526
FXUS63 KPAH 211050
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
550 AM CDT Sat Sep 21 2024

.KEY MESSAGES...

- Another very warm and humid day is expected to start off the
  weekend with highs around 90 again. The heat index may reach
  100 degrees in a few locations. There is a small chance of
  showers and storms, especially across southeast Missouri.

- A cold front will slowly push through the region Sunday into
  Monday, bringing periods of showers and storms. The risk for
  severe storms is marginal Monday, with isolated damaging winds
  and hail being the main hazards of concern during peak
  heating. Total rainfall between 0.5 to 2.0 inches is possible,
  with locally 3.0 inches along the I-64 corridor.

- Cooler and less humid conditions arrive behind the cold front
  for the rest of the week with highs only ranging from the
  upper 70s to lower 80s. Rain chances may linger on Tuesday,
  with additional low rain chances possible towards the end of
  the week.

&&

.DISCUSSION...
Issued at 323 AM CDT Sat Sep 21 2024

Upper level ridging will peak this morning across the FA as another
very warm and humid day is on track with high temps once again
rising to around 90 degrees. Dewpoints in the 70s will cause the
heat index to reach 100 degrees in a few locations. More isolated to
scattered showers and storms are possible today, especially across
portions of southeast Missouri, far southern Illinois, and far
western Kentucky due to subtle 500 mb energy. However, confidence in
the spatial coverage and timing is low as the 0z CAMs differ quite a
bit with how they handle a decaying complex of storms upstream and
additional diurnal development along residual outflow boundaries.
Cannot entirely rule out a strong storm or two with gusty winds
given pockets of DCAPE between 1000-1200 J/kg, effective bulk shear
of 25 kts, and steep sfc-3km lapse rates around 7.0-7.5 C/km. Despite
the uncertainty, most of the day is still likely to be dry
where storms do occur.

The second half of the weekend will turn even more unsettled as
additional 500 mb impulses upstream provide more forcing ahead
of a shortwave associated with a closed low that will move
across KS/NE. NBM PoPs turn likely to categorical along the I-64
corridor Sunday morning with the first wave of showers and
storms, followed by the potential for another round Sunday
night as a potent cold front slowly sags southeast. Similar to
Saturday, a strong storm or two cannot be ruled out again. Due
to locations further south remaining mostly dry with less cloud
cover, a sharp gradient in the temps will setup with highs only
in the low to mid 80s along the I-64 corridor. Meanwhile, all
of southeast Missouri and western Kentucky are progged to reach
the upper 80s to near 90. This may very well be the last day
most locations if not all in the FA reach 90 degrees as we
transition into the fall season.

Rain chances peak Monday afternoon into Monday night to start off
the new week when widespread showers and storms will be likely
across most of the FA due to more robust forcing associated with a
500 mb shortwave and sfc convergence. SPC does have a marginal
risk of severe weather in their D3 convective outlook across
much of the CWA with isolated damaging winds and hail being the
main hazards of concern during peak differential heating. The
parameters are certainly supportive with MLCAPE between
1000-2000 J/kg, sfc-6km shear between 30-40 kts, and sfc-3km
lapse rates between 7.0-9.0 C/km. Any severe risk likely wanes
after sunset, but additional storms will still be possible
through the overnight.

As for the flooding potential, the risk for excessive rainfall
remains very marginal due to the recent dry soil conditions.
However, QPF has trended even higher quite a bit with among all the
model ensembles. Total rainfall through Monday night between 1.0 to
2.0 inches, locally 3.0 inches is possible across southern
Illinois, and southwest Indiana, while 0.5 to 1.5 inches is now
possible in southeast Missouri and western Kentucky. Once again,
there will be a large diurnal range in the temps from northwest
to southeast, with highs in the upper 70s to upper 80s.

The rest of the week will feature much cooler conditions and
lower humidity as 500 mb troughing will be in control over the
central CONUS. Rain chances may linger on Tuesday, but it is
possible the middle of the week turns drier before low rain
chances return at the end of the week. This is contingent on
when a 500 mb cutoff low develops as models differ quite a bit
with northern stream energy that ejects out of Canada. The
placement will have implications on if we see any moisture from
the potential tropical system next weekend, and is why forecast
confidence remains very low. The synoptic setup is certainly
quite a wild one to put it in simple terms as some of the model
guidance shows the tropical disturbance phasing with the 500 mb
cutoff low.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 550 AM CDT Sat Sep 21 2024

Patchy fog impacting mainly KMVN will diminish shortly with
sunrise. Clouds will thicken through the day with some scattered
mid-level cu developing during peak heating as a weak
disturbance approaches the region. Included PROB30 mention for
TSRA at KCGI/KPAH through the afternoon as scattered diurnal
development is possible. Some model guidance is hinting at
TSRA impacting the northern terminals in the evening, but
confidence is too low to include any TAF mention. Winds will be
S-SW between 5-10 kts.

Clouds will thicken even more tonight as a cold front slowly
approaches the region from the west. The first wave of TSRA may
begin to impact KMVN towards the end of the TAF period.
Otherwise, model guidance is hinting at the potential for BCFG
at KCGI in the early morning on Sunday due to exceeding the
crossover temp. Winds will turn mainly calm after sunset as the
boundary layer decouples.

&&

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

&&

$$

DISCUSSION...DW
AVIATION...DW