Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 270813
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
313 AM CDT SAT AUG 27 2016

.SYNOPSIS...
Issued at 312 AM CDT Sat Aug 27 2016

Early this morning, showers and thunderstorms were ongoing in
association with a stationary front and a shortwave transversing
the flow. A bullseye in moisture transport was moving across the
southern CWA. Rainfall totals range from a little more than a
tenth of on inch, to over two inches, especially across western
Illinois. These showers and thunderstorms are expected to move out
of the area through daybreak. Residual clouds, the frontal
boundary, a weak shortwave in the sw flow and a trof to the west
will be the main players in the short term forecast.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 312 AM CDT Sat Aug 27 2016

Main forecast concern for the short term is how long to hold onto
the chances for rain and thunder this AM and whether or not
diurnal heating is strong enough to fire convection near the
residual front just south of the CWA. Current thinking is that the
chances for rain and thunder this afternoon is low. This is
contingent on the cloud cover, and thinking it will limit overall
heating.

Deep trof rolling north of the area may dynamically force the
frontal boundary slightly north into the CWA. Guidance suggests
that the boundary will be near I80 this afternoon. Think this is a
little too far north considering that there should be residual
clouds that need to be burned off before any mixing of the front
north could occur. Later in the day, a weak wave is prog to move
south of the CWA. Depending on the position of the boundary and
any instability from heating, showers and thunderstorms may form.
Confidence is low on this, so kept schc pops across the southern
CWA. Latest CAM guidance supports this forecast as well with
extremely isolated showers this afternoon in vicinity of the
front.

Once the trof moves through the area, the front slides just south
of the CWA overnight tonight. Cloud cover should aid in keeping
temps slightly warmer tonight across the area.

.LONG TERM...(Sunday through Friday)
ISSUED AT 312 AM CDT Sat Aug 27 2016

A developing zonal upper level flow shifting northward into Canada
will favor a less active weather pattern by midweek, followed by a
developing upper ridge and warming trend toward next weekend.

Ahead of this, lingering high atmospheric moisture levels and a
series of weak upper level systems will keep a threat of showers and
thunderstorms over the area Sunday through Tuesday. Close consensus
of forecast models portray temperatures holding near to above
normal, with highs in the lower to mid 80s and lows in the 60s.

Wednesday and Thursday: surface high pressure building into the
Great Lakes and an associated low level easterly flow should provide
slightly cooler temperatures and lower humidity. The GFS remains an
outlier, continuing to paint QPF over especially the southwest
portion of the forecast area. At the same time, the ECMWF and
Canadian models are mainly dry, which looks more reasonable in this
setup and have removed the slight chance pops.

Friday and Saturday: The 00z GFS and ECMWF have come into better
agreement showing a building upper ridge over the central U.S. This,
along with a developing strengthening southerly flow at the surface
and returning deep moisture, should lead to warmer temperatures.
Along with this will be an increasing the potential for
thunderstorms, over at least the northern half of the area by
Saturday.&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
ISSUED AT 1131 PM CDT Fri Aug 26 2016

Generally MVFR/IFR conditions will prevail until 27/15Z at all or
most of the terminals as a large area of showers and thunderstorms
passes. After 27/15Z, as a warm front passes, skies will become
partly cloudy to mostly sunny with VFR conditions. Light easterly
winds will shift to the south and southwest by Saturday mid to
late morning.


&&

.HYDROLOGY...
Issued at 312 AM CDT Sat Aug 27 2016

Many area rivers are forecast to rise over the next week due to
heavy rainfall over the area this past week and runoff from rain
falling over the area tonight. The most the notable impact on
tributary rivers is minor flooding depicted in the most recent
forecasts for the Wapsipinicon River near DeWitt and the Cedar River
near Conesville. Along the Mississippi River, the most recent
forecasts show Gladstone reaching into minor flooding and Burlington
approaching minor flooding. The timing of the onset of this
potential flooding at all sites is still 4 to 5 days out, or around
the mid to late part of next week. Due to continued adjustments of
routed flow, the uncertainty of tonight`s rainfall, and the long
period of time before potential flooding, no watches or warnings
have been issued for river flooding at this time.


&&

.DVN Watches/Warnings/Advisories...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Sheets
AVIATION...Nichols
HYDROLOGY...Sheets


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