Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 181132

632 AM CDT Sat Oct 18 2014

.SHORT TERM:  (Through Tonight)
Issued at 334 AM CDT Sat Oct 18 2014

Early morning water vapor imagery and RAP PV analyses both
depicted a strong shortwave located over northern MN and
southwestern ONT. This feature is forecast to dive southward and
southeastward today, moving through parts of central IL before
reaching KY and TN by 00z. This system appears to be
moisture-starved and no pcpn is expected with its passage near the
LSX CWA. Meanwhile, a cool Canadian high pressure center will
build in at the surface today and tonight. The ridge axis should
be nearly overhead by 12z, resulting in good radiational cooling
conditions and rather cool overnight/early morning lows for Sunday
morning. Patchy frost in sheltered areas is not out of the


.LONG TERM:  (Sunday through Friday)
Issued at 334 AM CDT Sat Oct 18 2014

Winds become southerly to southwesterly on Sunday once the
aforementioned high pressure center shifts southeastward. Another
shortwave moving through the Great Lakes will lead to increased
precipitation chances from late Sunday night through Monday
afternoon. Models are showing at least some moisture being drawn
into the area ahead of the shortwave, therefore slight chance to
chance PoPs look appropriate at this time.

A pattern resembling an omega block is forecast over the CONUS for
most of next week. Dry easterly or southeasterly surface flow is
expected through the middle of the week across the LSX CWA.
ECMWF/GFS/GEM all agree that the highly amplified upper ridge axis
will shift eastward with time, but initially small differences in
the handling of a weak vort max crossing the Rockies ultimately
lead to large differences between models regarding the large scale
upper air pattern over the central CONUS by next Thursday.



.AVIATION:  (For the 12z TAFs through 12z Sunday Morning)
Issued at 619 AM CDT Sat Oct 18 2014

Fast moving short wave aloft will move through today reinforcing
the cool air and keeping a north northwest wind flow. MVFR clouds
will move quickly across Iowa into UIN by late morning and into
COU by Noon. Guidance keeps the clouds VFR, and given the time of
of arrival and the fact the short wave will be shearing east more
than diving south, will go with this scenario. However an hour or
so of MVRF is possible. High pressure will move in overnight with
light and variable wind. Guidance wants to bring in fog at the
usual suspects (SUS, CPS) about 12z. With 00kt wind and clear sky,
possible, but will leave out for now given the time of expected
formation being at the end of the forecast period.

Specifics for KSTL: VFR expected with a northwest wind today
becoming light and variable overnight as high pressure moves
overhead. Southerly wind returns Sunday moring as the high quickly
moves east.





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