Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KLSX 141048

548 AM 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.


.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

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.



.AVIATION:  (For the 12z TAFs through 12z Monday Morning)
Issued at 518 AM CDT Sun Sep 14 2014

River valley fog impacting CPS and SUS will dissipate by 14Z this
morning. Mid level clouds around 7000-8000 feet will advect
eastward into COU early this morning, and into the rest of the
taf sites later this morning. Showers may move into UIN and COU
late tonight as a swly low level jet brings low level warm air
advection and increasing moisture to this area. The surface wind
will become sely as the surface ridge extending from NY southwest
into northeastern MO moves slowly eastward, although the winds
will remain fairly weak.

Specifics for KSTL: Mid level clouds around 7000-8000 feet in
height will spread eastward into the STL area later this morning.
Calm wind will become sely this afternoon, only increasing to about
5-6 kts. Showers may move into STL Monday morning.



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)




WFO LSX is the U.S. government's official web portal to all federal, state and local government web resources and services.