Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 141737
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1237 PM CDT Sun Sep 14 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 357 AM CDT Sun Sep 14 2014

Patchy fog mainly in river valleys early this morning will dissipate
shortly after sunrise.  High level cloudiness will continue to
stream eastward through at least the southern half of our forecast
area.  Warm air advection mid level cloudiness advecting eastward
through western MO will move into the western portion of our
forecast area this morning, although some of these clouds may thin
out or break up later this morning into the afternoon.  High
temperatures will be a little warmer today than yesterdays highs
despite greater mid-high level cloudiness as 850 mb temperatures
gradually warm across our forecast area, and surface winds become
s-sely as the surface ridge now extending from MI southwest into
northeast MO moves eastward.

GKS

.LONG TERM:  (Tonight through Saturday)
Issued at 357 AM CDT Sun Sep 14 2014

All models are forecasting another shortwave to sweep across the
upper Mississippi Valley on Monday.  This system will be preceeded
by a brief shot of WAA and moisture advection over our area tonight
into Monday, followed by a reinforcing surge of cool Canadian air
Monday night into Tuesday.  The combination of moisture return and
low level lift from the WAA should bring a chance of showers and a
few thunderstorms to about the NW third of the CWA late tonight,
with the precipitation threat increasing and overspreading the
remainder of the forecast area on Monday; first with the
aforementioned low level WAA/moisture advection (especially over
northern sections of the FA), and then perhaps with redevelopment
during the afternoon along the cold front as it pushes into the
region.  Believe that most of our area will see some precipitation
with this system, but with best upper level dynamics remaining north
of our FA don`t believe rainfall amounts will be especially high.

Showers and thundestorms will end from north to south on Monday
night as the next cold front pushes through the mid-Mississippi
Valley, and by Tuesday dry and cool weather should be the rule
throughout the FA thanks to the next Canadian surface ridge building
into the Mississippi Valley.

Due to the persistent longwave trof over the eastern CONUS the
eastward progression of the Canadian high will be quite slow, so it
should maintain control over the weather across the region
into Wednesday and Thursday.  GFS is suggesting much more rapid
breakdown of the western periphery of the ridge and actually hints
at a bit of light precip as early as Wednesday, but this trend is
not supported by the other medium range solutions so have maintained
a dry forecast for now.

Temperature trends through midweek will certainly remain below
normal. The possible exception to this may be in southeast Missouria
dn southern Illinois tomorrow where warm air ahead of the cold front
will send afternoon highs into the upper 70s.   However, in northern
parts of the FA Mondays highs will likely be in the 60s due to the
combination of clouds, rain, and the arrival of the cold air during
the afternoon.  The southward surge of this cooler air Monday night
should mean highs in the 60s and lower 70s over most of the area by
Tuesday.

Highs should remain in the lower to middle 70s on Wednesday and
Thursday.  However, temperatures will return to more typical
mid-September levels by the end of the week as the axis of the
longwave trof shifts to the east and allows warmer air to push back
into the Mississippi Valley.  Precip threat should remain fairly low
until perhaps Saturday, with the last few hours of the medium range
models suggesting a cold front pushing into the central CONUS.

Truett

&&

.AVIATION:  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1228 PM CDT Sun Sep 14 2014

VFR flight conditions are expected through at least 06z tonight
with some batches of sct-broken clouds from 6000-10000 ft. The
brunt of these through this afternoon will impact mid MO including
KCOU. Overnight a west-southwest low level jet will develop and
this should lead to a growing area of showers and some
thunderstorms across northern MO into central IL that should
impact KUIN late tonight and into Monday morning. This region of
showers and thunderstorms should sind southward with time on
Monday but the coverage and intensity are difficult to gage.

Specifics for KSTL:

VFR flight conditions are expected throught daybreak on Monday.
From Monday morning into the afternoon, an area of showers and
thunderstorms originating in northern MO will be settling
southward. The coverage and intensity are difficult to gage the
potential impact to the terminal should ramp up from mid morning
into the afternoon.

Glass

&&

.CLIMATE:
Issued at 236 PM CDT Fri Sep 12 2014

Record Lows This Weekend:

       STL        COU        UIN
13   43(1975)   33(1902)   33(1902)
14   46(1996)   40(1892)   38(1996)


&&

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

$$

WFO LSX






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