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fxus63 klsx 222034 
afdlsx

Area forecast discussion
National Weather Service Saint Louis MO
334 PM CDT Sat Jul 22 2017

Short term... (through late Sunday afternoon)
issued at 334 PM CDT Sat Jul 22 2017

Oppressively hot and humid conditions were noted across the region
early this afternoon, and several ASOS sites had already passed the
century mark by 18-19z. At 20z, kstl reported a temperature of 104
degrees with a dew Point of 69 degrees, yielding a heat index of 111
degrees.

A boundary was located near the MO/Iowa border as per regional metars
and satellite imagery. A shortwave moving along the US/Canada border
towards the Great Lakes will push this boundary southward as a cold
front into MO/IL. Isolated to scattered thunderstorms are expected
to develop near this boundary within an unstable air mass. A few
storms could be strong to severe given steep 700 mb-500 mb lapse rates and a
very unstable air mass. A separate area to monitor for potential
rain showers/thunderstorms and rain development late this afternoon and this evening will be
along a remnant outflow boundary which moved across the region
earlier this morning.

Although the cold front will move through the region tonight, there
won't be much change in the air mass characteristics until tomorrow
night when a second cold front moves through the region (see
discussion below). Highs will be around 5-7 degrees cooler on Sunday
compared to today, which will translate to peak heat index values of
100-105 rather than 110+ across the southern half of the County Warning Area.
Although the heat will be slightly less intense on Sunday, it still
appears dangerous enough to keep the existing heat headlines in
place.

Kanofsky

Long term... (sunday night through next saturday)
issued at 334 PM CDT Sat Jul 22 2017

Not a lot of changes from the prev forecast. A cooler cdfnt is progd
to push into the County Warning Area sun evening with sct thunderstorms and rain possible near the
fnt.

Unfortunately, the cooler temps will be short lived as the thermal
ridge begins to build into the region with height rises by tues.
Still, with a somewhat nly and Ely sfc flow, have trended slightly
cooler. Regardless, the dewpoints shud still be much cooler allowing
temps to drop into the 60s at night.

The upper ridge continues to build into the area on tues and Wed
with 850mb temps in the 21c to 24c range by Wed. This shud result in
temps in the upper 90s to near the century mark for the St. Louis
Metro area. This heat event shud be short lived with a deep upper
trof and associated sfc cdfnt pushing thru the area Wed night and
thurs. Depending on the progress of the fnt, temps on thurs may not
be warm enuf across srn portions of the County Warning Area. Behind this fnt, much
cooler and drier air returns on Fri into next weekend with a 1016 mb
sfc ridge, 850mb temps around 15c and northwest flow aloft.

Tilly

&&

Aviation... (for the 18z tafs through 18z Sunday afternoon)
issued at 1202 PM CDT Sat Jul 22 2017

Specifics for kuin: an outflow boundary was still affecting the
prevailing wind direction at KUIN at taf issuance, but winds
should continue to veer this afternoon and become southwesterly to
west-southwesterly during the first 6-8 hours. Isolated to
scattered rain showers/thunderstorms and rain are expected to develop late this afternoon
near a weak front, but KUIN may be too far north of the boundary
to experience much precipitation. Winds will become northwesterly
after fropa.

Specifics for kcou: scattered rain showers/thunderstorms and rain are expected to develop
late this afternoon and early this evening invof a weak front as
it sinks southward through the region. Winds will become
northwesterly after fropa.

Specifics for kstl, ksus, kcps: an outflow boundary moved through
the St. Louis Metro area terminals a few hours ago, which shifted
the winds to 030-060. Winds have been slowly veering in the wake
of the boundary and were 130-160 at taf issuance. Based on
upstream observations, winds will continue to slowly veer over the
next few hours before returning to the prevailing southwesterly
or west-southwesterly flow. Scattered rain showers/thunderstorms and rain are then expected
to develop this evening invof a front as it slowly sinks
southward through the region. Winds will become northwesterly
after fropa.

Kanofsky

&&

Preliminary point temps/pops...
Saint Louis 80 97 72 91 / 30 20 20 0
Quincy 74 92 66 85 / 30 10 20 5
Columbia 74 93 68 88 / 40 20 10 0
Jefferson City 75 94 69 90 / 40 20 10 5
Salem 77 94 70 88 / 30 10 10 5
Farmington 76 94 69 90 / 30 30 20 10

&&

Lsx watches/warnings/advisories...
MO...excessive heat warning until 8 PM CDT Sunday for Boone MO-
Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
Montgomery MO-Osage MO-Reynolds MO-Saint Charles MO-Saint
Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
Genevieve MO-Warren MO-Washington MO.

Excessive heat warning until 8 PM CDT this evening for Audrain
MO-Knox MO-Lewis MO-Marion MO-Monroe MO-Pike MO-Ralls MO-
Shelby MO.

Illinois...excessive heat warning until 8 PM CDT Sunday for Bond Illinois-Calhoun
Illinois-Clinton Illinois-Jersey Illinois-Madison Illinois-Marion Illinois-Monroe Illinois-
Randolph Illinois-Saint Clair Illinois-Washington Illinois.

Excessive heat warning until 8 PM CDT this evening for Adams Illinois-
Brown Illinois-Fayette Illinois-Greene Illinois-Macoupin Illinois-Montgomery Illinois-
Pike Illinois.

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