Area Forecast Discussion
Issued by NWS St. Louis, MO

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423
FXUS63 KLSX 301111
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
611 AM CDT SAT JUL 30 2016

.SHORT TERM... (Today and Tonight)
Issued at 320 AM CDT Sat Jul 30 2016

A weak surface boundary presently stretching from the OH Valley
across southern IL and southern MO will settle southward this
morning stalling to the south of the CWA this afternoon. Meanwhile
another weak surface wind shift boundary will move into northern
MO and west central IL late morning/early this afternoon. Any
threat of precipitation today should occur in the vicinity of
these two weak surface features, with generally limited coverage.
Otherwise we should see another day with temperatures just below
average and lower than normal humidity.

Glass

.LONG TERM... (Saturday through Friday)
Issued at 320 AM CDT Sat Jul 30 2016

Predominately dry tranquil weather is expected tonight with weak
surface high pressure dominating. The main focus for showers and
thunderstorms should be across the central Plains where the
western portion of the stalled front will begin a slow northward
retreat and a veering south/southwesterly LLJ will provide
forcing. The threat of showers and thunderstorms should begin
ramping-up Sunday, and especially Sunday night into Monday as the
front continues a slowly north/northeastward retreat thru the CWA,
a focusing southwesterly LLJ evolves and provides lift, and a
series of weak disturbances track across the region. The location
of the later disturbances and model QPF varies considerably with
the NAM most robust. This forecast is weighted most heavily towards
the ECMWF which has been rather consistent in its depictions.

Present indications are that by late Tuesday the front should
finally shift to the northeast of the area, and heights aloft
will be rising as an upper ridge shifts/builds from the Plains
into the MS Valley and Great Lakes region. This will set the stage
for a return to potentially dangerous heat and humidity in the
Tuesday-Thursday time frame and especially the later 2 of these
days. The current high temp forecast is conservatively in the
lower-mid 90s this period and this still yields heat index values
in the 100-105 range. Progressive flow aloft across southern
Canada and the northern tier of the U.S. and interaction with a
vortex in eastern Canada ultimately leads to development of a
broad mean trof from the Upper MS Valley through the Great Lakes
and into the northeast CONUS by next Saturday. Associated with the
eventual pattern change would be a cold frontal passage in the
Friday/Saturday time frame.

Glass

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 608 AM CDT Sat Jul 30 2016

LIFR conditions at both KUIN and locally at KCPS early this
morning should improve rapidly after sunrise. VFR conditions
expected otherwise with light northwest wind today. Winds will
become calm tonight.

SPECIFICS FOR KSTL: VFR conditions expected through this forecast
period. Light northwest winds will become calm shortly after
sunset tonight.

Browning

&&

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

$$

WFO LSX



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