Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 202046

246 PM CST Thu Nov 20 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 246 PM CST Thu Nov 20 2014

Quiet conditions are expected tonight as surface high pressure
drifts southeastward across the region. Northwest flow aloft will
start to diminish overnight as the upper trough slides off to the
east; however, light winds and generally clear skies will still
promote temperatures falling into the teens to lower 20s by early
Friday morning.


.LONG TERM:  (Friday through Next Thursday)
Issued at 246 PM CST Thu Nov 20 2014

A warm front currently lifting northeast out of central OK will
push a slug of warm air and increased moisture into the forecast
area on Friday. Progressively lower stratus will develop from SW
to NE during the daylight hours, and may be accompanied by patchy
drizzle during the afternoon and evening. As moisture and lift
from WAA continue to increase overnight, light rain will become
increasingly likely across the region. Highs Friday may only reach
the mid 30s to lower 40s due to the arrival of the surface warm front
late in the day, but overnight lows will be quite similar with
little to no diurnal temperature fall, and highs will climb into
the 50s for both Saturday and Sunday in the wake of tomorrow
evening`s warm front.

Showers and perhaps a few isolated thunderstorms will become
increasingly likely on Saturday and Saturday night as a shortwave
trough begins to push into the southern Plains. Precipitation
amounts should remain fairly light until Sunday morning, when the
upper low shifts from central TX into northern AR, and surface low
pressure begins to deepen over central and eastern MO. Widespread
rainfall of an inch to perhaps an inch and a half is possible
Sunday as the upper low moves from eastern MO into central IL and
the surface low continues to deepen as it lifts northeast. Rain
should gradually taper off on Sunday night as the southwestern
system departs; however, a light rain/snow mix or a brief period
of light snow is possible Monday as a separate system drops down
from the northwest and drags a surge of cold air into the region.
No impacts are expected from any wintry precipitation should it
occur, since most moisture should be swept out of the region by
the weekend system, and the combination of light QPF and warm/wet
ground should prevent any snow accumulation.

High temperatures will fall into the 30s to lower 40s for early
next week as a deep upper trough develops and lingers over the
central CONUS. Things become quite a bit muddier by midweek to
especially late week when models diverge on the timing/position of
the exit of the longwave trough, and any systems following in
behind. For now, have removed PoPs beyond Monday night due to a
large amount of uncertainty, and will re-evaluate with future
forecast issuances.



.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1127 AM CST Thu Nov 20 2014

VFR conditions are expected to persist through the next 24 hours
as morning stratus scatters out east of the terminals and mainly
clear skies prevail. West northwest winds will gradually veer to
the north this afternoon, then will become light and variable
overnight. Stratus will begin to build in from the southwest on
Friday morning, but should remain VFR through 18z.

Specifics for KSTL: Skies should remain clear through Friday AM,
then stratus will begin to build in by 17-18z Friday. Ceilings
will initially range from 3-4 kft, then will gradually lower
during the early afternoon hours. By 21-22z, ceilings will drop to
1500 ft or less, and drizzle will become possible slightly after
00z Saturday.





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