319 
FXUS63 KLSX 080425
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1125 PM CDT Mon Oct 7 2019

.SHORT TERM... (Through Wednesday)
Issued at 206 PM CDT Mon Oct 7 2019

Surface high pressure will provide tranquil and seasonal
conditions to the lower Missouri and middle Mississippi River
valleys through Wednesday. Temperatures will edge a few degrees
higher each day, with 70s for highs and 40s for overnight lows.
Steam fog will likely develop the next few nights along the 
rivers/lakes as water temperatures remain quite warm compared to 
overnight lows. This will locally reduce visibility.

CVKING

.LONG TERM...  (Wednesday through Next Monday)
Issued at 206 PM CDT Mon Oct 7 2019

Meanwhile, big changes will be happening aloft to our west as a
deep trough of low pressure is carved out across the Rockies. By
Thursday deep southwest flow will send temperatures soaring 
across the CWA with highs forecast in the lower to middle 80s. Low
level moisture will be on the increase as well, with PW values 
approaching 1.5 inches ahead of the cold front (more than 200 
percent above normal). 

There is some timing differences between the ensemble mean of the
GFS and ECWMF of the cold front and best chances of measurable 
precipitation. The GFS ensemble mean is faster than ECWMF 
ensemble mean by 6 to 12 hours and more robust with QPF ahead of 
and along the cold front. The spread of model solutions for high 
temperatures on Friday is huge due to the uncertainty with the 
timing of the front. Current forecast is a blend of guidance with 
a high bust potential, as operational and mean ensemble GFS would
have temperatures much colder, while the ECWMF warmer. Investigating
the individual members of the GEFS revels a clear bimodal distribution
of solutions, with many members favoring the slower ECWMF solution.

There seems to be at least a conditional threat of severe 
convection Thursday night (GFS) or Friday (ECWMF). The CIPS 
Experimental Analog-Based Severe Probability Guidance has started 
to highlight an area from northwest Arkansas to west central 
Illinois with low probabilities (l5 percent or less) for severe 
thunderstorms Thursday night and Friday. I see two scenarios that 
could lead to severe thunderstorms impacting our area. 

1. "Leftovers" Thursday night from what develops along the front 
to our west and this would likely limit the areal extent of the 
threat to central Missouri.

2. The slower FROPA solution verifies and locations along and 
east of the Mississippi River become under the gun late Friday 
morning and afternoon for severe thunderstorms as the atmosphere 
is able to destabilize ahead of the front.  

The biggest story will probably end up being the temperatures 
plummeting Friday night thanks to strong cold advection in the 
wake of the front. A gusty west/northwest wind will usher in the 
coldest temperatures of the young fall season with most folks 
waking up to temperatures in the 30s Saturday morning.

Cool and dry conditions are expected for the weekend with highs 
in the 50s on Saturday and 60s on Sunday. Overnight lows Sunday 
morning will dip back into the 30s with the potential of some 
frost in low lying areas if the atmosphere can decouple.

CVKING

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1123 PM CDT Mon Oct 7 2019

VFR flight conditions will prevail with clear skies and light
winds through the end of the period.


MRM

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX