Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 252040
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
340 PM CDT THU AUG 25 2016

.SYNOPSIS...
Issued at 307 PM CDT Thu Aug 25 2016

18Z surface data has the inferred frontal boundary from southern
Lake Michigan into northern Missouri. Dew points were in the 70s
along and ahead of the front with 50s and 60s behind the front.

&&

.SHORT TERM...(This Evening through Friday)
ISSUED AT 307 PM CDT Thu Aug 25 2016

Through late afternoon, light rain associated with induced upper
level disturbance will continue to dissipate to sprinkles or
isolated light showers.

This evening, dry conditions look to be in store for the area as the
upper level disturbance moves into Indiana. Attention then turns to
late tonight.

Late tonight, the overall synoptic set up points to another
nocturnal convective complex initiating across Missouri. If this
scenario occurs, showers with some thunderstorms would start moving
into the south third of the area in the pre-dawn hours with areas
generally south of a Galesburg, IL to Centerville, IA line being
favored.

Going on the idea that a convective complex will develop and move
into the south third of the area by sunrise, said convective complex
will move east northeast during the morning and slowly decay. The
area that would be favored for rain is south of a Princeton, IL to
Centerville, IA line.

Internally, the models are also suggesting another nocturnal
convective complex will develop in Kansas and move northeast. If
this complex develops, then it should start moving into the area by
late morning as it slowly dissipates. As such, roughly the south
half of the area runs the risk of seeing showers and possibly a few
thunderstorms Friday afternoon.

.LONG TERM...(Friday Night through Thursday)
ISSUED AT 307 PM CDT Thu Aug 25 2016

Friday Night through Saturday...It is probable that a
convectively induced vorticity max will move through the Upper
Mississippi Valley - most likely to be late Friday night into
Saturday morning. POPs during this period are 60-70%.

The main mid-level trough axis is forecast to slide through North
Dakota, South Dakota, and into Minnesota. For E Iowa/NW Illinois,
convective chances are dependent on convective complexes forming
within the greater instability over SE Nebraska, NE Kansas, and NW
Missouri Friday afternoon and evening. Mean 850-300mb flow will
then guide the storm clusters to the ENE.

Chances for showers and thunderstorms continue for Saturday
afternoon but thinking areal coverage will not be as widespread -
forecast confidence is lower during this period.

Thunderstorm Threats: Similar to the past several events, heavy
rainfall rates and localized flash flooding are the main concerns.
Anomalous PWATs approaching 2" are near the 95th percentile for
the end of August according to the NAEFS.

Saturday Night through Thursday...Continued warm and humid. Temps
in the lower to middle 80s for highs (possibly warmer by Wednesday
and Thursday), dewpoints well into the 60s or occasionally into
the 70s. Have lower end POPs of 20-40% in the forecast. However,
there will be plenty of prolonged dry periods. At this time,
models are forecasting an absence of organized shortwave troughs
across the Midwest; rain chances are likely to be contingent on
diurnal processes and mesoscale boundaries. Uttech

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
ISSUED AT 1235 PM CDT Thu Aug 25 2016

Mainly VFR conditions will be seen through 06z/26 as light rain
associated with an upper level disturbance moves through eastern
Iowa and northern Illinois. KMLI might see a very brief period of
MVFR conditions if a stronger shower impacts the TAF site. After
06z/26 VFR conditions are expected to continue but some patchy
MVFR conditions may develop. There are indications another
nocturnal convective complex will develop that may affect KBRL
with SHRA and possibly a TSRA with MVFR conditions.

&&

.HYDROLOGY...
Issued at 307 PM CDT Thu Aug 25 2016

Recent heavy rains across the Upper Mississippi Valley have led
to rises on area rivers. On the Mississippi River, Gladstone LD18
(GLDI2) and Burlington (BRLI4) are currently forecast to reach
minor flood stage by early next week. Since these river level
forecasts are approximately 5 or more days away, confidence on
reaching minor flood stage is low and a Flood Watch has not been
issued.

If significant changes to the forecast occur, we will express our
confidence in this section of the AFD. Please continue to monitor
for updates into next week. Uttech

&&

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

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...Uttech
AVIATION...08
HYDROLOGY...Uttech



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