Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 222010
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
210 PM CST Thu Jan 22 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 206 PM CST Thu Jan 22 2015

Surface ridge extending from eastern CO east through northern MO
will gradually weaken and shift southeastward tonight.  Mostly
cloudy conditions may continue tonight as high level cloudiness
continues to stream northeastward through the southeastern portion
of our forecast area from the storm system passing to our south.
Stratus clouds may linger through much of the night underneath the
inversion.  There may be some clearing over the northwestern portion
of the forecast area late tonight, but it appears that the more
pessimistic NAM model MOS guidance may be more correct than the GFS
MOS with respect to the low level cloud forecast tonight.  There has
been some clearing in central MO this afternoon, but this may fill
back in as more stratus advects southeastward into this area.  These
low level clouds will lead to slightly warmer minimum temperatures
tonight and keep them slightly above seasonal normals for late
January.

GKS

.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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