Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252026
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
326 PM CDT SUN SEP 25 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 325 PM CDT Sun Sep 25 2016

A cold front extending from just west of UIN southwest to near COU
will continue moving southeastward tonight.  Widely scattered
showers and storms have developed ahead of the front this afternoon,
mainly across parts of southeast MO and southwest IL.  Much of this
convective activity should shift southeast of our forecast area
early this evening, but there should be some post frontal light
showers or rain moving through our area tonight as a deepening upper
level trough with embedded shortwaves moves eastward through the
northern Plains and into the Great Lakes region.  Cooler and less
humid air will filter southeastward into the region tonight behind
the cold front as a large and strong surface ridge builds east-
southeastward into our area.

GKS

.LONG TERM...  (Monday through Next Sunday)
Issued at 325 PM CDT Sun Sep 25 2016

The synoptic pattern at the start of the long term period will
feature an upper-level low digging into the north-central CONUS.
This upper-level low will slowly meander to the ESE along the
eastern seaboard through the end of the period, becoming closed off
from the better upper-level flow which will help to set up a
blocking pattern across much of the CONUS into the upcoming weekend.

The cold front will have pushed to the southeast of the region by
Monday morning, ending the precip chances.  Surface ridging will
build into the Southern Plains, which will place eastern MO/western
IL in a fairly tight pressure gradient due to deepening low pressure
across the northern Great Lakes.  Forecast soundings show mixing to
about 850mb, where 25 knots of flow will exist.  Therefore, think it
will be fairly breezy tomorrow, especially across northern MO with
sustained winds around 15 to 20 mph with gusts to around 25 mph.

Otherwise, expect surface ridging to dominate the upcoming week.
This will keep dry and seasonably cool conditions in the forecast
through the period.  Look for highs generally in the low to mid 70s,
with overnight lows in the upper 40s to low 50s.


KD

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1112 AM CDT Sun Sep 25 2016

A cold front extending from near IRK southwest to near SZL will
move southeastward through the taf sites this afternoon and this
evening. Post frontal showers were moving northeastward through
northwestern MO late this mornng. Scattered showers and storms
will develop along and just ahead of the front this afternoon. A
post frontal band of showers or rain can also be expected to
impact the taf sites late this afternoon and tonight. The cold
front should move southeastward through the St Louis metro area
around 00Z Monday. There will be a post frontal band of low level
clouds moving through the taf sites late this afternoon and
tonight. The MOS guidance keeps these post frontal clouds VFR,
but would not be surprised to see a brief period of MVFR cigs.
West-southwest surface winds will veer around to a northwest
direction after fropa. Rain and showers will shift southeast of
the St Louis metro area by 12Z Monday. A clearing sky can be
expected late tonight in UIN and COU and in the St Louis metro
area Monday morning.

SPECIFICS FOR KSTL: A cold front extending from near IRK southwest
to near SZL will move southeastward through the STL area around
00Z Monday. Post frontal showers were moving northeastward through
northwestern MO late this mornng. Scattered showers and storms
will develop along and just ahead of the front this afternoon. A
post frontal band of showers or rain can also be expected to
impact STL tonight.  There will be a post frontal band of low
level clouds moving through STL tonight. The MOS guidance keeps
these post frontal clouds VFR, but would not be surprised to see a
brief period of MVFR cigs. Southwest surface winds will veer
around to a northwest direction after fropa. Rain and showers will
shift southeast of the STL area by 12Z Monday. A clearing sky can
be expected Monday morning.

GKS

&&

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

$$

WFO LSX



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