Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 221038
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
638 AM EDT Sat Jul 22 2017

.Short Term...(This afternoon through Sunday evening)
Issued at 345 AM EDT Sat Jul 22 2017

...Oppressive Heat and Humidity Today...

The primary weather impact in the short term continues to be the
heat. The combination of max temps solidly in the mid 90s and high
humidity will result in heat indices peaking in the 105-110 range
this afternoon and evening. The main forecast change was to bump up
high temps today, which is also why the Heat Advisory was expanded 1-
2 rows of counties eastward. High temps overachieved a bit on
Friday. A couple of factors suggest today could end up a bit hotter
in certain areas. 1000-850 mb thickness increase from 1436-1440 m at
00z yesterday to 1444-1446 m later today. Cloud cover may even be
less of an issue today than yesterday. Mid and upper level ridging
over the region won`t weaken a great deal today. Much like
yesterday, the majority of central KY and southern IN will be dry
today. Convection is expected to remain just off to the northeast.
An MCS is currently weakening as it moves southeast through central
IN, and there is a slim chance an outflow boundary could generate
convection over the northern Bluegrass. Stronger low-level SW flow
will boost highs into the 93-98 degree range.

Some notable changes start to occur tonight into Sunday. The
relatively fast, zonal flow across the northern U.S. will get
disrupted by a wave dropping southeast out of southern Canada. This
trough will gradually shunt the upper ridge further south and west.
The surface boundary that has been draped across IL/IN for multiple
days will finally get pushed into southern IN and central KY Sunday-
Sunday night. Less capping along with a low-level trigger will
likely mean scattered thunderstorms. Convection, which should be
weakening, will approach our southern Indiana counties early Sunday
and gradually diminish near or north of the Ohio River. Diurnal
destablization may allow convection to redevelop along the remnant
boundary over central KY. Storms that do develop could be strong,
with gusty winds as the main hazard.

Sunday will again be hot and humid, but more cloud cover and
convection should help suppress temps a bit. Highs will range from
the upper 80s to mid 90s. Peak heat index values should be between
100-105, so an extension of the Heat Advisory could be necessary.

&&

.Long Term...(After midnight Sunday night through Friday)
Issued at 400 AM EDT Sat Jul 22 2017

High pressure noses down into the lower Ohio Valley on Monday though
the surface front is forecast to stall out around the KY/TN border.
This will keep slight chances of showers/storms in the forecast for
those border counties while the northern areas and southern Indiana
get slightly drier air and more normal temperatures.

Moisture returns to the area mid-week with pop-up showers and storms
possible across the area. Temperatures will trend toward climatology
- upper 80s to low 90s and lows in the upper 60s to lower 70s.

&&

.Aviation...(12Z TAF Issuance)
Issued at 637 AM EDT Sat Jul 22 2017

Upper ridging will continue our hot and hazy weather through this
TAF package. Winds will continue to come in from the southwest as we
sit between high pressure off the East Coast and low pressure over
the Midwest.

A weakening cold front dropping south towards the Ohio Valley will
bring a slightly increased chance of thunder to the last several
hours of the TAF at SDF.

&&

.Climate...
Issued at 445 AM EDT Sat Jul 22 2017

While no record highs are in jeopardy, we may end up setting one or
two record warm low temperatures. On Friday, Bowling Green tied the
record warm low of 76 degrees from 2008. Below are the record warm
low temperatures for July 22-23.

Record Warm Lows   Louisville   Lexington  Bowling Green  Frankfort
July 22nd           81 (1934)   79 (1983)    77 (1983)    79 (1901)
July 23rd           81 (2011    75 (2011)    77 (1983)    79 (1901)

Based on the most recent observations, Louisville and Bowling Green
have a shot to break the record warm minimum temp for July 22nd.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     INZ076>079-083-084-089>092.

KY...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     KYZ023>041-045>048-053>055-061>065-070>077-081.

&&

$$

Short Term...EBW
Long Term...EBW
Aviation...13
Climate...EBW



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