Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 141926
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
326 PM EDT Mon Aug 14 2017

.Short Term...(This evening through Tuesday night)
Issued at 315 PM EDT Mon Aug 14 2017

Scattered to numerous showers (and a few rumbles of thunder) will be
possible across southern and central KY through the remainder of
the afternoon and evening as a high PWAT (>2") airmass moves in
ahead of an upper level disturbance. This feature is evident on
water vapor moving into the mid Mississippi River Valley and will
cross our southern CWA into the evening hours. Overall,
instability isn`t impressive but mid level lapse rates are
marginal enough to warrant a slight chance at a t-storm.

Temps in the upper 70s and low 80s will struggle under mostly cloudy
skies for the rest of the afternoon, however will see a small
diurnal trend tonight as lows only drop to the upper 60s to around
70.

A few showers linger in the south and east into the first half of
Tuesday, before going dry by mid to late afternoon in that region.
Elsewhere, everyone else should see a dry day with highs topping out
in the mid to upper 80s in most spots.

Most dry conditions continue into Tuesday night, with the exception
of near the Bowling Green region where a weak warm front will begin
to setup. A few showers or storms could develop in that area
overnight. Lows will again be around 70.

&&

.Long Term...(Wednesday through Monday)
Issued at 320 PM EDT Mon Aug 14 2017

Wednesday - Thursday Night...

Shortwave troughing will slowly move into the upper Midwest and Mid
Mississippi River Valley Wednesday through Thursday. Meanwhile, a
weak surface low associated with this feature will cross into the
western Great Lakes by Thursday afternoon. As the system approaches
the region, a warm front will slowly lift north across our CWA. This
will provide warm and muggy conditions at the surface beneath modest
mid level lapse rates, resulting in moderate (perhaps some pockets
of strong) instability by afternoon evening. The end result will be
a chance for some scattered thunderstorms. The main threats with
Wednesday storms will be lightning, brief heavy rainfall, and gusty
winds however the threat for severe storms will be mitigated by the
lack of stronger deep layer shear. That changes on Thursday as we
see better deep layer flow ahead of the approaching trough, which
will combine with moderate to strong instability. Forecast soundings
look like they would support a localized damaging wind and/or large
hail threat in addition to lightning and brief heavy rain. Wouldn`t
be surprised if an outlook is needed for the area in the coming days.

Otherwise, expect the cold front to pass through later Thursday
night, shutting precipitation chances off from west to east.
Temperatures during the Wed-Thur time frame will feature highs
mostly in the upper 80s, with lows mostly in the low to mid 70s.

Friday - Sunday Night...

A few light rain showers may linger in east central KY on Friday
morning as the front finishes passing through. Otherwise, this
should be a mostly dry and improving day. Highs top out in the mid
80s.

Overall upper troughing develops over the eastern CONUS through the
weekend as another shortwave dives into the overall broadly troughed
flow, and amplifies it. Overall, this shortwave looks to be lacking
deep moisture ahead of it so any, if any, precipitation chances will
be small Saturday night. Otherwise, expect mostly dry with high
temps mostly in the mid 80s each day. Lows each night will be a bit
more comfortable back in the upper 60s.

Monday (Solar Eclipse Day)...

Most of the medium range model data suggests that we start to see
rising heights by Monday as the weekend upper trough axis departs to
the east, and some degree of upper ridging builds in the central and
southern CONUS. Should this pattern hold, it would tend to lean
toward a dry and mostly sunny day. That being said, confidence is
still in the low to moderate range as there is some disagreement in
how the upper air pattern will evolve by this time. The GFS has been
trying to suggest a weak upper disturbance will meander into the mid
Mississippi River Valley on Monday. If this were the case, increased
sky cover and precipitation chances would be on the table. The good
news (if you like eclipses) is that the operational GFS seems to be
the outlier from most of the rest of the data, including the GFS
ensemble mean. The individual members of the GFS ensemble 500mb
heights are split about 50/50 right now, and would like to see more
consensus one way or the other before being too confident in a
forecast. Will mention a dry, mostly sunny, and near normal
temperature day given the bulk of the data.

&&

.Aviation...(18Z TAF Issuance)
Issued at 135 PM EDT Mon Aug 14 2017

A shortwave passing to our south will continue to provide rain
showers over the area through this evening.  BWG may even see a
rumble of thunder this afternoon.  The shortwave should exit to the
east with showers diminishing late tonight.  However, fog and low
cigs look to become a problem late tonight with BWG declining to
MVFR and LEX declining to IFR between approx 8-15Z.  Conditions
should improve to MVFR/VFR by 18Z tomorrow.  Winds will be
predominantly light vrb throughout the TAF period.

&&

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

$$

Short Term...BJS
Long Term...BJS
Aviation...AMS



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