Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280834

Area Forecast Discussion
National Weather Service Saint Louis MO
334 AM CDT THU APR 28 2016

.SHORT TERM...  (Through Late This Afternoon)
Issued at 333 AM CDT Thu Apr 28 2016

A stacked storm system was centered over western IA early this
morning.  At the surface, an occluded front extends southeast from
this storm center to a triple point in southwest IL, where a cold
front extends further south from there and a warm front extends east
from the triple point.  Temperatures were in the 60s ahead of the
cold front in southern IL, and have fallen into the 50s elsewhere.
Skies had also cleared over most areas, but some wraparound clouds
have recently moved back into sections of northwest MO.  A small
area of dense fog has developed just north of the front and triple
point, but the favorability to sustain this fog should decrease
heading towards dawn as the fronts move thru and the triple point
pulls away.

The surface triple point is expected to move out of the forecast
area into east-central IL by 12z this morning, taking the other
fronts out of the forecast area as well, leaving westerly flow in
its wake, and a surface TROF just to our north in southern IA and
central IL.  During this time, the storm center will track from
western IA into northeast IA with an upper level disturbance
will rotate thru southern IA by this afternoon.

The combination of some weak upper support and a surface boundary
and residual moisture should be enough for isolated to scattered
showers to develop with the heating of the day, but this all should
be just north of the forecast area.  Otherwise, clear skies are
expected for much of the area with additonal clouds in northeast MO
and west-central IL.  Westerly flow will support deep mixing,
resulting in max temps from the 60s in northern MO and central IL to
the 70s elsewhere.


.LONG TERM...  (Tonight through Wednesday)
Issued at 333 AM CDT Thu Apr 28 2016

A weak sfc ridge builds into the area tonight, keeping the area dry
and cooler thru Fri morning.

The leading s/w may spread precip into the region as early as Fri
afternoon. Mdl differences continue with this system, but have
trended twd the slightly faster/more nrly ECMWF/NAM/local WRF solns.
This system will keep precip in the area thru much of the weekend,
tho Fri night thru Sat night still appears to be the bulk of the
precip. Given the mdl differences, uncertainty remains, but can not
rule out a severe threat on Sat. This threat will largely depend
upon where the sfc fnt sets up and if precip from overnight Fri can
move out of the area early enough for recovery.

Next week and beyond, sfc ridge builds into the area, keeping the
remainder of the forecast period largely dry. A secondary cdfnt
pushes thru the area sometime Wed. Mdls suggest this fnt will have
enuf moisture to generate precip, tho timing differences remain.
With Gulf cut off, do not believe enuf moisture will exist for
precip, but have kept low PoPs in for now.



.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1213 AM CDT Thu Apr 28 2016

Thunderstorms are clearing the area to the east at this time. Any
storms will be capable of producing gusty wind, hail and IFR
conditions in heavy rain. To the west of the storms, expect VFR
flight conditions to prevail across most of the area for the rest
of the night. There is some fog developing over northeast
Missouri...which could spread into west central Illinois...however
am not very confident in how low to go. Regardless, fog threat
should be done by 12-13Z as drier air moves into the area. Some
MVFR ceilings likely across northeast MO and west central IL
Thursday as well...though some guidance has the clouds above 3,000

Specifics for KSTL:

VFR flight conditions are expected at Lambert through Thursday.



Saint Louis     74  50  70  56 /   0   5  10  70
Quincy          64  44  66  51 /  10   5  10  60
Columbia        70  47  68  56 /   0   5  40  80
Jefferson City  73  49  70  57 /   0   5  40  80
Salem           74  50  70  56 /   0   5  10  60
Farmington      77  50  72  56 /   0   5  30  70




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