Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 211706
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1206 PM CDT Sun Sep 21 2014

.SHORT TERM: (Through Today)
Issued at 1116 PM CDT Sat Sep 20 2014

Convection along the prefrontal trough/wind shift has been pretty meager
this evng into the overnight hrs with most of the activity remaining
in our IL counties. Cold front has been slower...as advertised from
last night...not reaching the nthrn counties until close to 6Z. At this
rate the bndry should exit the sthrn zones between 10-12Z...taking any
threat for lingering -SHRAs with it. a strong short wave will pass just
to the NE of the CWA later today. Due to limited moisture, should only
see an slight increase in clouds...mainly across our IL counties. At
the SFC, cooler and drier air assoc with high pressure building into
the region from the nthrn Plains will cause high temps to be some 5-10
degrees cooler than yesterday. Winds may gust 20-25 mph for awhile this
aftn as decent CAA drops 850 temps to the upper single digits by 00Z.

2%

.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.

2%

&&

.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.

&&

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

$$

WFO LSX






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