Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 272344
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
644 PM CDT Sat May 27 2017

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 313 PM CDT Sat May 27 2017

Severe weather watches will continue across central and southeast
MO and southwest IL into the evening hours. Supercells were
occuring across parts of southeast MO with bow echoes in central
and southwest MO. These bow echoes may consolidate into a larger
squall line late this afternoon. Once this squall line clears our
forecast area by late evening we should just have some lingering
showers and a few storms. Most of the convection should shift
south of our forecast area by midnight. Will still have a chance
of showers and storms on Sunday until an upper level trough
centered over the northern Plains and a cold front shift east-
southeast of our forecast area. Any severe weather threat should
be southeast of the forecast area on Sunday.

GKS

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 313 PM CDT Sat May 27 2017

Cooler conditions can be expected Sunday night due to a clear sky
and lower surface dew points. Another cold front will drop
southeastward through our area Monday afternoon and evening, but
little if any precipitation is expected with this front. A better
chance of showers may occur on Tuesday as a northwest flow
shortwave moves through our area. A surface ridge will build into
the region from the northern Plains on Wednesday shunting better
moisture and any precipitation threat south of our forecast area.
As this surface ridge shifts east of the region Thursday return
southerly flow on the backside of the ridge should lead to
increasing moisture and the potential for convection Thursday
night and Friday.

GKS

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 550 PM CDT Sat May 27 2017

It looks like one more thunderstorm will pass through the COU
area early this evening per radar trends, with thunderstorms
moving southeast of the St Louis metro area early this evening. It
appears that the convection will shift south of the taf sites
later this evening. The models continue to indicate stratus clouds
and light fog late tonight and early Sunday morning as surface
winds become light with surface dew points still high. For now
will just forecast MVFR cigs and vsbys late tonight and early
Sunday morning, although a brief period of IFR conditions is
possible. Surface wind will become northwesterly and strengthen
Sunday morning after the passage of a cold front with any fog
dissipating and cloud ceilings slowly rising. Could not rule out
some post frontal showers on Sunday with an upper level
disturbance moving through the area, but will leave precipitation
out of the tafs for now.

SPECIFICS FOR KSTL: Thunderstorms will move southeast of the STL
area early this evening. It appears that the convection will
shift south of the St Louis metro area later this evening. The
models continue to indicate stratus clouds and light fog late
tonight and early Sunday morning as surface winds become light
with surface dew points still high. For now will just forecast
MVFR cigs and vsbys late tonight and early Sunday morning,
although a brief period of IFR conditions is possible. Surface
wind will become northwesterly and strengthen Sunday morning after
the passage of a cold front with any fog dissipating and cloud
ceilings slowly rising. Could not rule out some post frontal
showers on Sunday with an upper level disturbance moving through
the area, but will leave precipitation out of the taf for now.

GKS

&&

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

$$

WFO LSX


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