Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 211350 AAA
AFDLMK

Area Forecast Discussion...UPDATED
National Weather Service Louisville KY
950 AM EDT Mon Sep 21 2020

.Forecast Update...
Corrected at 949 AM EDT Mon Sep 21 2020

Skies are clear this morning with winds around 5 mph out of the
southeast. A robust mid/upper ridge is positioned over the Ohio
Valley, and the 12z ILN sounding shows a substantial warm
nose/subsidence inversion between 800-700 mb. The sounding is also
very dry. Further west, over PAH, there is a narrow ribbon of
moisture around 850 mb moving north. A small BKN cloud deck on
visible imagery extends as far east as Madisonville, but these
clouds should remain west of the area for the most part.
Temperatures are now in the mid and upper 50s, rising steadily under
full sun.

&&

.Short Term...(Today and tonight)
Issued at 235 AM EDT Mon Sep 21 2020

Pleasant fall weather continues under the influence of a 1032mb sfc
high over southern Quebec and a strong upper-level high over the
Tennessee Valley. Low-level thickness progs support temps close to
persistence, that is slightly below normal by day and substantially
below normal by night, as clear skies and light easterly winds
create favorable radiational cooling.

.Long Term...(Tuesday through Sunday)
Issued at 322 AM EDT Mon Sep 21 2020

When we look at the long term after Wednesday, guidance has changed
dramatically in the last 24 hours. The global models have come into
better alignment.

At the start of the long term, on Tuesday, the Lower Ohio Valley
begins to see clouds move into the region from the west. This is
moisture from the remnants of Beta, but we are expected to remain
dry as surface high pressure remains overhead through Wednesday
night.

Thursday, a closed off low embedded in upper flow, which is
splitting the jet stream, will begin to move into our area from the
southwest. This will bring lower surface pressure with its own
moisture feed from the Gulf of Mexico. Precipitable water values in
the 1.5 to 1.8 inch range will reach northward to near the Ohio
River. This all happens ahead of a shortwave that will result in
showers and thunderstorms chances throughout the day.

Friday through Saturday, southern moisture will keep streaming
northward into the CWA, but precipitable water values will drop
somewhat to just over 1 inch. Small disturbances will keep shower
chances in the area.

For Sunday, a large cold front is expected to move through the
region. This will provide for widespread elevated chances (60%) at
rain showers/storms.

Behind the front, the models begin to go different ways, so keeping
low PoPs in the forecast until the guidance finds better agreement.

&&

.Aviation...(12Z TAF Issuance)
Issued at 645 AM EDT Mon Sep 21 2020

VFR conditions expected through the valid TAF period under sfc and
upper ridging. Winds will be light out of the E-SE, even going
light/variable at times, especially tonight.


&&

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

$$

Update...EBW
Short Term...RAS
Long Term...KDW
Aviation...RAS



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