Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 301428

928 AM CDT Tue Jun 30 2015

Issued at 919 AM CDT Tue Jun 30 2015

With the passage of the shortwave to the east with its isolated
convection have pretty dropped all PoPs from this morning except
over the far eastern CWA. Will monitor the weak cold front sliding
southeast through northern IL for any afternoon development. Satellite
imagery not showing any feature immediately upstream although the
12z NAM indicates a couple of weak h7 vorticity maxima that may or
may not exist. IL counties within the CWA will have the best
chance for afternoon convection.



.SHORT TERM:  (Through Late This Afternoon)
Issued at 434 AM CDT Tue Jun 30 2015

Scattered showers and storms are expected mainly this afternoon and
mainly across west central and southwest IL, east of the Mississippi
River as northwest flow shortwaves move southeastward through our
area.  The atmosphere will destabilize this afternoon due to daytime
heating, especially across IL near the axis of the upper level
trough centered over the Great Lakes region where mid level
temperatures will be a little colder and hence lapse rates steeper.
High temperatures should be a little warmer today compared to Monday
and close to seasonal normals for the end of June.


.LONG TERM:  (Tonight through Monday)
Issued at 434 AM CDT Tue Jun 30 2015

Showers and thunderstorms can be expected late tonight and Wednesday
as a southwesterly low level jet brings strong low level warm air
advection and moisture convergence to our forecast area, and a
surface low approaches from KS while a front sags slowly southward
through the region.  The models were also depicting strong upper
level divergence over our forecast area ahead of a northwest flow
shortwave.  There will be the potential for heavy rainfall which
could result in more flooding.  High temperatures on Wednesday will
be cooler due to the increased cloud cover along with fairly
widspread precipitation.  As the surface low and front sag slowly
southward the best threat for convection will shift to the southern
portion of the area Wednesday night and Thursday.  A surface ridge
across the Great Lakes region will nose into northeast MO and west
central IL likely ending the chance of precipitation across this
area Thursday and Thursday night.  Another upper level trough
dropping southeastward into the region will keep the threat for
showers/storms going at least across the western and southern
portion of our area Thursday through Friday.  The GFS model is a
little stronger with the surface ridge over the Great Lakes region
and is a little further south with its QPF than the NAM and the
ECMWF models.  Upper level troffing over the region coupled with a
moist low level southerly flow should lead to at least scattered
afternoon and evening convection Saturday and Sunday.



.AVIATION:  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 552 AM CDT Tue Jun 30 2015

Will add tempo groups for BR at KUIN, KSUS, and KCPS to accounts
to account for recent trends and low dewpoint depressions at these
airports. Then expect this fog to burn off by mid morning as
mixing takes place. Scattered thunderstorms will develop this
afternoon, particularly around KUIN and the St. Louis metro
airports. Have not included them in the TAFs at this point because
of uncertainty in coverage and timing. Otherwise rain chances will
increase late in the TAF period as an upper level storm systems
moves along a stalled front over the region.

Specifics for KSTL: There is a small chance for MVFR BR at the
terminal early in the period. Then, scattered thunderstorms will
be in the area this afternoon, but have not included them in the TAFs
at this point because of uncertainty in coverage and timing. Still
looks like rain chances will increase late in the period with the
potential for MVFR conditions after 12Z Wednesday.





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