Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 201954
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
254 PM CDT SAT AUG 20 2016

.SYNOPSIS...
Issued at 253 PM CDT Sat Aug 20 2016

At 19z, a narrow line of showers accompanied the secondary cold
front roughly from Freeport through Geneseo to Macomb. Behind this
boundary, winds were gusty from the northwest with temperatures
ranging from around 70 to 75. Dewpoints were in the lower to mid
60s, compared to upper 60s to near 70 between this boundary and
the main cold front that extended from low pressure over northern
Lake Michigan south across the lake and along the IL/IN border.
Strato cu was breaking up further west over central and western IA
with very isolated showers on area radars. This was under a dry
slot at the mid levels associated with the upper level wave
centered over central MN.

&&

.SHORT TERM...(This Evening through Sunday)
ISSUED AT 253 PM CDT Sat Aug 20 2016

Main challenge centers on temperatures as high pressure, currently
over the western high plains builds southeast under a NW flow aloft,
spreading a cooler and much drier Canadian airmass into the region.
This evening, isolated showers over IA and a few thunderstorms well
upstream over SW MN should dissipate as an area of steeper mid level
lapse rates will not spread over the local area until well after
sunset. Incoming level subsidence and the open cell cumulus clouds
on visible satellite points toward clear skies over most of the area
by midnight. The cyclonic curved surface pressure gradient and
continued cold air advection at 850 mb should keep winds in a 5 to
10 kt range, preventing any fog issues. Lows from the lower 50s NW
to mid 50s SE look reasonable, based on upstream mins this morning
and similar MOS guidance.

Sunday, high pressure builds over the area to provide mostly sunny
skies, low dewpoints and light west to northwest winds. Temperatures
only topping out in the lower to mid 70s would be the coolest highs
over much of the area since early July.


.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 253 PM CDT Sat Aug 20 2016

Little change in the long term forecast as main concerns remain the
wave on Tuesday into Wednesday and another wave at the end of the
period. The periods between these waves will lead to cooler and
drier conditions for the area.

Monday, the flow turns more zonal allowing for the return of warmer,
more moist air into the region.  Temperatures will be more around
normal for this time of year.  A wave advecting out the 4 corners
region Monday night, will sets its eyes on the area.  The GFS and
ECMWF agree on the timing and positioning of the first wave.  Looks
like the H85 warm front attempts to setup across the area.  The best
H85 moisture convergence appears to be south and west of the area
Tuesday night, painting more of a NW MO and SW IA as a target for
the heaviest precip.  QPF from the models suggests that the heaviest
precip will be just north of where the mass fields suggest it will
be.  With this being close to the area, any small changes in the
forecasts could lead to our area seeing more or less of the rain.

Precip chances will continue as the boundary from this system stalls
out south of the area as a second wave, this time from the NW moves
south into the area.  This wave will lead to showers and
thunderstorms across the southern CWA.  Again, any change in
boundary condition means that we could see more or less rain across
the area.  This second wave eventually, brings in cooler and drier
air into the area, much like this current weekend. This will be
short lived as the flow turns SW again and leads to warmer more
moist air to return to the area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
ISSUED AT 1236 PM CDT Sat Aug 20 2016

Low clouds and scattered showers following a cold front that moved
through the area this morning will lift out of the region this
afternoon. Showers will exit east of the terminals early, but
lingering MVFR cigs will take at least until mid afternoon to
scattered out or have bases lift to VFR levels. Gusty northwest
winds overspreading the area will lose their gusts this evening,
and then drop below 10 kts overnight and trend slightly more
westward. VFR conditions are expected overnight through Sunday as
high pressure builds into the region

&&

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

$$

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



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