Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 162011
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
311 PM CDT Tue Sep 16 2014

.SHORT TERM:  (Through Tonight)
Issued at 230 PM CDT Tue Sep 16 2014

A weak s/w will approach the CWA late tonight bringing a chance
for storms to wrn and srn portions of the CWA late tonight.
Otherwise, expect clouds to continue to break up during the
afternoon and into the evening. Clouds are expected to build into
the region from the W tonight ahead of the s/w. Have trended twd
a compromise of guidance for wrn portions of the CWA and twd the
cooler guidance for ern portions. Latest guidance suggests FG will
develop late tonight impacting srn and ern portions of the CWA
where radiational cooling will be greatest.

.LONG TERM:  (Wednesday through Next Tuesday)
Issued at 309 PM CDT Tue Sep 16 2014

(Wednesday through Friday)

Main concern continues to be rain chances tomorrow into tomorrow
night over mainly central and southeast Missouri.  GFS/NAM/ECMWF are
still in relatively good agreement in dropping a weak shortwave
trough across Missouri during the day tomorrow.  Each of these
models shows some weak low level moisture lingering across central
and southeast Missouri into Wednesday night, so will continue a
chance of showers and thunderstorms in this area.   This scenario is
depicted pretty well at least through 00Z by the reflectivity on the
NSSL WRF.  Thereafter will maintain a dry forecast Thursday and
Friday as a surface ridge moves across the area at the same time a
upper ridge builds in from the west.

Went on the cooler side of guidance for highs the next couple of
days given the easterly surface flow and it matches up better with
mixing down the 900mb temperatures.   Likewise followed the cooler
NAM MOS for lows.

(Saturday through next Tuesday)

While there is still some disagreement between the GFS/ECMWF
regarding the speed and depth of a trough that will pass through the
area this weekend, it still appears that the attendant cold front
will move through on Saturday night and early Sunday.  Will keep
chances of showers and thunderstorms going Saturday into Sunday.
Will keep Monday and Tuesday dry at this point as we will be on the
back side of the the upper trough, though the latest runs of the GFS
is showing a secondary through dropping down in the northwesterly
flow on Tuesday.  This is a new trend that the ECMWF is not
showing.  Still expect at or just above normal temperatures ahead of
the front on Saturday before they drop back below normal for early
next week given expected 850mb temperatures in the 6-9C
range.


Britt

&&

.AVIATION:  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 638 AM CDT Tue Sep 16 2014

Over the past several hours the n edge of stratus deck has become
increasingly ragged, and at 1115z roughly stretched from just
south of KSPI to near KMHL with a secondary large hole developing
in the cloud deck over sw IL just east of STL metro area. Believe
these trends indicate that the drier air is beginning to make
inroads into the lower level moisture. The cloud deck will be
south of KUIN this morning, although some fog is still possible
with low t/td spreads. Low clouds have also exited KCOU which will
also make it susceptible to fog; however am also seeing a
westward expansion of the low cloud deck just e of KMYJ, so
believe that back edge of stratus may clip KCOU in the 14-15z
time frame. For STL metro sites have followed trends of obs in and
north of area, with a mix of MVFR ceilings/vsbys and occasional
IFR cigs for several more hours, followed by the low cloud deck
scattering out by late morning. By afternoon, clouds throughout
the FA should be limited to scattered CU/SC aoa 3kft.

Specifics for KSTL: Although hole has developed in cloud deck e of
KSTL, northerly low level trajectories should mean prevailing MVFR
ceilings aob 1500 ft through 15z, with lower stratus occasionally
producing vsbys 3-5sm and cigs 700-900ft. Believe there should be
a rapid improvement 16-17z, with scattered clouds aoa 3kft for the
afternoon hours.

Truett

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     53  72  63  76 /  10  20  10   5
Quincy          49  71  54  72 /  10  10   5   5
Columbia        53  74  59  74 /  30  40  20  10
Jefferson City  52  74  59  74 /  30  40  30  10
Salem           47  70  53  72 /  10  10   5   0
Farmington      50  70  55  73 /  20  30  20  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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