Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 220530
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
130 AM EDT Tue May 22 2018

.Forecast Update...
Issued at 940 PM EDT Mon May 21 2018

A few showers were able to ignite on the boundary north and east of
Louisville, but the main outflow passed right through SDF/LOU with
just a gusty wind shift. Now the storms from south KY earlier are
along a FTK to DVK line and are moving northeast. They still are
showing fairly vigorous updrafts, though the strongest wind gusts
we`ve seen today are in the 40 mph range with some smaller hail.

Still thinking several boundary mergers will focus shower activity
in the vicinity of the Ohio River overnight, so not expecting the
radar to totally clear out through the night.

Issued at 735 PM EDT Mon May 21 2018

Updated the forecast toward the hi-res models that are performing
well now. They indicate a new band developing from SDF northeast, in
the vicinity where a couple of outflow boundaries may be able to
intersect. These storms will not move much, and the effective
frontal boundary is expected to lay out along the Ohio River
overnight, providing a narrow focus for isolated to scattered
showers and storms through the night. Updated products are going out.

&&

.Short Term...(This evening through Tuesday)
Issued at 245 PM EDT Mon May 21 2018

...Strong Storms Possible this Evening...

An upper level shortwave approaching from the SW looks to move into
the Ohio Valley late this afternoon and initiate storms over our
area this evening.  While a few weak storms may develop over east
central KY late this afternoon, the main storm complex looks to
start over western KY/southwest IN/southern IL between 3-5pm and
move into our region west of I-65 between 5-7pm.  Efficient heating
has produced 1000-2000 j/kg of CAPE over our region with steep low
level lapse rates.  In addition, precipitable water values remain
high.  Although wind shear is not ideal, we should still have enough
combined with the previously mentioned ingredients to produce a few
strong storms this evening.  The main threats from these storms look
to be strong winds and heavy rainfall.  The best time frame for the
most widespread convection to move northeast through our area should
be between 6p-midnight.

Later this evening expect showers/storms to generally decrease in
coverage.  High-res models are in somewhat of a disagreement on if
some weaker convection may linger overnight across southern IN/north
central KY.  Did keep 20-30% POPs in after midnight through the
early morning hours. Lows tonight should range through the middle
60s.

Tomorrow we should see some lingering showers/storms as a cold front
slowly approaches the region.  Clouds early in the day should limit
instability and the better wind shear with the passing weather
system should remain displaced to our northeast.  Therefore, not
expecting any organized strong storms.  High temps should range
through the lower 80s.

.Long Term...(Tuesday night through Monday)
Issued at 305 PM EDT Mon May 21 2018

Tuesday Night...

A weak cold front will pass through the region Tue night bringing
one more round of showers/storms.  The better forcing looks to
remain to our northeast Tues night as the front pushes through and
instability could be limited due to day time clouds/convection.  At
this time, no organized storm threats look likely but can`t rule
out an isld strong cell with gusty winds/heavy rain Tues night.

Wednesday - Thursday...

Upper level ridging looks to slowly build over the region from the
west for the latter half of the work week providing a period of dry
weather. Wed will be slightly cooler behind the weak cold front with
highs in the upper 70s/lower 80s.  The coolest night looks to be Wed
night with lows in the upper 50s/lower 60s.

Friday - Monday...

By Friday though, we`ll see highs back into the upper 80s with upper
60s dewpts.  This weekend a weather system of tropical origin looks
to bring precipitation chances back into the Ohio Valley from the
south. While exact track/strength of this weather system are still
uncertain, most model solutions result in multiple rounds of
showers/storms for southern IN/central KY this weekend and into
early next week.  Stay tuned to coming forecasts as we refine timing
of precip and rainfall amounts.

&&

.Aviation...(06Z TAF Issuance)
Issued at 130 AM EDT Tue May 22 2018

Low pressure centered over Illinois early this morning will push
east and drag a cold front through the Ohio Valley this evening. As
we sit ahead of this front in warm, moist, unstable air, scattered
shower and thunderstorm development will be possible.

Will need to keep an eye on low level moisture manifesting itself in
low clouds or fog early this morning. HNB has the strongest signal
for low cloud formation, with the best chance for MVFR fog at BWG.

&&

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

$$

Update...RJS
Short Term...AMS
Long Term...AMS
Aviation...13



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