PAH issues Area Forecast Discussion (AFD) at Jul 24, 10:55 PM CDT770
FXUS63 KPAH 250355
AFDPAH
Area Forecast Discussion
National Weather Service Paducah KY
1055 PM CDT Wed Jul 24 2024
.KEY MESSAGES...
- A daily chance of showers and storms for all or a portion of
the region will continue through at least next Wednesday. The
Evansville Tri State may stay dry from Thursday night through
Saturday.
- Below normal temperatures continue through Sunday with highs
in the mid to upper 80s and lows in the upper 60s to lower
70s.
- Temperatures and humidity levels will trend upward early next
week, with head index readings 100-105 possible. The pattern
may also be more conducive for heavy rainfall and flash
flooding.
&&
.UPDATE...
Issued at 1055 PM CDT Wed Jul 24 2024
Updated Aviation discussion for the 06z TAF issuance.
&&
.DISCUSSION...
Issued at 136 PM CDT Wed Jul 24 2024
Today looks a lot like yesterday with an upper trough parked
from northeast Texas into the Great Lakes region. The surface
pressure gradient is very weak with low 70s dewpoint air and
high relative humidity in the lowest 200mb particularly along
the south half of the CWA. Mid-level lapse rates are very poor
and despite the strong low humidity should only have about
1000-1500 J/kg of MLCAPE this afternoon with any storms that get
going. Coverage looks isolated to widely scattered with no real
local forcing to initiate. Shear is fairly weak but perhaps just
strong enough to help organized a couple of updrafts. Given the
depth of the higher humidity in the lower levels and light
winds fog will probably be a factor tonight with a reasonably
favorable setup for more widespread dense fog if we can keep
middle and high clouds at bay.
Tomorrow looks similar to today with warm conditions and a
lingering trough overhead. Isolated to scattered thunderstorms
will be possible from late morning through the afternoon and
early evening. Friday the open upper trough starts to close off
more and retrograde westward, which may put us in a slightly
more favorable zone for large scale ascent. Column moisture also
increases quite a bit and we go from our current ~1.5" PWAT to
more of a 1.8 to 2.0" PWAT type airmass.
By Saturday GFS/ECMWF/NAM have a closed low over the MO/KS
border with southerly moisture advection through the column
ahead of it. An area of upper convergence sets up over the
eastern half of the CWA if you take the guidance at face value
with a more divergent flow over the west which then rotates
through the area overnight Saturday. This seems to give us a
pretty good shot at more organized/widespread precip. There is
not a slam dunk heavy rain signal in the guidance but with a
favorable pattern for thunderstorms and PWATs over 2 inches
flash flooding would appear possible. Will need to watch for
water loaded downbursts as well potentially. As previous shifts
noted the NAEFS standardized anomalies have a multi day period
of specific humidity/PWATs in the 90th percentile and its not
hard to assume something will squeeze out of that of
significance when all the mesoscale accidents come together.
GFS/ECMWF are different in their handling of the closed low
where the ECMWF is more progressive and seems to give us a
little bit drier conditions Sunday, where the GFS moves it
through slower and keeps things wetter. If we stay less cloudy
than currently modeled/forecast it will be hot as well.
Monday into Tuesday we get into a more northwesterly flow aloft
which nudges the closed low and a wannabe cold front towards the
area. Our PWATs stay very high with dewpoints in the mid 70s so
convective activity looks pretty likely as well. Essentially
just a sort of stagnant and stuck pattern where there will be
mainly daytime heating chances of showers and storms but likely
a few moments, currently looking like maybe Saturday and Monday,
where there will be more synoptic scale forcing helping things
out.
So in summary, today and tomorrow isolated to scattered storms.
Locally heavy rain in slow moving thunder, can't completely rule
out a downburst or two but probably not. Friday through Sunday
column moisture will be deeper and the chance of some flash
flooding looks to increase as both the rainfall efficiency and
coverage of storms will be higher. Monday afternoon through the
rest of the forecast period gets into northwest flow which can
be a recipe for MCS and stronger convective storms with a dash
of flash flooding mixed in but there is not any one obvious
signal for any of that at the moment. If it is a little less
cloudy excessive heat could come into play as well.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1055 PM CDT Wed Jul 24 2024
Fog and low stratus restrictions will impact the terminals
overnight, mainly between 09-13z. Most severe impacts (IFR/LIFR
conditions) will occur at CGI, PAH, and MVN. AT EVV and OWB, fog
restrictions will mainly be MVFR. After the fog dissipates,
scattered diurnal CU will develop under passing high cirrus.
Isolated to widely scattered convection will develop during the
heat of the day, so have maintained PROB30 groups at all the
terminals. Calm winds overnight will pick up from the E-NE in
the afternoon AOA 5 kts.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...DWS
DISCUSSION...JGG
AVIATION...DWS
Source:
PAH issues Area Forecast Discussion (AFD) at Jul 24, 10:55 PM CDT---------------
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