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317
FXUS63 KDVN 240736
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
236 AM CDT Tue Sep 24 2024

.KEY MESSAGES...

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- At or slightly above normal temperatures the rest of the week
  that become at or slightly below normal over the weekend.

- Rain in the area today will give way to dry conditions for
  mid-week.

- Potentially active weather late week and into early next week
  but there is high uncertainty regarding the rain and any
  impacts.
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&&

.SHORT TERM /THROUGH TONIGHT/...
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Issued at 234 AM CDT Tue Sep 24 2024

Upper low dropping through Iowa from Minnesota will keep rain and
possibly an embedded thunderstorm mainly east of the Mississippi.
The area coverage of the rain will slowly decrease this afternoon.
West of the Mississippi mainly dry conditions are expected but some
diurnal showers and even a rogue thunderstorm (areal coverage 10-
15%) is possible in the afternoon/early evening.

Tonight clearing will occur from west to east with dry conditions
across the area.
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&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
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Issued at 234 AM CDT Tue Sep 24 2024

Wednesday through Thursday
Assessment...medium confidence on dry conditions

The model consensus has dry conditions across the area with
temperatures at or slightly above normal.

The models appear to be keying in on the upper level high building
into the upper Midwest for the dry and potentially warmer than
normal conditions. However, the proximity of a cut off upper low
across southern Illinois and eastern Missouri does raise questions
regarding the possibility of some isolated showers (areal coverage
probably 10 percent at best) occurring Wednesday as a weak upper
level disturbance moves through in the flow aloft and drops into the
upper low.

Thursday night through Monday
Assessment...medium confidence on temperatures eventually dropping
to or below normal over the weekend. Low confidence (high
uncertainty) on timing of any precipitation.

The late week forecast and into early next week is one of high
uncertainty and thus low confidence.

A tropical system making landfall in the Florida panhandle (per NHC
guidance) normally has no impact upon the area. However, the cut off
low near the confluence of the Mississippi and Ohio Rivers creates a
potential problem. There will be a Fujiwara effect between the cut
off low and the remnants of what will be Helene which will tend to
pull the Helene remnants further to the north and west.

Here the global models diverge with their respective solutions.

A majority of the CMCE/GEFS/EPS members keep the deeper moisture
(and potential precipitation) well to the south and east of the
area. However, there are some members of the CMCE/GEFS/EPS that
bring the Helene remnants further to the north and west.
Interestingly if one does a dProg/dt of the deterministic runs, the
GFS has been pulling everything north. The CMC has been moving south
and east while the ECMWF has been stationary or a slow drift to the
east.

The only sensible weather element that does have high confidence is
that cloud cover will be on the increase as higher level moisture
aloft moves into the area. Additionally, if rain were to occur in
the area, areas south of an Ottumwa, IA to Galesburg, IL line would
have the better chances for precipitation.

So when this is all blended to create a model consensus, we arrive
with the following; 20-40% pops Thursday night/Friday that increases
to 30-60% pops Friday night/Saturday. Then 30-50% pops Saturday
night/Sunday that decrease to 20-30% pops Sunday night/Monday.

Now while there is a daily risk of rain from Thursday night through
Monday, there will be many hours of dry weather each day.
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&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1231 AM CDT Tue Sep 24 2024

Scattered SHRA and possibly a TSRA will continue through 16z/24
as an upper level disturbance moves through the area. The
highest probability of MVFR/IFR conditions through 16z/24 is
southeast Iowa and northern Illinois as the upper level
disturbance moves through the area. After 16z/24 any SHRA/TSRA
will become very isolated (15 percent or less) and conditions
across southeast Iowa and northern Illinois will slowly improve
to VFR.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...08