Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 011924
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
324 PM EDT Fri Aug 1 2014

.SHORT TERM (Now through Saturday Night)...
Issued at 315 PM EDT Fri Aug 1 2014

Sloppy gradient remains across the Ohio Valley as the center of
surface high pressure continues to retreat eastward. Upper
disturbance swinging across Missouri and Illinois to reinforce the
broader eastern CONUS trof has kicked off a cluster of T-storms over
central Illinois.

Just enough enhancement in the cu field along the Cumberland
Escarpment to justify keeping a slight chance POP in as the upper
impulse swings in. However moisture is sufficiently limited that any
convection will be diurnally driven, so whatever small POPs we carry
will drop out by late evening. Could see whatever is left of the
convection to our north and west make it into southern Indiana, but
that too should dissipate quickly with the loss of heating.

Newly sharpened upper trof axis will slide eastward through the Ohio
Valley on Saturday, slipping east of I-75 by early/mid afternoon.
With PWATs still well under 1.5 inches, any convection will be
diurnally driven, so will fade from scattered over east-central KY
to isolated east of I-65 to a dry forecast west of I-65. Slight
chance for a lingering shower over the Bluegrass on Sat evening, but
then dry once again by midnight.

Temps will be on the low side of climo, and moisture will continue a
gradual recovery, but dewpoints still fairly comfortable for August
in the lower/mid 60s.

.LONG TERM (Sunday through Friday)...
Issued at 258 PM EDT Fri Aug 1 2014

Upper trough will be in control over the region at the start of this
forecast period with its axis setting up residence over the Ohio
Valley through Tuesday. Building ridge over the southern Plains will
assist in pushing the trough off toward the east by Wednesday,
leaving the remainder of the long-term period unsettled as
shortwaves flow through. Closer to the surface, high pressure over
the region makes a feeble attempt to take control, keeping the
forecast area dry early next week but quickly loses its place. On
Tuesday, moisture looks to advect back into the area as PWATs rise
from around an inch or so to about an inch and a half. Nothing
terribly impressive as these numbers represent values near climo.
Deterministic model differences become apparent at the surface
relatively early on with noticeable differences appearing late
Tuesday into Wednesday, when comparing the 12Z runs of the GFS,
ECMWF, and the GEM. Therefore, uncertainty in the PoP forecast for
Wednesday onward increases as surface high pressure in the northern
Great Lakes determines where precip sets up on its periphery. The
GEM seems to be the compromise between the GFS and ECMWF. Given this
uncertainty this far out, have broadbrushed best guess precip
chances with just slight chances Wednesday (primarily in the
afternoon as diurnal heating assists) but couldn`t entirely rule
chances out in the overnight period through Thursday, thanks to the
uncertainty and unsettled pattern. The best chances appear to be
Thursday into Friday as a weak frontal boundary provides the focus
for precip and moisture by then has had plenty of time to advect in.

Temperatures throughout the long-term will be returning to near
normal for this time of year with highs in the upper 80s to around
90 degrees and lows in the 60s to lower 70s. The warmer days/nights
are expected to be from Tuesday onward with warm, moist air moving
on in.

&&

.AVIATION (18Z TAF Update)...
Issued at 1245 PM EDT Fri Aug 1 2014

VFR conditions and light NE surface winds are expected through the
valid TAF period, except for some brief MVFR visibilities in fog
near daybreak Sat at BWG and LEX. Could see a stray shower this
afternoon at LEX but probability is too low to mention.

&&

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

$$

Short Term........RAS
Long Term.........lg
Aviation..........RAS





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