Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 052036
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
236 PM CST Mon Dec 5 2016

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 217 PM CST Mon Dec 5 2016

Models are pretty close on moving out the closed low over sw Texas
and bringing an open wave across the area. They are also
contining the trend of moving the precipitation futher south and
east. Thus the forecast reflects this trend in the pops. Fog
could be an issue in some places again: Quincy and Columbia. The
wind and quickly advancing clouds may keep that down, but have put
patchy fog in the forecast. Temps pretty close to previous
forecast so have only made minor adjustments.

JPK

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 234 PM CST Mon Dec 5 2016

The synoptic pattern at the start of the long term period will
feature a broad trough across much of the CONUS, which will amplify
and shift eastward through the end of the week.  Despite the main
trough shifting east, active zonal to northwest flow will persist
through the period keeping cool conditions and a relatively active
pattern in store.

The latest guidance continues to trend towards less QPF with a PV
anomaly slated to move through the Midwest Wednesday afternoon into
Wednesday evening.  The reason for this drier trend appears to be a
quicker arrival of the cold, very dry airmass in the low-levels.
Forecast cross-sections continue to show a decent mid-level
frontogenetical circulation, albeit of fairly shallow slope.  But
given the quicker arrival of the very dry airmass, it appears most
snow falling from this circulation will sublimate before reaching
the ground.  Typically in these situations there are a few spots
where the precip rate is able to overcome the dry near-surface
airmass, thus a quick dusting to a couple tenths of snow continues
to look possible in a few spots, but this does not look to bring
widespread accumulations at this time. We will continue to monitor
this system given the late afternoon/evening arrival could lead to
some isolated travel issues even with only a dusting of snow.

The main story of the period continues to center on the cold airmass
which will arrive Wednesday night through the end of the workweek.
Highs Thursday and Friday will be confined in the mid to upper 20s
(with a few locations around 30), while lows will dip into the
teens.  Couple these temperatures with a light breeze, and wind
chill values will approach 0 at times.

Guidance begins to really diverge this weekend into early next week.
The GFS is stronger/quicker with the next PV anomaly crossing the
country, whereas the Euro is a bit slower and weaker.  Looking at
both the GEFS ensemble and the European ensemble members, the spread
during this timeframe continues to be large.  Therefore, will
continue with just a general guidance blend which keeps pops
generally in the 20-40 range.  Will go with a rain/snow mix in this
time as well given quite a range in thermal profiles with the
varying solutions.

KD

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 117 PM CST Mon Dec 5 2016

Real mess today. Except for extreme ne mo and wc il the fog and
ifr stratus has lifted. Ceilings remain a mix of vfr and mvfr
although most terminals are not vfr. The next fast moving system
will quickly push mvfr clouds across the area tonight with some
IFR quite possible. Models consistent in continuing to push the
precipitation further south. VCSH will cover it at a couple
locations.

SPECIFICS FOR KSTL: STL looked like it might stay mvfr so of
course it broke out. Will keep a tempo for mvfr going for a while
given the broken condition just to the se, considering the light
se wind. Next system spreads mvfr clouds back in tonight with
vicinity showers. IFR is possible but will hold off for now.

JPK

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     37  43  27  38 /  20  10   0  10
Quincy          33  38  22  32 /   5   5   0  20
Columbia        34  40  23  34 /   5   5   0  30
Jefferson City  34  42  25  37 /   5   5   0  30
Salem           39  43  27  39 /  40  30   0   5
Farmington      38  44  26  39 /  40  20   0  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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