Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 122308
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
608 PM CDT Sat Aug 12 2017

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 332 PM CDT Sat Aug 12 2017

High pressure over the area will slide east to the Great lakes by
tonight. Some scattered diurnal clouds will be possible over the
region on Sunday. Temperatures will continue at or just below
climatological normals through Sunday afternoon. Light northeast
winds will switch to the southeast by Sunday afternoon and remain
light.


Kelly

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 332 PM CDT Sat Aug 12 2017

A transitional period in the upper air pattern will begin Sunday
night into early next work week as the predominant northwest flow
regime becomes southwesterly by Tuesday/Tuesday night.
Expectation is for temperatures to warm back up to near to
slightly above normal for the middle of August along with much
more humid conditions as well. It will certainly feel more like
summer by the middle of this week, really for the first time this
month. High temperatures are expected to be in the upper 80s to
low 90s Tuesday through Thursday, with heat index values mainly in
the mid to upper 90s each afternoon.

Chances for showers and thunderstorms will also be on the increase,
though thinking most areas will be mostly dry through Tuesday. Best
chances for showers and thunderstorms appears to be from Tuesday
night through Thursday. Still have a lot of uncertainty with
specifics however, as model guidance has shown a lot of run-to-run
spread in timing/location of individual shortwave troughs ejecting
out of the desert southwest into the lower Missouri Valley.

Weak northwest flow aloft should reestablish itself late next week
into next Saturday as a shortwave trough moves through the Great
Lakes. This feature should help push a cold front through the area
down into the mid south. Slightly cooler and drier conditions
should greet the mid-Mississippi Valley as a result.


Gosselin

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 552 PM CDT Sat Aug 12 2017

Surface high pressure ridge centered over northern IL will move
eastward. Mainly northeasterly surface winds early this evening
will become light later tonight, then veer around to an east-
southeast direction on Sunday, albeit remaining weak. Few-
scattered diurnal cumulus clouds will dissipate early this
evening, then may redevelop late Sunday morning and afternoon. The
northern fringes of high level cloudiness across southern MO will
continue to impact COU and the St Louis metro area through at
least tonight.

SPECIFICS FOR KSTL: Surface high pressure ridge centered over
northern IL will move eastward. North-northeasterly surface winds
early this evening will become light later tonight, then veer
around to an east-southeast direction on Sunday, albeit remaining
weak. Scattered diurnal cumulus clouds will dissipate early this
evening, then may redevelop late Sunday morning and afternoon. The
northern fringes of high level cloudiness across southern MO will
continue to impact STL through at least tonight.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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