Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 122119

Area Forecast Discussion
National Weather Service Quad Cities IA IL
319 PM CST Thu Jan 12 2017

Issued at 317 PM CST Thu Jan 12 2017

18Z surface data has high pressure across the Plains with a front
from the Ohio Valley into Texas. An arctic front ran from the
arrowhead of Minnesota into South Dakota. Dew points were below zero
across the northern Plains to the teens and 20s from the Great Lakes
into the central Plains.


.SHORT TERM...(This Evening through Friday)
ISSUED AT 317 PM CST Thu Jan 12 2017

Quiet and dry conditions will seen from late this afternoon through
Friday morning. The combination of breaks in the clouds and the
passage of the arctic front will drop temperatures into the single
digits across the northwest half of the area. Wind chills may
approach 15 below zero prior to sunrise north and west of a Dubuque
to Belle Plaine line.

Friday afternoon a weak upper level disturbance will approach from
the Plains. The lower atmosphere is quite dry so only a general
increase in clouds is expected. There is a small chance of some
isolated flurries developing in the highway 20 corridor west of
Dubuque. Temperatures will average well below normal.

Attention then turns to the two storm systems that will affect the
area over the weekend.

.LONG TERM...(Friday Night through Thursday)
ISSUED AT 317 PM CST Thu Jan 12 2017

Headlines: Have issued a winter storm watch for ice storm potential
for locations south of Interstate 80. The watch begins at midnight
Saturday night and runs through 6 am Monday. Later shifts may need
to expand the watch northward and also extend it into Monday so stay
tuned to later forecasts.

Forecast focus on light freezing rain mixed with sleet in the south
Friday night then potential for an ice storm later this weekend and
into Monday across much of the cwa.

Friday night and Saturday: Upper low off Baja California will bring
a return of moisture northeast into the mid MS Valley. In the
meantime, arctic high pressure will be situated across the Dakotas
eastward into WI. Operational models indicate an area of
precipitation spreading across MO and into central IL, with the
northern fringe of the precipitation getting into our southern cwa.
Forecast soundings suggest this to be in the form of freezing rain
mixed in with some sleet with a warmer layer aloft and surface
temperatures well below freezing.

As of now, ice accumulations should be less than a tenth of an inch,
but with temperatures in the 20s, roads and sidewalks will quickly
become ice covered and hazardous. For now we will have chance pops
but later shifts can raise pops if needed. An advisory for either
freezing rain or a mixture may need to be issued assuming these
trends continue in the models.

Lows Friday night will range from the teens north to the lower 20s
south. Any lingering freezing rain or a mix should end in the
morning with skies remaining mostly cloudy. Highs on Saturday will
range from the mid to upper 20s north to the lower 30s south.

Saturday night through Sunday night: Winter storm watch for
potential ice storm in effect south of I-80. A potent slow moving
storm system will be tracking into the southern Plains as the
weekend progresses. This will pull Gulf moisture northward with
PWAT`s near an inch by later Sunday. To the north, arctic high
pressure will still be situated across the Upper Midwest and into
the Great Lakes. Forecast soundings indicate a classic freezing rain
situation with a warm layer of 4 to 5C at about 850 mb but surface
temperatures remaining at or below freezing.

Ice accumulations of greater than 1/4 inch is likely with the
potential for at least 1/2 inch at some locations through Sunday
night. As the warmer air aloft is transported northward on a
strengthening low level jet our northern cwa will experience the ice
accumulations Sunday afternoon and Sunday night. As stated before,
later shifts may need to expand the watch northward. There is lower
confidence on qpf amounts as the ECMWF is more aggressive with ice
accumulations compared to the GFS. Have lowered temperatures from
guidance as it will tough to warm up with ice on the ground. Highs
on Sunday should be in the upper 20s to lower 30s with lows Sunday
night in the 20s to around 30.

Monday and Tuesday: As the storm system lifts northward into
western/central IA this will pull much warmer air into the cwa
changing the freezing rain over to plain rain, but the timing of
this is in question this far out. Ice accumulations may continue for
a time into Monday in our north while the south has plain rain.
Headlines for ice accumulations may be needed on Monday in portions
of the cwa. The rain may continue over all the cwa Monday night
ending Tuesday morning. Highs on Monday is expected to push into the
30s north and 40s south but this may be too warm depending on amount
of ice on the ground.

Later in the week: Looks dry with above normal temperatures.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
ISSUED AT 1137 AM CST Thu Jan 12 2017

Current visible satellite image shows breaks in 3-5 kft cloud
deck and may briefly see SCT MVFR cigs at MLI/BRL early this
afternoon. Otherwise MVFR cigs will give way to VFR conditions by
late afternoon/evening at all TAF sites. North winds to veer to
the east by 12z/13 with increasing high clouds.


Issued at 317 PM CST Thu Jan 12 2017

An ice jam remains in place just downstream of Burlington, Iowa,
along the Iowa side of the river channel on the Mississippi. This
jam is producing minor to moderate flooding from near Fort Madison,
IA up to Gladstone, IL. This situation is expected to persist for
several days.

Another ice jam has formed just downstream of Joslin that is causing
minor flooding upstream. Ice action may continue to produce rises on
a few other forecast points as well, such as further downstream on
the Rock at Moline.


IA...Winter Storm Watch from late Saturday night through late Sunday
     night for Des Moines-Henry IA-Jefferson-Keokuk-Lee-Louisa-
     Van Buren-Washington.

IL...Winter Storm Watch from late Saturday night through late Sunday
     night for Hancock-Henderson-McDonough-Mercer-Warren.

MO...Winter Storm Watch from late Saturday night through late Sunday
     night for Clark-Scotland.



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