Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 152340

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
640 PM CDT Sun Apr 15 2018

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 332 PM CDT Sun Apr 15 2018

Low pressure centered over Ohio/West Virginia will drift north-
northeast over the next 24 hours and is forecast to be somewhere
between Lakes Ontario and Huron by this time tomorrow.  The deep
upper level low driving this system is taking on a negative tilt and
should start to move a little faster away from the Mid Mississippi
Valley tonight.  However, northwest flow will continue to bring
clouds and cold air down into the forecast area tonight.  I see no
reason that temperatures won`t drop below freezing tonight in this
cold advection pattern, so the freeze warning looks to be in good
shape.  The light snow/rain showers that have been moving across the
area today should continue to diminish through the remainder of the
afternoon and tonight as the upper level system moves out and drier
low level air filters in.  Clouds will likely persist through the
night tonight and into tomorrow morning, but guidance suggests the
clouds will scatter out fairly quickly over central Missouri in the
morning.  It will probably take longer to get rid of the clouds
along and east of the Mississippi but most models agree that most of
the clouds should be gone by 00Z Tuesday across the entire area.
Temperatures on Monday will still be well below normal due to the
continuing northwest flow and the cold start to the morning...stuck
close to the coldest guidance highs which keep us mainly in the low
to mid 40s.


.LONG TERM...  (Monday Night through Next Sunday)
Issued at 332 PM CDT Sun Apr 15 2018

Main focus thru the forecast period will be temps as little to no
precip is expected until Fri night. Overall, forecast temps are
below seasonal average, except for Tues and Wed that shud be at
least near average.

The upper low currently over SE IA is expected to be over the Great
Lakes region at the beginning of the forecast period. As an upper
level ridge builds into the region, temps shud warm and may be near
seasonal avg on Tues and perhaps Wed. There is some uncertainty in
timing of the wrmfnt lifting nwd thru the area Tues and Wed as well
as how quickly the cdfnt will push thru the region on Wed.

This fast moving low may bring showers to far nrn portions of the
CWA early Wed morning. With a sfc ridge stretching across the Gulf,
linking to another building east across the Plains, the area shud be
cut off from a good source of moisture. Have kept some low PoPs, but
believe the better chance for precip will remain north of the CWA.

Mdl solns diverge with the approaching system Fri night into next
weekend. Have kept PoPs on the low side for now given the
differences among solns. For now, the mdls do agree that much of the
area shud see rain on Sun and have therefore went with a little
higher PoPs.


.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 636 PM CDT Sun Apr 15 2018

Wrap around SC to persist across forecast area through tonight.
Cigs to remain MVFR before lifting and scattering out from west to
east beginning after sunrise Monday morning. As for winds, to
persist from the northwest and remain gusty through forecast
period. Some scattered showers possible over KUIN through 02z

Wrap around SC to persist across metro area through tonight. Cigs
to remain MVFR before lifting and scattering out by 17z Monday. As
for winds, to persist from the northwest and remain gusty through
01z Tuesday, then diminish.


MO...Freeze Warning from 1 AM to 9 AM CDT Monday for Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
     Montgomery MO-Osage MO-Reynolds MO-Saint Charles MO-Saint
     Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
     Genevieve MO-Warren MO-Washington MO.

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


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