Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 262053

Area Forecast Discussion
National Weather Service Saint Louis MO
253 PM CST Sat Nov 26 2016

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 249 PM CST Sat Nov 26 2016

Primary concern for tonight is the potential for fog and stratus
again.  There is still one area of persistent stratus over south
central Missouri this afternoon.  It`s possible that this stratus
will expand northward after sunset.  Forecast soundings across the
area are hinting at this with boundary layer dewpoint depressions
decreasing to zero or near zero at various times through the night
depending on which model is viewed.  Boundary layer wind is higher
tonight than last think fog is less likely than stratus.
Aforementioned boundary layer wind may also mix in drier air from
aloft to keep the stratus from do not have a whole
lot of confidence in either occurring.  Will tell the evening shift
to keep an eye out and keep their fingers on the "amendment" button.

Wind will be increasing on Sunday as low pressure strengthens over
the Great Plains.  Strong low level moisture convergence on a 40-
50kt 850mb jet should spread showers into northern and central
Missouri by the afternoon.  Normally, would lean toward warmest
guidance for temperatures with strong warm advection pattern, but
with increasing clouds and afternoon showers...expect temperatures
to top out close to today`s readings in the mid 50s.


.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 249 PM CST Sat Nov 26 2016

Moisture convergence is maximized across eastern Missouri and
Illinois between 00Z and 06Z tomorrow evening. A minimal amount
of instability is forecast and therefore only a slight
chance/isolated mention of thunder is retained with predominant
rain showers in the forecast for Sunday evening.

The storm system is expected to deepen and occlude across the
northern Plains and upper Midwest through Tuesday. This will result
in deep southwest flow across the lower Missouri and middle
Mississippi River Valleys and temperatures well above normal. Local
conditional climatology sugggesting high temperatures in the upper
50s to lower 60s areawide through Monday.

Appears that the heaviest precipitation with the approaching trough
Monday and Monday night will be across the southeastern half of the
CWA. It is here that the best signal for moisture convergence and
upper level divergence is shown by model guidance. Have once again
retained slight chance/chance of thunder for these time periods, but
believe the predominant weather will be rain showers.

Given the occluding nature of the system, the actual cold front
really doesn`t arrive until Tuesday afternoon. This should result in
in one more day of above normal temperatures and it actually could
be the warmest since the low clouds should have cleared to the east.

Cold advection takes hold the remainder of the work week as the deep
trough of low pressure slowly slides across the center of the CONUS
and the surface ridge remains anchored from the northern Plains to
the lower Mississippi River Valley.  This will result in
temperatures returning to normal and a dry forecast.



.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1134 AM CST Sat Nov 26 2016

Stratus with ceilings between 800-2000 FT over southeast Missouri
counties should continue to slowly dissipate through the
afternoon. Otherwise...VFR flight conditions are expected to
prevail across the area at least through the evening. There is a
chance that stratus could redevelop over the Ozarks after 06Z and
move northward to blanket a large part of the area. Not a lot of
confidence that this will happen though so did not put this in the
TAFs at this time.

Will see winds increasing and ceilings lowering and thickening
through Sunday as a strong storm system moves into the Great
Plains. Unless low stratus redevelops tonight...expect VFR
conditions to prevail through 18Z with ceilings between 4000-6000


VFR flight conditions are likely to prevail at Lambert through
Sunday. There is a chance that the stratus south of the terminal
over the eastern Ozarks could redevelop tonight and if that
happens it will likely move over Lambert after 06Z with IFR
ceilings. I don`t have enough confidence that this will happen to
put it in the TAF. If this does happen, think IFR and MVFR
ceilings will prevail at least through the morning. Wind will
increase from the south on Sunday as a strong storm system moves
into the Great Plains. If the stratus doesn`t redevelop
tonight...expect VFR ceilings to lower and thicken during the late
morning and early afternoon to between 4000-6000 FT.





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