Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 232034
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
334 PM CDT Wed Jul 23 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 333 PM CDT Wed Jul 23 2014

Front has pushed into southeast MO and extreme southern IL this
afternoon.  Although a few storms have been able to form in the
residual instability north of the front they too are sagging south,
and should exit southern tip of Reynolds county no later than 22z.

Weather trends for the FA heading into the overnight hours will be
controlled by large high pressure ridge working its way south from
the upper Mississippi Valley. Although dewpoints pooled north of the
frontal boundary have kept humidity levels fairly high along and
south of I-70 this afternoon, leading edge of much drier air is
currently working into northern sections of the FA, and this drier
airmass will overspread the entire CWA throughout the night.
This dry and cool airmass along with clear skies should yield min
temps that are about 10 degrees below late July averages, with lows
expected range from the mid 50s to low 60s.

Truett

.LONG TERM:  (Thursday through Next Wednesday)
Issued at 333 PM CDT Wed Jul 23 2014

Surface ridge will build southeast from Wisconsin into the
Mid-Mississippi Valley on Thursday, and then continue east into the
Ohio Valley Thursday night into Friday.  Should see temperatures
well below normal Thursday and Thursday night with low humidity.  As
the high moves into the Mid-Atlantic Region on Friday, we should see
a return of more typical summer heat and humidity, especially across
central and northeast Missouri as southerly flow ramps up.  Could
see some warm advection showers/thunderstorms Friday, primarily
across northern/northeastern portions of the CWFA as the low level
jet strengthens ahead of a weak shortwave rounding the upper level
ridge.  This should suppress temperatures somewhat on Friday
afternoon.

By Saturday the next strong ridge-running shortwave will be dipping
southeast out of Canada into the Northern Plains and Upper Midwest.
Strong southerly flow will bring more heat and humidity into the
region, and this will likely be the warmest day of the next 7 with
highs in the middle...and perhaps upper 90s.  The shortwave will
phase with the long wave trof over eastern North America allowing
another cool Canadian airmass to dip into the eastern CONUS.  Medium
range guidance is in decent agreement that the cold front ahead of
this airmass will plow through the area on Sunday with another shot
at precipitation.  There are some discrepancies between the GFS and
ECMWF as to the extent and perhaps the intensity of the
precipitation, so will stick with mid-high chance PoPs at this time.
After the front moves through and high pressure moves in, expect
another round of spectacular late July weather with below normal
temperatures and low humidity into the middle of next week.

Carney

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1245 PM CDT Wed Jul 23 2014

Band of post frontal st/sc that formed and/or advected into area
from sw and central IL has given all TAF sites but KCOU a very
definite autumn look throughout the morning. However, over the
last 90 minutes or so visible satellite pics indicate that this cloud
deck (which was roughly centered on a line from just w of KUIN to
near KSTL at 16z) is beginning to break up and ceilings are
beginning to rise. So...believe MVFR cigs in the STL metro should
climb aoa 3kft over the next hour or so...with sct-bkn clouds
3-5kft being the primary sky condition for most of the area during
the afternoon. All of this cloudiness should dissipate heading
into the evening hours with loss of heating and with much drier
air advecting into the region, with clear skies and light
northeast winds expected overnight.

Specifics for KSTL: Bases of MVFR clouds over the area at midday
should climb above 3 kft over the next hour or so...with
additional thinning of the clouds producing sct-bkn deck 3-5kft
throughout the afternoon. The clouds should totally dissipate by
early this evening, leaving clear skies and light northeast winds
for the overnight hours and into Thursday morning.

Truett

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     61  80  64  87 /   5   0   5  10
Quincy          57  79  60  85 /   0   0  30  40
Columbia        60  80  62  91 /   0   0  10  10
Jefferson City  60  81  61  91 /   0   0  10  10
Salem           56  79  58  86 /  10   0   0  10
Farmington      58  79  58  85 /  10   0   0   5

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







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