988
FXUS63 KLMK 291649
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1249 PM EDT Mon Apr 29 2024

.KEY MESSAGES...

*   Showers and scattered thunderstorms will be possible late this
    afternoon and into the evening and overnight period.  Gusty
    winds and heavy rainfall will be the main threats with this
    activity.

*   Additional showers and thunderstorms possible late in the week,
    though confidence in exact timing remains low.

&&

.UPDATE...
Issued at 958 AM EDT Mon Apr 29 2024

Main update to the forecast this morning was to slow the arrival of
precipitation to the region. Current radar/satellite analysis show
scattered showers across portions of central IN into southern IL and
southeastern MO ahead of a weak cold front. This activity will
gradually drift eastward today and we should see some additional
redevelopment by afternoon. Rest of forecast is on track.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 332 AM EDT Mon Apr 29 2024

Early morning satellite imagery and observations reveal mostly clear
skies across much of central and eastern Kentucky.  Some high level
cirrus was starting to invade western KY ahead of a line of storms
out near the St. Louis area.  Temperatures across the area were
generally in the low-mid 60s.  A few of our typical radiational
cooling spots (mainly valley locations) were down in the mid 50s.
For the remainder of the overnight period, dry weather is expected
with a gradual increase in upper level cloud cover coming in from
the west.  Convective line out near St. Louis will continue to move
eastward and gradually weaken as it moves toward the IL/IN border
region toward sunrise.

For today, an upper level trough axis over the Plains which has been
responsible for the wave of severe weather out that way will move
northeastward into the Great Lakes.  As this occurs, the flow
pattern aloft will deamplify a bit while a surface cold front pushes
through the Ohio Valley.  With the deamplification of the pattern,
synoptic scale forcing will become weaker with increasing time.
Ongoing convection out to our west is forecast to weaken as it move
eastward this morning.  However, we may see some convective outflows
that may generate some weak convection over southern IN as early as
lunchtime or shortly thereafter.  Much of the day looks to be dry
across central KY, though convection is likely to increase in
coverage by late afternoon in areas west of I-65.  Highs on the day
will range from the upper 70s to around 80 west of I-65, with
readings mainly in the lower 80s east of I-65.  Toward evening, we
should see scattered convection move into SW IN and western KY and
impinging into our western CWA.  Model soundings do show somewhat
steep low-level lapse rates with about 300-800 J/kg of MLCAPE
available.  The wind profile remains uni-directional with less than
30kts of bulk shear.  Multi-cellular convection and perhaps some
small linear segments look likely by late evening.  Overall severe
threat looks to be quite low given the limited shear/instability.
However, a few storms may produce some small hail and gusty winds
within the strongest cores.

For tonight, convection should be in progress this evening, mainly
west of the I-65 corridor.  This convection will spread eastward
through the I-65 corridor during the evening and into areas east of
I-65 overnight.  The storms this evening may be strong in spots with
gusty winds and small hail being the main threats.  As we get into
the mid-late evening and overnight, instability will fall off and
storms will weaken.  PWAT values will be above an inch in many spots
tonight, so periods of heavy rainfall will be possible as this
activity moves east overnight.  Total rainfall amounts for today and
tonight will be 0.75-1.50 inches with some isolated higher amounts
in spots that see repeated rainfall.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 332 AM EDT Mon Apr 29 2024

An upper level shortwave trough and weak sfc low are forecast to be
over central Kentucky Tuesday morning. This weak sfc reflection will
ride northeast along a cold front passing through the region.
Showery weather will be ongoing Tuesday morning, mainly east of I-
65. Any convective activity will be much weaker by this point, so
rainfall totals will be much lower than from Monday night
convection. Isolated embedded storms will still be possible into
early Tuesday afternoon, mainly from the southern Bluegrass Region
south into the Lake Cumberland region. Rain chances will taper off
from west to east during the day as drier air filters in behind the
cold front. Shortwave ridging builds in from the west Tuesday
afternoon and evening in the wake of the departing wave. Clouds are
forecast to clear out from west to east during this time frame.
Tuesday highs will be in the 70s, with low/mid 70s more likely in
the Bluegrass Region and mid/upper 70s along and west of I-65.

Ridging amplifies over the Southeast and Ohio Valley Tuesday night
through Thursday, and confidence continues to increase in a period
of dry, warm weather. Low to mid 80s will be common for highs
Wednesday afternoon. Temperatures are likely to soar into the mid to
upper 80s Thursday afternoon.

As upper level ridging amplifies over eastern portions of the
country heading into Thursday, a notable trough is forecast to swing
from the Rockies across the northern and central Plains. In the
lower levels, low pressure develops quickly northeastward from the
Plains to Upper Midwest. Meridional flow will help keep an axis of
deeper moisture and unstable air off to our west in the Plains and
MS Valley through Thursday. However, that changes Thursday night
into Friday as the low pressure system drags a cold front toward the
Lower Ohio Valley. Showers and thunderstorm chances are maximized
Friday into Friday night along and just ahead of the cold front.
While confidence in timing has increased a bit, forecast confidence
remains low on rainfall amounts and the strength of potential
convection/severe risk.

Rainfall chances decrease behind the cold front, but low rain
chances linger into the weekend due to increased model spread and
timing differences. 70% of ensemble members are dry by Saturday
afternoon. Current thinking is optimistic the drier trend continues
for Saturday, but model spread should narrow (thus increasing
forecast confidence) quite a bit over the next 48 hours.

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1247 PM EDT Mon Apr 29 2024

Well...flying conditions will be changing by this evening, first
for HNB, then SDF and BWG, and late this evening for LEX and
RGA.

For this afternoon...high based cu and breezy ssw winds of 15 to 20
mph with gusts to 28 kts. Diurnal heating and WAA pattern will
bring isolated shra/tsra in 20-22z range for HNB while all other
sites should be dry.

The overnight weakening ling of convection out by MS River is slowly
reinvigorating.  This is associated with a cold front and will be
the main focus for this evening and tonight. Storms do not have
enough instability or shear to become strong, but follow normal TS
avoidance procedures.

Will continue to mention VCTS at KSDF & KBWG after 22Z. Majority of
CAMs bring best thunder chances at 2330z to 0130z. LEX and RGA best
opportunity for TS chances are in the 02z and 04z timeframe.

Large stratiform precip shield along and behind the actual cold
front will keep mvfr cigs and mvfr to vfr vsbys for 6-9 hrs or
so. Some of the guidance bring cigs close to IFR (800-1200ft
overnight). Precip will continue at LEX and RGA in the morning.

Wind shifts for HNB around 09z, SDF/BWG around 12z, and LEX and RGA
14-15z. Wind gradient behind the front is nearly non existent and
will just keep WNW winds of 7-12 mph for Tue.

Llvl clouds will lift out of HNB by 16z and SDF and BWG 16-18z Tue
and into mid afternoon for LEX/RGA.

&&

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

&&

$$

UPDATE...DM
SHORT TERM...MJ
LONG TERM...EBW
AVIATION...JDG