421
FXUS63 KPAH 301058
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
558 AM CDT Sun Jun 30 2024

.KEY MESSAGES...

- Scattered showers and storms quickly diminish after daybreak
  as a cold front moves through the region. Cooler conditions
  with much lower humidity can be expected later this afternoon
  through Monday.

- The heat and humidity returns again by the middle of the week
  with heat index values around 100-105 degrees Wednesday and
  Thursday. Another cold front eventually moves through by next
  weekend.

- An unsettled pattern with daily chances of showers and storms
  begins on Wednesday and continues through Saturday. There is
  the potential for heavy rainfall and possibly some flash
  flooding. Although there is not a strong signal for scattered
  severe storms, Thursday afternoon into Thursday evening may be
  when the ingredients are slightly better for the 4th of July.

&&

.DISCUSSION...
Issued at 121 AM CDT Sun Jun 30 2024

Sfc observations upstream this morning show a cold front now pushing
southeast of the St Louis metro where dewpoints are quickly falling
into the 60s. This will eventually put an to the ample humidity as
dewpoints are still near 80 degrees across many locations. In the
wake of fropa, the CAMs show a disorganized cluster of scattered
showers and storms moving east across the FA through 12z before pcpn
tapers off shortly after. Did limit PoPs to a 40-50% chance as
models continue to struggle compared to current obs. The frontal
boundary remained just slow enough to prevent the better forcing
from overcoming the cap that was in place for much of yesterday.
Mesoanalysis does show about 2000-3000 J/kg of MUCAPE still in
place, but instability will gradually wane through daybreak. Given
poor low-level lapse rates, think the main concern with any storms
at this point will be lightning and torrential downpours with PWATs
between 2.00-2.25 inches, but a gusty storm still cannot be ruled
out.

Behind the front, sfc high pressure builds into the FA as northerly
winds advect in much lower dewpoints this afternoon into the
evening. In fact, most locations will see a 25-30 degree drop in the
dewpoint by 06z tonight when 50s and even a few 40s are progged.
Given model soundings support a deep dry layer around 850 mb mixing
down late this afternoon along with CAA, went with CONSShort for
dewpoints as it is likely to end up on the lower side. The dry air
may also mean a brief uptick in a few wind gusts around 17 to 20 mph
before sunset as there will be a modest increase in the pressure
gradient. Meanwhile, not only will there be big relief from the
humidity, but maxTs will only be in the low to mid 80s today with
minTs falling into the mid 50s to near 60 degrees tonight.

Tranquil conditions and low humidity prevail into Monday with maxTs
only in the low 80s. The unseasonably cool conditions will not last
for long as a trough exits the northeast and allows for a ridge over
the southern Plains to build into the FA with rising heights.
Southerly return flow will quickly cause WAA along with an increase
in humidity for the middle of the week. By Wednesday, dewpoints once
again may reach the mid to upper 70s causing the heat index to rise
back near 100-105 degrees, with the heat and humidity continuing
into the 4th of July.

The pattern also turns quite unsettled as a series of leading
shortwaves ahead of a more broad 500 mb trough that digs across the
northern Plains provides forcing for ascent. Multiple waves of
showers and storms are possible Wednesday through Saturday before a
cold front eventually moves through. It is still not out of the
question a round or two of scattered severe storms occurs at some
point. The GFS would suggest Thursday afternoon into Thursday
evening may be a time to monitor when better shear may line up with
instability when the nose of a 45 kt jet max at 700 mb passes by.
However, the heavy rain and flash flooding potential may end up
being the bigger concern as the ESATs show a strong signal for
robust water vapor transport around the 90th percentile with
westerly flow along with PWATs once again above the 95th percentile.
There is still lots of uncertainty, but it does appear we will be
entering a wet pattern for the holiday.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 557 AM CDT Sun Jun 30 2024

Scattered clouds around 5-10 kft AGL will give way to increasing
breaks of sun this afternoon as a cold front moves south of the
region. Dry air aloft will allow for better mixing in the
boundary layer with north winds around 10 kts and a few gusts
near 20 kts. After sunset, mostly clear skies are forecast with
light N-NE winds around 5-7 kts.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.

&&

$$

DISCUSSION...DW
AVIATION...DW