Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 221151
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
551 AM CST Thu Jan 22 2015

.SHORT TERM:  (Through Saturday)
Issued at 224 AM CST Thu Jan 22 2015

The low pressure system which brought 3-4"/hr snowfall rates to
Amarillo, TX last night will slowly progress eastward through the
southern CONUS today and tomorrow, having little effect on
conditions across MO/IL other than an increase in high level
clouds. A compact vort max is forecast to drop out of Canada and
move across MO on Saturday, perhaps leading to additional cloud
cover. Temperatures will gradually warm from today through Sunday,
reaching the mid 40s to mid 50s area-wide on Sunday ahead of a
clipper system.

Kanofsky

.LONG TERM:  (Saturday night through Wednesday)
Issued at 224 AM CST Thu Jan 22 2015

Speaking of that clipper system, the 00z model runs have
generally maintained the slight northeasterly track shift seen in
previous runs, which limits precip chances to the northeastern
CWA. One oddity is that although the 21/12z MEXMOS PoPs for Sunday
dropped off precipitously compared to the previous run (39% -> 10%
at KSTL, 46% -> 9% at KUIN), they came right back up on the 22/00z
MEXMOS (24% at KSTL, 28% at KUIN). Not real sure what to make of
that yet, if anything. The northeasterly track shift also means
that temperatures will be warmer across the CWA when any
precipitation occurs, therefore the ptype is likely to be mostly
rain. A few flakes could still mix in on late Saturday night or
early Sunday morning when temperatures are coldest, but snow
aficionados should consider moving south.

Northwest flow aloft persists through Tuesday with small
disturbances moving through the flow at times. Model solutions
show that the upper ridge across the west central CONUS starts to
shift eastward during the middle of the week and de-amplify,
although the 00z runs of the GFS and ECMWF offer different
versions of how this might occur.

Kanofsky

&&

.AVIATION:  (For the 12z TAFs through 12z Friday Morning)
Issued at 537 AM CST Thu Jan 22 2015

A large area of MVFR stratus across northern MO into central IL
was moving slowly southward near 15 mph. MVFR flight conditions
already at KUIN will persist until late evening. Elsewhere, current
projections have this stratus pushing into the St. Louis area
terminals between 1230-1400z then persisting through the afternoon
and slow clearing overnight. The impact of the stratus into mid MO
at KCOU are less certain and at this time the feeling is that the
southern edge may get to KCOU around 15-16z then slowly retreat
back northward by midday or early afternoon.

Specifics for KSTL:

Stratus across northeast MO and central IL is expected to move
into the terminal between 1230 and 1300z, bringing MVFR flight
conditions. These conditions are expected to then persist through
the remainder of the day and this evening, with the stratus
clearing overnight.

Glass

&&

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

$$

WFO LSX






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