000
FXUS63 KLSX 121728
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1228 PM CDT Wed Mar 12 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 303 AM CDT Wed Mar 12 2014

Deformation zone precipitation (largely snow based on recent surface
obs and intermittent spotter reports) which was ongoing across parts
of the CWA early this morning will taper off today as the main
system continues moving away from the region. No changes are planned
to the existing Winter Weather Advisory which expires at 12z.

Wind speeds will continue decreasing today as the pressure gradient
relaxes. No changes are planned to the existing Wind Advisory which
expires in 3 segments during 12-18z.

Today`s highs in the 30s and 40s will feel rather chilly compared
to yesterday`s highs in the 70s and 80s.

Kanofsky

.LONG TERM:  (Tonight through Tuesday)
Issued at 303 AM CDT Wed Mar 12 2014

NW flow aloft persists tonight followed by a brief period of
flattened shortwave ridging ahead of the next low pressure system
moving through Canada. Models depict a surface warm front extending
NNW-SSE through MN, IA, MO, and into TN by 18z Thu (this front is
associated with a strong low pressure system that will be located
over SK/MB on Thu), therefore expect to see warmer temperatures west
of the Mississippi River on Thu afternoon. Although a lead shortwave
is forecast to eject from a cutoff low over CA/NV/AZ, no
precipitation is expected with this feature as it crosses MO/IL on
Thu night since the H85 front will be east of the area.

Meanwhile, a strong low pressure system moving through southern
Canada towards the Great Lakes will send a cold front through the
Plains states on Thu/Thu night, eventually reaching our area on
Fri. The wind field induced by a new surface wave developing along
the baroclinic zone in TX will likely slow the southward advance
of the cold front on Fri, especially since it will be so far
removed from the parent cyclone. The cold front is forecast to
move through the LSX CWA on Fri night. Some precipitation is
possible across the southern CWA ahead of this front.

Models are still having difficulty with the timing, speed, and
strength of the cutoff low over CA/NV/AZ once it starts to eject
eastward. Instead of phasing it with a shortwave dropping out of
Canada, 00z EC/GFS runs now develop that shortwave into its own
cutoff low and retrograde it southwestward through Mexico towards
Baja California, leaving the remnants of the cutoff low to pass
south of MO/IL sometime between Fri and Sun. Some models also show
yet another vort max that could bring precipitation to MO/IL
sometime between Sat night and Sun night, but confidence remains
low due to model disagreement with these features.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1217 PM CDT Wed Mar 12 2014

MVFR CIGS currently extend from the Ohio Valley to around 30 miles
west of the St. Louis Area within the cyclonic/north northwesterly
low level flow. The general trend should be for improvement at the
St. Louis area TAFS this afternoon as CIG heights rise and coverage
becomes more scattered, as the whole cloud mass shifts to the east
southeast. Gusty northwest winds will persist until late this
afternoon and then diminish quickly this evening. Another batch of
clouds with CIGS in the VFR range will push southeast out of Iowa
and into the region during the late afternoon and early evening
and persist tonight as they slowly shift southeast. Light winds
tonight will become south to southeasterly on Thursday morning
with VFR flight conditions dominating.

Specifics for KSTL:

Broken MVFR CIGS currently extend from the Ohio Valley to around
30 miles west of the terminal within the cyclonic/north northwesterly
low level flow. The general trend should be for improvement at
KSTL this afternoon as CIG heights rise and coverage becomes more
scattered. Gusty northwest winds will persist until late this
afternoon and then diminish quickly this evening. Another batch of
clouds with CIGS in the VFR range will push southeast out of Iowa
and into the terminal this evening. Light winds tonight will
become south to southeasterly on Thursday morning with VFR flight
conditions dominating.

Glass

&&

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

$$

WFO LSX