA/TSRA from Wednesday
evening through even the day on Thursday. Not only would this
portend the potential for one or more episodes of storms, but also
the risk for repeated convectively-driven heavy rain leading to
hydro concerns as well. The better shear profiles are likely to
evolve Wednesday evening into early Thursday morning as LL
destabilization continues to increase from SW to NE during this time
frame. The primary source for lift on Wednesday evening/night will
be the convergent axis stretching from WNW to ESE across southern
IN/OH and N KY. Although the best H8 LLJ will be pulling E toward
later Wednesday evening/night, there will still be some subtle
convergence along the LL boundary amidst an environment of
increasing LL moisture advection/convergence. And as the initial S/W
energy pulls E, a better northward surge of deeper moisture will
commence for the second half of the day Wednesday, especially across
far S/SW parts of the OH Vly. One of the main questions that remains
for Wednesday evening/night is just how much forcing/lift will
evolve, which will ultimately dictate the degree to which convection
can reinitiate or be sustained along the aforementioned boundary.
One thing that does appear to be a concern is the potential for
renewed/repeated convection Wednesday evening/night near the
boundary with a steering-layer flow that will largely overlap the LL
boundary and source lift while sfc inflow into the boundary will
remain normal to it. This creates a scenario where training of
convection may be favored, potentially in the form of one or more
convective complexes, suggesting a hydro concern may very well come
into play. Of course, the details of where this would be favored are
far from certain at this point. There does remain some latitudinal
variability in the guidance regarding where this boundary will set
up, but it would appear that locales near/south of the OH Rvr would
be more in-line for this potential at this juncture. The signal is
certainly there for one or more convective complexes Wednesday
evening/night across the southern OH Vly, with the hydro threats
more of a concern locally than the severe threat with the best LL
thermodynamic environment staying in the far south, or potentially
just south, of the ILN FA.

With the potential for numerous SHRA/TSRA within a narrow WNW-ESE
corridor in the southern third or quarter of the ILN FA Wednesday
evening/night, the setup for the daytime Thursday becomes even more
uncertain, especially with questions regarding presence of a source
of lift and whether the cap can hold. One thing that does appear to
be likely is the continued theta-e advection N further into the ILN
FA, with high, to potentially extreme, instby developing during the
daytime period. The intricacies of how this will all unfold are far
from clear at this juncture. But... there appears to be enough
overlap in the shear/instby parameter spaces to yield more than just
a little concern for one or more rounds of strong to severe storms,
if the nosing of the LLJ by midday can promote enough lift to
generate some convective initiation. The overall pattern/setup is
more than favorable for a severe weather episode during this time
frame, but the degree to which this evolves, especially regarding
coverage of storms, will take some time to reveal itself. Very
bluntly, there is some guidance that shows a window for sufficient
overlap of high instby amidst sufficient deep-layer speed and
directional shear to suggest that all severe hazards, including
flooding, may come into play at one time or another Thursday,
particularly for locales south of the I-70 corridor. The caveat is
whether the environment becomes uncapped or there is sufficient
lift to overcome it. It could end up being a scenario where we
progress into the morning on Thursday and are still not certain
whether the cap will be overcome. Nevertheless, the signal is
strong enough that felt it is prudent to start mention in the
HWO, at least in a broad sense to begin with.

By later Thursday evening into the night, midlevel height rises will
commence locally as the trof across the upper Midwest digs into the
central plains. This amplifying midlevel ridge axis will position
itself across the heart of the ILN FA Friday, favoring drier, but
certainly plenty warm and humid, conditions for the final workweek
of the week. Friday looks to be the warmest and most uncomfortable
day of the week, with temps likely reaching into the upper 80s with
DPs in the mid/upper 60s. Guidance still differs quite a bit of
variation regarding the timing of the front through the ILN FA
sometime in the Friday night through Saturday time frame. Either
way, the FROPA will offer renewed chances for SHRA/TSRA pretty much
everywhere before drier and cooler conditions filter in late on
Saturday in the post frontal environment. While there certainly
could be a strong to severe storm potential with the FROPA, the more
concerning and pressing signal for Wednesday night (mainly hydro/low
end severe) and Thursday (hydro/severe) takes precedence at this
juncture. Will hold off on further discussions regarding the FROPA
Friday night/Saturday for now until the details come into better
focus.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
A few lingering showers may be observed at KCMH/KLCK this
morning before pushing eastward. Dry conditions are favored for
the remainder of the day, although an isolated shower/storm
cannot be completely ruled out this afternoon. Due to low
confidence and probability of occurring, did not include in the
tafs.

Low level moisture behind the cold front will keep some MVFR/IFR
CIGs over the terminals through the mid morning hours. Drier
air in the upper levels moves in and breaks apart those lower
CIGs, allowing MVFR CIGs to return by the late morning hours.

Wind gusts out of the west-northwest of around 20-25 kts will be
possible by the afternoon. Winds will subside by the evening and
decrease below 10 kts for Monday night.

OUTLOOK...Thunderstorms possible at times Wednesday into
Thursday. MVFR conditions possible Friday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...Clark
NEAR TERM...AR
SHORT TERM...Clark
LONG TERM...KC
AVIATION...Clark