Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 180907

Area Forecast Discussion
National Weather Service Saint Louis MO
407 AM CDT Sun Mar 18 2018

.SHORT TERM...  (Through Late Tonight)
Issued at 405 AM CDT Sun Mar 18 2018

Fog will continue to develop within areas of clearing skies early
this morning. Visibility should improve areawide by mid-morning.

Quiet weather is expected for most of the morning and at least the
first half of the afternoon due to the combined influences of upper
ridging and a surface high pressure center over the Great Lakes.
Meanwhile, a PV anomaly noted over SoCal and southern NV per water
vapor imagery and RAP 1.5 PVU analysis will progress eastward and
induce surface cyclogenesis near the CO/KS/OK/NM border. The
resulting low pressure system will slide through OK tonight and is
expected to be near the OK/MO border by 12z Mon. Although the
surface warm and cold fronts associated with this feature will
remain south of the region, moisture convergence along the elevated
warm frontal boundary will produce areas of showers and isolated
thunderstorms from late afternoon through tonight. The rain will
move into the area from southwest to northeast as the warm front
lifts northward, and favorable LER jet dynamics aloft will provide
additional lift after midnight.

Temperatures will be 5-10 degrees warmer today across nearly all of
the CWA. The exception will be in the extreme southernmost areas
where high temperatures will be similar to yesterday. The presence
of clouds tonight, as well as precipitation across at least the
southwestern one-third to one-half of the CWA, will keep overnight
lows around 5-7 degrees warmer than last night.


.LONG TERM...  (Monday through Saturday)
Issued at 405 AM CDT Sun Mar 18 2018

System to continue sliding east across southern Missouri on Monday.
Will see showers and a few thunderstorms persist before tapering off
from west to east early Tuesday morning.

Beyond that, surface ridge to build in by mid week with northwest
flow aloft. Models show weak shortwaves sliding southeast through
region during this period. However, moisture will be limited, so
kept forecast area dry through Thursday morning for now.

Extended guidance still have major timing, placement and strength
differences with next system that will affect region for the last
part of the work week and into next weekend. For now kept things as
is using what NBM gave for pops, with best chances of precipitation
Thursday night through Friday night.

As for temperatures this week, below normal conditions expected
Monday through Wednesday, before moderating for the last half of the
extended period.


.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1152 PM CDT Sat Mar 17 2018

Still believe clouds will largely remain in place with cigs in the
low MVFR cat. While COU is currently in the higher MVFR, lower
cigs may be moving south twd the terminal. UIN is on the edge of
the cloud deck and may actually go VFR. However, believe the swwd
push will slow before clouds pivot and actually move back east.
That said, if clouds to clear out of UIN, fog is expected to
develop, although, do not currently expect visbys would drop below
MVFR cat.

SPECIFICS FOR KSTL/KSUS/KCPS: Expect low MVFR cigs to remain in
place thru Sun morning. Cigs will improve during the afternoon
hours. Conditions may actually improve to VFR during the late
afternoon hours. Expect lower cigs to move back into the area late
in the period with SHRA beginning around 09z.


Saint Louis     55  42  51  34 /   5  40  80  40
Quincy          52  37  50  30 /   5  10  40  20
Columbia        55  41  50  33 /  20  70  90  20
Jefferson City  56  42  51  34 /  20  70  90  20
Salem           54  40  52  33 /   5  40  90  50
Farmington      56  42  53  34 /  20  80  90  30



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