Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDVN 241724 AAA
AFDDVN

Area Forecast Discussion...UPDATED
National Weather Service Quad Cities IA IL
1224 PM CDT Mon Jul 24 2017

...HYDROLOGY UPDATE...

.UPDATE...
Issued at 1159 AM CDT Mon Jul 24 2017

The inversion remains intact, and with that the cloud have
persisted through late morning. That has been well handled by the
original forecast today, and only minor updates have been needed
to increase the opaque cloud cover. Temperatures were already
conservatively forecast, and that is working well.

&&

.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 18Z TAFS through 18Z Tuesday Afternoon)
ISSUED AT 1159 AM CDT Mon Jul 24 2017

MVFR stratus is over eastern Iowa and northwest Illinois late this
morning, and this will thin, and break up to an VFR cumulus deck
this afternoon. The timing of this is expected to be VFR by 19Z or
so. After that, VFR/Clear conditions should persists through
tonight and Tuesday morning with light northeast winds.


&&

.HYDROLOGY...
Issued at 1205 PM CDT Mon Jul 24 2017

River flooding remains a high concern for the Pecatonica, Rock,
Wapsipinicon, and Mississippi Rivers. The Pecatonica River at
Freeport is sitting just under major flood stage where it is
expected to stay for near the next 24 hours. This is due to
continued water moving in from upstream as well as some backwater
effects as flood waters are also entering the river just
downstream of the gage from Yellow Creek. Both of these river
systems are causing impacts in the Freeport area as water
struggles to get through the system. On the Rock, the crest was in
the Erie area late this morning. Measurements from the USGS along
with observed trends have brought forecasts down slightly from
yesterday. Crests will still be high, with both Joslin and Moline
cresting in the top 7 historical crests at 18.3 and 16.0 feet
respectively. Also of note, while the river has crested at Como,
the river here hasn`t seen levels this high since 1929.

On the Wapsi, the crest occurred at Independence lower than the
original forecast, therefore crests have been lowered downstream
at both ANSI4 and DEWI4. Will continue to watch upstream readings,
but may need to lower forecasts a bit more once confidence is in
place that all water upstream has been accounted for.

Then looking at the Mississippi, crest forecasts are just reaching
moderate flood stage at many points. Confidence is not high on
this, especially as tributary flows have been coming in lower than
expected. Thinking we`ll see a healthy minor flood event unfold on
the Mississippi.

There is rain in the forecast for Wednesday. Early model runs are
showing QPF amounts from WPC would entail a slower recession on
the Rock River, with maybe a slight upwards bump. But this would
not occur until after levels have dropped below major flood
stage.

&&

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

$$

UPDATE...Ervin
SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...08
AVIATION...Ervin
HYDROLOGY...Brooks



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.