Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 020134

834 PM CDT Fri Aug 1 2014

Issued at 832 PM CDT Fri Aug 1 2014

Updated grids and zones as showers and a few thunderstorms
continue to diminish early this evening. Otherwise, could see fog
develop especially in areas that saw some rain today.


.SHORT TERM:  (Through Late Tonight)
Issued at 330 PM CDT Fri Aug 1 2014

Water vapor imagery depicts a shortwave trough currently along the
Missouri River SE of KOAX heading southeast and will be the main
feature of interest tonight. Scattered showers and thunderstorms
have persisted through early this afternoon and believe they will continue
to survive into the evening hours. However...with loss of
instability...precipitation should become more showery and devoid
of thunder similar to what happened last night across northwest

Drier weather with decreasing cloudiness is expected behind this feature
setting the stage for another cool summer night. Other concern then turns
to fog as winds remain light/variable or calm. Combine that with fairly
clear skies expected late tonight and higher dewpoints compared to a
of days ago...did add mention of patchy fog for the entire CWA as
forecast minimums in most of these locales are several degrees
below crossover temperatures. Dense fog will be more likely in
areas which receive higher rainfall totals through this evening.


.LONG TERM:  (Saturday through Next Friday)
Issued at 330 PM CDT Fri Aug 1 2014

(Saturday - Friday)

Secondary shortwave trough looks to be a bit further to the east tomorrow
than it was modeled 24 hours ago. Consequently...did drop the sch PoPs
along and east of the Mississippi River. Also yielded toward the warmer
guidance with respect to highs tomorrow due to less expected diurnal cu
as well as a slight warming in 850-hPa temperatures.

Sunday and Monday also look dry with high temperatures back to near normal
for early August.

A more active pattern still could be in the offing for the middle to late
next week as bi-state area will lie beneath quasi-zonal/WNW flow
aloft. At least a few shortwave troughs will come across during
this time frame and should interact with a tightening low-level
baroclinic zone. Only have chance PoPs Wednesday - Friday for now
due to uncertainty/timing issues...but does appear that we will be
heading into a much wetter pattern than the past couple of weeks.
As for temperatures...lows will likely remain near or even
slightly above normal but highs are forecast to return to slightly
below normal due to expected clouds/rain chances.


.AVIATION:  (For the 00z TAFs through 00z Saturday Evening)
Issued at 615 PM CDT Fri Aug 1 2014

Scattered showers and isolated thunderstorms will slowly dissipate
with loss of daytime heating and will shift east of the
Mississippi River between 01-02Z. Have kept VCSH in the St. Louis
metro TAF sites and at KUIN through 01Z to allow for this trend.
Main concern overnight is fog development because there is more
moisture in the air than the past few nights. Have fog between
9-13Z going at most of the terminals. Think IFR conditions will
once again be at KCPS where they were last night and light rain
has been the most persistent. Then expect dry and VFR conditions
on Saturday with scattered clouds bases developing around 5000ft
by midday with continued light winds.

Specifics for KSTL: Expect scattered showers to move away from the
terminal around 01Z. There is more moisture in the air tonight
than previous nights, so expect some VFR fog between 10-13Z.
Expect dry and VFR conditions on Saturday.



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