Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 221945

Area Forecast Discussion
National Weather Service Saint Louis MO
245 PM CDT Fri Sep 22 2017

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 243 PM CDT Fri Sep 22 2017

Early this afternoon, a sharp upper level RIDGE axis extended from
southeast Lower MI thru southeast MO and into eastern TX and has
moved very little from 24hrs ago.  Under this RIDGE, "airmass"
storms have developed in spots, particularly in eastern IL and
Indiana and also in northern AR.  Surface high pressure was centered
over the Ohio River Valley, resulting in a light southerly flow over
our region.  The only clouds today have been a scattered diurnal
cumulus field, and thanks to the plentiful sunshine still yielded,
has allowed temps to surge into the 90s for another day of much
above average values.  Already one record max temp has been tied (at

Some "airmass" showers or storms could sneak into southern and
eastern areas of the CWA thru early this evening and have small PoPs
to account.  Otherwise, look for the diurnal cumulus cloud field to
dissipate around sunset with clear skies overnight.  Persistence
will be hard to beat for min temps overnight, with 65-70 for most
areas, save 70-75 for urbanized areas of STL metro.

The upper RIDGE will still be a dominant player over our region on
Saturday with similar issues:  much above average temps and possibly
an isolated "airmass" shower or storm with the usual diurnal cumulus
cloud field forming with the heat of the day.  Edged max temps down
a couple degrees from persistence with surface flow anticipated to
be more easterly than southerly but still trended on the high side
or slightly higher than MOS.  Kept PoPs dry for now, but need to
evaluate the usual more susceptible areas (eastern Ozarks) for these
showers and storms for possible inclusion of a low PoP.


.LONG TERM...  (Saturday Night through Next Friday)
Issued at 243 PM CDT Fri Sep 22 2017

The upper level pattern through next week has a long wave trough
over the western US and high pressure ridge over the central and
eastern US. The long wave trough will slowly move to the east toward
the central US through the week. The weather will be dry and quiet
through Monday. A cold front will move into central Missouri by
Tuesday morning. The cold front will have limited low level moisture
and ascent to work with thus both showers and thunderstorms will be
scattered in nature. The cold front will clear the area by Wednesday
morning. The unseasonably warm temperatures are expected through
early next week, then give way to a more seasonal air mass by
Wednesday. A continuation of seasonal temperatures and dry weather
are forecast through  next  Thurday and Friday.



.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1248 PM CDT Fri Sep 22 2017

VFR conditions, dry wx, and light S surface winds will prevail at
the TAF sites initially, with the only real change being that the
surface winds are expected to back more from the E by Saturday. A
brief occurrence of mist with minor VSBY reductions looks probable
at SUS and CPS again with the better chances S and E of STL metro.
An isolated SHRA/TSRA possible this afternoon but S and E of STL
metro as well.



Record Max Temperatures Through Saturday

              KSTL  KCOU  KUIN
Sept 22     95 (1956)   97 (1937)   96 (1937)
Sept 23     94 (1891)   94 (2007)   95 (1937)
Sept 24     94 (1891)   95 (1891)   94 (1935)

Record High Min Temperatures Through Saturday

              KSTL        KCOU        KUIN
Sept 22     73 (2005)   71 (2005)   71 (1930)
Sept 23     73 (1884)   73 (1937)   73 (1937)




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