Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 181032

Area Forecast Discussion
National Weather Service Louisville KY
632 AM EDT Thu Apr 18 2024

...Updated Aviation Discussion...


*   Strong to severe storms possible Thursday evening and overnight.
    Highest risk of severe storms will be generally west of I-65.

*   Much cooler weather this weekend. Next chance of rain
    arrives in the Tuesday/Wednesday timeframe.


Issued at 303 AM EDT Thu Apr 18 2024


Ridging aloft and weak surface high pressure is over the region
leading to clear skies and light winds. Weak WAA is keeping
temperatures from falling too fast, so we will see lows in the upper
50s and low 60s.

Thursday morning - afternoon...

Weak WAA and southerly winds will persist over the region today.
Ample atmospheric mixing will bring momentum aloft down to the
surface leading to gusty winds on the order of 25-30mph and lower RH
in the 30-35% range. High temperatures will be in the mid 80s,
higher side of guidance. Should be a warm and breezy, but pleasant

Thursday evening - Thursday night...

A low pressure system originating from the central Plains will
deepen and move east, reaching the Ohio Valley this evening. Linear
convection will develop along the cold front and begin to push east
into the region. Some discrete cells ahead of the line are possible
along the axis of instability along the lower and mid Mississippi
Valley. Timing of these discrete cells would be around 23Z and the
linear convection will enter the region around 2Z. Given that the
timing of this event is near the end of the day, instability will be
fleeting quickly, therefore, the greatest threat for severe weather
will be in areas along and west of I-65. As the nocturnal inversion
grows ahead of convection, there will be a greater potential for
elevated convection, especially over areas east of I-65.

Given ample mixing up to about 800mb today, sufficient CAPE and low-
mid level shear, and elevated DCAPE, the greatest severe weather
threat will be damaging winds. Given the nature of linear
convection, spin-up tornadoes along bowing segments would be the
secondary hazards for this event. Hail is possible in discrete cells
ahead of the front, but less of a concern with the line of storms.

The cold front and associated convection will exit the region by
Friday morning. As the line of storms and front moves through, some
post-frontal tapering light rain is possible.


Issued at 303 AM EDT Thu Apr 18 2024

Friday - Monday Night...

Cold front will quickly push east of our area on Friday morning,
with any lingering showers across our east ending. From there,
expect steady clearing from NW to SE through the afternoon as high
pressure begins to build in the post-frontal regime. Temperatures
will be notably cooler behind the front and under a steady NW cool
advection component. As a result, looking for highs topping out in
the 65 to 70 degree range. A few spots could gust up in the 15 to 20
mph range through the afternoon.

Dry conditions will continue through the weekend as surface high
pressure holds over our region with dry zonal flow aloft. We do get
another shortwave trough axis that scoots through the Great Lakes
region on Saturday, which should help to keep most, if not all, of
the southern stream activity suppressed south of our area. Can`t
completely rule out a very light shower across our far SE CWA
sometime between Saturday/Sunday, but overall will keep a mostly dry
forecast going down across the southern tier also.

The passing Saturday shortwave may help to bring a few mid/high
clouds across our region, but will keep a dry forecast for all of
southern IN and central KY otherwise. It is looking to be a cool day
with highs only in the low to mid 60s and a steady NW surface wind.
A few gusts up around 15 to 20 mph will again be possible.

Dry conditions continue through the end of the weekend and into the
start of the new work week as surface high pressure centered to our
west continue to dominate. We will see some better radiational
cooling nights both Saturday and Sunday night, which will allow for
some chilly overnight lows. After upper 30s (N) to mid 40s (S) on
Saturday night, Sunday night looks to be the coldest with values in
the 36 to 41 degree range. As mentioned in the previous discussion,
some frost could come into play, especially across our northern CWA
an in some of the sheltered/cooler valleys. Sunday will be the
coolest day as far as high temperatures go, with peak values in the
upper 50s to around 60. These highs will be around 10-13 degrees
below normal for this time of year. Monday starts a bit of a
recovery back to the low and mid 60s.

Tuesday - Wednesday...

Confidence continues to grow in another chance at showers and a few
storms by the later Tuesday into Wednesday time frame as another
shortwave rotates through the zonal flow pattern aloft. Will
continue solid chances during this stretch with a continued trend in
milder temps climbing to the upper 60s and low 70s.


Issued at 631 AM EDT Thu Apr 18 2024

Calm to light winds and clear skies overnight led to some fog
development over BWG and RGA. This fog will begin to thin with

For the remainder of the day, ample atmospheric mixing will bring
breezy winds down to the surface on the order of 18-22kts. In the
late afternoon clouds will begin to fill in ahead of the low
pressure system.

In the evening and overnight hours, strong to severe storms will
develop along the cold front and move through the terminals from
west to east. Western terminals may see storms between 0-3Z and
eastern terminals may see storms around 3-6Z. As the exact timing
becomes more clear, TAFs will be adjusted.





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