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000
FXUS63 KLMK 060702
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
302 AM EDT Thu May 6 2021

.Short Term...(Today and tonight)
Issued at 301 AM EDT Thu May 6 2021

Latest surface analysis shows high pressure across the OH Valley
with lower pressure and a wavy stationary boundary across
NE/KS/IA/MO. Satellite shows mostly clear skies across the region
with some river valley fog becoming apparent. Fog will likely remain
confined to the river valleys and burn off quickly after sunrise.
Expect increasing high and mid cloud as a 5H shortwave swings around
the base of a persistent closed low over southern Hudson Bay.
Surface winds will turn to southerly later this morning into the
afternoon helping to push afternoon max temps into the mid to upper
60s.

Showers will begin to move into our NW counties by early evening and
spread eastward across the CWA through midnight. Instability is
greatest in the early evening hours with highest CAPE values noted
west of the I-65 corridor. As a result, could see some thunderstorms
reach into our area. Shear is weak and CAPE profiles are tall and
skinny, so not expecting anything severe. But with WBZ heights
around 5-6kft, wouldn`t be surprised to see pea size hail within the
strongest storms. Otherwise, expecting showers with moderate to
heavy rain at times pushing through the area and dropping a tenth to
a quarter of an inch of rainfall with the highest accumulations west
of I-65. Clearing will follow with mostly clear skies for most by
sunrise. Expect min temps Friday morning in the low 40s.

&&

.Long Term...(Friday through Wednesday)
Issued at 300 AM EDT Thu May 6 2021

Friday - Friday Night...

Friday starts out dry and mostly clear with NW flow aloft over our
region. Steady cold advection on gusty NW surface winds will keep
temperatures confined to the low to mid 60s, despite plenty of
sunshine. By afternoon, forecast soundings show very steep low level
lapse rates with deep mixing allowing for gusts in the 20-25 knot
range. A shortwave embedded in the NW flow aloft will drop out of
the Great Lakes region, and will likely provide enough forcing for
some isolated to widely scattered convective showers (and perhaps a
few rumbles of thunder) later in the afternoon and evening. Given
the steep low to mid level lapse rates, and some notable positive
area above the freezing level would expect some small hail and gusty
winds with any stronger shower or storm. In fact, wouldn`t be
surprised if some of the showers get quite gusty given the higher
momentum air aloft and dry low levels of the thermal column. For
now, continue to have the pops confined to the Bluegrass region, and
mainly dry west of I-65.

Expect we`ll clear out Friday night in the wake of the departing
shortwave. Winds are expected to slacken, and this could create
favorable radiational cooling for some pretty chilly temperatures by
Saturday morning. In fact, we have some upper 30s in our far NE CWA.
Could a few spots see some frost? Farther west, look for low to mid
40s for lows.

Saturday - Sunday Night...

The main focus in the long term continues to be for the weekend time
frame as a surface low ejects out of the Great Plains on Saturday,
into the mid Mississippi River Valley on Sunday, and then through
the Ohio River Valley on Sunday night. On Saturday, expect a warm
frontal zone to begin to develop over our area, and slowly lift
north. Some light precipitation is possible with the isentropic lift
component, although details are still a bit uncertain on exactly
where the main focus will be. In general, the best chance for rain
on Saturday is expected to be across our west earlier in the day,
and across our north by later Saturday into Saturday night. Saturday
highs are expected to be well below normal in the low 60s with the
frontal zone over our area. However, by Sunday a warm sector is
expected to become established at least across the southern half our
CWA where some low 70s are anticipated. Farther north along the warm
front, look for low to mid 60s and better rain chances. The south
looks to be drier.

The most widespread rainfall looks to occur later Sunday into Sunday
night as the surface low moves through our region, and drags a
trailing cold front through with it. You never like to see the
triple point of a notable surface low moving through your area in
early to mid May as that will bring the question of strong to severe
storms on the table. At this time, instability looks to be fairly
meager across our central and north CWA, and could be the limiting
factor despite shear profiles that would otherwise be quite
favorable. Do think some instability will at least get into our
southern CWA where some strong to severe storms can`t be ruled out
later Sunday into Sunday night. Given looping hodographs, some
rotating storms would be on the table if convection becomes robust
enough. Something to watch.

The bigger concern at the moment will be how much rainfall we get?
The northern CWA is currently forecast to get amounts closer to the
2 to 3 inch range, with southern KY more in the 1 to 2 inch range.
The good news in this is that at least areas that saw the recent
heavy rain aren`t projected to get as much. Overall, feel we can
handle a good chunk of this rainfall, but some minor flooding issues
may arise, and any lingering elevated river levels may be
aggravated.

Monday - Wednesday...

We should be quickly drying out on Monday as the shortwave trough
axis and trailing cold front sweep east of the area. Fairly benign
zonal flow should then hold through Tuesday, keeping a dry forecast
with temps still below normal in the mid to upper 60s. Confidence is
pretty low by Wednesday, but another system could move into our
general region by then, so will be carrying some precipitation
chances for that period.

&&

.Aviation...(06Z TAF Issuance)
Issued at 140 AM EDT Thu May 6 2021

IMPACTS: VFR conditions through 21z Thursday. A chance for
thunderstorms beginning 21z at HNB followed by SDF and BWG.

DISCUSSION: Current satellite shows mostly clear skies across the
region with only a few high clouds streaming across HNB and SDF.
Expect VFR conditions to continue through most of the day Thursday
before a low pressure system swinging through central IL/IN/OH
brings showers and a chance of thunderstorms to HNB, SDF, and BWG in
the evening. MVFR CIGs will likely fill in behind the cold front for
a few hours late Thursday night into the early morning hours Friday
before clearing occurs and VFR conditions resume.

Confidence: Medium confidence of thunderstorm occurrence. High
confidence on all other forecast elements.

&&

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

$$

Short Term...CG
Long Term...BJS
Aviation...CG