Area Forecast Discussion
Issued by NWS Louisville, KY

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913
FXUS63 KLMK 211944 AAA
AFDLMK

Area Forecast Discussion...UPDATED
National Weather Service Louisville KY
344 PM EDT Mon May 21 2018

...Updated Long Term Discussion...

.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...(18Z TAF Issuance)
Issued at 210 PM EDT Mon May 21 2018

Well...low level lapse rates are increasing and there is increasing
instability with MUCAPES climbing to 1500 j/kg. We are for storms to
develop between 19-20z around S KY and then increase in areal
coverage and move towards SDF 22-01z and to LEX 23-03z. Will mention
VCTS and CB across the board starting early in the afternoon, with
the potential for a direct impact on SDF and LEX in the 00z time
frame.

These storms will be efficient rain makers and contain some gusty
winds and plenty of lightning. Pilots should be prepared for
deviations around buildups late this afternoon and evening.

Confidence diminishes after sunset, but this pattern hasn`t shown
signs of sustaining organized convection too deep into the night.
Will go dry after 03Z with mid and high level cloud debris.

Boundary will hang up close to Ohio River Tue morning and as it
moves east will kick off more shra and storms especially across LEX
and anyone flying towards Lake Cumberland.

&&

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

$$

Short Term...AMS
Long Term...AMS
Aviation...JDG



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