Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 182325

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
625 PM CDT Sun Jun 18 2017

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 215 PM CDT Sun Jun 18 2017

Sfc ridge continues to build into the region this afternoon
bringing a drier and cooler airmass. Gusty nwly winds will
diminish this evening with sunset, tho expect continued mixing
thru much of the night. Some fog may develop late tonight across
srn portions of the CWA where low lying areas decouple and winds
are expected to be lighter. Current thinking is that this will be
somewhat limited with advection of cooler dewpoints into the
region aided by mixing today. As for temps tonight, trended aob
the cooler guidance based on scenario mentioned above.

On Mon, NW flow will remain across the CWA both at the sfc and
aloft. Expecting fewer clouds on Mon thru the early afternoon
hours and have therefore trended slightly warmer compared to
temps today. Mdls prog a s/w dropping sewd into the region late
Mon afternoon. This s/w shud support isod TSRA across nrn portions
of the CWA. However, some uncertainty remains how far south these
PoPs shud extend. Some guidance suggests these SHRA/TSRA will be
possible earlier in the afternoon and further south into central
portions of the CWA. While this can not be ruled out, believe main
threat will remain further north closer to the very weak cdfnt
associated with the s/w.

.LONG TERM...  (Monday Night through Next Sunday)
Issued at 352 PM CDT Sun Jun 18 2017

Quiet weather is expected until Wednesday night when an
approaching trough interacts with the warm/moist return flow
spreading into MO/IL around the back side of a surface high
pressure center. Models are in slightly better agreement with the
upper air pattern compared to 24hrs ago, but there are still
significant model timing differences with the upper vorticity
maxima which will provide upper support for a few rounds of
SHRA/TSRA. A broad swath of SChc-Chc PoPs for the end of the
upcoming week seems appropriate due to this model uncertainty.

Temperatures will be seasonably warm with highs in the upper 80s
to around 90 degrees. The warmest day of the upcoming week will
probably be on Wednesday after a warm front has lifted northward
through the region and favorable southwesterly winds spread across
the region ahead of the approaching trough.



.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 624 PM CDT Sun Jun 18 2017

Expect mainly dry and VFR conditions through the period. Isolated
thunderstorms will be possible over northeast Missouri and west
central Illinois including KUIN on Monday afternoon. Westerly
winds will be light through mid morning on Monday, but will become
gusty at times on Monday afternoon.

SPECIFICS FOR KSTL: Expect dry and VFR conditions through the
period. Light westerly winds are expected through mid morning on
Monday, but will gust up to 18kts on Monday afternoon.





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