Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 292312
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
612 PM CDT FRI JUL 29 2016

.SHORT TERM... (Through Saturday)
Issued at 245 PM CDT Fri Jul 29 2016

(Tonight)

Main area of consideration at this time for showers and storms
heading into early evening is what is now produced underneath upper
TROF digging in overhead.  Enough storms have formed and congealed
to our southwest for some organization to this convection, with any
threat from these storms being focused on short-term downburst wind
potential.  The area of concern for this will be southeast MO thru
sunset.  Some activity from this TROF may linger overnight but
should be few and far between and be restricted to a small portion
of southeast MO.

Otherwise, storms along the old frontal boundary have now exited
our CWA to the SE, and showers and storms to the north associated
with a surface TROF should remain to the north and are not expected
to drop sufficiently south to affect our region.

MOS min temps of mainly 60s with around 70 in STL heat island look
reasonable.

(Saturday)

The two main wx-makers from today will remain in play on Saturday
but probably not to the extent they were earlier.

The upper TROF axis will remain and may create enough lift in some
portions of the southern CWA to result in widely scattered showers
and storms again.  PoPs of 20-30% are forecast.

The surface TROF to our north will once again try to edge into our
northern CWA (mainly areas near central IL) and may result in a
small chance for a shower or storm in that area.

Otherwise, most areas should remain dry with max temps close to
average for late July, or a couple degrees higher than persistence,
with values in the mid to upper 80s.

Britt

.LONG TERM...  (Saturday night through Next Friday)
Issued at 245 PM CDT Fri Jul 29 2016

(Sunday and Monday)

NAM and GFS still appear similar in their handling of the upper
trough that will lift eastward out of the Midwest early next week.
One weak shortwave trough will move across the area on Sunday that
will cause the surface front to move slowly northeastward into
central and southeast Missouri by late in the day.  Upper high will
build over the Central Plains on Monday causing the upper flow to
become more northwesterly and the front to move farther to the
northeast.  This will cause the chance for showers and thunderstorms
to spread northeast across the area on by Monday.

Temperatures will stay in the 80s on Sunday, but likely warm into
the 90s by Monday over central Missouri as 850mb temperatures
climb to around 20C.

(Tuesday through Friday)

Global models are showing a similar evolution to the pattern mid to
late next week.  Shortwave trough will move southeast across the
area on Tuesday with an upper high centered over the Central Plains.
This will bring scattered showers and thunderstorms to the area.
Upper ridge will then build over the area Wednesday and Thursday
causing the front to lift northeastward. An upper trough will move
from the northern Plains into the Great Lakes late in the week
causing a cold front to move south into northern Missouri and
central Illinois by late Friday.  This will bring an increased
chance of showers and thunderstorms to Missouri and Illinois.

Temperatures will warm up into the lower-mid 90s with heat index
values exceeding 100 by the middle of next week given that 850mb
temperatures are expected to be around 22C and surface dewpoints
will be in the mid 70s.

Britt

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 603 PM CDT Fri Jul 29 2016

Not much change in the TAF forecast. Still expect predominantly
VFR and dry conditions thru the period. Some light fog is still
possible tonight and may need to be added to COU in future
updates. Area of MVFR/IFR cigs may reach UIN tonight. For now, it
appears the lower cigs will remain north of the terminal, but
therefore increasing chances of fog development. Otherwise, TSRA
redevelopment on Sat is expected to remain south of
COU/STL/SUS/CPS. There is a slight chance for TSRA at UIN Sat
afternoon, but will wait for confidence to increase before adding
to the forecast.

Tilly

&&

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

$$

WFO LSX



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