Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 130755

255 AM CDT Sat Sep 13 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 255 AM CDT Sat Sep 13 2014

A strong storm system was located over Titletown early this morning
and driving a large shield of rain out ahead of it into Michigan.
Extending further to the south towards our region was a lobe of
moderately strong vorticity.  While this had helped, among other
things, in giving most locations last night some light rain, too
much bone dry air thru the column has since invaded for this forcing
to be of any good any longer.  In fact, skies are rapidly clearing
from north-northwest and should result in clear skies for much, if
not all, of our region shortly after sunrise.  Another big story
here is the first likely venture of temps into the 30s of the very
young meteorological autumn season with readings at several sites
northwest of STL metro teetering around 40 degrees.  Otherwise, a
strong 1030mb Canadian airmass centered near Omaha dominated the
weather map and provided our region with a light north wind.

The upper level system and any lift associated with it will be long
gone by 12z this morning and at that point it will be just a matter
of timing the leading edge of the clearing.  Looks like most of our
region will be clear by 12z save some of the southeast MO sections
and these should clear out by mid-late morning.

Full sunshine is then expected through the day with a light
northeast wind.  Conditional climo supports diurnal rises of at
least 20 degrees and this casts a strong preference for the warmer
MAV MOS temps:  maxes in the low-mid 60s.


.LONG TERM: (Saturday through Next Friday)
Issued at 236 PM CDT Fri Sep 12 2014

(Saturday through Monday)

Overall, mdls are in good agreement thru this period. Period begins
with a large sfc ridge settling across the region. This ridge will
keep temps around 15 degrees below seasonal average despite ample
insolation. As the ridge retreats, the approaching trof and sfc fnt
will bring another chance for precip to the region late in the
period. Some minor differences in timing are apparent among the mdl
guidance. Will keep PoPs lower except where mdls are in agreement.

(Tuesday through Friday)

Not much change from the prev forecast. Mdls remain in good
agreement overall thru the period with respect to mass fields
anyway. Sfc ridge builds into the region on Tues with precip coming
to an end Mon night. Cool temps will prevail thru mid week, tho not
as cool as this weekend. Mdls differ regarding precip chances for
late Wed into Thurs. The ECMWF is more robust with nocturnal
convection developing along a stationary fnt across the region. The
GFS would suggest height rising with the sfc ridge still holding on
into the area. Have kept PoPs low given the uncertainty forecasting
mesoscale features on day 7.

As for temps, have trended twd the warmer guidance thru the period
given heights over the region.



.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1119 PM CDT Fri Sep 12 2014

Subsidence and dry air advection at low levels are significantly
eroding the MVFR stratus in place across the region. The clearing
line has already moved through KUIN and KCOU and should reach St.
Louis metro TAF sites during 06-09z. There could be some isolated
spots of fog once clearing occurs, but the combination of drying
low levels and sustained winds AOA 7kts should act to limit any
fog formation to those sheltered areas with higher low-level
moisture. Generally VFR conditions are expected thereafter.



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)


Saint Louis     64  46  71  55 /   0   0   0  10
Quincy          61  41  68  51 /   0   0   0  40
Columbia        63  43  72  55 /   0   0   0  20
Jefferson City  64  42  73  55 /   0   0   0  20
Salem           63  42  71  51 /   0   0   0  10
Farmington      64  40  72  50 /   0   0   0  10




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