ILN issues Area Forecast Discussion (AFD) at May 13, 3:43 AM EDT613
FXUS61 KILN 130743
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
343 AM EDT Tue May 13 2025
.SYNOPSIS...
An area of upper level low pressure will continue moving northeast
through the region today and tomorrow, bringing occasional showers
and storms. Warmer conditions are expected for the end of the week,
after the low moves out of the area. There will be additional chances
for showers and storms, beginning Thursday night.
&&
.NEAR TERM /THROUGH TODAY/...
The slow-moving upper level low is now centered over western
Tennessee. It will continue moving northeast, and by afternoon, it
will be centered just north of Nashville. With theta-e advection
continuing ahead of the low, there could be some showers at just
about any time -- though most of the ILN CWA will likely remain dry
through morning. Central and eastern Ohio will have a better chance
at rain through 16Z than the rest of the area.
With the low just upstream, the ILN CWA will be in a favorable
position for forcing, with an atmosphere that will be destabilizing
heading into the afternoon. This will remain a moist environment,
with CAPE values remaining generally below 1000 J/kg, and narrow CAPE
profiles in a moist adiabatic column. This will keep the severe
threat very low. Heavy rain is a slightly greater concern, with
precipitable water values of 1.3 to 1.5 inches, and very light
steering flow (contributing to slow storm motions). With activity
still expected to be somewhat disorganized, flood concerns should be
isolated -- limited to areas receiving repeated storms, or locations
where storms anchor or back-build, resulting in slow propagation.
Will keep a mention of this in the HWO.
Max temps today are forecast to be in the lower to mid 70s, although
the chances for rain and generally cloudy skies will mean that some
locations could come in a couple degrees below the current forecast.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
The overnight hours heading into Wednesday morning are likely to be
mostly dry, though some scattered showers under the upper low could
still occur -- some low end PoPs will be kept in the forecast.
On Wednesday, the low will be in the process of opening into a wave,
with the axis shifting east of the ILN CWA by mid-day. Despite this,
the environment will remain moist and somewhat unstable -- so even in
the absence of forcing, diurnal convection is again likely to occur.
Will keep PoPs a little lower than Tuesday, owing to the weaker
forcing. Hazardous weather appears unlikely as of now, though there
would likely remain a low-end isolated threat for heavy rain. Highs
should be a couple degrees warmer than Tuesday, generally in the mid
70s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Wednesday night, the surface pressure pattern begins to finally lose
the final remnants of the surface low pressure associated with the
upper level closed low that had lingered for several days over the
Ohio Valley. High pressure to the east and a surface low pressure
digging into the northern and central Plains provides light
southeasterly flow into Thursday morning. Overnight low temperatures
largely remain in the lower 60s with some mid and upper 50s in the
far east (Scioto Valley).
Severe potential (Round 1): Thursday afternoon, mid-level ridging
builds over the Ohio Valley, supporting above normal temperatures in
the low to mid 80s. Some cloud cover likely limits temperatures a few
degrees as warm air advection aloft increases over the region,
causing more cloud cover. During the evening hours, the low pressure
and trough remain well to the northwest of the region, located across
the upper Midwest (Minnesota & Wisconsin). This presents a challenge
regarding the overall strength of the forcing over the local area.
Steep mid-level lapse rates and surface dewpoints in the upper 60s
provides a pool of moderate to high instability, but a forcing
mechanism to push surface air through the warm air advection
inversion is lacking. Some height falls support broad ascent, which
may be enough to trigger elevated convection across Illinois and
Indiana. Throughout the evening, this activity will attempt to enter
the local forecast area, with highest chances across the far west,
especially the northwest and north. Steep mid-level lapse rates and
strong shear support the potential for strong updrafts and large
hail. Damaging winds may also be a threat, but widespread activity
doesn't appear likely at this time.
An occluded cold front moves through the area Thursday night into
Friday morning, with some uncertainty as to how far south it
advances. This brings us into the uncertainty for Friday...
Severe potential (Round 2): Friday morning, the same occluded low
pressure is still positioned over the upper Midwest, sliding slowly
eastward into the Great Lakes region by the evening. Depending on its
location, the ability for more moisture-charged air to move
northward is highly dependent. NBM probabilities for at least 1000
J/kg of MLCAPE and at least 40 knots of bulk shear continues to
increase for Friday afternoon and evening. This is directly tied to a
pool of upper 60s dewpoints that moves northward, back into the
local area, behind the Thursday night/Friday morning cold front. If
the moisture is able to return, a shortwave trough advancing through
the southern periphery of the trough will initiate the second
potential severe threat. Given the location of the shortwave,
favorable moisture and strong shear, there appears to be a higher
severe weather potential Friday when compared to Thursday. As the
most aggressive solution, the 00Z GFS depicts a "higher-end" scenario
with a well organized MCS targeting areas from south central Indiana
into the southern Ohio.
Uncertainty: Comparing the aggressive solutions to the less
concerning outcomes reveals the placement of the primary trough over
the Midwest is critical. Returning air mass scenarios always carry
very low confidence because convectively driven cold pools and/or
cold front almost always resolve farther south, making it difficult
for moist air to return north. Trends to monitor will be the eastward
advancement of the trough Friday evening. The farther east, the more
challenging it will be for moisture to return northward. The
shortwave trough will still provide the potential for showers and
thunderstorms, but the potential for widespread severe impacts would
be lower. The most recent 00Z ECMWF ENS trended slightly slower
(farther west) with the trough, but still isn't as slow as the GEFS.
Whatever occurs Friday night will ultimately provide a push of
moisture south of the region for the weekend. The trough will
continue its eastward progression across the Great Lakes with weakly
amplified jet stream flow over the Ohio Valley. Lower chances for
showers/thunderstorms are forecast for the weekend, with much of the
activity focused to the south and east. Temperatures are more
seasonable Sunday and Monday before the next ridge builds in Tuesday.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Ceilings around the area right now are a mix of VFR, MVFR, and even
some IFR. Over the next few hours, there should be a trend toward
lower ceilings, so the TAF sites all have some MVFR to IFR ceilings
in the forecast through morning. Some light rain is possible, but
coverage will be very low through the morning hours.
Ceilings will improve tomorrow morning, but showers and thunderstorms
are expected to expand in coverage. -SHRA with PROB30 -TSRA has been
included for all TAF sites to indicate the most likely timing as
currently analyzed. By evening, most of the precipitation should be
dissipating, leaving VFR conditions and just a few widely scattered
showers.
OUTLOOK...Thunderstorms are possible on Wednesday, then again at
times from Thursday night through Saturday. MVFR ceilings are
possible Wednesday morning.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Hatzos
NEAR TERM...Hatzos
SHORT TERM...Hatzos
LONG TERM...McGinnis
AVIATION...Hatzos
Source:
ILN issues Area Forecast Discussion (AFD) at May 13, 3:43 AM EDT---------------
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