Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 281647
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1147 AM CDT Sun May 28 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 316 AM CDT Sun May 28 2017

Much quieter weather expected across the area today.  High pressure
will begin building across the area behind a cold front which will
move through the area this morning.  The upper level shortwave is
lagging the front back over southeast Nebraska this morning,
and it will move overhead this afternoon.  Models still show some
lingering instability behind the front this afternoon, and most
guidance prints out a few hundredths of QPF ahead of the shortwave
primarily east of the Mississippi River.  Have therefore kept some
slight chance PoPs going for the afternoon hours as the wave moves
through.  The airmass behind the cold front is drier more than it is
cooler.  Afternoon highs will be pretty close to yesterday`s
highs...in some cases it might actually be a little warmer where
there`s more insolation than yesterday.  With a clear sky and a
relatively light wind tonight we should see some decent
radiational cooling with temperatures falling into the mid and upper
50s.

Carney

.LONG TERM...  (Monday through Saturday)
Issued at 316 AM CDT Sun May 28 2017

Will continue to keep a slight chance of showers and thunderstorms
on Monday afternoon and evening as a cold front moves southeast
across the area.  The atmosphere will become modestly unstable along
and ahead of the front as a weak shortwave rotates around the
southside of the upper low that will be over the northern Great
Lakes. Another weak shortwave trough will bring another chance of
showers to the area late Tuesday and Tuesday night. The upper
level low will move east of the Great Lakes on Wednesday and high
pressure will move across Missouri and Illinois bringing mainly
dry weather.

By late in the week, low level winds will turn out of the southwest
advecting moisture from the Gulf.  With instability increasing over
the area, will keep a chance of showers and thunderstorms over the
area Thursday through Saturday, particularly on Saturday when a
cold front will be dropping south into the area.

Highs will vary from the middle 70s to lower 80s this week which
is supported by the GEFS ensemble guidance.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1127 AM CDT Sun May 28 2017

A weak cold front extending from a surface low over southwestern
MI southwest through the St Louis metro area will continue moving
southeastward. There were some isolated, post frontal showers
across west central IL late this morning ahead of a weak upper
level disturbance. Could not rule out a few light showers in the
St Louis metro area early this afternoon. The stratus clouds in
the St Louis metro area should clear out early this afternoon as
drier air advects into the region with only some mid level clouds
remaining. A clear sky is expected tonight with some mid-high
level clouds moving in Monday morning ahead of another upper
level disturbance and associated weak cold front. West-northwest
surface winds should become light later this evening as they back
around to a southwest direction.

SPECIFICS FOR KSTL: A weak cold front extending from a surface low
over southwestern MI southwest through the St Louis metro area
will continue moving southeastward. There were some isolated, post
frontal showers across west central IL late this morning ahead of
a weak upper level disturbance. Could not rule out a few light
showers in the STL area early this afternoon. The stratus clouds
in the St Louis metro area should clear out early this afternoon
as drier air advects into the region with only some mid level
clouds remaining. A clear sky is expected tonight with some mid-
high level clouds moving in Monday morning ahead of another upper
level disturbance and associated weak cold front. There may be a
few showers in the STL area Monday afternoon. West-northwest
surface winds should become light later this evening as they back
around to a southwest direction.

GKS

&&

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

$$

WFO LSX


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