Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 232052
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
352 PM CDT Sun Jul 23 2017

...HYDROLOGY UPDATE...

.SYNOPSIS...
Issued at 322 PM CDT Sun Jul 23 2017

Isolated showers and thunderstorms were developing across
northern Illinois as of 230 PM as a trough pushed across the
Mississippi River. Ahead of this trough, dew points were in the
lower to mid 70s while behind it dew points were in the mid to
upper 60s. temperatures ranged from the lower 80s northwest of a
line from Cedar Rapids to Dubuque with the lower 90s across
northeast Missouri.

&&

.SHORT TERM...(This Evening through Monday)
ISSUED AT 322 PM CDT Sun Jul 23 2017

The main forecast concerns in the near term are scattered showers
and thunderstorm chances then the focus is on temperatures and cloud
cover.

In the near term, isolated showers and thunderstorms are associated
with the convergence along the wind shift boundary as well as colder
temperatures aloft.  Near term models have the shortwave energy
associated with this  exiting the area by 21 utc and expect any
convection to dissipate or move out of the area as the main forcing
exits the area.

Dry and cool air advection will move into the area as high
pressure builds from the Northern Plains into the Upper Midwest
Sunday night.  Skies will clear this evening with the loss of peak
heating.  Expect noticeably cooler overnight lows with temperatures
slightly below normal.  The only process that may hold back
temperatures will be the amount of water and moisture across the
area. The moisture may also lead to the development of patchy fog
across the area north of Interstate 80 but current thinking is that
the dry air moving into the  region will prevent any fog development.

High pressure will remain to the northeast of our area across
Wisconsin with winds turning to the northeast and advecting in
cooler air off of Lake Michigan for the day on Monday. This may trap
some lower clouds across our northeast half during the day on Monday
as model cross sections and soundings show abundant low level moisture
tomorrow.

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 322 PM CDT Sun Jul 23 2017

No significant changes to the extended period.

Dry and comfortable conditions are expected over the area Monday
into Tuesday with northwest flow aloft and a large area of surface
high pressure settling in over the region.

The weather will become active again during the middle of the week
as an upper trough traverses southern Canada, forcing a cold front
into the region. Ahead of the front, a quick bout of higher humidity
(dewpoints in the 70s) with heat indices in the lower 90s north
to lower 100s across the south, is forecast for Wednesday. The 12z
model runs are still suggesting a progressive system, thereby
limiting the chances for storms to a 12-24 hr window. However,
PWATs around 2 inches are forecast to pool ahead of the cold
front, increasing the risk for heavy rainfall rates with any
thunderstorms that occur.

The Storm Prediction Center has a slight risk for severe storms
north of I-80 for Wednesday and Wednesday night. Confidence on the
timing and coverage of strong to severe storms is low at this lead
time.

An amplifying ridge in the West and an Eastern U.S. trough will
put the region in northwest flow again for the end of the week and
weekend. Expect a return to cooler temps in the upper 70s north
to lower/middle 80s south, along with lower humidity. Uttech/DLF

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 1238 PM CDT Sun Jul 23 2017

A cold front will move southeastward across the region this
afternoon. Winds will switch from westerly to southwesterly as the
front moves through with gusty northwest winds of 15 and 25 KTS.
CU are developing across the region this afternoon as the
convective temperatures are reached and are expecting ceilings AOA
4kft. I will continue to leave thunderstorms out of the TAFs for
today as confidence remains low that they will be in the vicinity
of any TAF site. Aviation fog is a concern overnight and have
introduced mvfr visibilities and some scattered low clouds for
now. Drier air working its way into the region may help to keep
the fog at bay.


&&

.HYDROLOGY...
Issued at 351 PM CDT Sun Jul 23 2017

Continuing to watch high river levels as runoff from heavy rains the
past few days makes its way down through the river systems. The
Pecatonica River at Freeport is has an ongoing slow crest just under
major flood stage. Local officials indicate impacts will be
manageable if there is no additional rainfall to provide
additional rises in the river. Spotty showers and storms this
afternoon could bring some rain to these areas, but heavy rain is
not anticipated so don`t believe the river level will be impacted
too much from today`s activity. However, Yellow Creek, which is a
tributary of the the Pecatonica has significant flooding ongoing.
On the Rock River, Como is cresting at levels not seen since 1929.
At Joslin and Moline, the forecast has been adjusted slightly
downward due to real-time measurements taken by the USGS this
afternoon, but still expect crests very near record levels at both
of these locations in the next 48 hours. Moving into Iowa, on the
Wapsipinicon, also forecasting Major flooding from Independence
to the entrance to the Mississippi. Local officials stated the
majority of the feeder creeks and streams were continuing to rise
this morning and after looking at observations from Tripoli, felt
the forecast needed to be increased a bit from last evenings
forecast. The river at IDPI4 is rising rapidly and is expected to
crest tonight. Downstream, it will take time for the river to go
up, where at DeWitt, it will fall below flood-stage, before rising
again due to the routed flows.

For the Mississippi, with lesser flows coming from some of the
tributaries, including the Maquoketa River, forecasts were adjusted
downward this morning. At Camanche, the river is no longer
expected to reach flood stage and the flood watch was cancelled.
Even with the forecasts dropping 0.5 to 1.0 feet from the previous
forecast, the expected crests will still be well above flood
stage for locations from Illinois City through Burlington, so
flood watches were upgraded to warnings. Do anticipate forecasts
could drop a little bit yet as we get a better handle on the
amounts and timing of the water coming out of the tributaries, so
many areas may crest in minor flood stage levels rather than
moderate.

Luckily, with the exception of some rain yet today, the next week
looks dry so levels will likely have a chance to fall before
additional rain falls across the area.

&&

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

$$

SYNOPSIS...Cousins
SHORT TERM...Cousins
LONG TERM...Uttech/DLF
AVIATION...Cousins
HYDROLOGY...Brooks



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