Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 200446

1146 PM CDT Sun Apr 19 2015

.SHORT TERM:  (Through Tonight)
Issued at 344 PM CDT Sun Apr 19 2015

Main rain shield that developed in response to the low pressure
system to our southeast will continue to slowly lift northeast late
this afternoon and into this evening. Meanwhile, scattered
convection will continue to develop in its wake ahead of the main
upper level trof and cold front. Believe much of the convection is
diurnally driven and will dissipate late in the evening, with only a
few showers remaining after midnight. Threat of any severe weather
should stay south of the CWA where better instability resides.


.LONG TERM:  (Monday through Next Sunday)
Issued at 344 PM CDT Sun Apr 19 2015

(Monday through Wednesday)

Focus finally turns to temps thru the period.

Have kept slight chance PoPs Mon morning across nern/ern portions of
the CWA as the system continues to pull out of the region. Some of
the explicit mdls suggest isod SHRA developing during the afternoon
hours. However, given the lack of precip behind the trof currently
across the Plains, believe mdls are simply showing CU developing.
Have therefore kept much of the day dry.

Next chance for RA is then Tues afternoon thru Wed with mdls
continuing to show a s/w rounding the base of the upper low. Mdls
continue to differ in placement and timing for this s/w. Have kept
similar PoPs going for this period until mdls come into better
agreement consistently.

Temps for Mon will be difficult with questions about cloud cover.
Expect CU to develop behind this trof. Based on latest sat trends,
wud expect more cloud cover than mdls are currently expecting.
However, am trending twd a more cloud free soln, and therefore
slightly warmer, for now. Temps shud moderate slightly with the
thermal ridge building into the area on Tues, but then CAA again on
Wed as a back door cdfnt pushes thru the area again.

(Thursday through Sunday)

Mdl differences continue thru the extd with the GFS/GEM a more zonal
soln and the ECMWF more amplified. Have therefore kept PoPs on the
low end except for periods where mdls were in better agreement
despite differences in setup.

Largely kept temp trends going as well twd a compromise given the
uncertainty in solns.



.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1136 PM CDT Sun Apr 19 2015

Specifics for KCOU, KUIN: 05z METARs show that the cold front has
already moved through KCOU and KUIN. Northwest winds with gusts of
around 25kts are expected to continue overnight. BUFKIT soundings
show that stronger gusts (perhaps 30-35kts) will mix down to the
surface during the day. Transient IFR cigs are possible through
12z but the prevailing ceiling ought to remain MVFR until diurnal
mixing starts to break up the cloud deck during the mid-morning
hours. A few isolated showers were noted near KUIN at TAF
issuance but these will quickly move away from the terminal.

Specifics for KSTL, KSUS, KCPS: Cold front should move through the
St. Louis metro area terminals a bit earlier than previously
anticipated. Winds will become northwesterly and gust to 25-30kts
after fropa. BUFKIT soundings show that wind gusts should persist
through the day then diminish around sunset. MVFR cigs noted
upstream at TAF issuance should reach KSTL within the next 1-2
hours, then start to mix out during the mid-morning hours. A few
spotty showers are possible before 20/10z but coverage is too
sparse to include in the TAFs attm.





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