Area Forecast Discussion
Issued by NWS St. Louis, MO

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183
FXUS63 KLSX 260456
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1156 PM CDT Sun Jun 25 2017

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 301 PM CDT Sun Jun 25 2017

Area of light rain currently across central Kansas is primarily
forced by weak low-level moisture convergence and low/mid level
frontogenesis. Models suggest this area of forcing will translate
east/southeast with light rain trying to move into far western
and southern portions of the forecast area overnight tonight. With
forcing fairly transient and not particularly strong, ~10,000
foot dry layer will be difficult to overcome, and any top-down
saturation will certainly take time. Have only schc/chc PoPs
tonight, mainly for portions of southeast Missouri. Could be a
case where precipitation does break through the dry layer it is
just a few sprinkles and does not accumulate.

Lows tonight across the area will be seasonably cool with most
locations in the 50s. MOS guidance tonight looked reasonable across
the northern 1/2 of the area where a more clear sky is expected.
However, did lean a few degrees above MOS numbers across portions of
central and southeast Missouri where thicker midlevel clouds are
expected overnight tonight.

Believe Monday morning will start off dry for most areas, with
possible exception of some isolated showers or sprinkles down across
far southern sections of the forecast area. Shortwave trough will
approach the mid-Missouri Valley late Monday afternoon, which should
help produce isolated-widely scattered showers and thunderstorms
predominantly affecting portions of northeast Missouri and west-
central Illinois. Highs on Monday should be similar to that of today
across much of the area. Due to most areas seeing plenty of sunshine
during the peak heating hours, went above MOS numbers a couple of
degrees for high temperatures.

Gosselin

.LONG TERM...  (Monday Night through Next Sunday)
Issued at 301 PM CDT Sun Jun 25 2017

It still looks like the upper pattern that will be somewhat
amplified on Monday night will turn zonal by Wednesday as the Great
Lakes trough moves off to the east and the West Coast ridge dampens
out. Scattered showers and isolated thunderstorms will be moving
out of the region on Monday night as a weak shortwave trough moves
southeast of Missouri and Illinois in the northwesterly flow
aloft. Then the GFS/ECMWF still shows a brief period of dry
weather from Tuesday into early Wednesday before a shortwave
trough moves across the Midwest bringing an attendant cold front
into northern Missouri by late Wednesday/Wednesday night. Both
models show a second, deeper trough moving across the Midwest late
in the week as the cold front moves farther south into the CWA.
The upper flow will be aligned with the front which will cause the
front to move slowly south across the area. There will be plenty
of moisture over the area with PWATS between 1.5-2.0 inches. This
will set up the potential for some locally heavy rainfall over
parts of the area late in the week. Will have to watch future
model runs to refine where this potential sets up. By next
weekend...the GFS and ECWMF show the upper trough deepening as it
passes through Missouri and Illinois causing the cold front to
push through the CWA.

Temperatures are still on track to go from below normal on Tuesday
to above normal on Thursday to back below normal over the weekend as
the front moves south of the area.  This is reflected well in the
GFS and GEFS mean MOS guidance.


Britt

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1151 PM CDT Sun Jun 25 2017

VFR conditions are expected for the first 0-6 hours and perhaps
for the first 0-12 hours. There is greater uncertainty regarding
VFR conditions after 26/15z because an approaching disturbance
will generate widely scattered SHRA/TSRA across the area, although
the best opportunity for precipitation at the terminals will be
after 26/18z. Winds will become westerly after 09-12z.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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