Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 311136
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
636 AM CDT WED AUG 31 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 307 AM CDT Wed Aug 31 2016

A slow moving cold front continues to slowly migrate southeast
across the forecast area early this morning. At 2 am, the boundary
was evident mostly by a drop in dewpoints from the low 70s to its
south the 60s northward, roughly from Sterling through the Quad
Cities to Iowa City. Behind the front, high pressure was building
southeast from the Canadian prairies into MN. Extensive mid and
high level cloud cover over the forecast area has so far prevented
any discernible fog formation.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 307 AM CDT Wed Aug 31 2016

Main challenge is centered on temperatures as the ridge of
Canadian high pressure builds into the region under an
increasingly more subsident northwesterly flow aloft. The day
will begin with cloud cover associated with a storm complex over
eastern KS/western MO and an impulse in the mid level flow, over
at least the southern half of the area. This should move out by
midday as upper level subsidence and much drier air aloft builds
into the region. There is also the potential for a push of lake
effect strato cu, to possibly reach into northwest IL around mid
to late morning, but this would be short lived if it can make it
this far southwest. Otherwise, skies should be mostly sunny from
late morning through afternoon. Moist surface conditions may hold
dewpoints in the lower 60s, despite continued advection of much
lower values on light north winds. Looking at yesterday`s highs
upstream in MN and SD and a general model blend, kept highs close
to the previous forecast in the upper 70s and lower 70s.

Strong upper level subsidence and surface ridging over the area will
provide mostly clear skies tonight with light north to northeast
winds. This should lead to a much cooler night with lows in the 50s
over most of the area. The drier air in place by this time, along
with at least light boundary layer winds, should prevent anything
beyond only patchy shallow fog over the area.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 307 AM CDT Wed Aug 31 2016

Main forecast concern in the long term are the chances for
thunderstorms towards the end of forecast period.  Between now and
then, temperatures will average slightly below normal with quiet
weather.  The forecast is still on track for lower humidity and
temperatures through Saturday.

Sunday on, guidance has been consistent on broad sw flow with
ripples in that flow leading to showers and thunderstorms.  Expect
changes to the pop forecast during this period as the transient
nature of these waves make them difficult to prognosticate.  Latest
blend has pushed back pops until Sunday night across the area.  This
SW flow will lead to the return of warmer and more moist air.  Main
difference between this past week and next week, is that there is
greater deep layer shear.  This should lead to more organized
convection with a greater chance for strong storms.  This broad SW
flow stays in place until another end of the week cold front
attempts to clear the area out.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
ISSUED AT 635 AM CDT Wed Aug 31 2016

High pressure will continue to build into the area providing VFR
conditions and light north winds today and tonight. A deck of lake
effect low clouds advancing southwest across southern WI and
northern IL this morning may produce a brief period of MVFR cigs
at MLI around mid morning. Confidence in this occurring remains
too low to mention in the forecast at this time.

&&

.HYDROLOGY...
Issued at 307 AM CDT Wed Aug 31 2016

No changes to previous forecasts with the exception of the Green
River at Geneseo. The river has crested, just below moderate
flood stage and dropping rapidly. This rapid rise and fall was due
to locally heavy rainfall over the past few days. This warning
will likely be able to be cancelled later today.

Otherwise, no changes to the warnings that are out and the
confidence in potential warnings on the Wapsi river at Dewitt.

&&

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

$$

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


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