Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 222138

338 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


.LONG TERM:  (Friday through Next Thursday)
Issued at 332 PM CST Thu Jan 22 2015

A positively tilted upper level trough will move southeastward
through the region on Friday.  Precipitation will remain southeast
of our forecast area, closer to the vicinity of the surface low.
Little change in temperatures is expected Friday and Friday night,
but then warmer temperatures can be expected for Saturday and
Saturday night as the surface winds back around to a southwesterly
direction.  An upper level trough/low will drop southeastward
through the northern Plains and into the Great Lakes region Saturday
night and Sunday.  This will bring a chance of rain to northeast MO
and west central IL Saturday night, and to west central and
southwest IL on Sunday mainly along and left of the track of the
associated surface low.  The ECMWF model was initially quicker with
the progression of the uppper level low and associated surface low
Saturay night, and it was also deeper with the low as well compared
to the NAM and GFS model solutions.  The ECMWF model was also colder
with its temperatures Saturday night and Sunday.  For now will trend
toward the weaker and warmer solutions of the NAM and GFS and just
include chance or slight chance pops for rain.   Colder temperatures
can be expected Sunday night through Monday night, particularly
across west central and southwest IL due to a deep upper level
trough over the eastern US and fast northwesterly mid-upper level
flow over our region.  Warmer, above normal temperatures will return
by Wednesday as upper level heights rise with the approach of an
upper level ridge, and as surface winds become southerly on the back
side of the surface ridge as it shifts east of our area.



.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

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.





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