Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 170900

Area Forecast Discussion
National Weather Service Quad Cities IA IL
400 AM CDT Sun Sep 17 2017

Issued at 330 AM CDT Sun Sep 17 2017

Incoming cool front was currently pushing acrs the northwestern
third of the DVN CWA, with associated clusters of showers and
embedded thunderstorms streaming up along it and mainly post-
frontally. Aloft, mid and upper level moisture flow patterns on the
current water vapor loop was indicating a rather strong short wave
trof rolling northeastward acrs the Dakotas and western MN.  After
the frontal passage and precip chances pass this morning, the mid
and upper flow pattern projected to de-amplify/flatten some acrs the
mid CONUS into early this week. The LLVL boundary will get caught up
parallel and try to retreat north Mon into Tue, with precip chances
increasing again acrs the area in the process.


.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Sun Sep 17 2017

Today...Will walk the incoming showers/storms east acrs the rest of
the DVN CWA through 9-10 AM CDT, but signs of better llvl moisture
convergence and support should make for more widespread
showers/storms moving acrs MO to the south, which may rob to the
north as the morning progresses. This may make for waning trends in
both strength and coverage through the next 3-5 hours as the
convection sweeps east acrs the local area. But until then, there
may be better coverage developing along and south of I80 as the
south central IA into southeastern IA showers/storm clusters
propagate eastward. If some of the upstream precip can maintain it`s
current strength for just awhile as it moves in, extent of moisture
saturation and PWAT feed supports localized swaths of a 0.50 inch to
close to an inch. Most other areas that manage to get under a
passing precip cluster to get 0.15 to 0.30 or less through mid
Sunday morning. After 10-11 AM just see some lingering showers
through late morning/midday southeast of a line from Keosauqua in SE
IA, to Burlington IA, and to Princeton IL. Several of the latest
HiRes CAM runs support this idea as well, with maybe a temporary mid
to late morning uptick in these areas just behind the passing front
before LLVL convergent flow fully veers.

Then as the front sags south and east of the area and high pressure
builds in from out of the northern plains, the afternoon should be
mainly dry with clearing skies especially along and north of I80.
Cooler post-frontal highs today mainly in the 70s. the models may be
under doing sfc winds from the north-northwest this afternoon in
incoming high pressure gradient, but for now will not stray too far

Tonight...the first half of the night to be dry, but then the next
upstream vort max lurks acrs the east central plains in cyclonic
curving west-southwesterlies pushing east acrs the MO RVR Valley.
Increasing lift/isentropic motions along and north of a llvl front
draped west-to-east acrs northern MO along with elevated moisture
feed, should help more showers and even a possible elevated
thunderstorm to peculate and increase acrs the southwestern third
of the CWA after Midnight into early Mon morning. Will adjust POPs
accordingly, and go with cool overnight lows down in the 50s. Some
northern areas/Hwy 20 corridor will have the potential to dip into
the upper 40s if high clouds off the next "weather maker" delay in
thickening until late acrs those areas.    ..12..

.LONG TERM...(Monday through next Saturday)
ISSUED AT 330 AM CDT Sun Sep 17 2017

The good news is the pattern will become more active and feature
rain chances, as a longwave upper trough forms in the western
CONUS and a ridge strengthens over the eastern CONUS and
potentially evolves into a Rex block as one or more tropical
systems undercuts the ridge. The bad news... I don`t foresee
any real significant or drought busting rains, and while the
forecast will have nearly daily chances for rain realistically
this will likely boil down to just a couple days or so. The
first of these rain chances will be arriving Monday lingering
into Monday night. In fact, guarded optimism exists on the
likelihood of rain and also being fairly widespread given synoptic
lift enhanced by right entrance region of 100+ kt jet streak
over the Upper Midwest. In addition, a mid level shortwave is
depicted along with decent moisture advection north of a stalled
boundary to our south. Rainfall is likely to be mostly around
0.25 to 0.5 inch... or less. The boundary to our south is shown
to lift back north as warm front on Tuesday. However, increasing
heights aloft will likely limit rain chances with this front.
Midweek may then harbor our next better chance for rain, although
do have concerns this could trend drier given main height falls and
upper jet and attendant synoptic lift passing well to our north/west.
Then by next weekend may come another better chance for rain due to
increasingly meridional flow ahead of deep western CONUS trough
aiding advection of deep moisture into region ahead of next frontal
system. However, if Rex block develops and slows eastward progression
of systems this moisture plume and front, and subsequent better rain
chances could end up further west while we would be more governed
by dry Great Lakes high pressure.

As for temps, Mon-Tue likely to be coolest of the period and offer
challenges due to clouds/rain Mon and then movement/timing of warm
front. By mid to late week a warming trend back above normal is
anticipated with a deepening southerly flow.


.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
ISSUED AT 1151 PM CDT Sat Sep 16 2017

06z TAFS updated for less confidence in coverage of showers and
storms overnight, based on some of the latest high resolution
model runs. Also adjusted timing of rain slightly later, with a
2-3 hour tempo group. Expect MVFR to IFR ceilings and MVFR
visibilities prevailing after rain ends, then improving conditions
by late Sunday morning.




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