Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 131131

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
631 AM CDT Tue Mar 13 2018

.SHORT TERM...  (Through Late Tonight)
Issued at 343 AM CDT Tue Mar 13 2018

High pressure over the Northern Plains will be the main influence
over the region and will move southeast through Tuesday evening. A
broad trough over the eastern one third of the country will continue
to very slowly move to the east through Tuesday evening. Some mid
and high clouds will be seen over parts of the area by Tuesday
afternoon mainly along and east of the Mississippi River. Winds will
pick up and become breezy late this morning over the area with some
gusts of over 20 mph possible during the afternoon hours before
weakening after sunset. The region will continue to be under the
influence of northwest flow through Tuesday evening with
temperatures up to 10 degrees below climatological high temperatures
for this time of the year.


.LONG TERM...  (Wednesday through Monday)
Issued at 343 AM CDT Tue Mar 13 2018

Warmer temperatures can be expected by Wednesday afternoon as the
surface winds back around to a southwest direction as the surface
ridge shifts south of our area, plus full solar insolation is
forecast with little if any clouds.  Highs on Wednesday will be at
or slightly above normal.  A cold front will sag southward into our
area Wednesday night and Thursday.  The warming trend will continue
on Thursday across central and southeast MO into southwest IL south
of the front with highs well above normal in this area on Thursday.
Showers will break out along and just north of this front by late
Thursday night due to increasing low-mid level warm air advection
over the surface front as an upper level low and associated surface
low approach from the central Plains.  A southwest low level jet
will also bring increasing low level moisture into the area as well.
There may be some elevated convection/storms across central and
southeast MO late Thursday night into Friday.  The chance of showers
will continue Friday and Friday night as the upper level low and
associated surface low move eastward into western MO by 12Z
Saturday. The rain should taper off and end by Saturday afternoon as
the upper level low opens up and weakens as it shifts east of the
forecast area with the surface low moving into the TN Valley region.
Cooler temperatures can be expected Friday due to cloud cover,
precipitation, and as the surface front shifts south-southwest of
the forecast area as a surface ridge builds southward into the Great
Lakes region.  Could not rule out a few light snow/sleet showers
late Friday night and early Saturday morning across northeast MO and
west central IL as the upper level low moves over this area, but not
expecting any accumulation at this time.  Warmer temperatures will
return by Sunday due to an upper level ridge over our region.
Another round of showers is expected Sunday night and Monday as
another upper level low and associated surface low approach the area
from the Plains.



.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 619 AM CDT Tue Mar 13 2018

Dry and VFR conditions will persist through Wednesday morning
over the area. Northwest winds will become breezy by this
afternoon with gusts over 20kts likely. Winds will remain out of
the northwest but weaken after sunset and become light through
Wednesday morning.

SPECIFICS FOR KSTL: Dry and VFR conditions will persist through
Wednesday morning. Northwest winds will become breezy at the
terminal around 16z with gusts over 20kts likely during the
afternoon hours. Winds will weaken after sunset but remain out of
the northwest through Wednesday morning.





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