466
FXUS63 KLMK 091048
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
648 AM EDT Sun Jun 9 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Scattered showers and isolated thunderstorms today south of
    Interstate 64. Severe weather is not expected.

*   Below normal temperatures and humidity Monday and Tuesday,
    followed by a warming trend with hot and dry conditions likely
    for late this week into next weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 305 AM EDT Sun Jun 9 2024

At 06Z a surface boundary stretched from central Ohio through
southern Indiana to southeast Missouri. This will push southward
across Kentucky this morning, possibly accompanied by scattered
showers south of Interstate 64. Lapse rates will be weak and
soundings don`t indicate much in the way of instability, with debris
clouds streaming in from robust convection to our west helping to
further hamper destabilization. Still could hear some thunder, but
it should be isolated. Better chances for storms and any severe
weather will be to our south this afternoon ahead of the front,
especially from Arkansas into west TN/MS/AL. Highs this afternoon
will be around 80.

Tonight high pressure will build from the Prairie Provinces into the
upper Mississippi Valley, ridging southward to the Ozarks. This will
provide the Ohio Valley with clearing skies and a light northwest
breeze. The air mass should be dry enough to prevent much fog from
forming, though there could still be some sheltered river valley fog
by dawn. Lows will generally be in the lower and middle 50s, 4 to 8
degrees cooler than normal, though HREF grand ensemble
(HRRR/HRW/NAM) indicates a 10-20% chance of briefly dipping into the
upper 40s in rural, low-lying parts of southern Indiana.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 305 AM EDT Sun Jun 9 2024

The extended forecast period will feature quite a bit of change
across the Ohio and Tennessee valleys as the pattern across the
central and eastern CONUS transitions from one favoring mild and dry
weather to a more typical hot summertime regime. Model guidance is
fairly consistent in the pattern evolution through much of the
upcoming week, with some discrepancies noted in the finer details.

On Monday, an abnormally amplified pattern for mid June will be
present across much of North America, with deep troughing extending
from SE Canada down into the eastern US. A mid-level shortwave
disturbance will swing through the Ohio Valley during the daytime
hours, although it should bring little more than extra cloud cover
for the afternoon hours. This cloud cover, combined with cool N/NW
flow, should keep temperatures below normal on Monday. Ensemble
confidence in below normal temperatures Monday afternoon is
relatively good, as indicated by the ECMWF MaxT EFI, which is around
-0.7 in our region. Below normal temperatures are expected to
continue into Monday night and Tuesday, with EFI values continuing
to indicate medium to high confidence in below normal temperatures.
In addition to below normal temps, there is also high confidence in
anomalously dry air Monday night into Tuesday. The NAEFS and EPS
mean PWAT values are both below the 5th percentile of model climo,
with ensemble mean values around 0.50" Tuesday morning. The
combination of cool and dry air should help temperatures fall into
the low-to-mid 50s in most locations Tuesday morning, with a few
upper 40s possible in the typical cool spots.

Late Tuesday into Wednesday will be the transition period as
troughing lifts into the North Atlantic and positive height
anomalies over the desert southwest begin to spread eastward. Sfc
high pressure will remain close to the region, with continued dry
air overhead and subsidence aloft negating precipitation chances. By
Thursday, ensemble mean 850 mb temperatures are progged to be around
15 degrees warmer than on Monday, with warmer temperatures aloft
translating down to the surface as many locations across central KY
and southern IN approach 90 degrees for highs. Dewpoints and PWAT
values should still be fairly modest (Td low-to-mid 60s), so while
temperatures will be hot, it will be more akin to an oven than a
sauna, keeping expected heat indices in check. An upper level wave
is expected to slide through the upper Great Lakes and the northeast
US during the late week, with an associated sfc cold front washing
up near the Ohio Valley Friday into Saturday. While this could
provide a trigger for showers and storms, moisture and kinematics
look to be lacking at this time, so we`ll keep PoPs largely dry. The
hot pattern looks to continue into next weekend, though we`ll have
to keep an eye to the Gulf of Mexico as some long range guidance
brings tropical moisture into our area during the June 16th-18th
time frame.

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 648 AM EDT Sun Jun 9 2024

At 11Z a cold front had crossed the Ohio River and was located
roughly from LEX to OWB. This front will push south across central
Kentucky this morning with scattered showers and a few thunderstorms
along and ahead of it, primarily affecting BWG.

A broken deck of MVFR ceilings formed earlier over southern parts of
Illinois and Indiana and will spread southward through the terminals
this morning before returning to VFR heights.

The front will pass through BWG by early afternoon on its way into
Tennessee, pushing convection to our south. Skies will gradually
clear from north to south this afternoon and evening, with high
pressure over the northern Plains giving us light breezes tonight
under mostly clear skies. Though some valley fog will be possible by
dawn, dry air moving in should prevent widespread fog.

&&

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

&&

$$

SHORT TERM...13
LONG TERM...CSG
AVIATION...13