Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280532
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1232 AM CDT Wed Oct 28 2020

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 217 PM CDT Tue Oct 27 2020

The cloudy, unseasonably cool, and wet period will continue.
Another area of mainly light rain was spreading back into portions
of central and southeast MO and southwest IL as southwest flow
shortwaves continue to move through our region with a persistent
stratus cloud deck across most of the forecast area. The models
were pretty consistent that most of this precipitation will
dissipate this evening with mainly just patchy drizzle possible
for tonight into Wednesday along with continued below normal
temperatures tonight. More significant rain will shift northward
into much of the forecast area Wednesday afternoon and evening as
the cut-off upper level low now over southwestern NM moves
eastward into the southern Plains and begins to tap into tropical
moisture from tropical storm Zeta. Low level moisture convergence,
theta-e advection, and warm air advection will increase across
southeast MO and southwest IL by late Wednesday night on the nose
of a southerly low level jet ahead of an 850 mb low over eastern
OK. Anomalously high precipitable water values are also expected
across southeast MO and southwest IL Wednesday night. Highest pops
and QPF are expected across southeast MO and southwest IL.

GKS

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 217 PM CDT Tue Oct 27 2020

The rain will continue on Thursday into Thursday evening in the
deformation zone ahead of and left of the track of the upper
level low as it moves through AR and into the TN Valley region as
it begins to open up and weaken. The GEFS ensemble guidance was
depicting the highest probability of one inch or greater rainfall
amounts across southern portions of MO and IL Wednesday night and
Thursday. Went ahead and issued a Hydrologic Outlook for
Wednesday night and Thursday across southeast MO and southwest IL
where 1 to 3 inches of rain is expected. As confidence increases
in the amounts and the exact area where the highest QPF will
occur a Flood Watch may be needed. A much drier period of weather
will begin late Thursday night as the upper level trough shifts
east of the region. Below normal temperatures will continue for
the rest of the work week, although daytime highs will be warmer
with a return of the sun. Even warmer temperatures can be
expected on Saturday due to southerly winds ahead of an
approaching cold front. It appears that any precipitation will
remain north of the forecast area Saturday night when the front
moves through our area, closer to an upper level trough over the
Great Lakes region. Colder temperatures can be expected on Sunday
and Sunday night after the passage of the cold front as a strong
surface ridge moves through the region.

GKS

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1231 AM CDT Wed Oct 28 2020

IFR to LIFR flight conditions and occasional light drizzle will
continue to affect the St. Louis metro terminals and KCOU into
Wednesday morning. Conditions should improve gradually after sunrise
as drizzle dissipates and ceilings rise to MVFR flight conditions by
Wednesday afternoon. Rain will begin to overspread the area
Wednesday night with ceilings lowering again to near IFR flight
conditions late in the period. Stratus and precipitation should
remain south of KUIN throughout the forecast period; therefore, only
period-wide dry VFR flight conditions can be expected.

SPECIFICS FOR KSTL:
IFR to LIFR flight conditions and occasional light drizzle will
continue to affect KSTL into Wednesday morning. Conditions should
improve gradually after sunrise as drizzle dissipates and ceilings
rise to MVFR flight conditions by Wednesday afternoon. Rain will
begin to overspread the area Wednesday night with ceilings lowering
again to IFR flight conditions late in the period.

Elmore

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     43  50  35  54 /  90  80  30   0
Quincy          38  49  30  51 /  60  50   5   0
Columbia        39  48  30  53 /  80  70  10   0
Jefferson City  41  49  31  55 /  90  70  20   0
Salem           45  51  35  54 /  90  80  30   0
Farmington      43  50  32  54 / 100  90  40   0

&&

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

$$

WFO LSX


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