Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 261011
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
411 AM CST Wed Nov 26 2014

.SHORT TERM: (Today and Tonight)
Issued at 310 AM CST Wed Nov 26 2014

Clipper system over Nebraska/Iowa border will continue to drop
southeast today, bringing the area some light snow/rain. Short
range guidance including the HRRR, RAP, NAM and GFS are in good
agreement that light precip will overspread the area through the
morning hours, reaching the Mississippi River between 16-18Z.
Primary lifting mechanisms continue to look like low level
moisture convergence, frontogenesis, and broad scale lift
generated by the parent shortwave. Precipitation will initially
have to fight some pretty dry low level air as it moves into the
area as dewpoints are in the upper teens and low 20s. Evaporative
cooling as well as favorable vertical profiles would indicate that
initially most if not all of the precipitation will fall as
snow...especially over central and northeast Missouri. Insolation
through later in the morning and afternoon, combined with
southerly flow along and east of the Mississippi river (which will
be east of the low track) will probably cause the snow to mix with
rain across a good portion of the area for at least part of the
afternoon. Between the mix, above freezing temperatures, and warm
ground conditions (2 inch soil temperatures range from 32 to 40
degrees across the area), expect only minor accumulations of and
inch or less today. The tail end of the clipper will continue to
affect the area this evening with additional minor accumulations
possible...generally along and east of the Mississippi in
southeast Missouri and southwest Illinois. The lingering
precipitation should end before 06Z this evening.

Carney

.LONG TERM:  (Thursday through Tuesday)
Issued at 410 AM CST Wed Nov 26 2014

Quiet period of weather for Thanksgiving Day through Saturday as the
pattern transitions from high amplitude to more zonal.  After a cold
day on Thanksgiving with highs struggling into the upper 20s to mid
30s, the trof currently over the eastern CONUS will shift offshore
by early Friday morning which will start a moderating trend.  Low
level southwest flow will bring temperatures up to near normal in
the low 50s, and temperatures will warm further on Saturday into the
upper 50s and low 60s.  Continuing to keep a dry forecast on
Saturday in spite of the GFS and ECMWF which continue to spit out
light QPF.  Still think this is due to the rapidly moistening
boundary layer and the model`s tendency to make precipitation when
this occurs.  Sunday`s highs are still in question as a 1035mb high
dips down into the Northern Plains and Upper Midwest.  The resulting
cold front will be moving into northern sections of our area during
the day which makes high temperature forecasts for Sunday quite
difficult.  Should be mild south of the front with highs in the 50s
and 60s...possibly warmer.  North of the front it will be sharply
colder.  As there will be frontal-scale lift as well as weak low
level moisture convergence, have kept low chance PoPs in the
forecast south of the front in the warm sector.  High will shift
eastward Monday and Tuesday.  Medium range guidance agrees that
Monday should be cool and dry under the influence of the high, with
the potential for temperatures rising back above normal for Tuesday
as southerly flow returns to the area.

Carney

&&

.AVIATION:  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1125 PM CST Tue Nov 25 2014

VFR flight conditions and dry weather will persist overnight with
clouds increasing and thickening across the region. A northwest
flow storm system is still on track to impact the area on
Wednesday with precipitation spreading in KCOU around 14z and KUIN
and the St. Louis area terminals between 16-17z. Temperature
structure at the onset of the precipitation suggests all snow at
KCOU and KUIN with predominately MVFR flight conditions, while
there is more uncertainty in the ptype at and KSTL/KSUS/KCPS with
snow at the onset and then mixing with rain. Flight conditions
could lower into the IFR category during the precipitation.
Precipitation should taper to very light snow/flurries by mid-
afternoon to evening with a northwest wind shift as the system
passes.

Specifics for KSTL:

VFR flight conditions and dry weather will persist overnight through
mid morning on Wednesday with clouds increasing and thickening. A
northwest flow storm system will impact the area on Wednesday with
precipitation spreading into KSTL between 16-17z. There is some
uncertainty in the ptype, however the current thinking is that we
will see snow at the onset and then mixing with rain in the afternoon.
Flight conditions could lower into the IFR category during the
precipitation. Precipitation should taper to very light snow/flurries
by early evening with a northwest wind shift as the system passes.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     39  28  34  27 /  70  60   0   0
Quincy          38  20  27  22 /  80  20   0   0
Columbia        39  23  34  27 /  70  20   0   0
Jefferson City  40  25  35  27 /  70  20   0   0
Salem           40  29  33  24 /  70  60   0   0
Farmington      40  28  36  26 /  70  60   0   0

&&

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

$$

WFO LSX





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