Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 241041
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
641 AM EDT Fri Apr 24 2015

...Updated Aviation Discussion...

.SHORT TERM (Now through Saturday)...
Issued at 330 AM EDT Fri Apr 24 2015

...Severe Weather Possible Saturday Afternoon...

Main challenge in the short term will be the placement and impacts
of potential severe wx on Saturday afternoon.

Upper-level disturbance lifting out of the Desert Southwest will
crank up a 994mb surface low over the central Plains, with a
sharpening warm front ahead of it. Isentropic lift will develop over
the Ohio Valley on Friday night, with a decent precip shield
expanding north and east across Kentucky and into southern Indiana
as the night progresses. Friday night POPs ramp up to categorical
throughout the area, even if the precip doesn`t reach the Bluegrass
region until nearly daybreak on Saturday. Will carry a slight chance
for embedded thunder, but low-level stability will keep the SVR
threat minimal with that round of precip.

Warm front will hang up somewhere across Kentucky on Saturday and
strengthen dramatically through the day. Expect temps to hang in the
50s across southern Indiana, while south-central Kentucky climbs
solidly into the 70s, and a sharp gradient along the warm front
somewhere in between. Still some uncertainty, but that location is
starting to zero in somewhere south of I-64, but north of the
Cumberland Parkway. Steepening mid-level lapse rates will create
strong instability, with up to 3000 J/kg of CAPE and -10 LIs in the
warm sector. A modest cap in the 850-800mb layer might only serve to
focus convection into discrete cells for a time, and wetbulb-zero
heights around 8000 feet will put a damaging hail threat on the
table. SPC`s enhanced risk is more than justified for whatever
portion of the area ends up in the warm sector, and backed surface
winds along the warm front could also locally increase the tornado
threat. Any interests in central Kentucky and southern Indiana
should pay close attention to later forecasts, as well as weather
conditions on Saturday, especially given the number of outdoor
events planned.

.LONG TERM (Saturday Night through Thursday)...
Issued at 301 AM EDT Fri Apr 24 2015

Saturday Night - Sunday...

The threat of severe weather will quickly diminish Saturday evening
as the surface low tracks ESE across our CWA and shuts the warm
sector off. A mid level shortwave and cold front trailing from the
surface low will slide through early Sunday and will shut off
lingering shower chances behind these features as they quickly work
through the area. So, dry conditions will prevail by midday Sunday
with surface high pressure beginning to build into the area. We`ll
see highs in the low and mid 60s.

Sunday Night - Monday Night...

Dry northwest flow aloft with surface high pressure will dominate
the pattern through Monday night with below normal temps. Lows each
night will mostly be in the low 40s, with some upper 30s also
possible. Highs Monday will be a degree or two cooler than Sunday
however most spots will still reach the low and mid 60s. A few NE
spots may struggle to reach 60.

Tuesday - Thursday...

A closed low over the southern Plains will open up and weaken as it
slides across the Gulf Coast states through Wednesday. Meanwhile, a
northern stream impulse looks to dive sharply south through the
Great Lakes and Ohio Valley, interacting with the southern stream
system. Depending on how this phase occurs, enough deeper moisture
(from the southern system) may reach into our CWA. Will continue
with chance pops mainly along the Tennessee border Tuesday night
through Wednesday night.

Should see a return to dry conditions by Thursday as we find
ourselves in the dry NW flow between eastern trough and western
ridge. Temperatures are expected to gradually warm through this
period with max Ts expected to be in the low 70s by Thursday. Lows
will also be milder, generally in the upper 40s to around 50.

&&

.AVIATION (12Z TAF Update)...
Updated at 635 AM EDT Fri Apr 24 2015

Light/variable winds this morning will lock in on a SE direction as
high pressure retreats to the east. VFR all day and much of tonight,
with a mid-level ceiling coming in this afternoon and then gradually
lowering.

Precip will quickly spread SW-NE across Kentucky after midnight,
with restrictions to cig/vis most likely to start just before
daybreak Sat. High confidence in MVFR conditions before daybreak,
especially at BWG where we`ll go into fuel-alternate. Moderate
confidence that SDF will drop into IFR at some point in the planning
period Sat morning. Embedded thunder is a possibility, but
probabilities remain low with the initial round of warm frontal
precip. Thunder chances are much greater Saturday afternoon, beyond
even the SDF TAF.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...FREEZE WARNING until 9 AM EDT /8 AM CDT/ this morning FOR KYZ025-
     028>043-045>049-053>057-064>067-077-078-081-082.

     FROST ADVISORY until 8 AM CDT this morning FOR KYZ023-024-026-
     027-062-063-074>076.

IN...FREEZE WARNING until 9 AM EDT this morning FOR INZ076>079-084-
     090>092.

     FROST ADVISORY until 8 AM CDT this morning FOR INZ083-089.

&&

$$

Short Term........RAS
Long Term.........BJS
Aviation..........RAS





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