Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 281154

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
654 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 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


.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 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.



.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 638 AM CDT Sun May 28 2017

Area of IFR stratus and fog along a weak cold front in central and
northeast Missouri is moving into east central and southeast
Missouri. The big question is how far east it will get before
daytime heating makes the stratus lift and scatter. Current
indications are that it will get into the STL Metro area and parts
of southwest Illinois before dissipating between 14-16Z...although
confidence in the height of the stratus and visibility is only
moderate. Cannot ignore the 400ft ceiling at KFYG (Washington
Regional) just southwest of KSUS though.

As mentioned before, should see conditions improve rapidly between
14-16Z and VFR is expected to prevail thereafter. May see some
isolated showers or storms develop east of the Mississippi River
during the afternoon, but any showers that do form should
dissipate quickly after 00Z.


IFR ceilings west of the terminal will likely affect Lambert
briefly this morning. Am not very confident on the timing and
height of the cloud deck when it does come in. However, 400 ft
ceiling at KFYG southwest of Lambert cannot be ignored. The low
ceilings shouldn`t last long though and I expect rapid improvement
by 15-16Z. VFR flight conditions are expected thereafter.





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