Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 250156
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
956 PM EDT Mon Jul 24 2017

...Forecast Update...
Issued at 955 PM EDT Mon Jul 24 2017

Dewpoint gradient in central Kentucky is fairly sharp this evening,
with SDF and FFT down into the lower/mid 60s, while FTK and LEX
remain in the lower 70s. Effective boundary is quite a bit farther
south, as isolated T-storms over south-central Kentucky are finally
fading out with the loss of heating.

Setup continues to look favorable for patchy fog tonight, with a
weak push of drier air as we head farther south in Kentucky. Will
not get too carried away as it`s difficult to fog in the expected
NNE flow, but may see grid tweaks to better align fog potential with
the current dewpoints.

.Short Term (Now through Tuesday Night)...
Issued at 235 PM EDT Mon Jul 24 2017

Surface analysis reveals a weak cold front generally along or south
of I-64 at this time. The front has provided enough surface
convergence for isolated showers and thunderstorms to fire off,
though most have been pretty weak overall. SPC mesoanalysis does
show MUCAPE ~ 2000-3000J/KG and DCAPE ~ 1300J/KG ahead of the front,
but deep layer shear is very weak. With the amount of instability
present in the atmosphere, can`t rule out a strong wind gust or two
in the strongest showers or storms.

The isolated to scattered showers and thunderstorms will continue
into the early evening ahead of the weak cold front before dying
down around sunset with loss of surface heating. Should be pretty
quiet overnight as some slightly drier air filters in behind the
front. May have some patchy fog as well across south-central
Kentucky, where the higher dewpoint/moisture air resides.

High pressure over the Great Lakes will continue to funnel in drier
and slightly cooler air Tuesday. Dewpoints in southern Indiana and
northern Kentucky will generally be in the 60s, a bit more
comfortable than where they have been over the last several days.
Some isolated showers and thunderstorms could clip southwestern
parts of the CWA Tuesday afternoon, but most areas will remain dry.
Afternoon highs will vary quite a bit across the region, with low
80s in Lexington and northeastern parts of the CWA... to low 90s
across Bowling Green and southwestern parts of the CWA. Overnight
lows will be mild Tuesday with 60s generally for everyone.

.Long Term (Wednesday through Monday)...
Issued at 241 PM EDT Mon Jul 24 2017

Upper level ridging will build into the lower Ohio Valley on
Wednesday. This will keep the weather mostly dry and warm until
Thursday, when an approaching shortwave trough and associated
surface cold front come swinging in from the northwest. Model
guidance varies some on the timing of the front. The 12z Canadian is
one of the quickest models and has the front passing through
Thursday evening, while the 12z GFS doesn`t have the front clearing
the region until late Friday evening. The NAM/ECMWF are more in line
with the 12z Canadian and have the front passing through Thursday
evening into early Friday morning. With the GFS being the outlier,
will lean toward a frontal passage being sometime between Thursday
evening and early Friday morning. Widespread showers and storms will
be possible ahead of the cold front, and a quick look at
instability/shear parameters suggest there could be a few strong
storms as well, though much of that will depend on the timing of the
front.

Cooler and drier air will funnel in behind the cold front and set up
a fantastic weekend weather-wise. Latest guidance has come in
slightly cooler for temperatures, as most folks should see afternoon
highs in the upper 70s to low 80s and low humidity for the weekend
timeframe.

&&

.Aviation (00Z TAF Update)...
Issued at 710 PM EDT Mon Jul 24 2017

Weak front has pushed through SDF and LEX, but has yet to make it to
BWG. Convection along the front is isolated at best, and should
dissipate shortly after sunset. Can`t rule out a weakening shower
over BWG, but chances are too low to include in the TAF. Otherwise
north winds will continue through the night, not dropping below 6 kt
at SDF or LEX, while BWG will be light/variable. Lighter winds and
more low-level moisture could result in some MVFR fog at BWG for a
couple hrs either side of daybreak on Tue. Otherwise VFR with no
more than a few diurnal cu.

&&

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

$$

Update.........RAS
Short Term.....DM
Long Term......DM
Aviation.......RAS


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