Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 231137
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
637 AM CDT Sun Jul 23 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 303 AM CDT Sun Jul 23 2017

06Z surface data has a stalled frontal boundary running from
northern Ohio into northern Oklahoma. Dew points were in the 70s
from the southern Great Lakes into the central Plains with 50s and
60s from the upper Great Lakes into the northern Plains.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 303 AM CDT Sun Jul 23 2017

Through sunrise, quiet but humid conditions will continue.

The question for Sunday is when does the diurnal convection develop.
The large thunderstorm complex across Missouri and its associated
cloud cover will briefly hold temperatures down for part of the
morning.

The arrival of an upper level disturbance combined with diurnal
heating and the next cool front is expected to initiate isolated to
potentially scattered showers and thunderstorms across the southeast
half of the area starting around mid-day and continuing through the
afternoon.

Heat index readings will be in the 95 to 100 range for part of the
afternoon for areas south of a Sigourney, IA to Kewanee, IL line.
Once the cold front passes those areas around mid-afternoon, heat
index readings should drop back into the mid 90s. At this time there
are no plans for any heat headlines. However, an SPS will be issued
for the area at risk.

Tonight, the showers and thunderstorms will either move out of the
area or dissipate by sunset across the far east and south areas.
Otherwise, expect quiet conditions as less humid air moves into the
area.

.LONG TERM...(Monday through Saturday)
ISSUED AT 303 AM CDT Sun Jul 23 2017

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 late Tuesday night through
thursday as an upper trof traverses southern Canada, forcing a cold
front into the region.  The 00z model runs are suggesting a more
progressive system than earlier runs depicted.  Although the 00z
ECMWF was slowing the front at it moved into northern MO Wednesday
night.  A good fetch of PW`s just over 2 inches is progged to
precede the front, so any storms that occur could produce heavy
rainfall rates.  The progressive nature of the system though, should
limit rainfall amounts in any one area.

An amplifying ridge in the west and eastern U.S. trof will put
the region in northwest flow again for the end of the week and
weekend, resulting in a return of mild temps and lower humidity.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
ISSUED AT 632 AM CDT Sun Jul 23 2017

Patchy ground fog affecting KCID/KDBQ should burn off by 15z/23.
Otherwise expect VFR conditions through 06z/24. SHRA/TSRA are
expected to develop after 18z/23 but the risk of a TSRA affecting
a TAF site is under 10 percent. Density altitudes may approach 3
kft at KMLI/KBRL prior to sunset. After 06z/24 high pressure will
build into the Midwest with VFR conditions. Patchy MVFR
conditions are possible across eastern Iowa and northern Illinois
due to wet ground from recent rainfall.

&&

.HYDROLOGY...
Issued at 426 AM CDT Sun Jul 23 2017

Heavy rain fell across eastern Iowa and northern Illinois Friday
night which has resulted in flooding on some area rivers. The
potential exists for some fluctuations in the crest forecasts over
the next 24 hours as runoff from the rain becomes better known.
Little or no rain is expected across the area for the next 2 to 3
days.

Maquoketa River...

Based on the way the heavy rain fell across this basin, the flood
crests on the individual forks of the river are out of sync with
each other. The river is near crest at Manchester at just over 15
feet...minor flood stage. At Maquoketa, the crest forecast has been
lowered significantly. With the individual flood crests out of sync,
the river may only crest at 23 feet...or below flood stage Monday
evening.

Wapsipinicon River...

Major flooding is expected along the river. There are still unknowns
regarding routed flow and how much flow may get lost to off-channel
storage. Confidence is high in regards to flooding but there is
lower confidence regarding the crests.

Pecatonica River...

Freeport is cresting just short of 16 feet. Routed flow from
upstream will keep the river between 15 and 16 feet until Thursday
afternoon.

Rock River...

Major flooding will be seen along the Rock river. Como looks to
crest shortly after sunrise today and then begin falling. Joslin
looks to crest between 18.5 and 19 feet Monday evening. At Moline, a
crest is expected Monday night that will be 16 to 16.5 feet.

Mississippi River...

A flood watch remains in effect from Camanche south to Gregory
Landing. The exceptions are a flood warning for Lock and Dam 15 and
crests below flood stage at Le Claire and Keokuk.

Most locations on the Mississippi are forecast to reach flood stage
in the next 24 to 48 hours. Several of the current flood watches for
the Mississippi may go to a flood warning later today.

&&

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

$$

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


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