271
FXUS63 KLMK 011750
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
150 PM EDT Wed May 1 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Dry and warm today and Thursday with highs in the 80s. A few
    locations could touch 90 degrees Thursday.

*   Widespread showers and scattered thunderstorms on Friday, with
    brief heavy rain and lightning.

*   Rain chances linger into Saturday, but forecast confidence
    remains low at this time.

&&

.UPDATE...
Issued at 1036 AM EDT Wed May 1 2024

Skies are mostly clear over southern Indianan and central Kentucky,
but ahead of a weak cold front to our northwest, a few isolated
sprinkles remain. This light precipitation will continue to
dissipate, but a sprinkle or two could make it into southwest
Indiana. In an otherwise sunny day, southerly winds will help drive
highs into the low to mid 80s. The forecast remains on track with
only minor tweaks as needed.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 312 AM EDT Wed May 1 2024

The weather is quiet early this morning with very light to calm
winds and partly cloudy to mostly clear skies. Separate areas of
convection continue in portions of IL and MO/OK, but we will only
see thin cirrus spread overhead from the west. Temperatures range
through the 50s, except in Louisville`s urban heat island. Fog
development has been limited thus far and confined to eastern KY.
However, we are now seeing valley fog develop in the Bluegrass and
Lake Cumberland regions. Will keep an eye on those eastern counties -
 may need to consider a SPS for patchy dense fog south of the BG
Parkway and perhaps east of a Glasgow to Lawrenceburg line.

The low pressure system currently over the Upper Midwest will
continue to lift northeast today across Lake Superior and southern
ON. Meanwhile, upper level ridging will gradually amplify over the
Southeast and Ohio Valley. The northern stream wave`s weakening cold
front will sink toward the Lower Ohio Valley this evening.
Southwesterly sfc winds will increase to 5-10 mph today to the south
of the sfc boundary. Moisture does pool along the boundary, with
precipitable water rising to 1.0-1.2 inches. HREF mean SBCAPE is
around 1500 J/kg around 21-00Z across southern IN and portions of
central KY. However, lift provided by the increasingly diffuse sfc
boundary is very weak. Most CAMs suggest little to no convection, so
will cap PoPs around 10%. Expect a cumulus field to develop for the
second half of the day, along with continued thin cirrus floating
overhead. Overall, a nice warm Spring day with afternoon highs in
the low to mid 80s.

A sfc ridge of high pressure will extend along the Appalachians
tonight, and we`ll see diminished cloud cover and light
southeasterly flow. Expect a mild, quiet night with lows in the
upper 50s to lower 60s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 312 AM EDT Wed May 1 2024

========== Long Term Overview ==========

Low-amplitude western trof/eastern ridge pattern aloft on Thursday
will further flatten out heading into the weekend. Progressive zonal
flow tends to feature disturbances that are difficult to time, so
forecast confidence is limited especially over the weekend.

High confidence in hot temperatures (by early May standards) on
Thursday and rain on Friday, with much lower confidence regarding
rain chances on Saturday. Unsettled weather pattern continues Sunday
into the first half of next week. Look for daily rain chances and
temps above normal for this time of year.

========== Heat Potential for Thursday ==========

Unseasonably warm temps are expected on Thursday with deep southerly
flow, but the question is just how hot we get and how much of a
player the humidity will become. Look for temps at least in the
mid/upper 80s throughout central Kentucky and southern Indiana, and
some locations could still easily touch 90F given that roughly half
the NBM ensemble members show highs AOA 90, especially for the urban
heat islands. Dewpoints in the upper 50s or lower 60s will not push
heat indices above the actual temp, but will be just enough to feel
"muggy."

Experimental HeatRisk for the 24-hr period still shows minor
impacts, but the max temps are solidly into the territory where a
large, vulnerable outdoor population would be impacted. If you`re
planning to spend substantial time outdoors on Thursday, be sure to
practice heat safety be staying properly hydrated and taking breaks
indoors if possible.

========== Thunder Potential for Friday ==========

Widespread showers and a few thunderstorms are expected on Friday as
an upper wave lifts ENE into the Great Lakes and pushes a weak cold
front into the Ohio Valley. Plenty of moisture available and enough
instability to support scattered thunderstorms, the wind fields are
too weak to support severe convection. Rainfall rates could be
briefly heavy, but it`s not a continuous, all-day rain. The rain
chance for the day is roughly 80 percent, but thunder chances will
peak around 40 percent in the late afternoon and evening.

Cold front is expected to pass through Friday night or early
Saturday morning, resulting in lower PoPs as we get into the
weekend. Confidence in the details beyond Friday night is low, as it
depends on where the front hangs up.

========== Uncertainty for Saturday ==========

Ensemble forecasts continue to be a crapshoot with roughly half the
ensemble members still kicking out measurable precip near
Louisville, with higher POPs to the south and east and lower POPs to
the west and northwest. The operational GFS and ECMWF are in
surprisingly good agreement in hanging the front up between
Louisville and Bowling Green, and trying to wave it back to the
north later on Saturday. Given the subtle nature of the upper wave
forcing it, will take this solution with a grain of salt and stay
close to the NBM for now. That will run our precip chances near 40%
anytime Saturday, with about a 20% chance for thunder. It may take a
few forecast cycles before this comes into any clearer focus, so
stay tuned.

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 149 PM EDT Wed May 1 2024

VFR conditions are expected through the TAF period, but there is a
small chance that HNB could be impacted by an isolated thunderstorm
later this evening into the early overnight period along a west to
east oriented cold front draped through southern Indiana. For all
locations, winds will remain light but will back from the southwest
towards the southeast early tonight.

&&

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

&&

$$

UPDATE...KDW
SHORT TERM...EBW
LONG TERM...RAS
AVIATION...KDW