Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 191722
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1122 AM CST Thu Jan 19 2017

...Late Morning Hydrology Update...

.UPDATE...
Issued at 844 AM CST Thu Jan 19 2017

The dense fog advisory has been extended until noon. Observations
indicate some improvement on the edges of the fog. However, the
low sun angle means the fog will likely persist until mid-day.

Showers are moving north in a narrow band across the southern
third of the area. Radar trends do show a trend of dissipation as
they move north of an Ottumwa to Peoria line.

&&

.SYNOPSIS...
Issued at 308 AM CST Thu Jan 19 2017

Light southerly flow continues this morning which has held dewpoints
in the lower 30s in most locations. The northern half of the area
has seen clear skies or very low stratus earlier in the evening,
resulting in dense fog formation. Dense fog continues as of 2 AM,
roughly northwest of a Ottumwa to Iowa City, to Dubuque line. A cut
off upper low is positioned in northwest KS, this low is now tapping
a moisture feed over the lower Mississippi valley.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 308 AM CST Thu Jan 19 2017

Moisture will steadily feed into the area from the south today and
this evening, with rain spreading over the area from south to north
during the mid morning through early evening hours. The upper
low will provide the best lift for 6 hour period as the moist
plume works over the area. After that time, some light rain or
drizzle will continue to be possible through the night. Models
continue to support convective potential in the east, where I will
maintain isolated thunder potential this afternoon. Otherwise,
this should be a light to moderate rain event, with locations
receiving a tenth to half inch in a broad range. Most locations
will be under a quarter inch.

Complicating this rain forecast will be the fog potentially
lingering today under the stratus deck in the northwest. This is not
an easy call, as there is currently improving conditions along the
southern edge of the fog area, but with moisture feeding north
today, the fog may linger through at least mid morning.  Tonight, as
rain ends, or at least reduces to drizzle, fog may again form as
ceiling heights lower to under 200 feet. This will be discussed
further in the aviation section today.

Hydrologic concerns continue on area rivers. Please see the
hydrology section in the afd.
ERVIN

.LONG TERM...(Friday through Wednesday)
ISSUED AT 308 AM CST Thu Jan 19 2017

Main forecast concern in the long term is the H5 closed low over the
central United States.  This low is slowly lumbering east.  Once
this moves out of the area another stronger and more progressive
system is forecast for later in the period.

Friday, the wave will be north of the area and we may see some
drizzle and fog on Friday afternoon.  Another wave is forecast later
in the day on Friday.  Soundings depict a dry layer and models
struggle to produce much QPF overnight.  The main story with this is
that temperatures will be warm enough for all rain and no frozen
precip.

This weekend still is on track for well above average temperatures.
Average highs will be 10 to 20 degrees above average.  Overnight
lows will also be above freezing.  Cloud cover will keep
temperatures from rising any higher.  In fact, if clouds break on
Saturday, temperatures could reach near 60 in some spots.

Midweek next week, guidance is starting to agree on timing of the
next wave.  There are differences between location and thus
subsequent sensible weather affects.  This system will be the next
chance we have to see some frozen precip.  However, at this time, it
looks to be mainly rain.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
ISSUED AT 531 AM CST Thu Jan 19 2017

Very low clouds and poor visibility will continue to plague
airports through the day today and again tonight. Dense fog over
northeast Iowa will continue through around 15Z today, before
lifting to around 1 mile visibility in fog. The CIGS will remain
low through the day, while rain spreads north our of Illinois and
Missouri. The rain should arrive in terminals around 18Z and last
through 00-02Z this evening. After the rain ends, another round
of dense fog and drizzle should be expected during the overnight
hours into Friday morning.
ERVIN

&&

.HYDROLOGY...
Issued at 1120 AM 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 while area officials monitor
flooding impacts along this stretch of river and high water
enhancement/flooding on portions of the Hennepin Canal in that
area.

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 today for Buchanan-Delaware-
     Dubuque.

IL...NONE.
MO...NONE.
&&

$$

UPDATE...08
SYNOPSIS...Ervin
SHORT TERM...Ervin
LONG TERM...Gibbs
AVIATION...Ervin
HYDROLOGY...12


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