Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 172044

Area Forecast Discussion
National Weather Service Saint Louis MO
344 PM CDT Thu May 17 2018

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 308 PM CDT Thu May 17 2018

Focus thru the period will be PoPs. MCV evident in sat image over
wrn MO with another further south into AR will continue to impact
the area thru Fri. With the trof stretching thru the region, these
MCVs will have a Fujiwhara effect with a s/w moving precip back
northwestward into the area late tonight and Fri morning.

Mdls differ exactly where the precip will be in the morning, but
best chances shud be over the ern half of the CWA where the s/w is
tracking nwd. After sunrise, believe a band of TSRA will develop
along the wrn flank of the upper low where insolation is possible.
The 18z NAM just arriving suggests a more ern soln, but will need
to continue to monitor trends. Wherever the lower-res mdls wud
suggest periods of heavy rain possible thru the early morning
hours. If the more wrn soln verifies, going temps for tomorrow are
too high. While I have trended further west slightly, have not
moved PoPs as far west as the NAM soln.

The upper trof will slowly pull newd out of the area Fri afternoon
and evening as the main trof ejects into the Plains. Some precip
shud linger into Fri evening across ern portions of the CWA, but
the threat of precip shud shift east fairly quickly.


.LONG TERM...  (Friday through Wednesday)
Issued at 405 AM CDT Thu May 17 2018

Unsettled pattern is expected through the weekend into the first
half of next week.  Global models are in relatively good agreement
that upper low over Missouri and Illinois on Friday will open up and
lift out over the weekend.  This upper low will bring a chance of
showers and thunderstorms to the area on Friday.  Highs on Friday
will be close to normal with the clouds and chance of rain under the
upper low.

A weak upper ridge will move across the area on Saturday once the
upper trough lifts out.  There will be a warm front move north into
the area on Saturday and Saturday night bringing an additional
chance of showers and thunderstorms.  The upper flow will become
southwesterly behind the weak upper ridge and a series of upper
level disturbances will move over the area in the southwesterly
flow.  The upper flow will eventually become zonal by the middle of
next week in response to a large upper trough dropping into the
western CONUS and closing off.  With a stalled front and unstable
airmass over the area, will keep at least a low chance for showers
and thunderstorms over the area each day.

Expect temperatures to rise back 10-15 degrees above normal next
week as the warm front moves back north into the area and 850mb
temperatures climb into the 15-20C range.



.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1230 PM CDT Thu May 17 2018

TSRA continue along nrn periphery of MCV tracking slowly ewd south
of the area. Believe TSRA will slowly expand/propagate newd this
afternoon. Better chances remain south of KSUS/KCPS, however,
still cannot rule out TSRA impacting these terminals. As upper low
remains over the region tonight and into Fri morning, lower cigs
are expected to move into the area from the east, impacting
KSUS/KCPS early Fri morning. Confidence on the trends for these
lower cigs is somewhat low and therefore kept in going TAF.

SPECIFICS FOR KSTL: Believe bulk of TSRA will remain south of the
terminal, but cannot rule out a stray storm impacting the terminal
this afternoon. Otherwise, MVFR cigs expected to move into the
area early Fri morning. Somewhat low confidence in these cigs and
may need to be adjusted with future updates.



Saint Louis     64  79  64  88 /  40  40  10  20
Quincy          60  76  60  83 /  10  20   5  10
Columbia        59  79  61  85 /  50  30   5  20
Jefferson City  59  80  61  87 /  60  30   5  20
Salem           64  76  62  85 /  50  50  30  20
Farmington      60  75  59  86 /  60  40  10  20




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