Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 281041
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
641 AM EDT Sun Sep 28 2014

...Updated Aviation Discussion...

.SHORT TERM (Now through Monday Night)...
Issued at 245 AM EDT Sun Sep 28 2014

The synoptic pattern early this morning features a strong closed
upper low across the western CONUS, with a downstream weak ridge
over the Ohio Valley.  A weak disturbance will pass north through
this weakening ridge today into tonight, bringing increasing
cloudiness and a small chance for a few showers.

Upper-level cloudiness continues to increase across the region this
morning as moisture advects in on weak southwest flow aloft.  The
main forecast challenge for today will be precipitation chances.
The latest guidance, specifically the higher-resolution guidance,
continues to advertise some showers developing along a very weak
surface trough and/or a weak deformation axis in the mid-levels.
However, forecast cross-sections continue to depict very dry
mid-levels.  Additionally, guidance suggests a mid-level cap will be
in place which would help to limit coverage/intensity of anything
that does try to develop.  Therefore, have limited pops to just
slight chance for today, as most will certainly stay dry.
Additionally, given the lack of strong surface convergence along
this trough and the presence of the mid-level cap, have taken
thunder mention out for this afternoon.  Can`t rule out a stray
rumble, but do not think it`s worth mentioning across the entire
region given the above reasoning and the fact that instability is
quite weak to begin with.

Otherwise, the main slug of moisture associated with this system
will push into eastern KY tonight, leaving just some lingering cloud
cover over our region.  These clouds should begin to clear from west
to east overnight, making the temperature forecast a bit tricky.
Will go with lows cooler in the west where clearing should occur
first, and warmer further east where clouds will linger.  Expect
readings in the mid 50s west to lower 60s east.

Pleasant conditions will continue into Monday as sunshine becomes
abundant and surface ridging re-establishes itself.  Highs will be
mild, topping out in the lower 80s.

.LONG TERM (Tuesday through Sunday)...
Issued at 250 AM EDT Sun Sep 28 2014

Dry and warm pattern will continue through the middle of the week as
the Ohio Valley will be under the influence of shortwave upper
ridging. By Thursday moisture begins to increase as SW flow deepens
ahead of a strong upper trof. GFS and ECMWF hinting at the potential
for showers in the warm advection Thursday, but not about to include
POPs given how moisture-starved we have been for much of the summer.
Another point in favor of a dry forecast is the tendency of the
models to be too fast with this type of system.

Showers and storms are a safe bet at some point either Thursday
night or Friday, as PWATs increase to 1.5 inches or better, and a 40
kt low-level jet cranks up ahead of the front. Still enough
uncertainty in the timing that we will limit POPs to 50% in any
given period, but that is really the only limiting factor.

Front is still progged to sweep through on Friday, with a fairly
sharp cutoff in precip and strong cold advection for the first half
of the weekend. Look for Saturday temps to be well below normal,
with most locations topping out in the 60s.

&&

.AVIATION (12Z TAF Update)...
Issued at 640 AM EDT Sun Sep 28 2014

VFR conditions are expected to prevail through the valid TAF
period.  For today, mid and high clouds will continue to stream over
all sites.  There will likely be some diurnal cu as well, but all
cigs will remain VFR.  Cannot rule out a stray shower at any site
today, but the expected coverage will be too low to warrant any
mention with this package.

For tonight, mid/high clouds will begin to push out from west to
east, leaving clearing skies and continued VFR conditions.  Winds
through the period will be rather light and variable.

&&

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

$$

Short Term........KJD
Long Term.........RAS
Aviation..........KJD




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