Area Forecast Discussion
Issued by NWS St. Louis, MO

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802
FXUS63 KLSX 191150
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
650 AM 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.

42

.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
Monday.

42

&&

.AVIATION:  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 650 AM CDT Tue May 19 2015

Over the last few hours some of the cold air SC (with MVFR cigs) in
the wake of the Great Lakes low has managed to drift south and
sneak into our far N counties...including KUIN. 00z and 06z
guidance as well as the latest RUC solutions suggest that this
cloudiness should become stationary and quickly dissipate over the
next few hours. Otherwise and elsewhere...VFR conditions are
expected today, with cloudiness limited to some high level CI
spreading from the Plains into the mid-Mississippi Valley. Mid and
high clouds will then slowly thicken overnight as WAA ramps up
ahead of upper level trof. Overnight synoptic guidance suggests
that only threat of rain during this TAF period will be limited to
KCOU just before daybreak, with cigs here possibily lowering to
around 5kft by this time.

Specifics for KSTL: Clouds aoa 10kft expected today and into
tonight, with north-northeast winds aob 10kts. Ceilings should
begin to lower on Wednesday morning as WAA intensifies across
area, with ceilings dropping into the 3-5kt range by late morning
as rain begins to push into the area.

Truett

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX






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