Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 212034

Area Forecast Discussion
National Weather Service Saint Louis MO
334 PM CDT WED SEP 21 2016

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


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.


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


.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.



.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1231 PM CDT Wed Sep 21 2016

Quiet conditions are expected this afternoon through Thursday
morning. VFR conditions likely with light southerly winds. SCT-BKN
cumulus affecting KUIN should dissipate this evening. Fog is
possible again tonight at KSUS and KCPS but believe mixing will
make chances lower tonight than the past few nights.


VFR conditions expected over the next 30 hours. Light southerly
winds along with a few diurnal cu possible Thursday afternoon.





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