Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 092031
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
331 PM CDT Wed Apr 9 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 322 PM CDT Wed Apr 9 2014

Surface ridge axis continues to move east of the Mississippi River
Valley with temperatures warming into the 60s on an increasing
south/southwest flow in the boundary layer. Cold front just now
entering North Dakota will quickly move southeast tonight, but
remain to the northwest of the CWA through 12Z. Increasing high
level clouds and a southerly wind will keep temperatures some ten
degrees warmer than last night with MOS advertising upper 40s
areawide.

CVKING

.LONG TERM:  (Thursday through Next Wednesday)
Issued at 322 PM CDT Wed Apr 9 2014

A relatively weak cold front will drop southeastward through our
forecast area Thursday.  There may be isolated to widely scattered
showers along and just behind this front, although the models may
have a little too much surface/boundary layer moisture.  There will
be at least weak cold air advection behind this front across
northeast MO and west central IL, but high temperatures should
still be above normal, especially across the southeast half of
the forecast area. This front will weaken and become nearly
stationary across southern portions of MO and IL. There will be a
continued chance of showers and a few storms across the southern
half of the forecast area near this front. The NAM model was also
depicting increasing upper level divergence late Thursday night
ahead of an approaching shortwave. The threat for showers and a
few storms may continue on Friday across southeast MO and
southwest IL with residual moisture near the dying front. Should
be dry Friday night and Saturday with unseasonably warm
temperatures on Saturday due to increasing s/swly surface/low
level winds and relatively strong low-mid level warm air
advection. Precipitation will return to northeast MO and west
central IL Saturday night as a stong cold front approaches the
area. Showers and storms will overspread most of the area,
especially north and west of STL on Sunday as an upper level
trough approaches. Rain will continue Sunday night as a surface
wave moves northeastward along the front and drags the cold front
through the entire forecast area by 12z Monday. Much colder
conditions are expected on Monday with the models dropping the
-4 degree C 850 mb isotherm south southeastward into central MO
behind the 850 mb trough. The ECMWF and GFS model solutions
diverge after this with the GFS trying to warm it up heading into
Wednesday, while the ECMWF model brings a reinforcing cold front
southeastward through our area Tuesday with a fairly strong upper
level trough over the Great Lakes region. For now will forecast
below normal temperatures beginning Monday, after an unseasonably
warm weekend, and continue with below normal temperatures into
Wednesday.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1248 PM CDT Wed Apr 9 2014

VFR conditions expected with a south wind tonight. Low level wind
shear anticipated overnight/Thursday morning as low level jet
increasing overhead. Cold front expected to pass through KUIN and
KCOU between 15Z and 17Z and between 18Z and 21Z for the St. Louis
Metro TAF sites. Wind will shift to the north behind the cold
front. Probability of precipitation is too low to include in
forecast.

Specifics for KSTL:

VFR conditions expected. Low level wind shear anticipated
overnight/Thursday morning. Cold front will move across the
terminal late in the forecast, around 20Z, shifting the wind to
the north.

CVKING

&&

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

$$

WFO LSX






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