Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 201749
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1149 AM CST Tue Feb 20 2018

...18Z AVIATION UPDATE...
...HYDROLOGY UPDATE...

.SYNOPSIS...
Issued at 304 AM CST Tue Feb 20 2018

An area of rain and embedded storms is moving across the outlook
area at 3 AM CST. Some freezing rain is noted just to the west of
the region. Trends suggest some freezing may impact western few to
several counties this morning before ending. Radar trends suggest
SE portions of the area may receive another .5 inch or more of
rain before ending late today.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 304 AM CST Tue Feb 20 2018

Short term forecast confidence assessment...fair to poor with
timing and coverage of precipitation today. Ice chances rising in
far NW counties this morning main concern.

Today...categorical pops ending NW to SE this PM with some ice far
NW counties. High nearly steady to falling east by PM as cold air
moves in. No water issues noted yet though some rivers are approaching
bankfull at 3 AM. Highs lower 30s NW to mid/upper 50s east.

Tonight...precipitation should move east by midnight with clearing
skies toward morning. Minor accumulations of mostly rain with some
mixed precipitation far SE this evening. Mins teens NW to lower
20s SE sections.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 304 AM CST Tue Feb 20 2018

The longwave trof has retrogressed to the west coast which is its
normal climatological position. Southwest flow aloft means that an
active weather pattern will continue for the Midwest through the end
of the month.

Quiet, dry, and much colder conditions will be seen across the area
on Wednesday. Temperatures will average below normal. Attention then
turns to the next two storm systems.

Wednesday night through Thursday night two separate systems will
move through the area. For the first system, the atmosphere will
need to saturate. Saturating the atmosphere will drop temperatures
below freezing so the precipitation will initially start out as snow
late Wednesday night.

As temperatures warm on Thursday the snow will change over to rain.
During the transition period some sleet and freezing rain will be
possible.

Thursday night could be very interesting with the second system.

There are differences among the models regarding the track of the
second system. Track will be very important in regards to
precipitation type. As the atmosphere cools Thursday night, sleet
and freezing rain will mix back in with the rain along with some
snow. Right now the potential is there for an ice event across much
of the area.

Friday on...

Sleet and freezing rain will change back over to all rain on Friday
and end as the atmosphere warms. Temperatures will average above
normal.

Friday night through Saturday night another one or two systems will
move through the Midwest. Again, the track of each system will
determine precipitation type. Right now the model consensus has
chance to likely pops from Friday night through Saturday night.

Sunday/Sunday night the model consensus has dry conditions for the
area as high pressure moves through the Midwest.

On Monday, the next storm system begins moving into the Midwest. The
models are highly varied on the track and timing of this storm
system. As a result of these differences, the model consensus has
slight chance pops for roughly the southern half of the area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
ISSUED AT 1140 AM CST Tue Feb 20 2018

More organized rain with embedded thunder shifting east of the
terminals, but secondary rain bands still to move up through at
least mid afternoon and affect all sites except maybe CID. Varying
MVFR to IFR Cigs and VSBYS through mid to late afternoon with the
lingering precip, with increasing west to northwest sfc winds of
10-15+ KTs. Some concern a strip of freezing rain, possibly mixed
with snow and sleet will occur on the western fringe of the
departing precip shield during the late afternoon and early
evening, especially at BRL and MLI. The freezing rain will look to
hang on longest at BRL possibly to 8-9 PM before shifting east of
the MS RVR. Brisk northwest winds overnight into Wed morning with
improving CIGS behind a frontal passage.   ..12..

&&

.HYDROLOGY...
Issued at 1116 AM CST Tue Feb 20 2018

Rainfall since yesterday was 1 to 2 inches across much of the cwa
with isolated 3 inch amounts in western IL. Additional 1/2 to 1
inch of rain is expected today. This amount of rain, falling on
frozen ground, has resulted in rapid rises on many rivers and streams.
There is high confidence in these river forecasts.

Details:

Rock River:

Major flooding is forecast at Moline, with moderate
at Joslin and minor at Como. The river will rise above flood
stage Wednesday morning.

La Moine/Green/Wapsipinicon River:

Moderate flooding is forecast at Colmar, Geneseo, and De Witt.

Maquoketa/English River:

Minor flooding is forecast at Maquoketa and Kalona.

Pecatonica River:

A flood watch has been issued for Freeport.

Areal flood warning is in effect for portions of northwest IL and
extreme eastern IA until 1015 am on Wednesday. Additional flooding
is possible.

Please see the flood warning and flood watch products for updated
forecasts.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch until 6 PM CST this evening for Cedar-Clinton-Des
     Moines-Dubuque-Henry IA-Jackson-Jefferson-Johnson-Jones-
     Keokuk-Lee-Linn-Louisa-Muscatine-Scott-Van Buren-Washington.

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

IL...Flood Watch until 6 PM CST this evening for Bureau-Carroll-
     Hancock-Henderson-Henry IL-Jo Daviess-McDonough-Mercer-
     Putnam-Rock Island-Stephenson-Warren-Whiteside.

MO...Flood Watch until 6 PM CST this evening for Clark-Scotland.

&&

$$

SYNOPSIS...16
SHORT TERM...16
LONG TERM...08
AVIATION...12
HYDROLOGY...Haase


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