Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 231740

1240 PM CDT Sat Aug 23 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 332 AM CDT Sat Aug 23 2014

Warm frontal boundary remains across region early this morning
with isolated/scattered storms firing north of it. A few have
moved into far northern portions of forecast area early this
morning. So have added isolated mention in this area through 15z
today. Otherwise, summer has returned with a vengeance with
dangerous heat and humidity. Because of the high dewpts in the
upper 60s to mid 70s, lowered high temps a degree or two for
today. This will not affect heat indices as the higher dewpts and
slightly lower highs still create indices in the 100 to 109 degree
range once again. High resolution models want to generate
thunderstorm activity mainly east of Mississippi River this
afternoon but feel it will just skim our far eastern portions, so
added slight chance pops in this area.


.LONG TERM:  (Tonight through Friday)
Issued at 332 AM CDT Sat Aug 23 2014

Models are keeping boundary draped across forecast area through
at least this evening before it weakens and lifts north late tonight.
So with front north of area on Sunday, it could be our hottest day
with temps approaching 100 for southern half of forecast area.
Heat indicies will once again be between 100 and 109. Will remain
hot through at least Monday, so will keep advisories and warnings
going through that period.

Still not confident on exact timing with next weather system, which
could begin to bring some rain to region by Tuesday, but just a
slight chance. Could see hot enough temps and heat indices on
Tuesday to keep headlines through then, but not confident enough to
do that at this time. Otherwise, will see better chances of rain
Wednesday through Thursday with temperatures cooling off.



.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1219 PM CDT Sat Aug 23 2014

Specifics for KCOU, KUIN: VFR through the period. An outflow
boundary briefly caused winds to become northerly, but recent obs
show that winds are returning to the prevailing southeasterly
direction. Scattered thunderstorms are possible this afternoon
along an outflow boundary, but any convection that develops will
probably remain south of KUIN and east of KCOU. Will continue to
monitor for TSRA development this afternoon.

Specifics for KSTL, KSUS, KCPS: VFR for the majority of the TAF
period. An outflow boundary was approaching the St. Louis metro
terminals at TAF issuance and could briefly swing the winds around
to the north for a few hours with speeds below 10 kts. There is
some uncertainty over the next 6-8 hours because scattered
thunderstorms could develop near the boundary during peak
afternoon heating. Kept out VCTS for now because of the lack of a
cumulus field over eastern MO. Will continue to monitor for TSRA
development this afternoon.



MO...HEAT ADVISORY until 7 PM CDT Monday FOR Audrain MO-Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-
     Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike
     MO-Ralls MO-Reynolds MO-Shelby MO-St. Charles MO-St.
     Francois MO-Ste. Genevieve MO-Warren MO-Washington MO.

     EXCESSIVE HEAT WARNING until 7 PM CDT Monday FOR St. Louis City
     MO-St. Louis MO.

IL...HEAT ADVISORY until 7 PM CDT Monday FOR Adams IL-Bond IL-Brown
     IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey IL-
     Macoupin IL-Marion IL-Monroe IL-Montgomery IL-Pike IL-
     Randolph IL-Washington IL.

     EXCESSIVE HEAT WARNING until 7 PM CDT Monday FOR Madison IL-St.
     Clair IL.



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