Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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752
FXUS63 KDVN 211000
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
400 AM CST Sat Jan 21 2017

.SYNOPSIS...
Issued at 342 AM CST Sat Jan 21 2017

Sfc warm front extends southeastward from broad 994mb low over
the Dakotas into central IA and NW IL. Across the DVN forecast
area, dense fog was the primary sensible weather impact overnight.

As of 3 AM, areas south of the sfc warm front have seen a rapid
improvement in visibilities from increasing southerly winds mixing
the near sfc layer. Areas of dense fog, with visibilities less than
1/4 mile at times, were mainly being observed along and north of
a Memphis, MO to Quad Cities to Princeton, IL line.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 342 AM CST Sat Jan 21 2017

This Morning:

Dense Fog Advisories in effect through the mid to late morning for a
good chunk of the CWA, except for parts of the south/southeast
where visibilities have already improved.

If traveling this morning be prepared for dangerous driving
conditions from very low visibilities of less than 1/4 mile. Slow
down and use extra caution.

Hi-res models and sfc obs indicate the worst conditions to likely be
along and north of highway 30 during the mid to late morning due to
weak low-level convergence near the warm front. Spatial
arrangement of the sfc pressure gradient will force the warm
front to take on a SW to NE orientation, so we may see this
manifested in the fog/low stratus on visible satellite imagery
later on this morning.

This Afternoon and Tonight:

As previously mentioned, a warm front will be moving northward
through E Iowa/NW Illinois today. Forecast sfc temps are
impressively mild by mid to late January standards, ranging from mid
40s NW to mid 50s SE. Not into record territory, but still very mild!

Pressure field reorganizes tonight in response to new sfc low
forming in the Mid Mississippi Valley region - southern
MO/northern AK/southern IL. For E Iowa/NW IL, light N/NE winds
develop late as residual moisture lingers, again setting up the
potential for more fog, possibly dense. NMM is already picking up
on this idea. Forecast lows are near 32 F in some areas,
especially NW. Therefore, could have some slick
roadways/sidewalks if the fog coincides with freezing temps.
Uttech

.LONG TERM...(Sunday through Friday)
ISSUED AT 342 AM CST Sat Jan 21 2017

The mild winter weather pattern continues into the early part of
next week. A system lifting through Tue night into Wed is looking
likely to bring precipitation in the form of rain and possibly light
snow, followed by a cooldown back closer to more typical late
January temperatures as a large upper trough over the eastern U.S.
and northwest flow allows colder Canadian air to spill into the
region.

Sunday: A weak low level flow under a weak ridge between a passing
low well to the south and much weaker low to the north points toward
a persistence forecast. Forecast soundings indicate lingering low
level moisture trapped below a sharpening inversion, likely starting
the day with widespread fog and then low clouds that may break up
for a period in the afternoon. Following a model blend, kept highs
from around 40 northwest to the upper 40s east and southeast.

Quiet and mild weather continues Monday as a surface and upper level
ridge passes through the region. A developing more complex upper
pattern sends a wave of low pressure at the surface northeast
through the area Tuesday night into Wednesday, continuing the high
chances for precipitation. Latest models are mostly in agreement
tracking the surface low directly over the forecast area, favoring
mainly liquid precipitation. However, there are considerable
differences in timing, lending to a low confidence, blended
forecast. In the warm advection wing out ahead, rain overspreads
especially the north Tuesday afternoon. Depending on timing, this
would likely mix with, then change to snow before ending Tuesday
night into Wednesday, where highest pops are maintained in the
north.

A large scale cyclonic upper level flow that follows sends a colder
continental-polar airmass into the area for Thu and Fri, suppressing
highs back to the upper 20s to upper 30s and lows in the 20s or
colder. While not currently mentioned in the forecast, there may be
periods of flurries or very light snow with upper level waves both
days.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
ISSUED AT 1128 PM CST Fri Jan 20 2017

Low clouds and dense fog will continue overnight with LIFR/VLIFR conditions
at all the terminals with a light southeast wind. After 20/10Z...a
warm front will bring improving conditions to MVFR and possibly episodes
of lower end VFR from south to north by afternoon on Saturday sct-bkn
clouds and visibilities 2-6 miles. By early evening...areas of MVFR/IFR
fog will develop again with IFR stratus also possible due to still moist
low level moisture.

&&

.HYDROLOGY...
Issued at 342 AM CST Sat Jan 21 2017

Rock River: Observations and latest gage readings indicate there is
an ice jam near and possibly upstream from Joslin, extending
downstream to somewhere between Joslin and Moline. Joslin has been
fluctuating between 16.2 and 16.5, which is major flood stage, over
roughly the past 8 hours. At the same time, Moline, after taking a
sharp drop Friday morning to minor category flooding, has since been
slowly falling, indicative of an upstream obstruction. Will need to
continue to monitor the situation closely as any movement of this
jam could lead to rapid fluctuations of water levels as much as
several feet over the weekend. Thus, river stage forecasts for these
sites are low confidence.

Mississippi River: Gladstone continues to slowly fall after cresting
Thursday. The stage is presently on a trend to drop below 12 feet to
minor category flooding today, but this should be short lived as
routed flow from upstream should send the stage back into moderate
category flooding, where it is expected to stay through the next
week. At Burlington, major flooding continues due to the elevated
flow levels and the impact of the downstream ice jam. The stage has
leveled off over the past day with a slight downward trend. The
forecast showing a slow fall is low confidence and greatly
dependent on when the downstream jam breaks up.

Other sites: Recent and forecast rainfall/run-off, combined with
ice action is also producing significant rises on portions of the
Skunk, Wapsipinicon and Pecatonica Rivers, and flooding on portions
of the Iowa River and English River. With the ongoing mild weather,
area rivers in general will still have to be watched this weekend
for more ice action and jams possibly producing additional
flooding.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Dense Fog Advisory until noon CST today for Benton-Buchanan-
     Cedar-Clinton-Delaware-Dubuque-Iowa-Jackson-Johnson-Jones-
     Keokuk-Linn-Washington.

     Dense Fog Advisory until 4 AM CST early this morning for Des
     Moines-Lee.

     Dense Fog Advisory until 10 AM CST this morning for Henry IA-
     Jefferson-Louisa-Muscatine-Scott-Van Buren.

IL...Dense Fog Advisory until noon CST today for Jo Daviess-
     Stephenson.

     Dense Fog Advisory until 4 AM CST early this morning for Hancock-
     Henderson-McDonough-Putnam-Warren.

     Dense Fog Advisory until 10 AM CST this morning for Bureau-
     Carroll-Henry IL-Mercer-Rock Island-Whiteside.

MO...Dense Fog Advisory until 4 AM CST early this morning for Clark.

     Dense Fog Advisory until 10 AM CST this morning for Scotland.

&&

$$

SYNOPSIS...Uttech
SHORT TERM...Uttech
LONG TERM...Sheets
AVIATION...Nichols
HYDROLOGY...Sheets



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