Severe Thunderstorm Warning 44, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
330 AM EDT Fri Mar 20 2020

.Short Term...(Today and tonight)
Issued at 320 AM Fri Mar 20 2020

Only scattered showers have been noted in central KY so far early
this morning with surface temps holding mainly in the upper 60s and
lower 70s. However, this is about to change as the main axis of
convection from SW IN through western KY to beginning to move into
our western counties in south-central IN. Pockets of very heavy rain
are within this axis.

For the next few hours (now thru 12 UTC), latest high-res models
show this rain axis moving east across southern IN and central KY
with additional showers and storms forecast to develop over TN and
move into south-central KY. Given high tropospheric moisture content
and efficient rainfall processes within convective cells, high rain
rates could easily produce local flood concerns, so will keep the
current Flash Flood Watch as is with its expiration at 12 UTC.

In addition, current Tornado Watch 59 over western KY goes through
09 UTC (4 am CDT/5 am EDT) and includes our counties of Ohio and
Hancock in central KY and Perry in southern IN. Will keep this Watch
as is as well as cells approach. Low-level wind shear and SRH values
are very high. For example, the KLVX Doppler radar at Ft. Knox shows
winds of 50-55 kts at 2000 ft agl and 65-70 kts from 3000-5000 ft.
However, low-level instability is weak with a little surface-based
CIN, so most cells have remained below severe limits as a result.
Also , most of the storms are moving roughly with the mean wind
(meaning less surface wind potential), with an occasional transient
bowing segment that could cause isolated strong surface wind gusts.

SPC does not plan to issue any new watches east of the current one.
However, a local eastward extension of the watch is possible by us,
but given even less low-level instability farther east across
central KY, any extension would likely just be for a few counties.
Will continue to monitor cell trends.

After these storms exit our area late this morning, still need to
keep an eye on a cold front that will move SE into our area this
afternoon. Models suggest the atmosphere may destabilize enough for
isolated to scattered convection along and just ahead of the front.
With some dry air aloft this afternoon and steep low-level lapse
rates (given highs in the 70s), will need to watch for isolated
strong pulse-like storms with strong wind gusts and small hail.
Models also suggest some additional showers and storms could work
back to the NE into parts of south-central and southeast KY this
afternoon ahead of the front. Outside of any precip this afternoon,
surface winds will remain gusty from the SW.

By tonight, the front moves through our region, and conditions dry
out but temps take a plunge. Expect some low-level clouds behind the
front with much colder air on the heels of a NW breeze. There will
be an abrupt drop in temps with frontal passage. Also, the
difference in high temps this afternoon in the 70s to low temps by
Saturday morning in the mid-upper 30s could be close to 40 degrees!

&&

.Long Term...(Saturday through Thursday)
Issued at 250 AM EDT Fri Mar 20 2020

Saturday into Sunday morning look to be dry as high pressure moves
by to our north. Cloud cover should linger through Saturday morning
at least, but expecting some scattering out in the afternoon. Clouds
return Sunday as a shortwave trough moves into the Mid-MS river
valley. Rain chances will pick up in the afternoon as this trough
interacts with an inverted surface trough over southern KY. A low
should form along that latter trough and shift eastward...pulling
any rain chances well east of the region by Monday morning.

Another brief dry period ensues before another warm front lifts
north and brings in rains for Tuesday. Then another high pressure
builds in from the north and dries us for Wednesday and probably
Thursday as well, though there are signs of another front
approaching the region for late week.

After a below-normal start to temperatures for the period, we should
steadily go up to above normal by midweek.

&&

.Aviation...(06Z TAF Issuance)
Issued at 145 AM EDT Fri Mar 20 2020

Showers and thunderstorms continue to move NE early this morning in
an axis from southern IL to central/southern IN, including HNB.
Meanwhile, isolated showers exist across central KY at this time.
Conditions at TAF sites currently are VFR with a south wind gusting
to around 20 kts. KLVX radar shows around 50 kts at 2000 ft and this
should continue next few hours. Therefore, have included low-level
wind shear in TAFs.

Axis of showers and storms will sag E and SE as cells move NE
overnight. Thus, rain will affect other TAF sites in time, with
briefly lower ceilings/vsbys in heavier rain. This rain should move
past the TAF sites after sunrise this morning. Surface winds will
remain gusty to around 25 kts from the SW ahead of an approaching
cold front.

As this front passes through the region this afternoon, winds will
switch to NW and eventually N and slowly subside tonight. There
could be isolated to scattered storms along the front and this has
been included at each TAF site except HNB.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Flash Flood Watch until 8 AM EDT /7 AM CDT/ this morning for
     INZ076>079-083-084-089>092.

KY...Flash Flood Watch until 8 AM EDT /7 AM CDT/ this morning for
     KYZ023>040-045-061.

&&

Short Term...TWF
Long Term....RJS
Aviation.....TWF

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