Area Forecast Discussion
Issued by NWS St. Louis, MO

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862
FXUS63 KLSX 261205
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
705 AM CDT FRI AUG 26 2016

.SHORT TERM...(Through Tonight)
Issued at 402 AM CDT Fri Aug 26 2016

Region is in SW flow aloft with the area between high pressure along
the E Coast and a broad low amplitude trough across the West. Cold
front has stalled aligned roughly along I-70 as of early this mrng.
The short wave and assoc SFC low will continue to drift east thru
the prd across SErn Canada. S/SW flow thru the column will
eventually cause the bndry to begin lifting back N late
today/tonight. This bndry will once again be the focus for SHRA/TSRA
dvlpmnt this aftn. Best chances appear to be along and N of I-70.
PWATs continue to be near 2 inches...so locally heavy rainfall will
be possible...esp if any training occurs. Also...SPC has locations
along and N of I-44 in MO and I-70 in IL in a marginal risk. A
couple thousand Joules of CAPE coupled with 25-40 kts of 0-6 km bulk
shear support SPC. So...a few strong to possibly severe storms are
possibly with gusty winds the primary threat.


There will be plenty of cloud cover today which should help keep
temps in check...esp N of the bndry. Still expect it to be a warm
humid day S and E of the STL metro area. Should be a decent temp
gradient across the FA. Locations N of the bndry that have
substantial cloud cover may not get out of the upper 70s whereas SE
MO and sthrn IL may get close to 90.

2%

.LONG TERM... (Saturday through Thursday)
Issued at 402 AM CDT Fri Aug 26 2016

Saturday through Sunday night

The cntrl CONUS will remain in SW upper flow with a short wave
tracking along the US/Canadian border. The bndry should either be N
of the CWA by the beginning of the prd or be exiting the nthrn FA
Sat mrng leaving the area under sthrly flow for the rest of the
wknd. The advancing warm front will allow the humid unstable air
mass that has been residing across sthrn MO and sthrn IL to
overspread the entire FA. The unstable air mass should lead to PM
SHRAs/TSTMs. Even though there will be a lack of focus...700mb
temps near 10C will allow at least isld/scttrd aftn/evng
SHRAs/TSTMs to dvlp. PWATs are expected to remain above 1.5 inches
keeping the threat for isolated heavy rain. Temps should be near
avg with highs in the mid/upper 80s with lows near 70.

Monday through Thursday

The week begins with zonal flow aloft with the main belt of
westerlies along the US/Canadian border and transitions to a cntrl
CONUS ridge by Wed/Thu. Needless to say SFC flow remain S/SW thru
the prd with no cold front in sight. Given the same unstable air
mass in place...the fcst really doesn`t change...so still expecting
isld/scttrd diurnal convection. High PWATs mean heavy rain remains a
threat. 850 temps in the upper teens to near 20C correspond to high
temps in the 80s...which is very near seasonal norms. Dps though are
fcst to continue to be in the low/mid 70s keeping a summery feel
going.

2%

&&

.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 656 AM CDT Fri Aug 26 2016

Scattered thunderstorms are expected during the valid TAF period
at all terminals. Thunderstorms were occurring near KUIN at TAF
issuance and may affect the terminal over the next hour or two.
Another round of scattered thunderstorms is expected to develop
near a warm front during the afternoon hours, then TSRA/SHRA
should dissipate after sunset. Brief pds of MVFR or IFR conditions
are possible when SHRA/TSRA moves directly over the terminals.
Winds will gradually become southerly after 27/06z after the warm
front has lifted north of the terminals.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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