717
FXUS63 KLMK 130712
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
312 AM EDT Mon May 13 2024

.KEY MESSAGES...

*   Active pattern with 2 storm systems bringing chances of showers
    and storms through Saturday. Best chance for a dry day will be
    Wednesday afternoon and Thursday. Severe weather is not expected.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 312 AM EDT Mon May 13 2024

This morning, satellite imagery shows lots of cirrus arching over
the Lower Ohio Valley as it rides around an upper ridge, but it`s an
upper low embedded in a little trough over western Kansas that is of
interest. Zonal flow will keep pushing this upper low east towards
Indiana, and as this happens, its corresponding surface low will
strengthen and increase pressure gradients between it and the
surface high off the Atlantic Coast. This will help generate
southerly winds from the Gulf of Mexico north through the CWA as it
transports moisture into the region, and as the low pressure system
inches towards the Ozarks this evening, ceilings will steadily fall
throughout the day as precipitation chances begin increasing across
central kentucky and southern Indiana. Models continue to show that
the environment over the CWA will lack instability and shear, so
severe weather isn`t expected. Even as precipitable water values
increase to around 1.25", model soundings show some dry air near the
surface this evening. This could help to delay/limit showers, so
expect isolated to scattered showers with dry periods through the
afternoon and evening hours. Most in the area should see a few
hundredths of an inch or less. High temperatures are expected to
make it into the 70s at most sites. A few low 80s might be reached
in southern Indiana and northern Kentucky.

Tonight, as the the surface low cuts across Missouri and enters
southern Illinois, ceilings will continue to fall across the CWA.
Rain showers are expected to continue being scattered in nature, but
as the low nears the CWA later in the night, an axis of higher
PWATs, around 1.5", will likely help make showers more widespread.
Instability and shear continue to be weak, so a rumble or two of
thunder will be possible but not expecting anything severe. Cloud
cover will limit low temperatures to the upper 50s to low 60s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 312 AM EDT Mon May 13 2024

Tuesday - Wednesday...

Well...a very slow meandering closed low pressure will go from Show
Me State and eventually thru the Ohio Valley. This low will pass
thru the LMK CWA with plenty of deep lift and moisture. Time
sections show deep tropospheric moisture along with omega fields and
deep layer isentropic lift.  This portends a rainy day (hyetal
pattern).

Moisture/clouds will keep instability in check and deep-layer shear
will remain weak, so expecting no severe weather. However...thin
long CAPE, PWATS of 1.4" and WBZ around 10K bring a few shra/tsra
with graupel and some 30-40 mph gusty showers. Rainfall amounts of
0.60-1" inch are possible through Wednesday, with some locally
convectively-enhanced totals not out of the question. With a wet
ground and streams above normal flow...might result in some ponding
and minor flooding issues in low-lying or flood-prone areas.

Rain chances linger into Wednesday with moiFeel confident the later
in the day there will be isentropic lift and rain, but first part of
the day is not clear yet. sture wrapping around the slow-moving
system, with Bluegrass stuck in low clouds and sct shra. Meanwhile
clouds will be trying to thin and clear out from the the west
heading towards I 65 corridor.

Area west of I 65 should see some later afternoon peaks of sun and
perhaps some crepuscular rays. Areas of east of I 65 and especially
east of US 127 will be stuck in the clouds til sunset. Temps west of
I 65 should see mid 70s. Towards the Bluegrass region, soundings and
time sections show 850 moisture stuck in east of I 65,
consequently temps might struggle to get to 70F.

Wednesday night - Thursday Night...

Shortwave ridging building east over the Ohio Valley will bring dry
weather Wednesday night through Thursday. Look for mostly clear to
partly cloudy skies with lows in the 50s and highs in the upper 70s
to low 80s. Behind this front and with the transitory high pressure
with winds switching from northerly 5-10 mph to the south 5-10 mph
during the afternoon.

Friday...

Two pieces of energy, a distinct southern stream over ARLATX and one
from Great Lakes with cold front into MO/IL.  Will they phase or be
separate will determine Fri.  The GFS combines them and the ECM does
not. Deterministic GFS shows an all day rain but there is quite a
spread in GFS ensemble data.  WRT the northern stream the ECM has
the low at 18z Fri w over Lake Winnipeg with trough across E ND/E SD
to Lincoln NE. The GFS is much further east over Gitchee Gumee to N
IL.

Friday night and Saturday...

A cold front will be taking over Friday night with what should be
plenty of lift and abundant moisture. Some thunderstorms will be
possible, with marginal instability for convection. Another 0.50-1
inch is possible with this wave.

Major differences in GFS and ECM (old 12Z) for Sat with ECM showing
closed low over Ohio Valley and IL/OH, and GFS showing hints of
ridging moving in.  Now I see why NBM has sct precip for this
coming weekend.  The 12z ECM would result in cloudy, intermittent
rain and temps well blo normal. The new ECM has sped things up and
will opine, still significant differences in the data.

Weather Factoid...

May 14 1995...Widespread severe weather event. Fort Knox gusted to
104 mph...baseball hail caused 5 million in Marion County, Bullitt
County F2 downed trees, Franklin County tornado touched down near
Frankfort, and in Nelson County, house struck and destroyed by
lightning, and 17 year old boy was struck and injured by lightning.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 147 AM EDT Mon May 13 2024

VFR conditions are expect through 21z, but as a low pressure system
approaches from the west, ceilings will begin lowering into MVFR
levels at BWG. Then, HNB an hour or two later. This trend will
continue east across southern Indiana and central Kentucky. Around
0z Tuesday, IFR ceilings will begin working in from the west, near
HNB. As these ceilings lower, rain chances will begin increasing.
Widespread coverage currently isn`t expected until closer to Tuesday
morning.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...KDW
LONG TERM...JDG
AVIATION...KDW