Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 202042

Area Forecast Discussion
National Weather Service Saint Louis MO
342 PM CDT Thu Jul 20 2017

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 342 PM CDT Thu Jul 20 2017

Hot and humid conditions will remain in place across the region
tonight and tomorrow. Overnight lows will only fall into the mid-
70s, except in the urban core of St. Louis where temperatures may
not fall below 80 degrees. Highs in the upper 90s to low 100s
combined with dew points in the 70s will yield heat index values of
100 to 114 degrees on Friday.

There is little opportunity for widespread precipitation tonight or
tomorrow given that shortwaves and boundaries will remain well to
the north of the area, although a few afternoon SHRA/TSRA across
southwest Illinois cannot be entirely ruled out.


.LONG TERM...  (Friday Night through Next Thursday)
Issued at 342 PM CDT Thu Jul 20 2017

Focus for the forecast period continues to be the ongoing heat.

Not a lot of changes for this forecast cycle. Upper ridge currently
overhead begins to break down by Sat which will hopefully allow a
cdfnt to drop into the area Sat evening and into Sun. With good
upper air support, expect at least sct TSRA to develop along what
appears to be a pre-frontal trof of sorts while the actual cdfnt
hangs up over IA.

Mdls continue to show 20C to 24C 850mb temps across the region thru
Sat. Slightly cooler 850mb temps are expected on Sun, tho if
convection is limited, the going forecast may be too cool by a few
degrees.  The actual cdfnt shud push thru the area early Mon morning
allowing for a couple of days of cooler and drier weather before the
next warmup on Wed.

Have overall trended aoa the warmer guidance thru the period. The
ECMWF soln is an outlier with an MCV moving across srn portions of
the CWA Tues night into Wed. Have trended away from the ECMWF soln
for now.



.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1204 PM CDT Thu Jul 20 2017

VFR through the period with diurnal cumulus and occasional cirrus.
Southwest winds will diminish overnight and become more southerly,
then increase and become southwesterly again after 21/12z.



Saint Louis     82 106  84 107 /   0   5   5   5
Quincy          76  97  77  97 /   5  10   5  20
Columbia        75  98  76  98 /   0   0   0  10
Jefferson City  76  97  76  99 /   0   5   0   5
Salem           76 100  77 100 /   0  10   5   5
Farmington      75  97  75  98 /   0   5   0   5


MO...Heat Advisory until 8 PM CDT Sunday for Crawford MO-Iron MO-
     Madison MO-Reynolds MO-Saint Francois MO-Sainte Genevieve
     MO-Washington MO.

     Excessive Heat Warning until 8 PM CDT Saturday for Audrain MO-
     Boone MO-Callaway MO-Cole MO-Franklin MO-Gasconade MO-
     Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-Moniteau
     MO-Monroe MO-Montgomery MO-Osage MO-Pike MO-Ralls MO-Saint
     Charles MO-Saint Louis City MO-Saint Louis MO-Shelby MO-
     Warren MO.

IL...Heat Advisory until 8 PM CDT Sunday for Randolph IL.

     Excessive Heat Warning until 8 PM CDT Saturday for Adams IL-Bond
     IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-
     Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
     Montgomery IL-Pike IL-Saint Clair IL-Washington IL.



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