Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 212327
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
627 PM CDT WED SEP 21 2016

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 333 PM CDT Wed Sep 21 2016

(Tonight)

Surface ridge will remain nearly anchored across the lower Ohio
Valley extending northeastward into the northeastern United States
overnight tonight. Diurnal cumulus should dissipate this evening
with just some cirrus spilling in from the west northwest tonight. A
clear or mostly clear sky is expected along with slightly above
normal temperatures. Lows in the 60s are expected with the coolest
conditions once again across the eastern Ozarks which will be in
close proximity to sfc ridge.

(Thursday)

Persistence looks like a good forecast for Thursday. Another very
mild day for late September is in store with plentiful sunshine.
Highs in the mid 80s to near 90 degrees are forecast as the CWA will
remain affected by light southeasterly surface flow with the warm
front remaining well to the north across the Upper Mississippi River
Valley.

Gosselin

.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 333 PM CDT Wed Sep 21 2016

Unseasonably warm weather pattern will continue into the weekend
with upper level ridging over our area along with persistent
southerly surface/low level flow.  It appears that convection will
remain north of our forecast area near a stationary front and ahead
of shortwaves overtopping the upper level ridge.  A backdoor type
cold front will drop southward Friday night and Saturday as surface
ridging builds southward through the Great Lakes and Ohio Valley
regions, but it now appears that it will remain just northeast of
our forecast area.  Still looks like convection may move into
northeast and central MO as early as late Saturday night as a deep
upper level trough moves slowly eastward into the Plains and the
upper level ridge begins to shift southeast of our area. Upper level
divergence will be slowly increasing over parts of our region ahead
of the upper level trough.  A cold front will begin to slowly drop
southeastward into our forecast area on Sunday.  It appears that
most of the showers/storms will be north and west of STL on Sunday.
The GFS and ECMWF model solutions begin to diverge for the next work
week with the ECMWF model much slower with the eastward progression
of the upper level trough, eventually closing off an upper level low
over the southern Plains by Tuesday morning. The GFS model is more
progressive with the cold front and closes off the upper level low
much quicker over the northern Plains.  The GFS model solution
shifts the precipitation southeast of our forecast area already by
Monday night, while the ECMWF keeps the rain going over parts of our
area through Tuesday night due to the slow moving upper level low
west of the region which will induce a surface low along the slow
moving cold front.  Prefer the slower solution of the ECMWF model,
but due to the inconsistency between the models will only forecast
at most low chance pops from Monday night through Tuesday night. The
temperatures will gradually trend cooler from northwest to southeast
for the next work week down to near normal values for late September.

GKS

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 624 PM CDT Wed Sep 21 2016

There will be some high cloudiness tonight and the low level air
mass is a bit drier this evening compared to 24 hours ago, so I don`t
think we will see overnight IFR fog issues at KSUS and KCPS like
last night. Overall VFR flight conditions should prevail throughout
the forecast period.

SPECIFICS FOR KSTL:

VFR flight conditions should prevail throughout the forecast
period.

Glass

&&

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

$$

WFO LSX


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