Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 221748

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1248 PM CDT Fri Sep 22 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 320 AM CDT Fri Sep 22 2017

Summer-like weather pattern will continue today and tonight despite
being the first day of Fall.  An upper level ridge extended from TX
northeast through MO to southern MI.  South-southeasterly surface
winds will continue in our forecast area on the western periphery of
a surface ridge centered over the northeastern US. Little cloud
cover is expected, maybe a little high level thin cloudiness, and
possibly a few diurnal cumulus clouds this afternoon. Unseasonably
warm and humid conditions can be expected today and tonight, more
typical of August.  Highs today will be about 15 to 20 degrees above
normal, and close to record values for this date.


.LONG TERM...  (Saturday through Thursday)
Issued at 320 AM CDT Fri Sep 22 2017

The synoptic pattern at the start of the long term period will
continue to feature a fairly amplified regime, with a deep trough
over the western CONUS and a downstream ridge over the central and
eastern part of the country. Deamplification of this pattern is
expected through the period, which should allow for the trough to
slowly build into the north-central CONUS by the end of next week.

Given little change expected to the upper-level pattern through
early next week, the sensible weather will remain largely unchanged
as well with hot and dry conditions continuing. Temperatures this
weekend into early next week will continue to run 10-15 degrees
above normal. Saturday appears to be the warmest day of the period
with highs likely to climb into the low 90s.  However, Sunday into
Monday will also feature upper 80s/low 90s temperatures as well.
Dewpoints should mix out enough in the afternoon to keep heat
indices below 100 degrees, but it will certainly feel hot for the
start of fall!

A slow-moving cold front will approach central/northeast MO by
Monday afternoon, sagging southeast through the rest of the area
Tuesday into Wednesday.  Both low-level moisture and upper-level
forcing for ascent appear to be lacking with this front, thus expect
only isolated-scattered storm coverage Tuesday into Wednesday as it
passes through.  The frontal passage will bring a return to cooler
conditions, with highs dipping back into the 70s Wednesday and
especially Thursday of next week.



.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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