Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 221743
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1143 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 18z TAFs through 18z Friday Afternoon)
Issued at 1136 AM CST Thu Jan 22 2015

Latest storm system will stay well to the south of the areA/
Biggest problem is what to do with the stratuc that has invaded
most of the area. Meso type models want to move it out fast while
the GFS and NAM keep in around ovenight and the NAM until about
18z Friday. given the light north to northeast surface and
boundary layer wind am inclined to keep the MVFR ceilings in and
lift Friday monining, as the surface winds get a more westerly
component.

Specifics for STL: Looks like MVFR throuh about 18z Friday. Light
north to northeast wind at surface and boundary layer should keep
1500 to 2500 ft clouds, which are prevalent across eastern IA and
much of the northern half of IL over the terminal. NAM guidance
looks best right now so will go with gradual clearing Friday
morning as the surface wind becomes more westerly.

JPK

&&

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

$$

WFO LSX






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