Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 162350
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
650 PM CDT Mon Apr 16 2018

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 352 PM CDT Mon Apr 16 2018

The trough that provided snow flurries over parts of the area this
morning will finally push to the east into the eastern US by late
tonight. High pressure will build into the forecast area tonight.
This will allow for clear skies and good radiational cooling for
most areas to drop below freezing overnight. Since the growing
season is now underway, have posted freeze warnings across most of
east central Missouri and parts of southwestern Illinois.
Additionally, have posted a frost advisory for parts of central and
southeastern Missouri. High pressure over eastern Iowa and northwest
Illinois will push to the eastern US by Tuesday afternoon.  This
will allow for winds to switch around to the southwest by Tuesday
afternoon. The combination of southwesterly flow and good surface
heating will bring in warmer air bring temperatures to within a five
degrees of climatological values. Used a blend of MAV/MET MOS
guidance for Tuesday afternoon highs and toward the cooler MOS for
temperatures tonight.

Kelly

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 352 PM CDT Mon Apr 16 2018

An upper level low will move through the northern Plains
with an associated surface low moving east-northeastward through
northern MO late Tuesday night.  It appears that most of the
precipitation will be north or left of the track of the surface low
across northeast MO and west central IL late Tuesday night and
Wednesday morning where there will be better upper level forcing and
deeper moisture.  Temperatures will be warmer Tuesday night as a
warm front moves northeastward ahead of the surface low with surface
dew points gradually rising through the night.  Lows will be at or
slightly above seasonal normals.  The surface low will drag a cold
front southeastward through our forecast area Wednesday morning
ushering in colder temperatures for northeast MO, but highs on
Wednesday across southeast MO and southwest IL will still be
relatively warm.  A large and fairly strong surface ridge will build
southeastward into MO Wednesday night leading to below normal
temperatures Wednesday night through Thursday night.  There will be
a warming trend Friday into the weekend as an upper level ridge
builds over the central US, while the surface winds becoming east-
southeasterly on the backside of the retreating surface ridge.  The
operational GFS and ECMWF models were trending slower and further
south with the upper level low and associated surface low this
weekend.  Little if any precipitation is expected on Saturday with
showers moving through mainly southeast MO and southwest IL, south
of Interstate 70 Saturday night, Sunday, and into Sunday evening as
the upper level and surface lows pass south of our forecast area.

GKS

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 650 PM CDT Mon Apr 16 2018

Visible satellite shows the back edge of the cloud cover just east
of the Mississippi River, slowly pushing ENE. The clearing trend
will continue with mainly clear skies overnight and light winds
of less than 10 kts out of the WNW. Winds shift out of the SE
through the day with the passage of a frontal boundary, but winds
remain rather light. Clouds may accompany the front, but it lacks
moisture, so expect any cigs/vsby to remain VFR through the
period.

SPECIFICS FOR KSTL:
No concerns through the forecast period. Gusts die off after
sunset tonight with clearing skies and light breeze. Light winds
shift out of the SE through Tuesday with the passage of a warm
front. Sct/bkn deck could push through Tuesday afternoon with the
front, but more likely north of the TAF site. There`s not a lot
of moisture with this, so expect VFR cigs/vsbys through the
period.

Maples

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Frost Advisory from 1 AM to 9 AM CDT Tuesday for Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Madison MO-Moniteau MO-Osage MO-Reynolds MO-Saint
     Francois MO-Washington MO.

     Freeze Warning from 1 AM to 9 AM CDT Tuesday for Jefferson MO-
     Lincoln MO-Montgomery MO-Saint Charles MO-Saint Louis City
     MO-Saint Louis MO-Sainte Genevieve MO-Warren MO.

IL...Freeze Warning from 1 AM to 9 AM CDT Tuesday for Bond IL-Calhoun
     IL-Clinton IL-Fayette IL-Jersey IL-Madison IL-Marion IL-
     Monroe IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX



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