Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 122241

541 PM CDT Fri Sep 12 2014

.SHORT TERM:  (Through Tonight)
Issued at 236 PM CDT Fri Sep 12 2014

Cloud cover continues to cover the area this afternoon as stratus is
trapped under a low level inversion and mid-high level clouds are
streaming in ahead of a mid level trough.  There has been some light
rain associated with the mid-level trough moving across northern
Missouri early this afternoon, but it`s coverage has been limited.
Latest runs of the RAP and HRRR still show some redevelopment of
some light rain over western Missouri this afternoon and this
evening ahead of the upper trough that will move across the CWA this
evening.  Then expect clearing of the clouds from north to south
after 06Z as the upper trough moves to the east allowing subsidence
to set in.  Drier air will move into the low levels as the inversion
weakens which should allow the low level clouds to move out.
Temperatures should fall close to agreeable MOS guidance for lows
once skies begin to clear with the light northeasterly winds.


.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 00z TAFs through 00z Saturday Evening)
Issued at 534 PM CDT Fri Sep 12 2014

An extensive area of MVFR stratus/stratocumulus was in place
across the region at TAF issuance. Although drier air will be
working into the region overnight, there is still a lot of
moisture trapped below an inversion. This suggests that clouds
will be slow to clear even with the drier air. On the other hand,
recent satellite imagery has shown that upstream stratocu was
breaking up over IA/NE, and it is possible that cigs may clear
earlier than expected. Ceilings could fall to IFR at times
overnight until the drier air arrives. Intermittent light drizzle
or light rain may also occur over the next several hours.
Initially northerly winds will back slightly overnight then veer

Specifics for KSTL: It is likely that MVFR ceilings will persist
overnight. Ceilings should rise by tomorrow morning at the latest
due to diurnal mixing and drier low-level air. Initially northerly
winds will back slightly overnight then veer tomorrow and become
easterly towards the end of the valid TAF period.



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)




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