Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 191131
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
631 AM CDT MON SEP 19 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 315 AM CDT Mon Sep 19 2016

06Z surface data has a cold front running from northern Minnesota,
into southeast South Dakota, and then across northern Nebraska. A
dry line ran from central Nebraska into eastern New Mexico. Dew
points were in the 50s across the Great Lakes and upper Midwest with
a tongue of 60 dew points from the southern Plains into Minnesota.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 315 AM CDT Mon Sep 19 2016

Quiet and dry conditions will be seen through sunrise and during the
morning hours across the area. Attention then turns to the afternoon
and evening.

The question for the afternoon and evening hours is when does
convection initiate.

Based on projected temperatures/dew points, convection should
initiate sometime between 2 and 5 PM along the cold front. This
convection will then grow upscale during the late afternoon over
roughly the northwest half of the area. Given the initial dry air in
the atmosphere, a threat of damaging winds and hail is reasonable.

The models indicate a weak surface low associated with the front
during the afternoon/evening. However, data through 08z does not
show this low having developed across Nebraska. This low is
important in regards to the overall threat for any isolated
tornadoes.

Tonight, the cold front moves through the area. Showers and
thunderstorms will be most numerous from late afternoon through mid-
evening. Afterwards, the areal coverage of storms will decrease as
the atmosphere stabilizes. Any lingering showers and isolated
thunderstorms will dissipate after midnight.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 315 AM CDT Mon Sep 19 2016

Above normal temperatures with chances of showers and storms
Wednesday through Monday.

Long Term Forecast Confidence Assessment...poor to very poor or below
to well below normal. Main issue is unsettled conditions with showers
and thunderstorms Wednesday on. Large variances may produce episodes
of precipitation that may produce heavier precipitation risks and could
affect high/low temperatures by 5+ to maybe 10 degrees. Preference is
a 70/30 mix of Hi-res ECMWF to GFS though run to run variances are
abnormally large.

Tuesday and Tuesday night...Fair and mild with highs 80 to 85 with
moderate dewpoints. Light easterly winds. Tuesday night...a
convective complex is expected to arrive in the northwest by
morning in the decaying stages. Severe risk appears low but gusty
winds and locally moderate to heavy rains up to an inch may be
possible into Wednesday. Best precipitation chances should be
along and west of the Mississippi River.

Wednesday through Monday...Area caught near a stalled boundary with
a major large scale regime change suggested by late this weekend.
Increasingly likely a backdoor cold front will nudge into the area
by the weekend and with precipitation highs and even lows may be
way too high. Current forecast are highs mostly 75 to 85 north to
south and lows mostly in the 60s with some 50s possible by early
next week. Could see locally heavy rains over this period but this
uncertain based on how front stalls. The uncertainly of this
front should be better known in the next 24 to 36 hours. Severe
risk appear low at this time.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 628 AM CDT Mon Sep 19 2016

VFR conditions will be seen through 20z/19 as a cold front
approaches eastern Iowa. After 20z/19 TSRA will develop along the
front and expand in areal coverage. VFR conditions are expected
with large areas of MVFR/IFR in TSRA. After 04z/20 VFR conditions
are expected but may deteriorate to MVFR prior to sunrise Tuesday.

&&

.HYDROLOGY...
Issued at 315 AM CDT Mon Sep 19 2016

The 3 area forecast river points are cresting or should crest in the
next 36-48 hours with no changes of moderate flood stage near DeWitt
and minor flood stages for Marengo and Conesville and possible secondary
crest at Conesville 3 days from now. Rainfall today mostly well below
an inch should not have significant impacts on area rivers. Precipitation
Wednesday into next Monday is too unclear to ascertain a heavy rainfall
risk at this time that would impact rivers.

&&

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

$$

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



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