Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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306
FXUS63 KDVN 240541
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1141 PM CST Mon Jan 23 2017

...06z AVIATION UPDATE...

.SYNOPSIS...
Issued at 258 PM CST Mon Jan 23 2017

The sky remained overcast across the area through the early
afternoon hours. An area of light sprinkles and flurries
persisted, from the Cedar Rapids and Iowa City areas, to near
Muscatine. A northwest wind averages 7 to 12 mph. Early afternoon
temperatures ranged from the mid 30s to low 40s.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 258 PM CST Mon Jan 23 2017

The main forecast challenge in the short term period is
precipitation type and timing on Tuesday.

In the near term, a small axis of light rain/sprinkles in eastern
Iowa is continuing to diminish this afternoon. For tonight, more
patchy fog is possible, especially across the northeast half of
the forecast area, but little or no impact is expected for
motorists.

During the day Tuesday, forcing will increase in the diffluent
flow ahead of the upper trough that is forecast to move through
the region late Tuesday and Wednesday. There may be a light
rain/snow mix in the far west by late Tuesday morning. However,
the bulk of the precipitation, mainly in the form of rain, should
hold off until Tuesday afternoon. Showers are favored over the
northwest half. Have included a slight chance of thunderstorm
pushing into the extreme northwest by late afternoon with forecast
soundings suggesting an uptick in the elevated instability. Highs
will be mainly in the upper 30s northwest to mid 40s far south.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 258 PM CST Mon Jan 23 2017

Main forecast concern in the long term is the system affecting the
area at the beginning of the period, Tuesday night through Thursday
morning.  The northern CWA will be close to the freezing line,
leading to a difficult forecast across this area.  Past this event,
a change in the pattern with NW flow and cooler, more seasonal temps
to round out the long term.

Weak H5 ridging will give way to SW flow around 00z on Wednesday.
CVA into the area corresponds well with fgen precip along the warm
front.  The best chance for this precip will be just to the north of
the CWA.   Lapse rates and MUCAPE suggest that convection with
lightning may be possible.  As a result, have added isoT to the
grids. Differences in the placement of the H5 vort and subsequent
sfc low means there are differences in the thermal profile for the
CWA.  The ECMWF is the furthest south of the solutions and suggests
a mix of ra/sn/pl across the northern CWA. Whereas the rest of the
models suggest more rain for the northern CWA.  With the ECMWF
solution being the most run to run consistent have adjusted thermal
profile towards this solution.  As a result, 1 to 2 inches of snow,
with sleet mixed in, is possible along the highway 20 corridor.

Main impact from this event will likely be slick untreated roads.
With the potential convection, there is a chance for increased snow
rates or even thunder sleet, across the highway 20 corridor.  As a
result, these increased rates could lead to greater impacts.  At
this time, confidence in this occurring is low as a slight jog north
to the system would bring all rain and a jog south would lead to
increased impacts.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
ISSUED AT 1131 PM CST Mon Jan 23 2017

Quiet weather overnight into Tuesday morning with generally MVFR
cigs and light winds. By late Tuesday morning through Tuesday
afternoon there is suggestions of a warm advection band of precip
lifting across portions of eastern IA, especially north of I-80.
Vertical temp profiles and evaporational cooling support a
rain/snow mix or period of snow with potentially vigorous showers
that may also contain a few isolated rumbles of thunder. This
could lead to quite variable conditions at CID and especially DBQ.
In the wake of this band anticipate cigs improving to VFR. Tuesday
night expect an expansion of precipitation across much of eastern
IA as the main upper forcing overspreads the area ahead of the
approaching low. The precipitation is likely to be showers with
a few storms, with mainly rain except at DBQ where strength of
lift and cooling may keep a rain/snow mix or all snow going.
Conditions will deteriorate to MVFR and IFR in the precipitation.
Winds on Tuesday will turn e/se and increase at or above 10 kts, then
become gusty by late afternoon and evening at 15-25 kts.

&&

.HYDROLOGY...
Issued at 258 PM CST Mon Jan 23 2017

Area rivers, with the exception of the Iowa River, have seen drops
today.  Ice action along the Iowa River has lead to Marengo reaching
above flood stage this morning.  Expect rapid and frequent changes
to the gage height until the ice moves through the system.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...RP Kinney
SHORT TERM...RP Kinney
LONG TERM...Gibbs
AVIATION...McClure
HYDROLOGY...Gibbs



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