Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 020425

1125 PM CDT THU OCT 1 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 327 PM CDT Thu Oct 1 2015

Sprawling high pressure centered over Quebec Canada and extending
southwest into the southeast Great Plains will continue to pump cool
dry air into the Mississippi Valley on northeast wind.  Diurnal
cumulus should dissipate rapidly toward sunset.  Expect
temperatures fall off quickly this evening and bottom out around
where they were this morning...generally in the low to mid 40s with
potentially some upper 30s in well sheltered low-lying areas.


.LONG TERM:  (Friday through Next Thursday)
Issued at 327 PM CDT Thu Oct 1 2015

High amplitude weather pattern will continue through the period.
The aforementioned Canadian high ridge will continue to keep
temperatures at or below normal through Sunday or Monday.  Will see
some moisture swing back across our area around an upper level low
which will be moving from the Lower Tennessee Valley southeast to
near the Florida/Georgia borer by Sunday.  It`s possible there could
be a few showers across Illinois produced by this moisture return,
but the dry air associated with the Canadian high will likely eat
into any precip that does try to fall.  Therefore kept PoPs below
mentionable levels through the weekend.  The upper ridge currently
over the Rockies will drift eastward across the Plains into the
Midwest by Monday.  This will start a warmup pushing temperatures
above normal by Tuesday/Wednesday.  Some disagreement at the end of
the medium range with the GFS moving a strong trof and associated
surface low across the Plains into the Midwest with precip breaking
out ahead of the system for Thursday.  The ECMWF is much slower with
the low, and considering the blocky high amplitude pattern, I`m
tending to agree with the ECMWF.  Opted to stick with ensemble
guidance and kept chance PoPs in on Thursday, but this may end up
being too fast.



.AVIATION:  (For the 06z TAFs through 06z Friday Night)
Issued at 1122 PM CDT Thu Oct 1 2015

Clear skies at the moment across the region with a light northerly
breeze. Latest guidance suggests area of MVFR ceilings developing
or advecting west shortly after sunrise across the St. Louis Metro
terminals. Have hinted at this with a SCT020, as confidence is not
high enough to include MVFR ceilings at this point. In any case,
ceiling should lift and scatter out in the afternoon with a gusty
northerly wind.

Specifics for KSTL:

Potential for a MVFR deck to form and advect west across the
terminal after 12Z. Have hinted at this in the latest forecast.
Otherwise, VFR conditions with diurnal cloud cover and a gusty
north wind.





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