Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 251935

Area Forecast Discussion
National Weather Service Saint Louis MO
235 PM CDT Mon Sep 25 2017

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 232 PM CDT Mon Sep 25 2017

Little change the next 12 hours as a cold front slowly makes it way
across the area. Light southerly winds overnight with perhaps some
mid or high clouds moving into the area. The front should be on a
Columbia to Quincy, IL line about 2pm - 3pm. Models not creating
much lift ahead of the front with model CAPE values barely cracking
500, and this is along and behind the front. 20% to 30% chances from
central to northeast MO into west central IL for Tuesday afternoon
look good. Until more clouds move in Tuesday afternoon, temperatures
will remain well above normal.  Plenty of 80s and 90s but high
temperature records look safe.


.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 232 PM CDT Mon Sep 25 2017

Upper pattern will be transitioning from southwest to northwest flow
mid-late this week as upper trough currently over western Canada
digs southeastward into the eastern CONUS.  There will be some weak
post-frontal forcing that will bring some scattered showers to the
area on Tuesday night and Wednesday morning.  After that, mainly dry
weather is expected through the upcoming weekend as the Gulf will
get cut off and any significant storm systems will stay north and
west of the area.  By early next week, the GFS is consistent with
showing southwesterly upper flow developing over the area with low
level moisture return.  This would allow for some isolated showers
early next week.

Global models are forecasting 850mb temperatures to fall into the 8-
10C range, so highs will be near normal late this week and this
weekend. Lows in outlying areas will likely fall into the 40s over
the weekend.



.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1153 AM CDT Mon Sep 25 2017

A cold front will continue to make a slow progression south and
east from the plains across MO and IL. Front should be in the
UIN/COU areas about 15z Tuesday. Rain has predominately been behind
the front with the sw flow aloft, and the models want to continue
this trend. Isolated showers/thunderstorms possible this
afternoon with model forecast 500 to 1000 CAPE. Best chances for
rain will be beyond the forecast period.

SPECIFICS FOR KSTL: Pretty much a VFR and dry forecast. If
precipitation is going to occur it looks to be after frontal
passage which will be near the end of the forecast period,
although I can`t rule out and isolated shower or thunderstorm
this afternoon.





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