Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 110704

Area Forecast Discussion
National Weather Service Louisville KY
304 AM EDT Fri Aug 11 2017

.Short Term (Now through Saturday)...
Issued at 255 AM EDT Fri Aug 11 2017

Upper-level impulse moving across the Upper Peninsula of Michigan is
strong enough to drive an otherwise weak cold front SE across the
Corn Belt toward the Ohio Valley. Decent amount of pre-frontal
convection is ongoing in central Illinois and Indiana just north of
the I-70 corridor. Main challenge is the timing and impact of any
precip associated with the cold front as it moves into the area late

Hi-res models suggest we will be hard pressed to see any precip
through midday, as ongoing convection to our north and west looks to
dissipate before reaching southern Indiana. First areas to see
showers or storms around midday may be in south-central Kentucky,
where yesterday`s inverted trof left behind a better moisture supply
to fuel isolated pop-up convection. However, shear is limited that
far south, so not much organization is expected.

By late afternoon as the front starts to drop into southern Indiana,
expect storms to fire along the boundary. Only looking for moderate
instability, and low-level shear is not impressive, but 35 kt of
deep-layer shear could support a few strong storms with marginal
hail and locally gusty winds through early evening. SPC has added a
Marginal risk area to the Day 1 Outlook for southern Indiana and
north-central Kentucky, and this forecast aligns fairly well with

Cooler and less humid air will be slow to filter into the region
tonight and Saturday as Canadian high pressure does not have a
strong post-frontal push. Slight shower chances will hold on across
south-central Kentucky through the night and well into Saturday
morning. However, don`t expect it to amount to much. Temps near
normal tonight as lower dewpoints don`t really arrive until during
the day on Saturday. Highs on Sat afternoon will be several degrees
below normal, with increasingly comfortable humidity levels.

.Long Term (Saturday Night through Thursday)...
Issued at 255 AM EDT Fri Aug 11 2017

Sat night and Sun will feature Canadian high pressure, which will
provide dry weather, mild temperatures, and comfortable humidity
levels to finish out the weekend.

Beginning late Sunday night and Monday, the medium-range models
diverge on their handling of progressive zonal flow for most of the
next work week. GFS and ECMWF are not really agreeing with each
other nor showing much run-to-run consistency. Expect 20-30% POPs
for much of the period, with the better chances mainly across south-
central Kentucky. Temperatures will run just on the low side of
normal for most of the week, with dewpoints gradually recovering to
typical summer levels by Thursday.


.Aviation (06Z TAF Update)...
Issued at 105 AM EDT Fri Aug 11 2017

Patchy fog may develop this morning across parts of the region and
could briefly drop visibilities to IFR/MVFR before 13z. Otherwise, a
weak cold front will approach the region this afternoon and bring
scattered showers and thunderstorms. Coverage and confidence in
timing isn`t high enough to go more than VCTS at the TAF sites for
now. Some of the heavier showers/storms could reduce visibilities
briefly to IFR/MVFR this afternoon and early evening.




Short Term........RAS
Long Term.........RAS
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