Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 271925
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
325 PM EDT Mon Jul 27 2015

.SHORT TERM (Now through Tuesday Night)...
Issued at 320 PM EDT Mon Jul 27 2015

Upper level shortwaves along the periphery of a ridge over the Ohio
Valley will continue to spark convection in a moist, unstable
environment.  Although the ridge keeps building limiting storm
strength and coverage, we are see an uptick in showery activity as
of 1830Z.  Many weak boundaries left over from previous convection
exist over our region which will help provide some focus for
showers/storms.  Isld to sct showers with isld t-storms will
continue through the evening hours before daytime instability is
lost.  These showers/storms will contain locally heavy rainfall at
best.

Later tonight some short range models indicate a complex of
storms may travel SE from central IL/MO into areas west of I-65.  It
would be in a weakening phase if it makes it this far southeast.
Also some areas may develop some patchy fog overnight with the light
sfc winds and moist low levels.  Low temperatures should range
through the low to mid 70s.

For Tuesday, expect a hot and muggy day.  The ridge will be stronger
over our area tomorrow limiting any convection to isld if it can
even get going.  Think that most areas should be dry.  With
continued dewpts in the 70 to 75 degree range and high temps
reaching the upper 80s to lower 90s, heat indices should top out in
the 100 to 103 degree range mainly along and west of I-65 in KY and
along the Ohio River in Indiana.  Therefore will issue an SPS about
the hot, muggy conditions for Tues/Wed (see long term discussion on
Wed heat indices).

Tues night will again be mostly dry with any lingering showers
quickly dying after sunset.  Low temps should range through the low
to mid 70s.

.LONG TERM (Wednesday through Monday)...
Issued at 245 PM EDT Mon Jul 27 2015

Main item of interest will be the timing of a front passing through
the region Wednesday to Thursday morning. The NAM favors a
pre-frontal trough coming into the region during peak heating and
forcing good coverage of storms, whereas the GFS keeps a stronger
cap in place and the best forcing in Indiana. The latest SREF would
argue towards the GFS solution and will lean that way as well, with
isolated pops in the east for the daytime period and scattered in
the west, highest in our northwest counties. Also with that
solution, best chance would be with diurnally driven storms.

Beyond that front, dry air comes back into place over the region,
with little in the way of triggers for daily storms. GFS has a
narrow plume of moisture associated with a weak front Saturday
afternoon, but will maintain continuity in the forecast for now and
go dry.

The warmest day should be Wednesday, just ahead of the front. Heat
indices will reach around 100 or higher along and west of the I-65
corridor. No need for a headline at this point, as the heat is not
atypical of summer. Behind the front, we should see near normal
temperatures the rest of the period.

&&

.AVIATION (18Z TAF Update)...
Updated 130 PM EDT Mon Jul 27 2015

The region will remain in an unstable airmass with many chances for
showers/storms.  Because overall coverage of storms is only isld at
best, will continue with VCSH mention through the TAF period and
amend with t-storm mention if an isld cell looks to hit a TAF site.
Convection will be limited in strength due to ridging trying to
build over the region resulting in mid level capping.  Showers and
storms will be possible overnight and early tomorrow morning, but
the best coverage is expected during the afternoon/evening hours.

MVFR flight restrictions look likely late this evening or early
tomorrow morning and through the morning hours at all TAF sites.
Some model guidance suggests that IFR or even LIFR might be possible
especially at LEX late tonight but not confident enough to include
that in the TAF yet.

Winds will be light WSW or light and vrb throughout the TAF period.

&&

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

$$

Short Term........AMS
Long Term.........RJS
Aviation..........AMS





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