Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252158

358 PM CST Tue Nov 25 2014

.SHORT TERM: (Through Wednesday Night)
Issued at 348 PM CST Tue Nov 25 2014

(Tonight through Wednesday night)

Main focus will be the potential for some accumulating snow over the
region during the day on Wednesday.  Low amplitude trough currently
entering the northern CONUS will dive southeastward and strengthen
over the Plains tonight.  The GFS has shown decent run-to-run
continuity with this feature and the ECMWF has come into agreement
with it`s solution that large scale ascent will become more
widespread as the trough moves into central and northeast Missouri
toward daybreak.  At this time it appears this ascent will be
concentrated along and west of the Mississippi River between 12-18Z
and then shift east into Illinois during the afternoon.  Most of the
forecast soundings suggest this will be snow during the morning
hours when the when the low levels will be the coldest and the
ascent will be the strongest.  By nightfall, the upper trough will
be moving quickly east of the area which will cause subsidence to
set by evening.  Have just slight chances of snow going during the
evening hours over Illinois.

MOS guidance temperatures are in good agreement during this period
and generally followed.  High temperatures tomorrow will be warm
enough to cause the snow to mix with or change over to rain which
will cut back on total snowfall amounts, particularly along and
south of I-70. Did not change going snow amounts too much. Still
appears that northeast Missouri will get around 1 inch of snowfall
with lesser amounts to the south centered along the Mississippi


.LONG TERM:  (Wednesday through Next Tuesday)
Issued at 348 PM CST Tue Nov 25 2014

(Thursday and Friday)

Upper pattern will gradually flatten out and temperatures will begin
to warm back up during this period as the models are in good
agreement that surface high will pass through the area on Thursday
night.  By Friday, south to southwesterly winds will advect warmer
air into the area which bring temperatures back to normal.

(Saturday through next Tuesday)

GFS and ECMWF still agree that upper pattern will be zonal over the
weekend with a cold front moving south across the CWA on Saturday
night and Sunday. Still looks like chances for precipitation will
increase along the the front by late in the weekend as both models
show a shortwave wave trough moving through the area on Sunday
night. Then model solutions become more divergent by early next
week as the GFS is slightly more southwesterly aloft with an
approaching storm system whereas the ECMWF stays more zonal.
Temperatures ahead of the front on Saturday still look like they
will be about 10 degree above normal with 850mb temps around +10C.
Then temperatures will be closer to normal behind the front as
coldest air will not be able to come down because of the zonal



.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1115 AM CST Tue Nov 25 2014

VFR and dry conditions expected thru 12z Tues. Clouds will
gradually move into the region, thicken and lower thru this
period. Winds will gradually back to swly this afternoon and
become sely late tonight. Precip is expected to begin as all SN
at all terminals Tues mid to late morning depending on site.
Latest guidance suggests COU will change to RA around 18z, while
UIN will remain SN thru the afternoon. Much more uncertainty
exists for SUS/CPS with the sfc fnt in the region, but may change
to a RASN mix in the afternoon.

Specifics for KSTL: VFR and dry thru 15z Tues. Winds will be aob 8
kts and gradually back and become light and vrb tonight. Winds
will pick up out of the SE Tues morning. Precip is expected to
start as SN and possibly mix with RA during the late afternoon.
However, have low confidence in precip type during the afternoon.





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