Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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830
FXUS63 KDVN 130928
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
328 AM CST Wed Dec 13 2017

.SYNOPSIS...
Issued at 326 AM CST Wed Dec 13 2017

06Z surface data has the center of the next storm system in
northwest Minnesota. A warm front ran from the low into southern
Wisconsin while the main cold front was across South Dakota. Dew
points were in the teens from the Great Lakes and the Ohio Valley
with 20s across the Plains.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 326 AM CST Wed Dec 13 2017

Main concern today is where the surface low of the clipper system
tracks. This feature will dictate the sensible weather.

Through sunrise, quiet and dry conditions will be seen across the
area.

After sunrise, the big question is where will the low track. Based
on trends with pressure falls, it appears the low will pass close to
Dubuque and then move toward possibly KGYY. If this occurs then the
potential for light snow would increase in the highway 20 corridor
from Dubuque on east. However, since this system is moisture starved
any accumulations should be less than an inch.

A track closer to Dubuque would also delay the start of the very
windy conditions that are expected to develop across the area later
this morning and afternoon.

Right now the current forecast is as follows...

Flurries/light snow showers should begin developing around mid-
morning and increase in areal coverage in the late morning and early
afternoon as the low heads toward Lake Michigan. As temperatures
warm during the day a mix of flurries/sprinkles or rain and snow
showers should develop. Any snow accumulations should be a dusting
at best.

Any precipitation should shut down quickly from west to east during
the afternoon as the main cold front sweeps through the area.

The main story will be the very windy conditions that develop late
this morning and continue through the afternoon hours. Sustained
winds will easily be 20 to 35 mph with gusts up to 45 mph possible.
An isolated gust to 50 mph cannot be ruled out. Thus will be issuing
a wind advisory for late morning and afternoon hours for roughly the
southwest half of the area.

Tonight, quiet but windy conditions will be seen across the area.
Like the clipper system on Tuesday, winds will stay up during the
evening hours with winds gradually diminishing after midnight.
Lows tonight should occur between 7 and 8 AM Thursday.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 326 AM CST Wed Dec 13 2017

Dynamic northwest flow pattern to keep region mostly dry but
increasing low confidence due to disturbances.

Long Term Forecast Confidence Assessment...fair to poor or average
to below average.  Two issues are likelihood of one or more light
precipitation event day 4 and beyond with second issue is diurnal
ranges again probably underdone.  Once again issues are highs up to
3 plus degrees too cool most days and lows with clear skies and
light winds too mild by 2 to 3 plus degrees.

Thursday through Saturday...minor changes, generally partly cloudy
with highs mostly in the 30s rising into the 40s by Saturday.  Lows
15 to 25, rising into the 20s.

Sunday...complex phasing of energy supports an increased chance of
light mixed precipitation.  This issue is poorly handled with also
lots of run to rum changes. This issue should be better known in
next 24 hours as dealing with a phasing of north and south energy
centers. Any precipitation totals would tend to be less than a
quarter of an inch in the form of mostly rain and snow with poor
confidence on precipitation types also for another 24 hours.  Highs
35 to 45 with lows in the 20s.

Monday through Wednesday ...northwest flow with weak disturbances
for a chance of rain and snow. Highs 35 to 45 with mins mostly in
the 20s with lower 30s possible in far south.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1115 PM CST Tue Dec 12 2017

South winds to southwest winds will increase the rest of tonight,
with clouds at all sites should be above 5000 ft AGL. Towards
morning, a strong low pressure system will quickly move southeast
through the region, bringing snow to locations mainly northeast of
Dubuque. Some isolated snow showers and rain showers are possible
over eastern Iowa and northwest Illinois, but at this time,
confidence is low, due to most model guidance keeping the system
too far northeast to produce snow this far south. That said, as
winds turn northwest and increase to 20 to 30 kts, possibly higher
Wednesday late morning, there could be a brief flurry or snow
shower. By sunset tomorrow, winds will decrease to under 20 kts.
As cold air arrives after 18Z, some MVFR cigs are likely in the
CID and DBQ regions, but farther south, this is less likely, and
VFR cigs are forecast for now.

ERVIN


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Wind Advisory from 11 AM this morning to 6 PM CST this evening
     for Benton-Buchanan-Cedar-Clinton-Delaware-Des Moines-Henry
     IA-Iowa-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-
     Muscatine-Scott-Van Buren-Washington.

IL...Wind Advisory from 11 AM this morning to 6 PM CST this evening
     for Hancock-Henderson-Henry IL-McDonough-Mercer-Rock Island-
     Warren.

MO...Wind Advisory from 11 AM this morning to 6 PM CST this evening
     for Clark-Scotland.

&&

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...Nichols
AVIATION...Ervin



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