Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 291137

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
637 AM CDT FRI JUL 29 2016

.SHORT TERM... (Today and Tonight)
Issued at 323 AM CDT Fri Jul 29 2016

The primary cold front is rather ill-defined early this morning
but best guess would place it across southwest IL and across
southern MO into northern OK at 08z. A shortwave trof will move
through the mid-upper MS Valley today and into the OH Valley
tonight. This will bring another secondary wind shift/front into
northern MO and central IL later this afternoon and across the
remainder of the area tonight. The combination of the boundaries
and the upper wave will result in a chance of showers and
thunderstorms, primarily across northern and southern sections of
the CWA this afternoon and this evening. Otherwise slightly cooler
and slight drier air will gradually filter into the region,
especially tonight in the wake of the second boundary as weak high
pressure settles southward from the upper MS Valley and Great
Lakes region.


.LONG TERM... (Saturday through Thursday)
Issued at 323 AM CDT Fri Jul 29 2016

The stalled front will be located in the vicinity of the MO/AR
border on Saturday and yet another weak wind shift will drop into
northern MO and central IL. Once again it would appear any threat
of precipitation, albiet low will be in close proximity to these
surface features. Heights aloft begin to rise a bit on Sunday as
ridging aloft begins building in from the west. In concert the
front will start a northward return, particularilly across the
central Plains and into western and southern MO. The front will
continue a slow northward retreat Sunday night-Monday-Monday
night, becoming increasingly north-south oriented. The threat of
precipitation should really ramp-up during this time frame as a
series of weak northwest flow disturbances traverse the area, and
as a west-southwesterly LLJ becomes established providing
increasing lift along and north/east of the boundary.

The boundary will lift well to the northeast by Tuesday with the
ridge aloft expanding through the MS Valley and into the Great
Lakes Tuesday-Thursday. The associated return of heat and humidity
is forecast to produce peak heat indices in the 100-105 range.



.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 627 AM CDT Fri Jul 29 2016

VFR conditions expected through this forecast period. A large area
of low end MVFR to IFR ceilings over northern illinois and eastern
Iowa should mix out along its southern extent with the strong
late July sun this morning before it reaches the KUIN TAF site.
Elsewhere only scattered to broken cirrus expected. Winds will be
light northwesterly during the day and light and variable
overnight. Isolated showers and thunderstorms are possible in the
KSTL area...but coverage will be very sparse if indeed they form
at all.

SPECIFICS FOR KSTL: VFR conditions expected. A scattered to
broken cirrus deck will move in by late morning. Isolated showers
and thunderstorms are possible by midday...however coverage is
expected to be very sparse. Northwest winds will be light during
the day and light and variable overnight.





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