Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 191753

1253 PM CDT Tue May 19 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 425 AM CDT Tue May 19 2015

High pressure building into Missouri and Illinois brings cool
temperatures and calm weather to the area today. Expect highs in
the 60s and light winds out of the northwest to north.


.LONG TERM:  (Tonight through Monday)
Issued at 425 AM CDT Tue May 19 2015

An upper disturbance induces a surface wave along a pre-existing
baroclinic zone stretching across the south central and
southeastern states. A southerly LLJ ahead of the low pressure
system interacts with the boundary to spread showers/thunderstorms
northward into the forecast area as early as late tonight.
Precipitation coverage seems most widespread on Wednesday, then
tapers off on Wednesday night when the surface wave both dampens
and moves farther away from the forecast area. High pressure
builds back into the region on Thursday for another day of cooler
temperatures and calm weather. The synoptic pattern for this
weekend resembles the synoptic pattern for the last two weekends.
A few periods of active weather appear likely between Friday and



.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1242 PM CDT Tue May 19 2015

Last bit of MVFR stratocumulus deck over northeast Missouri and
west central Illinois looks to be vaporizing based on current
satellite pics. Should see VFR flight conditions prevail until
around 12Z Wednesday. Rain and lower clouds will be moving in to
central Missouri by then as an upper level disturbance moves over
the area. MVFR cigs/vsbys in light to occasionally moderate rain
will overspread the area through the morning. Guidance is hinting
at IFR ceilings as well, but held off mentioning in the TAF for
now. Would like to let the evening and midnight shifts evaluate
the situation further as it develops.

Specifics for KSTL:

VFR flight conditions are expected to prevail at Lambert through
tonight into Wednesday morning. Rain will overspread the terminal
dropping cigs/vsbys into MVFR range sometime during the late
morning and early afternoon. 18Z in the TAF is just a first cut,
and expect the timing will change as more data comes in. Could see
IFR conditions as well during the late afternoon, but did not
mention in TAF at this time as it is yet uncertain if/when
ceilings will drop that low.





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