Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 200527
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1127 PM CST Thu Jan 19 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 PM CST Thu Jan 19 2017

18Z surface data has high pressure over the Ohio Valley with a weak
low near KMEM. Dew points were in the 30s from the Great Lakes into
the central Plains. Dew points in the 40s and higher ran from the
Ohio Valley into the southern Plains to the Gulf Coast.

&&

.SHORT TERM...(This Evening through Friday)
ISSUED AT 330 PM CST Thu Jan 19 2017

A band of light to moderate rain will continue moving north through
the area through sunset. The relatively heavier rainfall will be
along and east of the Mississippi.

After sunset, the question becomes how much more rain will develop
as the upper level disturbance rotates north into the Great Lakes.
Given how saturated the atmosphere is, it will not take much forcing
to generate rain.

The unstable air aloft suggesting isolated thunderstorms is more
stable than forecast and the forcing is weak. Thus it now appears
the threat of isolated thunderstorms is near zero.

Rain will end from south to north during the evening and winds will
become light. Fog/drizzle will increase in areal coverage during the
evening and overnight hours.

Given the light winds, wet ground, and high moisture content of the
atmosphere, a dense fog advisory will be issued for most of the area
tonight into Friday morning.

Patchy drizzle and fog are expected to persist into Friday afternoon
due to the saturated atmosphere and very weak lift. Temperatures
tonight/Friday will continue to average above normal.  ..08..

.LONG TERM...(Friday Night through next Thursday)
ISSUED AT 330 PM CST Thu Jan 19 2017

Friday night...With the area on the leeside of MO RVR wave and
convergent southwesterly cyclonic flow pivoting north acrs the local
area, adding support/lift to wring out some precip especially the
first half of the night/midnight. But fcst vertical profiles/
soundings continue to show dry mid layers above H85 MB and thus
mainly drizzle soundings or a very fine light rain in spots. Also
with any lingering easterly to southeasterly component to sfc winds,
see areas of fog continuing well into the night. Temps may not drop
off that much from late Fri afternoon values or hold steady
overnight.

Saturday and Sunday...Latest run medium range models suggest the DVN
CWA to be stuck in the middle of a complex upper air pattern and
mostly in-between weather-making lows pivoting around each other
through the mid conus this weekend. Saturday still in line to be a
very mild day, and with a few breaks in the overcast from time to
time, both the GFS and ECMWF suggest much of the CWA to be well up
in the 50s. Increasing west to northwest flow to advect somewhat
lower thicknesses acrs the region into Sunday, knocking highs back
into the 40s. Will have to keep nuisance low POPS at times in the
far north and east late Sunday into early Monday for consistency/
match up purposes.

Monday through next Thursday...After a bout of early week ridging
with continued above normal temps, eyes will focus on the next main
wave rolling out acrs the Midwest Tue into Wed. Many details on how
far north or south this low propagates still to be worked out until
then, as well as resultant thermal profiles for precip types and
amounts.   ..12..

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1123 PM CST Thu Jan 19 2017

Generally LIFR/MVFR conditions to prevail the next 24 hours due to
moist east to southeast flow and passing upper disturbances producing
fog and patchy drizzle. Episodes of extended VLIFR conditions likely
into mid morning hours at all terminals at or below airport flight
minimums. Near minimums or lower in fog possible again after 21/03Z.

&&

.HYDROLOGY...
Issued at 330 PM CST Thu Jan 19 2017

Rock River: Flood warnings for moderate flooding continue at Joslin
and Moline. At Moline, the river may be near crest now just under
the Major flood stage. There is still some uncertainty in routed
water flow toward this site from the Green River, making for ongoing
concerns that this location may still rise above the Major flood
stage. Also, more rainfall today and tonight, along with ice
movement in the river may cause rapid fluctuations in the stage at
this location.

Mississippi River: The latest river stage trends indicate that river
levels continue to rise slowly at both sites(Gladstone and
Burlington) that are in moderate and major flood respectively.
Increased flow from runoff from recent rainfall as well as new
rainfall tonight, and the ongoing ice jam downstream of Burlington,
will likely lead to at least minor additional rises on the
Mississippi in these areas through Friday night. The watch for the
eventual erosion of the ice jam continues, and once the ice jam
gives way, expect the levels in the river around the affected sites
in flood to drop noticeably.

Other sites: Recent and forecast rainfall/run-off, combined with ice
action is also producing rises to or near the flood stage at some
sites on the Iowa River in Iowa. On the lower Green River in IL, an
areal flood warning continues for now while area officials monitor
flooding impacts along this stretch of river and associated high
water enhancement/flooding on portions of the Hennepin Canal...but
some recent thoughts are that it may be allowed to expire this
afternoon.

With the ongoing mild weather and more rainfall forecast, area
rivers in general will still have to be watched into the start of
the weekend for more ice action and jams possibly producing
additional flooding.  ..12..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Dense Fog Advisory until noon CST Friday for Benton-Buchanan-
     Cedar-Clinton-Delaware-Dubuque-Jackson-Johnson-Jones-Linn-
     Louisa-Muscatine-Scott.

     Dense Fog Advisory until 10 AM CST Friday for Des Moines-Henry
     IA-Iowa-Jefferson-Keokuk-Lee-Van Buren-Washington.

IL...Dense Fog Advisory until noon CST Friday for Henry IL-Mercer-
     Rock Island.

     Dense Fog Advisory until 10 AM CST Friday for Hancock-Henderson-
     McDonough-Warren.

MO...Dense Fog Advisory until 10 AM CST Friday for Clark-Scotland.

&&

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...12
AVIATION...Nichols
HYDROLOGY...12



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