Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 211839

139 PM CDT Sun Sep 21 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 138 PM CDT Sun Sep 21 2014

Focus tonight will be temps. Sfc ridge builds into the region with
winds diminishing with sunset. Current cloud deck over nrn IL and
ern IA shud continue to break up this afternoon as it moves ese
leaving much of tonight clear. Greater mixing has occurred today
than prev anticipated, lowering dewpoints. While tonight is not a
great setup for radiational cooling as winds may stay up around 5
kts, believe CAA will help compensate. Have therefore trended aob
the coolest guidance for tonight.

.LONG TERM:  (Tonight through Friday)
Issued at 1116 PM CDT Sat Sep 20 2014

The short wave pushes SE of the region Sunday night. The long wave
trough moves off the East Coast early in the week as a ridge
builds across the Plains. This should be a very quiet week with
clear to mostly clear skies and dry conditions. Monday should be
the coolest day with highs holding in the lower 70s with 850 temps
still in the upper single digits. Monday night is expected to be
the coolest night of the week with the high drifting overhead
allowing most locations to drop into the 40s. A slow warming trend
will ensue on Tuesday as 850 temps warm into the low/mid teens.
850 temps are not expected to change much thru the remainder of
the week meaning any addtnl warming will arise from air mass
modification. Temps are fcst to rise a degree or two each day thru
Friday when highs should be near 80. The center of the SFC ridge
slides off the NE coast on Wednesday only to have the center
reform well to the west across the Grt Lks towards the end of the
work week. This keeps the ridge axis anchored thru the CWA and
maintains the E/SE flow thru Friday. With the sfc ridge in this
orientation...the coolest overnight lows should remain across
sthrn IL and SE MO thru the week. A caveat to this fcst is energy
coming onshore this wknd across CA. The closed 500mb low is fcst
to undercut the ridge and eventually be absorbed into the mean
flow by the middle of the week. This feature is fcst to leave a
weakness in the upper ridge across the center of the country that
persists thru the end of the week. Guidance doesn`t generally
handle this type of scenario very well...which means I am not
confident what affect this will have on the sensible wx. Am
inclined to think that this will not be an issue and have gone
with a dry fcst but...this feature bears watching.



.AVIATION:  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1155 AM CDT Sun Sep 21 2014

Nwly winds will gust to around 20 kts this afternoon and diminish
with sunset remaining aob 5 kts. Steam FG is possible at SUS/CPS,
but how much it will impact terminal is uncertain attm. Winds will
become nly on Mon aob 5 kts.

Specifics for KSTL: VFR and dry thru the period. Gusty nw winds
will diminish and remain aob 5 kts overnight. Winds will become
nly Mon morning around 5 kts.


Saint Louis     79  52  73  52 /  10   0   0   0
Quincy          73  46  70  48 /  10   0   0   0
Columbia        77  50  72  50 /   0   0   0   0
Jefferson City  79  49  72  49 /   5   0   0   0
Salem           78  47  69  47 /  10   0   0   0
Farmington      76  50  70  47 /  10   0   0   0




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