545
FXUS63 KLMK 130546
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
146 AM EDT Thu Jun 13 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Above normal temperatures expected Sunday into next week. Rain
    chances return early next week as southerly flow draws moisture
    northward from the Gulf.

&&

.UPDATE...
Issued at 922 PM EDT Wed Jun 12 2024

Quiet weather continues across the region at this hour. No much to
speak of a from a weather standpoint outside of comfortable
temperatures and clear skies. Like the idea of some patchy river
valley fog overnight, otherwise crossover Ts from peak afternoon
mixing don`t seem to support more widespread fog concerns. Forecast
is on track and no changes planned at this time.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 254 PM EDT Wed Jun 12 2024

High pressure continues to dominate over the Ohio and Tennessee
valleys this afternoon, with light winds, mostly sunny skies, and
seasonably warm temperatures present across southern Indiana and
central Kentucky. Low humidity values continue across the region as
anticyclonic flow in the low-to-mid levels carries most of the
returning moisture up into the upper Midwest. The upper level
pattern across North America is characterized by quasi-zonal flow
atop a broad ridge which will gradually spread eastward over the
next few days. As the ridge axis spreads to the east, increasing
heights and temperatures aloft will translate down to the surface,
with a warming trend continuing into the day on Thursday.

With the dry air mass remaining in place tonight, temperatures
should once again be able to cool efficiently in the presence of
light winds and mostly clear skies. While low-level atmospheric
moisture should be fairly mixed out by now and ground surface
moisture continues to decrease, short range model guidance continues
to suggest a low-medium probability of some valley fog just before
sunrise Thursday. Low temperatures will once again exhibit a
relatively wide range, from low-to-mid 50s in the coolest valleys to
just above 60 degrees in the urban heat centers.

Tomorrow, we`ll see another step upward in temperatures by around 5
degrees across the board. As lower sfc pressures along a frontal
boundary approach from the upper Midwest tomorrow afternoon, light
SW winds should pick up at around 5-10 mph. While there may be
scattered high convective debris clouds in the morning hours from
storms tonight over MN/WI/IA, continued abnormally dry air in the
low-mid levels should allow for another day with mostly sunny skies
and highs ranging from the mid 80s to around 90 degrees.
.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 254 PM EDT Wed Jun 12 2024

Overview

Not much has changed in the forecast thinking, as long-term models
continue to show excellent agreement in the large-scale features.
The finer details are coming into focus with more CAM`s available
for the Friday cold front and subsequent rain chances. Beyond that,
ridging across the region brings our warmest days Sun/Mon, but
Monday still is in question with moisture return and rain chances
short-circuiting the heat. The rest of the work week looks to be a
push/pull for whether it`ll be heat on any given day or whether
afternoon pulse storms will bring relief.

Thursday Night and Friday

Still seeing indication of rain chances in larger-scale models, but
now we have CAM guidance showing a decaying line of showers/storms
pushing in from the NW late Thursday night and into Friday morning.
Specifically, the 12Z FV3/HRRR show this with the NAM3k going for
the weakening even earlier in the evening Thursday. All three keep a
weak convergent boundary over our area Friday, that may serve to
spark off isolated storm development in the late morning and
afternoon hours. Will go a little above NBM guidance for this
period, keeping in at least isolated mention for rain chances. One
other thing, with afternoon development, it`s worth noting that
DCAPE`s are fairly high, though shear for organized storms is low.
Wouldn`t be surprised to see an isolated stronger wind gust come out
of these storms.

Friday Night through Saturday Night

This period will be a transition. We`ll start off with a little
cooler night Friday night, in the wake of that decaying frontal
boundary. Any showers/storms should quickly end with loss of daytime
heating. By Saturday night, high pressure at the surface will shift
northeast of the region, allowing for a return southerly flow to
being.

Sunday through Wednesday

That return flow will bring in warmer thicknesses as well as
steadily increasing moisture. The first will bring a quick shot
upwards in high temperatures for Sunday. 24-hour thickness change
progs still argue for readings some 10-15 degrees warmer than
Saturday. Mitigating factors though will be the humidity as well
still very green surface vegetation. NBM went with changes of 6-8
degrees over that span, and MEX guidance is in line with this
change as well.

As we shift over to Monday and the work week, our precipitable
waters get into the 75th-90th percentile and hover at those levels.
Thus the reason for the push and pull between heat from the ridge
expected to be centered over the Mid-Atlantic states, potentially
capping convection, and storms firing off in that moist environment.
Grand Ensemble guidance from the CMCE/GEFS/ENS show chances for
measurable rains each day in the 35-45% range.

Bottom line for now, we`ll continue to advertise the first heat wave
of the season and perhaps the first time getting into summer pulse
thunderstorm season as well.

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 145 AM EDT Thu Jun 13 2024

High pressure remains over the area, resulting in clear skies and
calm to light winds. VFR conditions are expected to continue through
the forecast period.

&&

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

&&

$$

UPDATE...BJS
SHORT TERM...CSG
LONG TERM...RJS
AVIATION...KDW