477
FXUS61 KILN 050505
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
105 AM EDT Sun May 5 2024

.SYNOPSIS...
A warm and moist airmass will remain in place across the region
into the middle part of next week, leading to occasional
periods of showers and thunderstorms into Thursday. Slightly
cooler and drier air will return by the end of the week,
although rain chances may persist at times into next weekend.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
In a very moist air mass, a broad and nebulous region of ascent
ahead of a shortwave has led to continuous shower and
thunderstorm development this evening. As the atmosphere is now
a bit more worked over, and diurnal heating has diminished,
there has been a gradual downward trend in both coverage and
intensity of storms. These storms earlier this evening were in a
regime of weak flow, with propagative effects contributing
significantly to their motion, and some storms seemingly
anchoring to previous outflow boundaries or other small-scale
features. Though isolated, some areas received as much as 3-4
inches of rainfall, with very close to 5 inches in southern
Highland County OH.

With PoPs diminishing overnight, one additional concern is fog
potential. Conditions remain moist and stagnant, and fog is
likely to form, especially in areas that received rainfall. Have
added patchy fog to the grids for all locations, but definitely
see some possibility of a few spots having more significant
reductions in visibility.

Previous discussion >
A very weak/broad LL low center (perhaps a remnant MCV)
continues to drift to the NNE through the ILN FA, providing a
focus for renewed convective development this afternoon amidst
an uncapped environment. This feature remains evident on both
radar and satellite loops, with the center migrating NNE
through the Miami Valley as of early this afternoon. SHRA/TSRA
continue to develop and move about this "circulation," moving
in various directions in response to the weak cyclonic flow.

Activity remains incredibly disorganized, owing to an anomalously-
meager flow regime that remains entrenched across the region,
with little more than 10kts through the lowest 15kft of the
profile as sampled on the 04.12z KILN RAOB. This being said,
SBCAPE on the order of about 1000J/kg has developed (with no
cap) in parts of the area, according to the latest
mesoanalysis, allowing for the development of numerous updrafts.
But with the incredibly weak shear in place, there are
questions about just how strong the updrafts will be able to
get, suggesting that the severe potential still remains quite
low. In fact, the greatest concern (albeit still relatively
low), seems to be the potential for brief heavy downpours
leading to ponding of water in isolated instances. But such an
occurrence should remain relatively spotty in nature (despite
the widespread coverage of activity), owing to lack of
clustering/backbuilding. The activity may attempt to organize
more into clusters as we progress into early evening, especially
for central/south-central OH, but the severe and flooding
potential should still be minimal.

It is not out of the realm of possibilities to see a few funnels
develop this afternoon given the setup of an incredibly moist BL
(low LCLs) amidst very subtle stretching along the boundary and
directional shear in the lowest part of the profile (augmented
somewhat by the MCV). Similar to Friday, this is not an
environment that supports severe weather or tornadoes/damage,
but the prospect of a few funnels developing beneath the
strongest updrafts is non- zero this afternoon/evening, so it is
mentioned here for awareness purposes.

As we progress later into the evening, coverage of SHRA/TSRA
should decrease from W to E past sunset, perhaps lingering for
several hours closer to midnight in parts of central OH.
Although a few spotty SHRA courtesy of a decaying cluster moving
in from the W will be possible in SE/EC IN between about
04z-08z, do think that most spots locally remain dry for the
overnight.

With a few peeks of sunshine emerging this afternoon, temps are
responding in the wake of early day convection for parts of the
area. In fact, temps have rebounded into the mid 70s for many
spots, with slightly cooler temps residing in the Tri- State
where clouds have persisted the longest. The environment,
however, remains incredibly humid, especially by early May
standards, with sfc DPs generally in the lower/mid 60s. This
will remain the case through tonight, inhibiting lows from
dipping too much.

Past midnight, there are some indications for fog development if
skies can remain sufficiently clear. But the prospect of the
development of some stratus may hinder fog development beyond
just patchy in nature (particularly in areas that receive(d)
appreciable rainfall today). Nevertheless, brief/patchy VSBY
reductions may be an item to contend with if traveling late this
evening/tonight, especially if brief clearing is able to
develop.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
More unsettled weather is on tap for Sunday, although not as
much so as has been the case yesterday or today. In fact,
guidance has trended slightly drier with the FROPA during the
afternoon, with the greatest chance for a few ISO/SCT storms in
the afternoon residing E of I-71 in parts of central/south-
central OH. Coverage should remain SCT at best locally, with
indications for a /slightly/ faster progression of the front
into/through the local area. In fact, the front should be near
I-71 into early afternoon, with locales further N/W in the
post-frontal environment during peak diurnal heating. This
should translate to /mainly/ dry conditions N/W of I-71 on
Sunday, with some much-welcome drier air /briefly/ building into
the area from the NW Sunday evening/night.

It will be an unseasonably warm day Sunday ahead of the front,
with highs topping out in the lower 80s in the lower Scioto
Valley, N KY, and central and SW OH, with mid 70s back to the W
in WC OH and EC IN. Winds will shift to out of the WNW behind
the front, allowing for sfc DPs in the mid 60s to slowly dip
into the mid 50s by the evening. Guidance has trended slightly
more aggressive with the infiltration of drier air Sunday
evening/night, moreso than is being currently depicted by the
blend. Would not be surprised at all to see DPs in the lower 50s
reach near the OH Rvr by late Sunday night as midlevel S/W
approaches from the SW toward daybreak Monday. This will allow
for renewed pcpn chances very early Monday morning in SE IN and
N KY as lows dip into the mid 50s near/N of I-70 to lower 60s
near/S of the OH Rvr.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
This period will feature unsettled weather thanks to disturbances
containing plentiful moisture on a persistent southwest flow aloft.

The first mid level short wave due to arrive on Monday will
interact with a warm front, producing the likelihood for showers and
thunderstorms, mainly over the southern half of the ILN area. Two
potent surface lows will bring the categorical threat for showers
and thunderstorms Tuesday and Wednesday, with stronger winds
enhancing storm strength and structure, resulting in a chance for
severe thunderstorms each day. A few additional disturbances will
provide chances for showers and thunderstorms Thursday through
Saturday. Heavy rain will be possible through the period as well,
thanks in part to precipitable water values remaining above an
inch.

Temperatures will stay above normal through most of the period,
before falling below normal next weekend under an decreasing
geopotential heights and a northwesterly low level flow.
Highs are forecast to range from the upper 60s to mid 70s Monday,
rising to the low 80s by Wednesday, before falling to the mid 60s to
low 70s on Friday. All locations may be limited to the 60s on
Saturday.

&&

.AVIATION /05Z SUNDAY THROUGH THURSDAY/...
Showers and thunderstorms likely will continue to diminish in
coverage early this morning despite the brief surge in activity in
the past hour. Otherwise, stagnant and moist conditions have
been left in the wake of earlier convection which could result
in BR forming later tonight before sunrise. MVFR ceilings are
also forecast to develop later tonight thanks to abundant low
level moisture ahead of an approaching front. Although BR should
mix out shortly after sunrise, MVFR ceilings may linger until
around 1800z before scattering and lifting. After 1800z, VFR
ceilings are expected and the best chances for showers/storms
are limited to the Columbus sites during the afternoon. MVFR
conditions may redevelop after 0600z Monday.

Winds remain light and variable across the sites tonight. Westerly
winds increase to around 10 knots after 1200z with a front moving
through the area. Winds are expected to take on more of a northerly
component after 0000z behind the front.

OUTLOOK...Thunderstorms are possible at times each day through
Thursday. MVFR conditions are possible Monday morning and
Tuesday morning.

&&

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

&&

$$
SYNOPSIS...KC
NEAR TERM...KC/Hatzos
SHORT TERM...KC
LONG TERM...Coniglio
AVIATION...Campbell