Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 250741

241 AM 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 depticted 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
descrete 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 06z TAFs through 06z Saturday Night)
Issued at 1145 PM CDT Fri Apr 24 2015

MVFR cigs are in the process of overspreading the CWA attm...and
latest MET and MAV MOS still strongly suggest that this
deterioration will continue into IFR cigs during the predawn
hours as the persistent low level WAA increases the low level
moisture in the region. A few hit and miss showers have formed
over NE MO the last couple of hours, with the anticipation that
there will be a general increase in coverage of well
as thunderstorms...during the predawn hours as forcing via low
level jet and upper level low ramp up the vertical motion across
the Mississippi Valley. 00z guidance is a bit further south with
track of low, which would keep UIN in IFR conditions and precip throughout
the day, with only limited improvement at KCOU and the STL metro
area. Still appears that there will be a narrow window for
redevelopment of thunderstorms in the STL area during the early
afternoon, and have continued to highlight with VCTS attm.

Specifics for KSTL: Ceiings expected to drop below 1000 feet
during the predawn hours, with showers and a few thunderstorms
developing by around 09z. Anticipate that the early morning
convection will advect out of the region during the early morning,
with ceilings slowly improving to MVFR as surface low works into
the area from mid MO. Have maintained a mention of some
thunderstorm redevelopment during the early afternoon in the form
of VCTS...hoping later shifts will be able to refine the location
and intensity of this redevelopment.



Saint Louis     70  47  62  41 /  80  70   0   0
Quincy          58  40  60  38 /  80  40   0   0
Columbia        68  45  62  39 /  70  30   0   5
Jefferson City  71  46  62  41 /  70  30   5   5
Salem           65  46  61  39 /  80  70   0   0
Farmington      75  48  61  39 /  60  40   5   5




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