696
FXUS63 KLMK 120721
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
321 AM EDT Mon Aug 12 2024

.KEY MESSAGES...

*   Below normal temperatures and low humidity will continue Monday.
    A few sprinkles possible by tonight.

*   Mostly dry weather through the first half of this week with
    precipitation chances increasing mid-to-late week.

*   Temperatures will gradually warm this week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 321 AM EDT Mon Aug 12 2024

Pretty quiet weather in the short term as surface high pressure
continues to control the region beneath fairly quiet zonal flow
aloft. Looking for the first part of the day to be mostly sunny with
a very light NE surface wind, and some occasional upper clouds. As
we move into the evening and overnight a weak shortwave will
approach within the low amplitude NW flow aloft. Mid and upper level
sky cover will increase with this feature, especially across the
western CWA. Models have been fairly consistent showing just enough
moisture between 850-700 mb to squeeze out some very light rain
and/or sprinkles. Have kept the very small chances for measurable
QPF (15-20%) across our far western CWA, however have taken a bit
more broad approach to mention of some sprinkle chances across much
of the northern two-thirds of the CWA. Overall, forecast soundings
show some pretty dry air below 850 mb, so a good bit precipitation
falling out of the mid deck will likely evaporate.

Outside of that, look for continued pleasant temperatures in the low
to mid 80s (a little below normal) for this afternoon. Overnight,
temps will be a bit milder thanks to some upper sky cover. Values
mostly in the low to mid 60s should be common. Leaned on the high
side of guidance here given the mid/upper sky cover.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 321 AM EDT Mon Aug 12 2024

Tuesday through Wednesday Night...

At the beginning of the extended forecast period, broad mid- and
upper-level ridging is expected across the middle of the CONUS, with
upper troughs located along both coasts. At the surface, a broad
area of high pressure is expected from the Great Lakes region down
toward the central Appalachians, with low pressure located along the
lee of the Rockies. The dry air mass which has been in place over
the region this weekend should still be hanging on across the Ohio
Valley Tuesday into early Wednesday, though low level moisture
return on the west side of the 850 mb ridge will bring anomalously
high PWATs toward the Ozarks and mid-Mississippi Valley. This should
create a fairly tight moisture and instability gradient along and
west of the Mississippi River, with occasional convective systems
riding along this gradient during the mid-week period.

Since the air mass over our area should still be fairly dry and
stable Tuesday into Wednesday, precipitation will struggle to make
it east of the Mississippi Valley. As a result, will keep a largely
dry forecast going through Wednesday night, with a very slight (10-
15%) chance for a few showers existing along and west of the Natcher
Parkway. Later during the mid-week period, an approaching upper
trough coming down from central Canada should help to increase
heights over the Ohio Valley as the ridge gets squeezed eastward.
This should help temperatures to warm over the mid-week period, with
highs and lows returning to near climatological norms by the end of
the week.

Thursday through Next Weekend...

The aforementioned shortwave will help to bring better low-level
moisture into the region by Thursday, also contributing to
increasing instability. This will allow subsequent convective
systems to progress farther eastward, increasing chances for showers
and storms. While CSU ML severe probabilities remain low and are not
particularly focused on any one area, the general pattern of
shortwave disturbances descending in NW flow would be supportive of
MCS-type systems which would carry an associated severe wind threat.
To reiterate, severe probabilities continue to look low, as the
moisture/instability gradient is expected to become more diffuse
later in the week; however, it will be worth monitoring later in the
week. The primary window for stronger storms is expected to be
Thursday night through Friday night, as faster flow aloft from the
approaching shortwave helps to bring additional wind shear. Outside
of storm chances, temperatures and humidity values should be more
typical for mid-August during the late week period, with afternoon
highs ranging from the mid-80s to around 90 and nighttime lows
falling into the upper 60s and lower 70s.

Next weekend, ensemble guidance continues to show a bit of spread in
solutions; however, there seems to be some convergence toward a
solution which evolves the late week shortwave into a closed low
over the Great Lakes and Ohio Valley. With moisture pooling in the
vicinity of the upper low, a continuation of active weather and
increased precipitation chances would be expected. This should also
help to bring temperatures back down a few degrees given extra
clouds/moisture, though forecast confidence remains modest at this
lead time.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 135 AM EDT Mon Aug 12 2024

VFR conditions will persist through the valid TAF period. Look for
mostly clear skies early this morning with calm or light and
variable winds. A light NE surface wind should develop by late
morning into the afternoon, along with some high clouds
overspreading the region. By this evening, looking for a mid deck of
clouds around 8-12 K feet, mainly for HNB/SDF/LEX. Perhaps a few
sprinkles could develop for HNB, but not impactful enough
to mention at this time.

&&

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

&&

$$

SHORT TERM...BJS
LONG TERM...CSG
AVIATION...BJS