Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 200533
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1133 PM CST Mon Feb 19 2018

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 316 PM CST Mon Feb 19 2018

Quite the contrast across the dvn cwa this afternoon with low
pressure tracking into eastern IA. A strong cold front was pushing
into central IA behind the low. South of Highway 30, temperatures
were in the 60s with dewpoints well into the 50s. PWAT`s were in
record territory for February (1.2 inches) in our southeast. To
the north of Highway 30 readings were only in the 30s where
several inches of snow was still on the ground this morning.
Widespread dense fog was also noted in our northern counties,
north of a warm front situated roughly along I-80. Out in
northwest IA temperatures were only in the teens with single
digits in the Dakotas!

Deep layer shear was strong in our southern cwa along with SBCAPES
of 250 j/kg. A few strong storms are possible with hail, heavy
downpours and strong gusty winds. We will be monitoring this
situation for the remainder of the afternoon. The surface low is
expected to push into northern IL by early this evening.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 316 PM CST Mon Feb 19 2018

Forecast focus on complex forecast with dense fog, freezing rain,
thunderstorms and heavy rainfall all expected. Did I miss anything?

Headlines: A dense fog advisory is in effect for roughly along and
north of Highway 30 through 10 am Tuesday. A winter weather
advisory is in effect from 9 pm this evening until noon Tuesday
for our far nw cwa for up to one tenth of an inch of ice.

Tonight and Tuesday: Low pressure will track into northern IL by
early this evening which will nudge the cold front into portions
of eastern IA. However, operational models bring another low
pressure system, in the fast southwest flow aloft, into eastern IA
Tuesday morning. In the meantime, a 50-60 kt LLJ will continue to
feed deep moisture northward into much of the cwa. The end result
will be widespread rainfall and a few thunderstorms during this
time frame with total amounts for this event of 1 to 2 inches,
roughly southeast of a Memphis, MO to Freeport, IL line. The
farther nw you go the lighter the amounts so by the time you get
to Independence, IA the amounts should be only about a quarter of
an inch. We will need to keep an eye on the flood potential for
area rivers and streams, especially east of the MS River, as much
of the ground remains frozen. Lows tonight will range from around
30 at Independence to the lower 50s at Macomb, IL. Highs on
Tuesday will range from the mid 30s at Independence to the lower
60s at Macomb and Princeton, IL.

As far as the winter weather advisory is concerned this is a
marginal situation for freezing rain, as temperatures will be
hovering slightly below and above freezing. A lot will depend on
road temperatures also. For now, we will keep the advisory going
but have lowered the ice amounts to a tenth of an inch or less.
The colder surface temperatures and higher ice amounts should
remain west and north of the dvn cwa. During the afternoon the
rain will be ending in the nw as a strong cold front pushes across
the cwa, with falling temperatures during the afternoon.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 316 PM CST Mon Feb 19 2018

Forecast focus on active pattern through the weekend.

Tuesday night: Much colder air will be plunging into the cwa in
the wake of the strong cold front. There should be enough moisture
lingering behind the front to create a wintry mix of rain,
freezing rain, sleet and snow for several hours especially during
the evening. A winter weather advisory may be needed for this
situation for later shifts to evaluate. Lows will dip into the
teens and lower 20s for most locations.

Wednesday through Monday: I will take one storm system at a time
but models suggest another system later Thursday and Thursday
night, and another Saturday and Saturday night. However,
confidence is low this far out on the track/timing of the system
and precipitation type, and also temperatures. As of this writing
the ECMWF is the coldest model for the weekend system and suggests
snow rather than rain.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
ISSUED AT 1125 PM CST Mon Feb 19 2018

Widespread showers and isolated storms will continue to impact
KBRL/KMLI overnight, and will eventually spread into KCID/KDBQ.
Convergence area has lifted north and the potential for dense fog
impacting TAF sites is now low. There will likely be a break in
the rain after 12z, before more rain by mid to late morning, then
ending during the afternoon from west to east.

&&

.HYDROLOGY...
Issued at 316 PM CST Mon Feb 19 2018

River flood watches remain in effect for the Rock River. Across Illinois
forecasted rainfall through Tuesday may be 1 to 2 inches on top
of frozen ground. Depending upon how much rain actually occurs
across the Rock and Green river basins, moderate flooding may
occur at Joslin and Moline, with minor flooding at Como. These
forecasts will change depending upon the timing and overall
rainfall amounts. Please see the latest river forecasts and
watches for the most up to date information. As of this writing
the Rock River is expected to rise above flood stage this
Wednesday, but subject to change, thus the flood watch.

Much smaller streams and creeks may also flood depending upon how much
rain falls through Tuesday.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Dense Fog Advisory until 10 AM CST Tuesday for Benton-Buchanan-
     Cedar-Clinton-Delaware-Dubuque-Iowa-Jackson-Johnson-Jones-
     Linn.

     Winter Weather Advisory until noon CST Tuesday for Benton-
     Buchanan-Delaware.

IL...Dense Fog Advisory until 10 AM CST Tuesday for Carroll-Jo
     Daviess-Stephenson.

MO...NONE.
&&

$$

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Haase
AVIATION...RP Kinney
HYDROLOGY...Haase


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