939
FXUS63 KLMK 300714
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
314 AM EDT Mon Sep 30 2024

.KEY MESSAGES...

*  Patchy dense fog is currently over the region and will last
   through the morning. Fog development is also likely
   tonight.

*  Isolated to scattered light rain is possible today, as the
   remnants of Helene move eastward.

*  Dry weather and seasonal temperatures to come by mid next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 313 AM EDT Mon Sep 30 2024

Current nighttime microphysics depicts low stratus filling into the
region. Some observation sites have shown intermittent drops in
visibility and mesonet cameras are showing similar trends. Will
continue to monitor these fog conditions through the remainder of
the overnight. If conditions deteriorate, a Dense Fog Advisory may
be necessary.

By the mid-morning, low stratus will begin to mix out. Skies will
continue to thin into scattered skies by the afternoon. The remnant
low pressure will continue to move east through the day, bringing
isolated to scattered chances for light rain. With more sun today,
temperatures will warm into the mid-upper 70s.

Tonight, troughing will finally move east of the region, allowing
for clouds to thin. With soil moisture still high and winds
remaining calm to light, fog (and potentially dense fog) will likely
develop. Unlike Sunday night, there is more confidence in seeing fog
development tonight given thinner skies. Low temperatures are
expected to fall into the low-mid 60s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 313 AM EDT Mon Sep 30 2024

Synopsis...Mid-level energy associated with the previous cut-off low
will depart the region on Tuesday as a northern-stream shortwave
trough races across the Upper Midwest/Great Lakes. Attendant weak
cold front will likely arrive late Tuesday afternoon or early
evening. Then, surface high pressure and upper-level ridge will fill
in immediately behind the front through Friday. In addition, the
resultant quasi-zonal flow aloft and expanding positive upper height
anomalies over the Ohio Valley will block any significant mid-
latitude or tropical influence this coming weekend with only the
subtle effect of a weak shortwave/cold front Friday night into
Saturday morning. Finally, pattern amplification is taking shape
early next week as another trough digs across the East CONUS and
ridge grows in the Intermountain West.

Model Evaluation/Confidence...Forecast confidence remains above
average through most of the period with only exception being the
potential for pattern amplification this weekend or early next week.
Latest deterministic models have trended towards a GFS-like solution
for the weekend with dry and slightly warmer conditions compare to
the ECMWF initial forecast. Nonetheless, such amplification seems to
be pushed for early next week, something that all consulted models
are signaling. In this sense, the ECMWF and CMC favor an early
(Monday) and more pronounced amplification while the
GFS/AIFS/GraphiCast-GFS support a later and less aggressive
scenario.

Tuesday...Weak cold front on Tuesday will move through the region
during the evening hours. Expect isolated to widely scattered
coverage of low-topped showers in the afternoon amid differential
heating forcing mechanisms. This activity will consist mainly of
showers and no thunder as mid-level subsidence and dry air along
with low instability will limit deep convection. Best chance for
towering cumulus will be if the approaching cold front catches up to
any pre-existent mesoscale boundaries. On the other hand, hi-res
models (RRFS and HREF) indicate a narrow line of weak convection
forming along the frontal zone that could spark showers beyond 10/2
0Z. Chances of thunder are low due to decreasing diurnal
instability.

Wednesday - Friday...Stable post-frontal airmass will promote dry
weather and seasonable temperatures, especially at night amid clear
skies and sufficient CAA. Lingering soil moisture will aid in fog
developing in the river valleys and protected areas.

Weekend...Increasing forecast confidence in dry and little
oscillation in temperatures through the weekend. Quasi zonal flow
aloft will limit moisture recovery across the region, so no
measurable rain is anticipated ahead of the weak cold front early in
the weekend.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 144 AM EDT Mon Sep 30 2024

Low stratus is beginning to fill into the region over southern
Indiana and southern Kentucky. This trend will continue bringing low-
end IFR CIGs/VIS, possibly LIFR CIGs/VIS. By mid-morning low
CIGs/VIS will improve to low-end MVFR and then VFR by the afternoon.
Winds will remain calm to light and variable through this TAF cycle.

&&

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

&&

$$

SHORT TERM...SRM
LONG TERM...ALL
AVIATION...SRM