Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 180011
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
711 PM CDT Sun Sep 17 2017

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 251 PM CDT Sun Sep 17 2017

Area of rain that has been trying to move east from central MO has
continued to dissipate. Scattered thunderstorms have developed
across Southeast MO and southern IL in a region of better
instability. Expect this trend to continue into the evening. Looks
like a lull in any rain for tonight before the next short wave moves
in Monday morning. Models pretty consistent in keeping the best
changes from nw MO into Iowa. Have kept 40-50 pops across the area.
Have trend temps toward the cool side of guidance for Monday given
the expected cloud cover.

JPK

.LONG TERM...  (Monday Night through Next Sunday)
Issued at 251 PM CDT Sun Sep 17 2017

With weak ridging aloft, warm front to develop across region by
Monday night with several shortwaves sliding along it. So best
chances of showers and storms will continue through early Tuesday.
Then activity to taper off later in the day Tuesday as upper level
trof deepens to our west.

Will see well above normal temperatures once again by Wednesday with
highs in the upper 80s to low 90s. Models having issues with next
system, so kept a blend with cold front eventually washing out as it
moves into western Missouri, so just isolated/scattered activity
Wednesday evening mainly over central/northeast MO and west central
IL.

As upper level trof continues to deepen over the western US, upper
level ridge will build over the area through the rest of the
forecast period. Could see isolated activity over region in warm
sector, so kept slight chance pops during the daytime hours for
portions of the area on Thursday and Friday. By Saturday, upper
level shortwave over southwestern US to begin lifting out, pushing
cold front closer to region. Will see increasing chances of showers
and storms beginning Saturday night and into Sunday.

As for temperatures, to remain above normal for this time of year,
in the 85 to 90 degree range.

Byrd

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 639 PM CDT Sun Sep 17 2017

Cold front has shifted south of the taf sites early this evening
with a surface ridge centered over southern MN building southward
into northern MO. North-northwesterly surface winds will weaken
and veer around to an east-northeasterly direction later tonight.
The MVFR cigs in UIN should dissipate later this evening as low
level drier air advects into the region. There will likely be some
light fog late tonight and early Monday morning in COU and the St
Louis metro area with MVFR ceilings possible with patchy stratus
clouds developing as well. An upper level disturbance will bring
at least scattered showers and storms to COU by late morning and
to UIN and the St Louis metro area Monday afternoon. The surface
wind should be mainly southeasterly in the morning, then become
more south-southwesterly in the afternoon as the surface ridge
shifts eastward and a weak warm front shifts northeastward through
the region.

SPECIFICS FOR KSTL: Cold front has shifted just south of the STL
area early this evening with a surface ridge centered over
southern MN building southward into northern MO. Northwesterly
surface winds will weaken and veer around to a northeasterly
direction late tonight. There will likely be some light fog late
tonight and early Monday morning with MVFR ceilings possible with
patchy stratus clouds developing as well. An upper level
disturbance will bring at least scattered showers and storms to
the STL area Monday afternoon. The surface wind should be mainly
southeasterly in the morning, then become more southwesterly in
the afternoon, albeit quite weak as the surface ridge shifts
eastward and a weak warm front shifts northeastward through the
region.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     68  82  69  88 /  30  40  40  20
Quincy          59  77  64  84 /  30  50  50  30
Columbia        65  79  65  86 /  50  60  40  20
Jefferson City  65  81  66  87 /  50  60  40  20
Salem           66  84  66  87 /  40  40  40  30
Farmington      64  81  66  86 /  40  40  30  20

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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