Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252124

Area Forecast Discussion
National Weather Service Saint Louis MO
324 PM CST Fri Nov 25 2016

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 322 PM CST Fri Nov 25 2016

Clearing line currently over central Missouri will continue to move
from west to east across the area late this afternoon and this
evening as a low level ridge moves into the area per the latest runs
of the the RAP.  Then some patchy fog will develop over parts of
area late tonight under mostly clear skies with light winds.  Expect
mostly sunny skies by tomorrow as the surface ridge moves east and
surface winds turn out of the southwest in the wake of the high.

With skies clearing out tonight with light winds, lows should fall
out to the agreeable MOS lows.  Temperatures should rebound nicely
into the 50s with full sunshine and southwesterly surface winds.


.LONG TERM...  (Saturday Night through Next Friday)
Issued at 322 PM CST Fri Nov 25 2016

(Saturday Night)

A moderation in temperatures is expected on Saturday night due to
continued southerly return flow around broad anticyclone near the
Tennessee Valley. South/southwest winds should stay up around 5
knots overnight...helping to inhibit radiational cooling.
However...some favored valleys that typically decouple easier will
still approach the freezing mark. Elsewhere...lows in the mid to
upper 30s are expected with the warmest lows across northern and
western sections of the CWA where slightly stronger sfc winds are

(Sunday - Monday Night)

More active weather pattern begins to take shape during the day on
Sunday. The first of what is expected to be two distinct waves of
shower activity is forecast to advect in from the west and
predominantly affect northern sections of the forecast area late
Sunday afternoon and evening. This area of shower activity looks to
be forced by broad low-level warm/moist advection in conjunction
with upper-level ascent via UL jet streak dynamics and DCPVA
downstream of negatively tilted shortwave trough. Highestlikelihood
of showers is across the northern portion of the forecast area
because this is where the best mid/upper level forcing for ascent
mentioned above should reside.

Second round of shower activity will be focused further to the south
and east mainly across portions of southeast Missouri and southwest
Illinois Monday afternoon and evening. This round will be aided by
very strong and focused low-level moisture convergence as well as
DCPVA ahead of another shortwave transversing the mean longwave
trough centered across the western Plains. Models are also
suggesting a line of showers and possibly a rumble of thunder or two
along/just ahead of a weak cold front and this is the reason why
there are likely PoPs extending further northwestward into the CWA
for Monday afternoon.

Rainfall amounts with each wave look fairly light...on the order of
a quarter of an inch to three quarters of an inch. As alluded to
yesterday...this rainfall will be beneficial to areas that have
dried out a bit the past couple of months.

Temperatures will remain mild and above normal through Monday night.
Warmest day should be on Monday ahead of the aforementioned cold
front for most. Highs in the upper 50s to low 60s are expected.
However...given the setup...would not be surprised if actual highs
are at least a few degrees warmer if clouds are more scattered than
currently forecast.

(Tuesday - Next Friday)

For the middle to end of next week...mostly dry weather with cooling
temperatures from above normal on Tuesday back to near normal for
the rest of the work week.  Could be some showery activity on
Wednesday as the third and what looks to be the final shortwave
swings through but higher chances look to be further to the south
and east of the area at the moment.



.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1123 AM CST Fri Nov 25 2016

Held on to MVFR ceilings at all of the TAF terminals through at
least mid afternoon. Earliest clearing will be at KCOU and KUIN at
22-23Z. The St. Louis area terminals may see clearing later this
afternoon, but may hold onto the ceilings into the evening hours
and may require amendments. Patchy fog may develop late tonight
causing MVFR visibilities.

SPECIFICS FOR KSTL: Ceilings between 2000-3000ft AGL will continue
through at least 23Z, and may last into mid evening.





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