Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 140149
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
949 PM EDT Wed Mar 13 2024

.SYNOPSIS...
More warm weather and gusty winds are likely on Thursday ahead
of a low pressure and cold front which will cross the area on
Friday. With the gusty winds will come higher moisture, and
shower and thunderstorm chances will increase with most areas
seeing rain at some point from Thursday into Friday. Behind the
front the airmass will cool considerably as high pressure builds
into the area. Secondary cold fronts will swing through the
Great Lakes during the weekend into early next week, reinforcing
the cooler air and continuing the mostly dry weather from the
upcoming weekend.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
The overnight period is starting with quiet conditions, but a
turn to much more active weather will begin several hours from
now. A surface warm front extends west-to-east across far
northern Indiana and Ohio, and there is a secondary surface
boundary also noted in observations in southern Indiana. The
main issue overnight will be warm frontal processes aloft, with
a robust feed of theta-e at 925mb on SW flow. Isolated
convection is currently ongoing near the IL/IN border, and a
blossoming in coverage is expected in response to the
increasing moisture. This will bring showers and storms into the
western and northwestern sections of the ILN CWA generally after
08Z, then progressing eastward across the northern sections of
the forecast area through 14Z. There are doubts about the
southern extent of this activity, and if the Tri-State
Cincinnati area or parts of southern Ohio / northeast Kentucky
will even get any precipitation from this first round.
Confidence is highest for areas further north and west. Model
soundings suggest a healthy near-surface inversion, but steep
lapse rates and some deep layer shear would suggest small hail
could accompany the elevated storms early this coming morning.

There remains considerable uncertainty with storm mode / timing
for the rest of tomorrow and tomorrow night, but by afternoon
and evening, the parameter space appears favorable for some
severe weather. The upcoming midnight shift will have a full
suite of 00Z data available to help assess this potential.

Previous discussion >
Primary concern tonight will be with shower and thunderstorm
chances/coverage.

Ample sunshine and warm breezes across the ILN CWA early this
afternoon, and dew points have held steady in the lower 40s
which is keeping humidities in the 30-40% range, so with the
more sporadic wind gusts vs yesterday`s more widespread and
stronger winds, did not feel a need to message any fire weather
concerns into this evening on a larger scale.

After midnight, increasing theta-e advection aloft will drive
the potential for an arc of showers and perhaps a few elevated
storms from southwest to northeast across mainly the northwest
half of the ILN forecast area. This is not a high confidence
signal across the suite of convective allowing and global
ensemble members, however, thus chances along I-71 are
maintained in the 20-40% range. A better /spatial and forcing/
signal exists for showers and thunderstorms to develop tonight
in Illinois and cross Indiana on an ENE trajectory toward the
northwestern third of the ILN forecast area, arriving in the
hours before or just after sunrise in west central Ohio. Likely
elevated in nature, these are unlikely to be strong / severe but
do warrant the maintenance of higher rain chances that were
ongoing in the forecast already across west central Ohio in the
10Z-12Z timeframe.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
Expect the cluster of showers/storms mentioned above entering
west central Ohio around sunrise to continue on a east-northeast
trajectory toward central Ohio during the morning hours, but it
is at this point where the forecast begins to lose some degree
of certainty, and how long these hold together downstream over
central Ohio (or perhaps moving more into northern Ohio) remains
to be seen.

In general, as a potent mid level speed max ejects northeast
owing to height falls digging into the Rockies and with heights
rising downstream over the Ohio Valley, activity should have
the propensity to either weaken/diminish over central Ohio or
lift more north into northern Ohio as forcing diminishes
immediately over the ILN CWA, leaving somewhat of an open-warm-
sector lull across much of our forecast area from late morning
into early mid afternoon.

That being said, as this speed max and embedded shortwave
arrives into Indiana/Michigan during the afternoon, expect a
renewed storm cluster/MCS to develop across ILN/IN and move
rapidly toward MI/OH. There are some convective-allowing
solutions which develop a rather robust MCS that rides along the
synoptic warm front lying either just north of our area or
across our northern tier, taking on linear/bowing
characteristics. Some solutions ride this activity well north of
our area, but there is a general / overarching trend in most
guidance /backed up by machine learning probabilities based on
GEFS/HREF/ that our northern half of our forecast area is under
a threat for severe storms tomorrow that could - if things come
together - exceed current Level 1 /Marginal Risk/ categories
from the SPC. But the uncertainty tied to the coverage / track
of this cluster of storms, coupled with marginal thermodynamics
are likely playing a role here. What we do know is that low
level and deep level shear /hodograph curvature/ is rather
optimal for storm longevity and organization for any MCS or
discrete cells which may form, but there is some concern for the
level of moistening that can be maintained in an open warm
sector scenario. If dewpoints can`t ascend past the mid 50s -
which is being hinted by some of the CAMS which have handled low
level moisture more optimally this week - overall convection
may struggle to maintain intensity outside a more optimal setup
with regards to shear/warm front/synoptic forcing with the jet
streak. This situation will need to be watched closely, and if a
more robust storm cluster can get going in this kind of shear
environment across the northern half of the ILN forecast area,
all modes of severe weather including a tornado or two will be
in play.

After the potential afternoon-early evening storm threats, we
are not out of the woods as the passing jet streak will begin to
push low pressure and associated cold front southeast toward our
area later Thursday night into Friday morning, and another wave
of storms /likely focused more to the southwest of the ILN CWA/
may impact areas along the Ohio River and points south later in
the night. While severe threats with this activity would be
less, there would still be ample low level shear in play,as
despite the more reduced instability by coming through at such a
late time of night.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Showers and a chance of thunderstorms will continue into Friday
morning, but should be tapering off from the northwest through late
morning and into the afternoon as the cold front moves southeast of
our area. In the developing CAA behind the front, highs on Friday
will range from the mid 50 northwest to the mid 60s in the
southeast. Surface high pressure will build briefly into the lower
Ohio and Tennessee Valleys Friday night into Saturday. This will
provide for drier conditions with highs on Saturday in the mid 50s
to lower 60s.

Mid level short wave energy, embedded in a broader upper level
trough, will drop down across the Great Lakes on Sunday, leading to
the potential for a few rain showers across our area. Temperatures
will continue to cool with highs on Sunday in the mid 40s to mid 50s.
A somewhat stronger secondary short wave will rotate through the
base of the trough and across the lower Great Lakes and upper Ohio
Valley on Monday. This will bring a chance for mainly snow showers
to the region as high on Monday will only be in the upper 30s to
lower 40s.

The upper level trough will shift off to the east and surface high
pressure will build into the region through mid week. This will lead
to drier conditions and slowly moderating temperatures. Highs on
Tuesday will be mostly in the 40s with highs on Wednesday in the
upper 40s to mid 50s.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
VFR conditions overnight will give way to more active weather
tomorrow.

Early tomorrow morning, some showers and thunderstorms may
affect KDAY/KILN/KCMH/KLCK. There remains a slight chance of
some showers at the Cincinnati airports as well, but too low to
include in the TAFs. Some brief MVFR conditions are possible
with these showers and storms.

After the early morning storms move off, dry conditions are
expected, with increasing SSW winds and gusts to around 25
knots. After that, there will be additional chances of
thunderstorms, beginning in the afternoon and continuing through
the evening and overnight. Confidence remains low in the
specific timing and location of these storms, but some of the
storms could be strong to severe, in addition to producing MVFR
to briefly IFR conditions. The forecast for VCSH and -SHRA VCTS
in the TAFs right now should be considered a very uncertain
prediction in terms of timing and impact, and this will need to
be refined in later forecasts. Despite this, prevailing
conditions (outside of storms) are expected to remain VFR
through the period, with chances for more widespread MVFR
ceilings and visibilities early Friday morning.

OUTLOOK...MVFR to IFR conditions are possible Friday morning.
Thunderstorms are also possible Thursday night into Friday.

&&

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

&&

$$
SYNOPSIS...Binau
NEAR TERM...Binau/Hatzos
SHORT TERM...Binau
LONG TERM...Binau/JGL
AVIATION...Hatzos


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