Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 281745
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1145 AM CST Wed Jan 28 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 339 AM CST Wed Jan 28 2015

Satellite data at 08z showed the area of low clouds that had been
across west-central IL had moved off to the north, propelled by low
level flow from the SE, leaving behind clear skies across the entire
forecast area.  Temps were in the 20s for most areas save central MO
where readings were in the low 30s.  A surface warm front extended
from southern NE to northeastern OK.  NW flow prevailed aloft with
an upper level RIDGE over the Plains.

The surface warm front is expected to make steady progress today
into central MO by late afternoon.  While moisture levels in the
atmospheric column are expected to rise to above average levels, the
lack of any real deep lift other than from the front will preclude
any pcpn development thru early this evening.  In fact, clouds are
expected to be rather thin for much of the day until late, allowing
plenty of sunshine.

The high levels of sunshine and what should be a stout southerly
surface flow will allow temps to surge today, especially in central
MO where the surface warm front is expected to reach.  MOS temps
have been consistently on the cool side for similar scenarios this
year.  Forecasted values that were around the warmer MAV MOS for IL,
yielding 45-50F for maxes, and went up to a few degrees above the
MAV MOS for MO, yielding low 50s near the MS river to the low 60s in
central MO.

TES

.LONG TERM:  (Tonight through Tuesday)
Issued at 339 AM CST Wed Jan 28 2015

(Tonight through Friday)

With little precip expected thru the period, focus remains on temps.

Mdls are in very good agreement thru the period with respect to mass
fields and thermal profiles. Still, spread among MOS temps increases
thru the period, tho is less than usual. Have trended twd the warmer
guidance for tonight as clouds shud help keep temps warmer. Trended
twd a compromise thru the remainder of the period as cloud cover and
CAA will oppose one another, increasing uncertainty.

Continued low PoPs for nern/ern portions of the CWA for tonight and
Thurs morning as the clipper pushes thru the area.

(Saturday through Tuesday)

Focus quickly turns to the system approaching the region this
weekend. Mdls are in remarkably good agreement thru the end of the
storm on Mon. Overall, mdls are rather consistent compared to 24 hrs
ago. However, the ECMWF is slightly less amplified and slightly
warmer while the GFS suggests a deeper trof and overall cooler. The
GEM is further nwd with the 850 mb track compared to the other
solns.

Increased PoPs for late Sat thru Sun as mdls continue to suggest
precip thru this time and precip is expected. However, a fair amount
of uncertainty remains regarding p-type thru this storm. Still, it
shud remain largely a RA vs. SN system. With the uncertainty in the
thermal profile, only minor changes were made to p-types for this
system. This storm will remain one to monitor.

Beyond this storm, much colder air filters into the region as the
arctic sfc ridge builds into the area. Have trended slightly cooler.
Any SN pack from the preceding system may drive temps even cooler
than forecast. Will continue with an overall compromise for now.

Tilly

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1137 AM CST Wed Jan 28 2015

VFR flight conditions are expected through this evening with winds
being the main issue. A tight pressure gradient ahead of an
approaching surface low and cold front will result in gusty
southeast winds this afternoon, which should diminish around or
just after sunset. Decoupling of the lower atmosphere after sunset
and the development of a stout south-southwesterly LLJ will
result in LLWS conditions for much of the evening and into the
overnight hours until the cold fropa. The cold front will move
through the TAF sites from northwest to southeast in the 08-12z
time frame accompanied by gusty northwest winds and MVFR flight
conditions.


Specifics for KSTL:

VFR flight conditions will persist this afternoon and evening with
gusty southeast winds into the early evening. The surface wind
will diminish during the evening and this will result in the onset
of LLWS as a stout south-southwest LLJ evolves. A strong cold
front will then move through the terminal in the 11-12z time frame
accompanied by gusty northwest winds and MVFR flight conditions.

Glass

&&

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

$$

WFO LSX






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