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000
FXUS63 KDVN 251724
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1224 PM CDT Tue Jul 25 2017

...HYDROLOGY UPDATE...

.SYNOPSIS...
Issued at 317 AM CDT Tue Jul 25 2017

High pressure from the Great Lakes through the Mid-Mississippi
Valley is providing tranquil conditions across the cwa early
this morning. Light easterly flow is advecting drier air (dew
points in the 50s) into much of east central/northeast IA and
northwest IL making for a very comfortable early AM. Regional
radar shows scattered elevated convection over portions of MN
driven by a shortwave trough and attendant strong mid level warm,
moist advection. Overall, our region is expected to remain
largely governed by departing high pressure and therefore mostly
dry next 24 hours, with the bulk of storms focusing along a
frontal zone from the Upper Midwest to portions of the Northern
and Central Plains.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 317 AM CDT Tue Jul 25 2017

Today, expect some increase in mid/high cloudiness attendant to
upstream elevated convection over MN as it slowly weakens and
dissipates while encountering drier air in low levels.
Before decaying however, can`t totally rule out a couple of stray
showers toward mid morning through midday north of Hwy 30 and
especially along/n of Hwy 20 with elevated warm advection wing
attendant to waning convection shifting across portions of WI.

Highs will be warmer today responding to more sunshine over that
of yesterday, and anticipate a general range from around 80 to
the upper 80s based on parcel trajectories in developing SE flow
and subsequent observed highs on MON.

Tonight, precip chances are not zero but appear too low for any
mention. Main focus for convection appears to be from MN/WI
to the Dakotas and NE with favorable juxtaposition of surface
front, elevated moist transport and entrance region of 125+ kt jet
max streaking eastward along U.S. Canadian border. Anticipate
some mid/high cloudiness at times with winds turning more
southerly ushering in more humid conditions and warmer lows well
in the 60s to lower 70s.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 317 AM CDT Tue Jul 25 2017

The nocturnal storms Tuesday night will play a role into how the
sensible weather evolves on Wednesday. Concerns Wednesday are heat
and the severe risk. Wednesday night concerns are the severe and
heavy rain risks.

Based on the overall large scale picture, the better forcing and
moisture return are north and west of the area Wednesday morning.
This would imply dry conditions for the area. However, where the
Tuesday night thunderstorm complex develops and moves will affect
the sensible weather Wednesday morning. All but the far northwest
looks to remain dry Wednesday morning. The far northwest areas have
slight chance pops.

One concern for Wednesday will be heat. Moisture/warmth will surge
back into the area and may create heat index readings above 100
along and south of a Sigourney, IA to Kewanee, IL line with 95 to
100 across the rest of the area. However, cloud cover from the
Tuesday night thunderstorm complex may hold temperatures down a
little. So as of now we will not go with any heat headlines.

The second concern Wednesday afternoon/night is the severe
potential. Again, where the Tuesday night thunderstorm complex
tracks will play an important role. The overall larger scale picture
does support a severe risk for the entire area. The primary risks
look to be damaging wind and hail. Interestingly, some models show a
weak low moving through the area late Wednesday afternoon and
evening while others do not. This low may or may not be the result
of storms that develop during the afternoon. If the low is legit,
then one cannot rule out some tornadoes immediately around the low
and to its east/south.

Wednesday night the overall severe risk will decrease after sunset
while the heavy rain risk increases. Here the models differ on the
overall details. The overall large scale picture suggests any heavy
rain risk should be roughly over the southern half of the area. The
models have varied from run to run on placement of the overall rain
axis but Dprog/Dt of the models does suggest a slight southward
adjustment.

The cold front should be fairly progressive so the risk of having
storms move over the same area should be low. However, high moisture
levels in the atmosphere means that storms will be very efficient in
producing rain.

Thursday, rain will slowly end from northwest to southeast during
the day.

Quiet and dry conditions will be seen Thursday night as high
pressure beings to build into the Midwest.

Friday on...

Quiet and dry conditions will be seen across the area Friday through
Sunday night as Candian high pressure moves from the Midwest into
the Great Lakes. The model consensus indicates temperatures at or
slightly below normal.

On Monday, the models differ on timing but all indicate another cold
front moving through the area. Moisture is limited and the forcing
is not overly strong. As a result, the model consensus has slight
chance pops for the area with the relatively better chances Monday
night. Temperatures should be at or slightly below normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
ISSUED AT 546 AM CDT Tue Jul 25 2017

Patchy shallow fog mainly in river valleys and other low lying
areas will burn off in the next hour. Otherwise, VFR conditions
expected to prevail through the TAF cycle with high pressure over
the Great Lakes still largely governing the terminals. A stray
shower is possible over portions of northeast IA by mid morning
through midday, as a weakening area of convection passes from MN
into WI. However, confidence and any coverage too low for any
mention. Winds will shift from easterly to southeast at 5-10 kts.

&&

.HYDROLOGY...
Issued at 1222 PM CDT Tue Jul 25 2017

Overview: The remainder of today will be dry across the area
allowing flood crests on the Rock and Wapsipinicon Rivers to move
further down stream. More thunderstorms are expected Wednesday
afternoon and night. However, there are still questions regarding
where the axis of heaviest rain will fall.

Wapsipinicon River...

At Independence, a second crest occurred early this morning close
to 15 feet and the river was beginning to fall late this morning.
Downstream of Independence, moderate flooding is forecast at Anamosa
Shaw Road with major flooding expected near DeWitt this weekend.

Rock River...

Major flooding is occurring along the Rock river from Como to
Moline. Joslin is near crest now with Moline expected to crest
tonight. Both crests at Joslin and Moline look to be in the top 7
historical crests.

Mississippi River...

Flood warnings remain in effect for minor to moderate flooding from
Lock and Dam 15 down to Burlington. Crests of 1 to 2 feet above
flood stage are expected. The flood watch continues for Gregory
Landing and the river is forecast to reach flood stage this Friday.

Pecatonica River...

Freeport will hold nearly steady between 15 and 16 feet through
this weekend before starting to fall. High water on the Pecatonica
and nearby Yellow creek continues to have impacts in Freeport.

Yellow Creek...

At 830 AM CDT, Stephenson County Emergency Management indicated
flooding continues, mainly on the lower end of Yellow Creek.
However, levels have dropped by several feet overnight. Water
levels on the creek are expected to continue falling through the
day. A flood warning remains in effect until later this afternoon.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...08
AVIATION...McClure
HYDROLOGY...Haase