Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 290423
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1123 PM CDT Thu Aug 28 2014

.SHORT TERM: (Tonight - Saturday)
Issued at 400 PM CDT Thu Aug 28 2014

Expect that convection from this afternoon will bleed over into
this evening before dissipating much like Wednesday night. Models
are redeveloping some nocturnal convection ahead of the trof in
the Plains to varying degrees, with the most bullish being the GFS
after midnight. The GFS cranks out .75 inch along and east of the
Mississippi river from St. Louis north. While I cannot totally
rule out overnight convection, the low level jet is pretty weak
and most of the isentropic lift will be well north of the area.
Have largely discounted the GFS for these reasons and only kept
slight chance/isolated PoPs overnight primarily for
northeast/northern zones.

Timing issues remain the primary problem for the approaching trof
Friday through Saturday.  Still thinking some scattered
thunderstorms will be possible Friday afternoon ahead of the trof;
but overall the models came in a bit faster with the eastward
progression.  Have sped up the introduction of likely PoPs Friday
night, and ended the likely PoPs sooner on Saturday.  Still holding
onto a chance/slight chance PoPs Saturday night as warm advection
aloft is forecast to begin again ahead of the next trof.  Seasonably
warm temperatures remain in the forecast through Saturday, though
highs will be very dependent on convection, especially on Saturday
afternoon.

Carney

.LONG TERM: (Sunday - Thursday)
Issued at 400 PM CDT Thu Aug 28 2014

Sunday should be drier than Saturday as the area will be stuck
between trofs with weak ridging overhead.  Can`t rule out scattered
afternoon storms over the southeast Missouri and southern Illinois.
The next trof in line is still forecast to move into the Midwest on
Monday.  There seems to be a little less agreement in the medium
range models on how far the south the associated cold front will
get.  Between the ECMWF and the GFS, the EC is further south with
the cold front, stalling it out near or just south of the I-70
corridor while the GFS keeps it further north near a line from St.
Joseph to Kirksville to Quincy.  Regardless, it looks like another
good chance for rain for parts of the area...primarily along and
north of the I-70 corridor Sunday night through Monday night or even
Tuesday.  The front will move back to the north Tuesday night and
Wednesday, but the GFS develops another round of convection Tuesday
night which pushes the effective front south into Arkansas
Wednesday.  This looks much less likely to me than the ECMWF
solution which simply pushes the front back to the north and allows
the heat to build back across the area.  Stuck pretty close to the
initial model blend for weather and temperatures Wednesday and
Thursday which keep highs in the mid to upper 80s, but this may be
too cool.  Will monitor trends and adjust over the next couple of
days as the models hopefully get a better handle on next week.

Carney

&&

.AVIATION:  (For the 06z TAFs through 06z Friday Night)
Issued at 1105 PM CDT Thu Aug 28 2014

The GFS model appears overdone with its precipitation forecast
late tonight and will keep tafs dry. There may be a little fog
late tonight/early Friday morning, mainly in the St Louis metro
area, and especially where there was recent rainfall early this
evening. The MOS guidance does not have as low of vsbys as it has
forecast the past few nights. It appears that the surface wind in
UIN and COU will be a little stronger than the previous couple of
nights. Sely surface wind late tonight will become sly on Friday
with scattered storms expected again during the late afternoon and
evening hours due to unstable conditions ahead of an approaching
upper level disturbance.

Specifics for KSTL: A light sely surface wind late tonight will
become sly on Friday and increase to 9-11 kts in the afternoon.
Scattered diurnal cumulus clouds should develop late Friday
morning and afternoon with scattered storms in the late afternoon
and evening.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     75  90  73  86 /  20  20  60  60
Quincy          72  86  69  84 /  30  40  60  40
Columbia        70  87  69  87 /  20  40  60  40
Jefferson City  71  88  70  87 /  20  40  60  40
Salem           73  88  72  84 /  20  20  50  60
Farmington      70  88  70  85 /  20  20  60  60

&&

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

$$

WFO LSX





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