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508
FXUS63 KDVN 211922
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
222 PM CDT Sat Sep 21 2024

.KEY MESSAGES...

- Marginal Risk for severe storms late this afternoon into
  tonight for the far NW CWA.

- Damp and much cooler for Sunday and Monday with highs in the
  mid 60s to lower 70s, which is slightly below normal.

- Dry conditions are expected to prevail Tuesday through
  Thursday with high temperatures in the low to mid 70s.

&&

.SHORT TERM /THROUGH TONIGHT/...
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Issued at 200 PM CDT Sat Sep 21 2024

An area of scattered showers and isolated storms has worked from
west to east through mostly the southern half of the outlook
area this morning into the early afternoon, leading to localized
downpours and gusty winds of 25-35 mph. This activity was likely
enhanced by a gravity wave propagating through the region as
shown on GOES visible satellite imagery and coincided with the
earlier uptick in areal coverage. The rain and widespread cloud
cover, especially south of I-80, has lowered temperatures to the
low/mid 70s across the south and southwest forecast area, while
locations to the north and east are in the upper 80s to near 90
degrees. For the remainder of this afternoon into this evening,
redevelopment of isolated showers and storms are possible but
with low coverage anticipated and much of the area likely to
stay dry. The prospects for severe weather remain low due to
waning instability heading into early tonight and only modest
deep layer shear around 25-30 kts per the 12Z HREF; SPC has
maintained the Marginal Risk (level 1 of 5) across the NW
portion of the forecast area.

A better chance for scattered showers/storms comes in late
tonight as convection initiating this afternoon over central
Iowa, and extending down into Kansas, slowly spreads ENE in
tandem with a surface cold front sagging in from the NW.
Additional rounds of rain with embedded thunder are expected
overnight into Sunday morning (highest chances southeast of
Dubuque to Iowa City ~80%). Rain amounts will vary quite a bit
across the region due to the spotty nature of the rain, but on
average anticipate 0.25 - 0.75 of an inch.
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&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
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Issued at 200 PM CDT Sat Sep 21 2024

Sunday - Monday: An upper wave will move through the area, with
showers and isolated storms likely to linger through Sunday AM
before diminishing during the afternoon. An increasing northeast
wind and cold advection will keep temperatures steady in the
60s to low 70s both Sunday and Monday.

The upper trough will influence our area into Tuesday, with
some shower chances continuing in the southern CWA. As dry air
arrives, the overnight lows will drop to the upper 40s to lower
50s, making for chilly mornings more typical of early fall.
Slow moderation is forecast by late week, along with a slight
chance for rainfall. Late week forecast highs are in the 70s,
and lows in the 50s.
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&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1235 PM CDT Sat Sep 21 2024

Scattered showers and a few thunderstorms near MLI and BRL are
expected to diminish early this afternoon, with VFR prevailing
at the terminals into this evening. Additional development of
isolated showers and storms are possible from this evening
through early tonight, but with low areal coverage anticipated.
A more widespread area of rain and embedded thunder is possible
late tonight into Sunday morning, which will likely be accompanied
by MVFR/IFR ceilings and MVFR visibilities. Confidence remains
low on the exact timing and location of any storms through the
period.

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...Ervin/Uttech
AVIATION...Uttech