469 
FXUS63 KLSX 292350
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
650 PM CDT Tue Oct 29 2013

.SHORT TERM:  (Through Late Tonight)
Issued at 305 PM CDT Tue Oct 29 2013

Much of the waa driven showers across the region late this aftn will 
shift e-se of our forecast area by this evng.  Additional convection 
was developing across swrn MO and nwrn AR where the atmosphere was 
more unstable, and close to a warm front which extended from a 
surface low over cntrl KS se through nern AR.  This convection may 
impact portions of sern MO and swrn IL early this evng.  This warm 
front will lift slowly nwd tgt, and this coupled with low level 
cloud cover and slowly rising dew points will lead to nearly steady 
or slowly rising temperatures through the ngt.  There was a lot of 
model differences as respects their qpf tgt, and much forecast 
uncertainty with timing and coverage of convection for late this 
evng and overnight.  At this time it appears that there may be 
scattered convection along and just north of the warm front as it 
lifts nwd into our area, with more organized convection across ern 
KS and wrn MO late tgt close to a s-swly low level jet across the 
cntrl and srn Plains.

GKS

.LONG TERM:  (Wednesday through Next Tuesday)
Issued at 305 PM CDT Tue Oct 29 2013

(Wednesday - Thursday/Halloween Evening)

Unsettled weather with mild temps will dominate this period. 

Once again, forecast on track and required little change.  This 
period will feature SW flow and a series of disturbances moving thru 
at the upper levels in a very moist atmospheric column, with a warm 
front moving thru tonight and Wednesday, and a cold front coming 
into play Thursday. 

The next wave of SHRA/TSRA is expected to occur very late tonight 
and Wednesday, as the surface warm front slowly pushes north thru 
the area.  Timing is generally a tad slower than what was depicted 
and forecast 24hrs ago, and has been pushed back more to Wednesday 
versus late tonight.  The main track is expected to go thru areas N 
and W of STL Metro, although a rain threat will hang over 
everywhere, especially during the morning hours, with rain chances 
diminishing from south to north on Wednesday afternoon.  This wave 
will have more instability to work with than its predecessor, in 
fact the most for this entire event, and should see much greater 
percentage of thunder with elevated hailers possible. 

The "main event" is still slated for late Wednesday night and 
Thursday in advance of the primary shortwave TROF exiting from the 
SW CONUS and surface cold front.  Plenty of shear and broadscale 
lift but limited instability, but not much is needed this time of 
year for strong-severe TSRA possibilities.  The best 0-1km shear 
continues to be depicted for areas S and E of STL Metro, and 
incidentally, this is where a severe Slight Risk exists for this 
time period from SPC.  Either way, should see widespread pcpn break 
out with the main event system. 

Widespread rainfall amounts for the entire period, beginning 
tonight, should be between 1-2", with the higher end amounts 
expected to apply more to NE MO and its immediate environs. 

Non-diurnal temp trends are to be anticipated for this period given 
the fronts and pcpn, with the slow rise tonight becoming a running 
start for the expected warm day on Wednesday Wednesday as temps 
surge into the 70s.  Modest fall only into the 60s on Wednesday 
night, and then finally a cold FROPA on Thursday, which will lead to 
a modest temp drop with airmass behind a Pacific one and not 
Canadian. 

While winds won't be exceptionally strong for much of this period, 
one period of concern is Thursday ahead of the front, where 500m AGL 
winds are expected to be 50-60kts.  Fortunately, mixing heights are 
expected to be just below this, but will sufficiently illustrate the 
potential for high wind gusts from the south for E MO and S IL.  For 
now have penciled in 30-35mph gust potential. 

(Friday - Sunday)

Despite another shortwave TROF passing thru on Friday, it will be 
moisture starved and should result in no rain.  Otherwise, a dry 
weekend is on tap with NW upper flow and a surface high building 
in.  Temps will be seasonable given the type of airmass moving in. 

(Monday - Next Tuesday)

Already by next Monday, flow shifts back to a more unsettled SW flow 
with the initial disturbance rolling up and becoming further 
augmented as we head into mid week.  Have maintained chance PoPs 
Monday and tacked on more for Tuesday with SHRA expected, possibly 
with some thunder.

TES

&&

.AVIATION:  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 640 PM CDT Tue Oct 29 2013

A warm front currently stretches from a low pressure system in
north central KS across southwest MO into the MO bootheel. IFR
conditions were fairly widespread to the north of the front and
will continue to expand this evening and become prevalent at the
TAF sites. There will also be bouts of light rain and/or drizzle
at times tonight. The warm front will lift northward on Wednesday
morning and this should lead to a rapid improvement in flight
conditions, however the area along and north of this front will
also be a focus for showers and thunderstorms. At this time the
general thought is a large cluster of showers and thunderstorms
will develop in eastern KS in the predawn hours and push eastward
Wednesday morning and afternoon with the possibility of additional
development near a KCOU-KUIN line through the afternoon hours. I
have attempted to reflect this with PROB30 and VCTS groups in the
new TAF forecast package.

Specifics for KSTL:

IFR conditions will become prevalent this evening and persist well
into Wednesday morning. There will also be bouts of light rain
and/or drizzle at times tonight. A warm front will lift northward
through the terminal between 15-16z on Wednesday morning and this
should lead to a rapid improvement in flight conditions. Thinking
at this time is a large cluster of showers and thunderstorms will
develop in eastern KS in the predawn hours and push eastward
possibly impacting KSTL between 17-21z Wednesday. 

Glass

&&

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

$$

WFO LSX