Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 251757

1257 PM CDT Sat Apr 25 2015

.SHORT TERM: (Through this Evening)
Issued at 240 AM CDT Sat Apr 25 2015

Well advertised storm system will bring two rounds of showers and
thunderstorms to the CWA over the next 12 hours. The first round is
just now taking shape as warm advection increases ahead of the
shortwave now lifting from the southern Plains into the lower
Missouri River Valley. Surface low pressure depicted by model
guidance the past few days seems to be associated with well defined
MCV on regional radar currently spinning in far southeast Nebraska.
Showers and thunderstorms should continue to develop from northwest
Missouri to southeast Missouri and lift north through the predawn
hours. Dry slot will push through the southeastern half of the CWA
ahead of the low pressure this morning and early afternoon.  This
will cause the band of warm advection showers and thunderstorms to
steadily march northeast of the CWA. It will also set the stage for
at least some breaks in the cloud cover south of Interstate 70 and
instability to increase this afternoon.

The second round of precipitation today will take shape later this
morning and into the afternoon as the low pressure center traverses
east-southeast across the CWA.  Rain showers and isolated
thunderstorms will accompany the low pressure center (MCV) and
additional thunderstorm development is likely ahead of and to the
south of the surface low. SPC continues to highlight the likelihood
of severe thunderstorm development this afternoon, mainly southeast
of the St. Louis Metro.  Latest explicit model guidance depicts
discrete storm development between 2 PM and 4 PM just south of St.
Louis, with this activity exiting the CWA shortly after 7 PM. Large
hail and damaging wind gusts will be the primary threats with the
supercells this afternoon and early this evening. The threat of
tornadoes is more conditional and will likely hinge on how much
instability can be realized ahead of the low and if the surface
winds can remain backed across this area.


.LONG TERM:  (Tonight through Friday)
Issued at 240 AM CDT Sat Apr 25 2015

Showers will come to an end from northwest to southeast this
evening and clearing is still expected on Sunday with below normal
temperatures. Rest of the forecast remains unchanged with
temperatures gradually returning to normal by the end of the week
and precipitation chances remaining low.



.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1253 PM CDT Sat Apr 25 2015

Quick aviation update as storms are developing on radar attm.
Generally expect coverage in rain and IFR to increase and move
south across the area this afternoon into tonight. Strongest
thunderstorm activity expected along and south of the I-70
corridor into early evening. Thunderstorms should taper off into
general showers and IFR ceilings. Rain will end through the mid-
late evening but IFR will persist into Sunday morning.





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