Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 252331
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
631 PM CDT Mon Sep 25 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 320 PM CDT Mon Sep 25 2017

At 2 PM CDT...a strong but slow moving front is just west of the
forecast area moving east at 5 to 10 mph. Temperatures are in the
50s and 60s with rain and lots of clouds behind the front with 80s
to around 90F ahead of the front with scattered areas of showers
and storms. Pressure rise/fall couplets support forcing is
weakening or frontolysis as it moves east with weakening areas of
precipitation. Upstream energy supports clouds until late PM
Tuesday and then clearing and near to below normal temperatures.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 320 PM CDT Mon Sep 25 2017

Short term forecast confidence assessment...fair or average with risk
of a bit more precipitation than forecast and clouds that may also
impact area lows and also highs on Tuesday.

Tonight...slight chance to chance showers and possible evening storm
in northwest this evening as front slowly moves east with spotty and
mostly light to very light precipitation. Overnight showers mostly
of isolated to very widely scattered nature though a brief few rumbles
are possible. Front will arrive in western 1/3 of outlook area by daybreak.
Clouds may keep mins a few degrees higher than forecast of mostly middle
60 readings.

Tuesday...mostly cloudy with areas of light showers with POPS 20-40
percent. Highs in the lower 70s northwest and possibly falling temperatures
by late morning as cool air arrives there. Highs should be in the mid
to upper 80s southeast before front arrives.

.LONG TERM...(Tuesday Night through next Monday)
ISSUED AT 320 PM CDT Mon Sep 25 2017

Tuesday night and Wednesday...Post-frontal push period Tue night,
with deepening LLVL NNW flow into Wed. Lingering isentropic lift in
hold-over southwesterlies aloft, and embedded(but becoming more
channeled) vort lobe to induce a few showers or even possibly a
thunderstorm in the east and southeastern CWA through mid evening.
But with latest run model variance and expected eventual switch over
to post-frontal subsidence, will keep just low CHC POPs in these
areas. Overrunning clouds to hold on until clearing trends from the
northwest later at night, and increasing sfc north-northwest winds
to 8-15 MPH will begin cold air advection regime into Wed. Wed
morning lows down in the 50s. With lingering H85 MB inversion with
undercutting cool air push well into Wed, models vary on mixing depth
and resultant high temps and wind speeds. But with history of
similar events, will bank on the models that mix out deeper into
base of the inversion especially with insolation, making for highs
in the upper 60s to lower 70s and northwest sfc winds of 10-20 MPH.
As a sfc ridge lobe adjusts overhead for sfc wind decouple under
lingering clear skies, the set up for lows well down in the 40s looks
on track. Some patchy fog possible too, but will not put those
details in the fcst at this point with limited confidence.

Thursday and Friday...Amplifying pattern with robust short wave
upper trof energy digging down the upper MS RVR Valley and western
GRT LKS by late Thu. Associated sfc front under this process, will
sweep down acrs the area Thu night. Moisture feed and convergence
into this feature look limited at this point for much of any precip
generation in our area and will keep Thu night dry, better chances
off to the northeast and east. Re-enforcing cool ridge behind this
frontal passage and it`s incoming gradient to make for a rather
breezy Friday with highs only in the mid 60s north, to the lower 70s
south. H85 MB cool ridge rule supports lows down in the low to mid
40s for Fri night into Sat morning. Even some upper 30s possible in
favored cool air drainage locations.

Saturday through next Monday...With cool start to the day and
limited mixing, Saturday looks to be held in the 60s acrs much of
the area. Longer range indications then suggest another temporary
blocking pattern to set-up acrs the CONUS, with the latest run
medium range solutions continuing to vary on eastern ridge break
down and timing of incoming western CONUS L/W trof. An ensemble
type approach for now would bring showers in Sunday night into
Monday with moderating temps. Where the passing front then lays out
more west-to-east along and north of another warm ridge trying to
form into later next week, still very problematic at this point.
 ..12..

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 631 PM CDT Mon Sep 25 2017

Widely scattered showers and isolated thunderstorms over eastern
Iowa, occurring well out ahead of a slow moving cold front in
central Iowa, may be at least in the vicinity of the terminals
early this evening. These are expected to dissipate this evening
with additional showers possible as the front moves into eastern
Iowa and northwest Illinois Tuesday morning. There is a potential
for low clouds behind the front possibly lowering to MVFR range,
but confidence of this occurring is not high enough to go lower
than prevailing VFR.

&&

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

$$

SYNOPSIS...Nichols
SHORT TERM...Nichols
LONG TERM...12
AVIATION...Sheets



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