Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 032342

542 PM CST WED FEB 3 2016

.SHORT TERM:  (Through Late Tonight)
Issued at 227 PM CST Wed Feb 3 2016

Low clouds will begin to clear out this evening as drier air
advects into the area from the west. The westerly winds will also
begin to diminish as the Great Lakes surface low continues to
lift northeastward which will weaken the pressure gradient over
Missouri and Illinois. Temperatures are already below normal
today with the clouds and the cold air advection, and they should
have no trouble falling to near MOS guidance for lows.


.LONG TERM:  (Thursday through Next Wednesday)
Issued at 227 PM CST Wed Feb 3 2016

By Thursday morning, the upper trough which has been in place for
the last few days will be nearly overhead and continuing to
shift eastward. A surface high pressure center then passes south
of the region on Friday beneath shortwave ridging aloft, ensuring
quiet wx conditions through the end of the work week. Models
depict a couple of upstream vorticity maxima which should have
little effect on the CWA other than increased cloudiness on Friday
night into Saturday or perhaps at best a few sprinkles/flurries
over parts of central/northeast MO. A gradual warming trend will
continue through Sat/Sun.

Attention then turns to the synoptic scale pattn change aloft
which is fcst to allow a strong low pressure system to dvlp and
potentially affect our area late this weekend and into early next
week. Compared to 24hrs ago, the 03/12z runs of the GFS and GEM
are farther south with the track of the initial impulse moving
onshore near WA/OR around 06/06z. The 12z ECMWF is not as far
south as the GFS and GEM but shows much quicker movement.
Consequently, the upper vort max makes more initial eastward
progress as depicted by the ECMWF solution compared to the GFS/GEM
solutions. There is a chance of RA/SN with the approach of this
system, especially Sunday night into Monday.

Meanwhile, a highly amplified ridge will be developing over the
west coast, and the downstream response will be troughing over
roughly the eastern half of the CONUS. Models also show several
shortwaves moving out of Canada within northwest flow aloft, some
of which may bring light snow to our area. However, the most
noticeable aspect of the upcoming pattern shift will be a return
to winter temperatures next week due to periodic intrusions of
Arctic air masses.



.AVIATION:  (For the 00z TAFs through 00z Thursday Evening)
Issued at 538 PM CST Wed Feb 3 2016

Deck of MVFR cigs continues to move swd this evening. Main
forecast question will be how much the nrn flank of the deck
dissipates this evening. Have pushed back timing of VFR slightly
as well as clearing. This is perhaps a more pessimistic forecast.
Otherwise, winds will diminish this evening and gradually back
Thurs morning and thru the afternoon. VFR conditions are expected
thru the forecast period once clouds move S of terminals.





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