Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 181823
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
123 PM 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
question.

Kanofsky

.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.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 109 PM CDT Sat Oct 18 2014

Scattered to broken clouds between 2.5Kft and 3.5Kft will continue
to move southward mainly over Illinois and parts of the eastern
third of Missouri. These clouds are in response to low-level
moisture moving southward between surface high from southern
Minnesota through eastern Nebraska and low center northeast of the
eastern Great Lakes region. Suraace winds of 10 kts with local
gusts of 15 kts can be expected this afternoon over eastern
Missouri and much of Illinois. As the surface high moves southeast
skies will clear this evening over the region.

Specifics for KSTL: Low level moisture from the north continues to
move southward over eastern Missouri and much of Illinois
resulting in scattered to broken layers of clouds. Surface winds
from the north-northwest of 10kts with gusts to 16kts will
diminish this evening. Skies will become mostly clear after
02-0300 UTC period.

Przybylinski

&&

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

$$

WFO LSX





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