278 
FXUS63 KLSX 032330
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
630 PM CDT Sun Aug 3 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 343 PM CDT Sun Aug 3 2014

The primary forecast issue for late this afternoon through the 
overnight hours is convective trends. Ongoing isolated to scattered 
SHRA/TSRA along an outflow boundary will probably keep percolating 
late this afternoon in central MO, then diminish tonight with the 
loss of daytime heating. Meanwhile, a vort max will dive south out 
of the Dakotas, providing a source of lift for new development later 
tonight. The 12z model runs did not seem to accurately capture the 
strength of the vort max based on its presentation on today's water 
vapor imagery. The western edge of the aforementioned outflow 
boundary was very pronounced on afternoon visible satellite imagery, 
and initial thoughts are that scattered SHRA/TSRA could develop late 
tonight in eastern KS or western/central MO due to lift over this 
boundary occurring ahead of the approaching short wave from its weak 
westerly LLJ. Limited moisture would tend to limit the coverage of 
any precip which develops. Overnight lows should be similar to last 
night in most locations, except a bit warmer due to increased 
mid/high clouds after 06z which will interfere with radiational 
cooling processes. 

Kanofsky

.LONG TERM:  (Monday through Next Sunday)
Issued at 343 PM CDT Sun Aug 3 2014

(Monday - Tuesday)

Area of showers and storms from overnight convection is possible to linger
through the morning hours over northern and western portions of
the forecast area. If such an area exists early tomorrow
morning...it should slide south and east with the mid to upper-
level flow pattern. Isolated to scattered convection is possible
tomorrow afternoon as the ams destabilizes across the
area...especially across northern sections of the forecast area in
close proximity to warm frontal boundary/wind shift and area of
diffluence aloft. A few of these storms may be strong due to the
degree of instability forecast...however any kind of organized
strong storms looks unlikely due to very weak deep layer shear
(aob 25 knots).

Frontal boundary is expected to sag south a bit on Monday night and Tuesday
along with the continued chances of showers and thunderstorms. Lows Monday
night look to be near seasonal norms or slightly warmer than the previous
nights due to increased cloud cover and southerly flow across portions of
the area.

(Wednesday - Sunday)

Unfortunately...still plenty of uncertainty regarding PoPs and effects on
temperatures for the rest of the extended period. GFS/CMC are now much
further north with MCS progged for Wednesday compared to more consistent
ECMWF. Did not make too many changes Wednesday on compared to previous
forecast as GFS/CMC do look too far north and east with convection not only
on Wednesday but also through the work week looking at mid/upper level flow
pattern and NW-SE oriented baroclinic zone. Highest threat of rainfall still
looks to be somewhere in the Wednesday night through early Saturday time frame
but bountiful uncertainity/disagreement in track/timing on indiviudal
shortwaves precludes pin pointing any time period(s) with much higher PoPs
than previously forecast. Still does look like a wet and active pattern
for the mid/upper Mississippi Valley...just a matter of exactly where and
when. 

Temperatures for the valid period look to be slightly below normal...mainly
due to daytime highs being cooler than normal because of clouds and rain
chances.


Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 613 PM CDT Sun Aug 3 2014

FG impacting SUS is possible once again late tonight. More
uncertainty exists for tonight as greater mixing occurred today.
Otherwise, ongoing SHRA near COU shud diminish with sunset.
Believe another area of TSRA will develop within an hour or two
across far wrn MO and ern KS, but these TSRA shud remain W of COU.
Isod to sct TSRA are expected Mon during the late morning and thru
the afternoon. Coverage is currently not expected to be great enuf
to mention in TAF attm. 

Specifics for KSTL: VFR and dry thru the period with winds aob 8
kts expected. TSRA poss Mon afternoon. 

Tilly

&&

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

$$

WFO LSX