Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 241149
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
649 AM CDT Mon Jul 24 2017

...12z AVIATION UPDATE...

.SYNOPSIS...
Issued at 247 AM CDT Mon Jul 24 2017

Weak backdoor front/wind shift pushing through N IL early this
morning. Satellite shows expansive area of stratus over
S WI and N IL as flow turns e/ne beneath low level inversion.
Meanwhile, large expanse of high pressure extends from James
Bay region swwd through the Upper Midwest into portions of the
Central Plains. Overall, generally near to below normal temps
and dry conditions on tap next 24 hours due to combination of
clouds and cooler temps aloft today followed by high pressure
tonight.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 247 AM CDT Mon Jul 24 2017

Today, expect periods of cloudiness to advect or develop across
much of the cwa through midday by way of moisture advection
from northeasterly low level flow and heating of cooler air aloft.
Expecting most if not all areas becoming mostly sunny by mid to
late afternoon as cloud bases lift and scatter out with heating
and building subsidence/slight drying attendant to high pressure
building southward through WI. The bouts of cloudiness for much
of today will lead to a bit cooler highs generally below normal
in the mid 70s to around 80 degrees over all but roughly the
southwest third where more solar insolation should push highs there
into the range of 81 to 86 degrees. With limited mixing aided by
light winds of less than 10 kts in 925-850 mb layer don`t anticipate
much draw down of dew points today (mainly L/M 60s), thus most areas
should be in normal July humidity especially over lingering wet soils
of northeast and east central IA into N IL.

Tonight, mainly clear skies and cooler, more comfortable conditions
are on tap for many with high pressure continuing to build southward
through the Great Lakes region providing easterly surface flow.
Lows expected to range from the mid/upper 50s (coolest readings N IL)
to the mid 60s far SW cwa.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 247 AM CDT Mon Jul 24 2017

Quiet and dry conditions will be seen across the area Tuesday and
Tuesday night as high pressure moves into the Great Lakes.
Temperatures will be close to normal. Attention then turns to the
mid-week storm system.

Based on trends from the various models, Wednesday morning looks to
be dry across the area. The models are suggesting a slowing of the
next front for Wednesday afternoon. If this is correct, then rain
may not arrive into the area until late Wednesday afternoon or
possibly Wednesday night. Right now the model consensus has chance
pops for all but the far east areas Wednesday afternoon.

With the cold front approaching during peak heating Wednesday, the
potential for severe storms must be considered. Nocturnal convection
across MN/WI Tuesday night will play into the overall severe risk
Wednesday/Wednesday night. However, there does appear to be a risk
of severe storms late Wednesday afternoon and night.

Wednesday night is looking to be the main event for areal coverage
of storms and severe weather associated with the passage of the cold
front. The model consensus has chance to likely pops for the entire
area.

The bigger question Wednesday night is the amount and location of
rain that will occur. Soils north of a Vinton, IA to Kewanee, IL
line are quite moist. The capability is there to absorb some rain
but not much.

The models disagree on the location of the heavier rain amounts. The
GFS suggests the northern half of the area while the CMC/ECMWF
suggest the south half of the area. The models also differ on
rainfall amounts with the GFS being the wettest, ECMWF driest, and
the CMC in between. Based on the overall large scale picture, there
would is some support for the relatively heavier rain amounts to be
across the southern half of the area.

The models indicate the frontal movement should be fairly steady so
the risk of storms moving over the same area producing heavy
rainfall appears very low.

Thursday on...

Rain and storms that develop Wednesday night will continue into
Thursday morning and dissipate by late morning or afternoon. The
model consensus has chance to likely pops across the southern two
thirds of the area.

Thursday night through Sunday quiet and dry conditions will be seen
across the area as another high pressure slowly moves through the
Midwest. Temperatures should be at or slightly below normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 648 AM CDT Mon Jul 24 2017

Weak surface trough will pass through the terminals this morning
followed by northerly winds shifting to northeast at 5-10 kts.
Accompanying this northeast wind will be lower clouds with periods
of MVFR cigs 1500-3000 ft agl. Bases should gradually lift to VFR
and coverage become more scattered as the afternoon progresses.
Mainly clear skies and light easterly winds are expected tonight.

&&

.HYDROLOGY...
Issued at 437 AM CDT Mon Jul 24 2017

Dry conditions will be seen across the area through Tuesday night
which will should allow the flood crest on the Rock river to finish
moving through the basin. More rain is expected Wednesday into
Thursday. However, there are questions regarding where and how
much rain will fall.

Wapsipinicon River...

At Independence, river levels continue to fall. The current forecast
has the river rising back above major flood stage and crest at
15.5 feet tonight. This forecast is based on the flows coming out
of Tripoli and the east fork of the Wapsipinicon river. If the
flows of the two branches occur at different times, then the river
at Independence may keep falling.

Downstream major flooding is still forecast at Anamosa Shaw Road and
near DeWitt.

Rock River...

Major flooding is occurring along the Rock river. Como has crested
and Joslin/Moline will crest in the next 36 hours. Data suggests the
current crest forecasts at Joslin and Moline should be close.

Mississippi River...

Flood warnings are 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.

Pecatonica River...

Freeport will hold between 15 and 16 feet through Thursday before
starting to fall.

Yellow Creek...

The flood crest is somewhere between Pearl City and Freeport with
significant flooding occurring along the length of the basin. Water
levels are receding in Pearl city.

&&

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

$$

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



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