162
FXUS63 KPAH 200726
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
226 AM CDT Mon May 20 2024

.KEY MESSAGES...

- Hot the next few days

- A front stalls over the area Wednesday bringing a daily
  chances of rain and thunderstorms through this weekend.

- Severe thunderstorm and especially flash flood risks will
  likely emerge in the Wednesday through Sunday period but each
  days risk will depend on prior activity and will have to be
  evaluated day to day.

&&

.DISCUSSION...
Issued at 225 AM CDT Mon May 20 2024

An active pattern continue through the week this week. A
decaying MCS and associated upper level shortwave will approach
the region. It is possible we will see a few showers or storms
along the Interstate 64 corridor very late this afternoon or
this evening, under the influence of this system but the
thermodynamic situation is pretty marginal overall. Hot
conditions are expected again today with the only shade some
variable high cloudiness from convective blowoff.

Tuesday a sharp shortwave over the upper midwest strengthens a
low level cyclone over MN/IA which sharpens our low level
pressure gradient leading to a decent south breeze in otherwise
warm conditions. Responding southwest winds aloft advect an
elevated mixed layer in over the area Tuesday which steepens mid
level lapse rates and provides a stout capping inversion to low
level parcels. GFS/NAM/ECMWF show a net height increase through
the day swapping after 00z (as upper diffluence moves overhead)
with deeper column moisture moving in from the west at the same
time. Rain and thunder chances start to increase in the late
evening in ensemble guidance but it may take a bit for the
residual capping inversion to be lifted out and there is not a
great deal of higher level moisture for elevated parcels. If an
organized MCS can approach in the Tuesday overnight it might cut
through the cap more effectively, otherwise we may have to wait
til the late overnight to get much precip.

Wednesday is a messy picture overall. Moisture is rich through
much of the column with model PWAT from 1.6-1.8 inches, which is
above the 90th percent climatologically. The region is projected
to sit in a broadly diffluent upper level pattern with a 120-kt
over IL/IN with a branch dipping southeast into AL/GA and
various ripples and speed changes in the jet to our north. So
fairly strong net height falls at time. The GFS/ECMWF generate
convection frequently enough in the day to prevent surface
heating - which makes sense in the pattern - where the NAM holds
things off until late afternoon amid 2500-3000 J/kg of MLCAPE.
Both solutions are plausible but I would tend to bet on the
wetter GFS for now. Deep layer shear would be sufficient for
storm organization and low-level shear is approaching strong
enough to make hodographs shaped in a way that might support
tornadoes. In general though the day has the look of a
developing flash flood threat. If a severe thunderstorm threat
can emerge it looks like a wind and hail threat primarily based
on the 00z guidance suite.

GFS/ECMWF keeps the upper level pattern pretty consistent
through Thursday with southwest to northeast flow that allows a
front to remain pretty stationary over the area.
Thunderstorms/rain develop along the front in the global
guidance. GFS/ECMWF send a shortwave trough overhead, the GFS is
a little further south with this feature pinging heavier rain to
the south of the area. It appears however there will at least be
potential for heavy rain/flooding and severe weather. Both
global models then send another shortwave to our northwest
sparking showers and storms again Friday into Saturday with a
larger scale storm system spinning up over the Plains Sunday.

PWAT values stay well above climo norms with areas of lift from
Wednesday through Sunday. Antecedent soil conditions are roughly
normal for this time of year, not really dry or overly wet
either but leaning towards wet overall. Some flash flooding
issues appear entirely possible with periods of severe
thunderstorm threat as well. Confidence is relatively low given
the complexity added by the interactions of multiple shortwave
troughs and multiple convective episodes so expect daily
adjustments to the outlook as the picture develops over the
coming days.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1131 PM CDT Sun May 19 2024

VFR conditions are forecast for all sites. Light winds tonight
will increase to between 5-10 knots on Monday.

&&

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

&&

$$

DISCUSSION...JGG
AVIATION...AD