Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 241149
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
649 AM CDT Wed May 24 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 352 AM CDT Wed May 24 2017

Upper low continues to sink swd early this morning. As it does, the
pocket of mid clouds over central MO will continue to move esewd,
although, any precip associated with it will likely be
light/sprinkles.

Otherwise, expect much of the region to be dry thru about mid
morning as SHRA begin to develop. Expect these SHRA to continue to
develop thru the afternoon with isod TS also during the afternoon.
Uncertain exactly what coverage will be, but kept PoPs in high
chance range. These SHRA shud dissipate quickly with sunset, except
over the ern portions of the CWA where precip is more dynamically
forced.

As for temps, have trended twd cooler guidance for today expecting
most breaks in clouds to fill in. Also trended cooler for tonight as
well with the clouds breaking up as the ridge builds into the area.
Winds will be light tonight, especially across wrn portions of the
CWA. Have held off adding fog to the forecast with better conditions
west of the CWA. However, will need to monitor and may need to be
added with updates.

Tilly

.LONG TERM...  (Thursday through Tuesday)
Issued at 352 AM CDT Wed May 24 2017

Weak surface ridge will be over region on Thursday with dry and mild
weather in store for the forecast area. Highs will be in the low to
mid 70s.

By Thursday night, surface ridge to move off to the east as next
system moves in from the southern plains. Fairly zonal flow aloft,
frontal boundary associated with system to stall out along I-70
corridor for the last part of the work week and into the holiday
weekend. Will see increasing low level moisture towards daybreak on
Friday with showers and some storms on the increase. Late Friday
night, with sufficient instability and shear could see an MCS
develop and slide east along boundary moving into forecast area
Saturday/Saturday night with main threats being large hail, damaging
winds and isolated tornadoes. So SPC has placed areas along and
south of I-70 in a slight risk for Day 4.

By Sunday night, precipitation moves off to the south and east with
dry weather for Memorial Day. However, could see some wrap around
showers/isolated storms along and north of I-70 Monday afternoon and
evening. Could see more isolated/scattered showers on Tuesday, as
another spoke of energy aloft rotates around system anchored over
Great Lakes.

As for temperatures through the period, will see at or below normal
temps on Thursday, then warm up a bit above normal for the holiday
weekend despite the chances of precipitation. Then cool down to near
normal Sunday through Tuesday.

Byrd

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 641 AM CDT Wed May 24 2017

SHRA are expected to develop this morning with isod to sct TS
possible this afternoon. These SHRA are expected to be largely VFR
with a bkn deck of VFR bases. However, visbys may briefly drop
into the MVFR range. SHRA are expected to dissipate quickly with
sunset with clouds gradually clearing out of the area. As winds
become light, can not rule out light fog developing affecting
mainly KCOU late tonight. However, currently expect enuf wind to
prevent fog development.

Tilly

&&

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

$$

WFO LSX


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