Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 221735

1235 PM CDT Fri Aug 22 2014

.SHORT TERM: (Through Sunday)
Issued at 312 AM CDT Fri Aug 22 2014

Well it finally feels like summer. Heat index values yesterday
afternoon topped out around 105 degrees in the immediate St. Louis
Metropolitan Area where the EXCESSIVE HEAT WARNING remains in
effect until Sunday evening. Elsewhere, heat indices remained
within the 100 to 104 degree range, including locations across
northeast Missouri and west central Illinois. Will be adding the
northeast Missouri and west central Illinois counties to the HEAT
ADVISORY to account for heat index values reaching longevity
criteria of 100 degree heat index for four or more days. I expect
that the longevity of the heat wave (now likely extending into
next week) will lead to future extensions in time as confidence

Have introduced some low chance POPs for thunderstorms this
afternoon and evening across the northern half of the CWA. Hard to
ignore mesoscale model guidance suggesting a secondary warm front
developing across the northern CWA by this evening as low pressure
deepens across the Central Plains. Both 00Z 4KM NCEP and NSSL WRF
runs depict an active late afternoon and evening across the northern
CWA - with the potential for an outflow to move south toward I-70.
Again, for now, I have only increased POPs so that there is a
mention in the forecast. Day shift will have to reevaluate as HRRR
and RAP comes into range later this morning.


.LONG TERM: (Monday through Thursday)
Issued at 312 AM CDT Fri Aug 22 2014

Hot and dry conditions extend into next week ahead of a cold front
that is now forecast to arrive on Wednesday. This front should
bring a chance of rain and utlimately cooler temperatures by



.AVIATION:  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1223 PM CDT Fri Aug 22 2014

Main forecast issue is the probability for any showers and thunderstorms
and the need for inclusion in any of the TAFS. An old thunderstorm
boundary has sunk to around I-70 and this has caused some havoc in
the wind direction although they are light. Indications the
boundary will retreat northward and could result in scattered
showers and thunderstorms this afternoon across northern Missouri
into central IL which might impact KUIN. Confidence is below
average and thus have just mentioned a VCTS for this afternoon. A
higher probability of showers and thunderstorms will exist at KUIN
during the overnight hours. Elsewhere can`t rule out isolated
shower or thunderstorms with afternoon heating but the coverage and
probability are too low to mention. Largely outside of any thunderstorms,
VFR conditions will dominate with surface winds at or below 8 kts
through the period.

Specifics for KSTL:

VFR conditions are expected to dominate much of the forecast period
with surface winds at or below 8 kts. Will have to keep an eye out
for any isolated showers or thunderstorms this afternoon, and then
overnight tonight will need to monitor any showers and thunderstorms
across northern MO sagging southeastward. Confidence and probabilities
at this time are too low to mention in the TAF.



MO...HEAT ADVISORY until 7 PM CDT Sunday FOR Audrain MO-Boone MO-
     Callaway MO-Cole MO-Franklin MO-Gasconade 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-Shelby
     MO-St. Charles MO-St. Francois MO-Ste. Genevieve MO-Warren

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

IL...HEAT ADVISORY until 7 PM CDT Sunday 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 Sunday FOR Madison IL-St.
     Clair IL.



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