Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 162308
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
608 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 00z TAFs through 00z Wednesday Evening)
Issued at 541 PM CDT Tue Sep 16 2014

Northwest flow aloft continues through the period with a
reinforcing short wave coming through tonight. High pressure at
the surface shifts east allowing for a weak southerly flow to
develop. Low level jet, about 5000 ft, kicks in pointing at KS/MO
border,thus most models want to develop precipitation overnight in
this area. Looks like rain will stay west of terminals with COU
having the best chance, but chances still low enough to leave out
of the forecast. VCSH may be needed for the next forecast. Models
also want to bring in some MVFR ceilings. Given the pattern is
more mid-Fall like rather than late summer, and with 60 dew points
not that far away, will go with this at COU and STL. Have a few
doubts about this at STL, so will not hit it extremely hard.

Specifics for KSTL: Looks like any rain that develops will stay to
the soutwest of the terminal. Big question is if MVFR ceilings
will arrive. Given the cool pattern, feel it is possible but have
doubts about how extensive the MVFR shield will be. Surface wind
will be weak, so it is up to the low level jet to bring in the
MVFR clouds. Will bring in MVFR ceilings for a while in the
morning, starting around 12z, then raise them about 4 hours
later. Rest of the period should be VFR

JPK

&&

.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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