Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 200510

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1210 AM CDT Fri Oct 20 2017

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 310 PM CDT Thu Oct 19 2017

With surface ridge to our east, southerly flow to persist through
Friday. So clear skies and light south winds tonight will allow
temperatures to dip down into the mid 40s to mid 50s.

On Friday, will see increasing mid and high clouds associated with
the next weather system to our west. With a tightening surface
gradient, south winds to pickup a bit, so despite increasing clouds,
highs will be similar to today, in the upper 70s to low 80s.


.LONG TERM...  (Friday Night through Next Thursday)
Issued at 310 PM CDT Thu Oct 19 2017

Period begins in fairly good agreement regarding mass fields. Very
amplified pattern overhead with an upper ridge over SE U.S as a trof
approaches from the west. This approaching trof will be the main
focus thru this period. Mdls continue to suggest elevated showers
possible Fri night into Sat as a s/w lifts thru the region with a
strong LLJ nosing into the area. At this point, best chances still
appear to be across central and into NE MO. However, low PoPs may
need to be pulled further east with updates. These showers shud
dissipate shortly after sunrise.

Mdls continue to be in good agreement with the approaching cdfnt.
However, the ECMWF has a stronger trof by Sun morning, with a cut-
off low developing over srn MO by Sun evening. The NAM and GEM are
faster soln with the GFS between these solns. Have generally trended
twd the GFS, but kept low PoPs lingering into next week to account
for the ECMWF. Mdls have not been consistent with the trof this
weekend into next week leading to lower confidence in the forecast.

As the storms approach the region, can not completely rule out a
threat of severe storms thru Sat evening across portions of central
MO. With CAPE diminishing quickly, the threat shud be limited.
However, with the trof approaching and LLJ increasing, deep layer
shear shud help to somewhat balance the reduced CAPE.

Have trended twd the warmer guidance for Sat, then cooler into next
week. With the differences among the guidance, generally trended twd
a compromise for the remainder of the period.



.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1102 PM CDT Thu Oct 19 2017

High pressure centered over the east coast will slowly move east
through Friday night. Dry and VFR conditions will persist through
the forecast period. There will be waves of high level clouds that
will stream over the area overnight with light south to southwest
winds in the region.


Dry and VFR conditions will persist through Friday night. The
terminal will see waves of high level clouds overnight and
Friday with light south winds.



Saint Louis     57  82  59  81 /   0   0   5  10
Quincy          53  77  59  78 /   0   0   5  20
Columbia        52  77  60  80 /   0   0  10  10
Jefferson City  50  79  61  81 /   0   0  10  10
Salem           53  80  54  78 /   0   0   5   5
Farmington      51  79  57  79 /   0   0  10  10




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