Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 121800

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
100 PM CDT Sat Aug 12 2017

Issued at 820 AM CDT Sat Aug 12 2017

High pressure over the northern plains will slowly move east
today to the Great Lakes with dry weather expected over the
region. Temperatures will be cooler today and tonight over the
area. Light north to northeast winds expected both today and



.SHORT TERM...  (Through Late Tonight)
Issued at 331 AM CDT Sat Aug 12 2017

The cold front which moved through the region yesterday was located
near the MO/AR border early this morning, and a surface high
pressure center was noted across the northern plains. Model
solutions depict the surface high moving into the Great Lakes region
today and tonight, which will ensure quiet weather conditions across
the LSX CWA. Overall, temperatures for today and tonight will be
similar to or slightly cooler than yesterday and last night.


.LONG TERM...  (Sunday through Friday)
Issued at 331 AM CDT Sat Aug 12 2017

The synoptic pattern at the start of the long term period will
feature weak cyclonic flow aloft due to continued troughing across
the northeast CONUS. This persistent regime will slowly begin to
break down through the middle and end of next week as heights build
across the southeast CONUS.

Sunday will begin with surface ridging located across portions of
the Great Lakes region. Guidance has come into general agreement
that this surface ridge will be strong enough to surpress a surface
front down into the southern Plains and lower MS Valley. Therefore,
think any convection caused by shortwaves diving through the
cyclonic flow aloft should stay mostly southeast of the area through
Monday morning.

By Monday afternoon, predictability begin to decrease as guidance
suggests the upper-level pattern will undergo a shift to more west-
southwesterly. This shift in the upper-level flow should allow the
effective surface boundary to lift back to the north. Convection
along/north of this retreating boundary could start to creep into
central/southeast MO as early as Monday afternoon into Tuesday
(GFS/GEFS faster than the GEM/Euro). However, precipitation chances
look maximized Wednesday into Thursday as the upper-level flow backs
to more southwesterly and moisture convergence maximizes along the
retreating boundary.

Temperatures will slowly moderate through the period given the
evolving upper-level pattern. After highs in the low 80s Sunday,
temperatures will climb back to near seasonal values (upper 80s) by
the end of next week.



.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1252 PM CDT Sat Aug 12 2017

High pressure will continue to move to the east to be located near
the Great lakes this evening. VFR ceilings and conditions along
with light winds expected through Sunday morning.

High pressure will continue to move to the east to be located near
the Great lakes this evening. VFR conditions and ceilings along
with light winds expected at the terminal through the forecast





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