Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 222317

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
617 PM CDT Tue May 22 2018

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 349 PM CDT Tue May 22 2018

High pressure over the area at the surface and aloft will persist
through Wednesday afternoon. The combination of clear skies and good
radiational cooling and light winds will lead to some river fog
again in the river valleys. Light north winds will switch to the
east by Wednesday morning and remain light. Lows tonight will be
60s across the area. Highs on Wednesday will mid to upper 80s
across the area.


.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 349 PM CDT Tue May 22 2018

An upper level ridge will continue to strengthen over the
Mississippi Valley on Wednesday before shifting slightly to the east
on Thursday. The combination of light east-southeast flow will keep
the area dry through Thursday night. The upper level ridge will
begin to break down on Friday as an upper level shortwave moves
through the Great Plains and into the upper Midwest. An isolated
shower or thunderstorm is possible over central Missouri on Friday

A weak cold front will slowly move into the forecast area on Friday
night and Saturday. The front will move to the southeast Missouri
and southwestern Illinois then meander over the area as a ridge over
the Great Lakes and one over the southeast coast of the US will keep
it from moving south. Similar to last week, a low will drift north
into the Mississippi Valley from Saturday through Monday, but a
upper level ridge to the north will cause it to stall. An increase
of low level moisture streaming north associated with the low will
aid in producing diurnal convection over the weekend and early next
week.  Temperatures will continue to be between 5 to 10 degrees
above normal for both afternoon highs and morning lows.



.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 617 PM CDT Tue May 22 2018

VFR conditions, dry weather, and light surface winds will prevail
at the TAF sites thru the valid period. Some potential for fog at
river valley sites (CPS, SUS) but current indications are VSBYs
should stay out of IFR. Otherwise, variable winds will become E to
SE by Wednesday.





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