Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 092117

Area Forecast Discussion
National Weather Service Saint Louis MO
317 PM CST Sat Dec 9 2017

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 315 PM CST Sat Dec 9 2017

Clouds have begun to break up over parts of the area, and will
continue to clear out over eastern Missouri and Illinois during the
late afternoon and evening hours.  This will occur as the upper
trough currently extending from the Great Lakes into the Ohio Valley
will move east tonight.  At the surface, the current northwest winds
will back out of the southwest overnight which should cause
temperatures to become nearly steady overnight.  Lows will fall into
the 20s tonight because of the cool temperatures today, but won`t
fall as much because of the southwesterly winds overnight.  Highs
tomorrow will climb into the 50s ahead of a cold front that will
move across the area.  Mostly sunny skies and southwest winds ahead
of the cold front will cause temperatures to climb above normal.


.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 315 PM CST Sat Dec 9 2017

Upper pattern promises little prospect for significant precipitation
for next week. Both the GFS/ECMWF is showing an amplified pattern
with MO/IL lying beneath northwesterly flow aloft. Currently the
global models are showing shortwave troughs with attendant cold
fronts moving through the Midwest on Monday and again Wednesday
and Wednesday night. Moisture will be limited with both systems,
so only have slight chances for rain/snow at this time.

Temperatures will warm up above normal again on Monday, but fall
back closer to normal the rest of the week.  The GEFS ensemble does
show a wide spread in temperatures over the week which lowers the
overall confidence in the temperature forecast this week under the
northwesterly flow.



.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1155 AM CST Sat Dec 9 2017

Dry and VFR conditions will persist through Sunday afternoon.
Cloudiness associated with cold front passage will continue to
erode from west to east as the parent low located in lower
Michigan continues pushing northeast. Most TAFs will likely only
see a few mid and high level clouds overnight. There will be yet
another front that will approach the region between 6z and 12z
Sunday with only mid and high clouds expected. Winds will pick up
briefly out of the southwest ahead of the front then decrease
behind the front.


Dry and VFR conditions expected for the terminal through Sunday
afternoon. Ceilings are expected to improve as cloudiness will
continue to push east as the cold front and parent low in lower
Michigan continues to push away from the region. The terminal
will likely only see a few clouds overnight. Winds will pick up
briefly out of the southwest around 16z during a frontal passage
on Sunday.





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