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FXUS63 KLMK 171605
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1205 PM EDT Tue Jun 17 2025

.KEY MESSAGES...

* Unsettled weather continues today with afternoon showers and
  thunderstorm chances. Localized swaths of heavy rainfall and flash
  flooding are possible.

* Chances for severe weather are increasing for later in the day on
  Wednesday as a cold front approaches the region. As of now, the
  best chances for severe weather in our area are across southern
  Indiana and north-central Kentucky.

* Hot and dry weather arrives next weekend.

&&

.UPDATE...
Issued at 1204 PM EDT Tue Jun 17 2025

Warm and humid air mass with PWATs around 2 inches remains in place
over the Ohio Valley. Convective temps are just now being reached,
so expect to see scattered showers and a few T-storms blossom over
the next couple of hrs. Weak lapse rates will limit SVR potential,
but the main concern will again be excessive rainfall where storms
manage to train. Confidence is still too low to headline a Flood
Watch, but it would not be surprising to see a Flash Flood Warning
or two this afternoon.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 334 AM EDT Tue Jun 17 2025

It is a mild and humid morning, with a weakening frontal boundary
across the area, and sfc temps in the lower 70s and dewpoints in the
upper 60s and lower 70s. Convective activity has entirely
diminished, leaving just some light rainfall across the CWA. With
this much low level moisture lingering, expect a mix of very low
stratus and patchy fog through much of the morning hours as the
inverted sfc trough continues to sit across the area.

Cloud cover is expected to persist for majority of the day, which
will help limit sfc heating to an extent. However, moisture
transport will remain favorable for a humid airmass across the
region, leading to higher PWATs and dewpoints. A mid-level shortwave
will be pivoting over the lower Ohio/Tennessee Valleys today, which
will provide forcing for additional shower and storm activity today.
Temps are expected to reach the lower 80s, which is slightly below
normal for this time of year. However, despite the expected cloud
cover, breezy southerly flow will allow for a WAA regime, and humid
dewpoints in the lower 70s will help us destabilize to around 1500
J/kg of SBCAPE this afternoon. HREF places a 50% prob of exceeding
this CAPE threshold today. There is good agreement among model
guidance for scattered showers and storms to blossom across the
entire forecast area this afternoon during peak daytime heating.
However, model soundings do suggest weak shear combined with tall
and skinny CAPE profiles, so do expect most convection to be messy
and unorganized. Meager lapse rates will be the main inhibiting
factor for overall severe potential, which SPC has kept us in a
general thunder risk for today.

PWATs near 2 inches this afternoon will support heavy downpours, and
quite possibly some nuisance flooding again today. Best chance for
slightly higher rainfall amounts today would be in the Bluegrass,
but overall convection should be quite scattered, and this area
missed out on the bulk of heavy rain from yesterday. Given the
widespread scattered nature of storms today, generally like the WPC
marginal risk for excessive rainfall across the entire area, and not
confident enough in one area having more flooding issues than
another. Due to this, opted not to join the Flood Watch in our east,
but the door is still open if we decide we need one later on today.

Shower and storm activity will decrease in coverage by this evening
as daytime heating is lost, though we may have some precip linger
east of I-65 tonight as the shortwave shifts to the east. It will be
another mild and humid night, with temps expected to be in the low
70s overnight. A mix of low stratus clouds and fog will be possible
again tonight.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 334 AM EDT Tue Jun 17 2025

===== Wednesday through Thursday Night =====

An amplified upper shortwave will be progressing from the central
Plains to the Great Lakes, trailing a cold front boundary
southwestward through the Midwest. Most of Wednesday is expected to
be dry, with deep southwest flow promoting stronger WAA across the
area. Sfc temps are expected to reach the upper 80s. The very humid
airmass will still have a hold on our region, with sfc dewpoints on
Wednesday forecast to reach the mid 70s. This will compute to heat
indices in the mid 90s in the afternoon. Under these conditions, our
environment will become strongly unstable ahead of an approaching
cold front. With out much of a trigger during the day, not expecting
much more than an isolated chance for a shower or storm.

Clusters of storms are expected to develop across portions of
Missouri and Illinois by the afternoon hours, and congeal into a line
along the front as it progresses eastward. Low level jetting ahead
of the front will enhance the low level wind shear parameters, with
some model guidance suggest 0-1km shear values over 30kts, and 0-1
SRH over 200 m2/s2. Timing the arrival of the line remains a bit
uncertain, but confidence is increasing for an evening into late
night round of severe weather. SPC Day 2 outlook has the Slight risk
basically from BWG to LEX, with the Enhanced risk located just to
our northwest. A later time of arrival would favor a less severe
threat due to diminishing CAPE. The Colorado State ML severe weather
forecasts draw a 30-45% prob for svr wind across IL and IN, just
north of the Ohio River. A 2% tor risk is also present given the low
level shear/helicity values, but a 5% risk is just to our northwest.
The area of greatest concern is covered well in the Slight Risk,
with lesser confidence the further east and south you go.

Precip will linger into Thursday morning as the upper shortwave axis
takes time to pivot through the region. Eventually dry weather is
expected later in the day on Thursday. Clouds will also linger for
most of the day, due to the upper shortwave axis, but should begin
to see improvements to our sky cover by the late afternoon and
evenings.


===== Friday through Sunday =====

A mid and upper level ridge is forecast to strengthen considerably
over the eastern US this weekend, while a deep trough descends over
the West Coast. A trend toward hot and dry weather is expected for
Kentucky and southern Indiana. Temperatures should warm a little bit
each day, with highs between 84-89 on Friday and 89-95 by Sunday. At
least upper 80s and low 90s are likely over the weekend.

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 709 AM EDT Tue Jun 17 2025

A mix of MVFR and IFR cigs this morning are expected to gradually
improve throughout the day. Besides a few isolated showers across
the region this morning, precip will increase in coverage and
intensity by the afternoon, with -TSRA possible at all terminals for
several hours. By this evening, conditions should be drier, though
cigs will begin to build again. MVFR and IFR cigs are expected
across the region for tomorrow morning.

&&

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

&&

$$

UPDATE...RAS
SHORT TERM...CJP
LONG TERM...CJP
AVIATION...CJP