Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280830
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
330 AM CDT Fri Jul 28 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 329 AM CDT Fri Jul 28 2017

Frontal boundary is exiting forecast area as of 08z. However, models
show secondary upper level shortwave rotating around upper low that
is over Great Lakes region. It will slide southeast through region
today, possibly triggering isolated diurnal showers during the
afternoon hours. Confidence is low at this time, so just have silent
14 pops for areas along and east of Mississippi River between 20z
and 00z. Will need to keep an eye on this. Otherwise, should see
stratus begin to lift and burn off towards sunrise with scattered
diurnal cu developing. As for highs, will be a bit below normal in
the 80s.

By this evening, skies to clear out as surface ridge builds in with
drier air and cooler temps. Lows will be in the upper 50s to mid 60s.

Byrd

.LONG TERM...  (Saturday through Thursday)
Issued at 329 AM CDT Fri Jul 28 2017

Focus thru much of the period will be temps with no precip expected
until next Wed to Thurs.

Period begins with the region under NW flow as the ern trof deepens
and the upper ridge remains locked in place over the Southern
Plains. NW flow is expected to continue thru the end of the forecast
period as the upper ridge is slowly broken down by a number of s/w
that round the top of the ridge.

Despite this, mdls do show a rather slow warm up about mid week as
the sfc ridge builds south allowing light sly flow to return to the
area ahead of an approaching cdfnt.

This fnt will bring a chance of TSRA to the region. However, with
the sfc ridge extending across the srn U.S. cutting the area off
from Gulf moisture, there is some uncertainty regarding how much
moisture the fnt will have to work with. Have kept PoPs rather low
for now.

Tilly

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1151 PM CDT Thu Jul 27 2017

Challenging cloud forecast for tonight as low-level moisture
continues to linger near a front moving through the area. Latest
trends suggest MVFR cigs may not last quite as long as previously
thought, due to drier air working in from the north. However,
expect MVFR cigs to develop over the next couple of hours in the
St. Louis metro sites (with a light shower not out of the
question), and last into the early morning hours. Then, drier air
infiltrating from the northwest should help raise cigs to VFR
through the rest of Friday. UIN/COU should remain VFR through the
period. Winds through the period will be generally out of the
north.

SPECIFICS FOR KSTL:
Still a challenging ceiling forecast tonight due to lingering low-
level moisture near a passing cold front. Upstream obs still
suggest enough low-level moisture persists for a period of
potentially MVFR cigs (and perhaps even a light shower) through
the early morning hours. Skies should then rise to VFR as drier
air works in behind the front. Winds through the period will
generally be out of the north.

KD

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     85  66  82  63 /  10   5   0   0
Quincy          82  60  80  59 /   0   0   0   0
Columbia        82  62  81  59 /   5   0   0   0
Jefferson City  84  64  82  60 /   5   0   0   0
Salem           83  61  80  58 /  10  10   0   0
Farmington      85  61  81  55 /  10  10   0   0

&&

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

$$

WFO LSX



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