Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 230846
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
346 AM CDT Mon Mar 23 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 346 AM CDT Mon Mar 23 2015

Surface low over north central Missouri will move southeast today
and should be in the vicinity of the STL Metro area around 18Z.  Low
level warm advection and moisture convergence ahead of the low is
producing isolated to scattered showers and even a clap of thunder
or two across northeast Missouri.  Expect this activity to continue
to spread southeast into the CWFA today.  Not really sure how far
south it will progress...but scattered showers producing a few
hundredths of an inch of rain look likely generally along and north
of I-70 today with decreasing chances for measurable precip further
south.  Temperatures are going to be tricky today...actually
temperatures are going to be tricky pretty much through Wednesday.
Decent warm advection ahead of the cold front today will likely be
offset somewhat by clouds and light precip.  Regardless, there will
probably be around a 20 degree temperature spread between Quincy and
Farmington.  In this kind of setup, highs are pretty much guaranteed
to be wrong across much of the area.  I just tried to minimize the
damage using a blend of guidance which yielded mid 40s across
northern zones to low-mid 60s along the I-70 corridor to near 70 in
southern zones.

Carney

.LONG TERM: (Monday night through next Sunday)
Issued at 317 PM CDT Sun Mar 22 2015

Attention then turns to a more significant system that will affect
the FA from Mon night thru Tue night. SFC low dvlps in the lee
trough Monday. The residual bndry remains in place and strengthens
Mon evng and starts lifting north as a warm front Mon night. WAA
precip should dvlp across Nebraska Mon aftn/evng and spread/dvlp
E/SE into nthrn MO by envg as the LLJ strengthens and moisture
convergence increases. Should be some embedded TSTMs with this
activity. Warm front lifts north of the FA Tue mrng ending the
precip threat. This puts the CWA in the warm sector with some at
least partial clearing expected. This sets the stage for an
interesting aftn/evng on Tue with a strong negatively tilted trof
impacting the area. There will be plenty of shear to work
with...and it appears that temps in the 60s to low 70s and Dps in the
50s will combine with steep lapse rates in excess of 7 C/km will be
sufficient to produce enough instability for vigorous convection.
Shear vector orientation favor supercells...so all modes of svr wx
are possible. Therefore...SPC has a good portion of MO in a Day 3
slight risk. Trough axis lifts NE overnight taking line of storms
with it. There is no true cold front assoc with this system so Wed
is expected to be another mild day...esp across the sthrn CWA with a
favorable west wind and an 850mb thermal ridge of 8-10C aligned over
sthrn IL/MO drng the aftn.

Meanwhile...a ridge is expected to dvlp along the west coast. This
should help dvlp NW flow across the region. A series of short waves
are expected to dig out a significant trough across the ern half of
the CONUS for the end of the week with 850mb temps in the -8C to
-14C by 12Z Sat. The first short wave will drive an actual cold
front into the area late Wed. A wave of low pressure is expected to
ride NE along the advancing cold front from the sthrn Plains into
the OH vly producing another chance for SHRAs/TSTMs across the
CWA...with the SErn half most favorable attm...from late Wed into
Thu mrng. Temps are expected to be held down by clouds and precip on
Thu...esp across the south. SFC ridge in control for the end of the
week with below normal temps expected into Sat. Highs on Thu/Fri/Sat
are expected to be in the low 40s to low 50s with lows in the mid
20s to mid 30s. Upper lvl trough and sfc ridge axis pass Sat with
sthrly flow dvlpng by evng. This will be temporary though with
another short wave and assoc cold front scheduled to arrive late
Sunday with a reinforcing shot of colder air.

2%

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1146 PM CDT Sun Mar 22 2015

Present indications are that VFR flight conditions should prevail
through 12z with a general increase in clouds from 5,000-7,000 ft
overnight. Still appears a cold front will progress across the
region on Monday accompanied by scattered showers, maybe an isolated
thunderstorms Monday morning. Maintaining the mention of showers
into the TAFS. While there is currently no visibility restriction
mentioned, that is more a reflection of the uncertainty in
coverage and intensity. MVFR flight conditions/CIGS should settle
into the terminals in the wake of the cold frontal passage and
persist through the end of the valid TAF period.

Specifics for KSTL:

Still thinking that VFR flight conditions should prevail through
12z with a general increase in clouds from 5,000-7,000 ft overnight.
A cold front is on track to move across the region on Monday
afternoon accompanied by scattered showers. Maintaining the mention
of showers into the TAFS. While there is currently no visibility
restriction mentioned, that is more a reflection of the
uncertainty in coverage and intensity. MVFR flight conditions/CIGS
should settle into the terminal in the wake of the cold frontal
passage at 21z and persist through the end of the valid TAF
period.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     61  40  64  49 /  30  40  70  70
Quincy          45  33  54  42 /  40  70  90  80
Columbia        62  41  69  44 /  20  60  70  70
Jefferson City  65  43  70  45 /  20  50  70  70
Salem           57  39  61  50 /  30  20  60  70
Farmington      66  44  70  51 /  20  20  40  60

&&

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

$$

WFO LSX






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