Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 162355

Area Forecast Discussion
National Weather Service Quad Cities IA IL
655 PM CDT Fri Mar 16 2018


Issued at 330 PM CDT Fri Mar 16 2018

Latest MSAS and several impressive GOES-16 satellite imagery`s
showing wrapped up/occluded low acrs north central KS ATTM, with
trailing warm front extending down into the northwest TN Valley.
Tight increasingly cyclonic pressure gradient between that feature
and western GRT LKS ridge axis making for brisk and dry easterly
LLVL flow acrs the local area...hindering precip wings from
advancing northeastward with latest models still a bit too fast to
do so. Wintry mix still on tap for tonight into Sat morning, with
another system potentially rolling along and south of the area by


.SHORT TERM...(This Evening and Tonight)
ISSUED AT 330 PM CDT Fri Mar 16 2018

Tonight...Brisk easterly LLVL flow with low wet bulb temp feed to
continue to hamper precip wings arrival and top-down saturation well as inducing robust evapo-cooling to the low to mid
levels. Thus, will slow the main advancing band of precip through
this evening, with additional areas of precip developing or moving
into the area with more saturation and approach of the upper
low(which will be filling some overnight into Sat morning. Strong
evapo-cooling processes may make for sleet profiles mixing in with
the rain this evening probably earlier than the models give it
credit for, and even some initial bouts of freezing rain on elevated
surfaces as the evening progresses. But the more optimum and
extended top-down cooling for the wintry mixture of sleet, freezing
rain and switch over to ice pellets/snow or all wet snow will look
to occur mainly from 10 PM on into the overnight especially along
and north of I80.

There could eventually be ice accumulation swaths of up to a tenth
of an inch or even more(0.1 to near 0.2 inch)in some locations, but
mainly on elevated surfaces as the ground temps will be marginal.
But still can`t rule out some pavement cooling to around freezing or
colder, especially on side and less traveled roads in these favored
areas after midnight thus making for some slick surfaces. A
challenging precip type and amount forecast for sure, with snow and
sleet taking away from higher icing potential. The highest icing
potential of 0.1+ of an inch may still occur in the original
advisory area counties...but am coming up with several hundreths to
a tenth of an inch of ice on elevated surfaces down to I80 as well.
with most accums occurring from Midnight on into early Sat morning.
Am also getting a swath of snow and sleet accumulations of an inch
or more from along the Hwy 20 corridor from Dubuque on westward, and
down toward Clinton IA and Mt Carroll/Sterling in NW IL. Will expand
the Advisory down to and along the I80 corridor for a wintry mix
tonight, and most trouble occurring from 10 PM into early Sat
morning. Mainly staying rain or drizzle south of I80 after mid to
late evening.

A band of precip with some embedded thunder(now organizing acrs
north central MO), will look to try and whirl into at least the
southern third of the DVN CWA by early evening, and then possibly
make it as far north as I80 through 9 or 10 PM CDT. Any more
developed storm cell will produce locally heavier downpours, as well
as small hail. May be hard to discern between the hail and sleet.
Lows tonight in the upper 20s north of Hwy 30, to the low/mid 30s in
the south.   ..12..

.LONG TERM...(Saturday through Friday)
ISSUED AT 330 PM CDT Fri Mar 16 2018

The two primary challenges are the on-going system affecting the
area with a wintry mix at the start of the period, then the next
system Monday into Monday night. This second system has shifted back
northward in the last couple runs of the GFS and NAM, suggesting
rain and possible snow, but confidence remains low with this system.

Saturday morning: Precipitation will be winding down as the
filling/weakening upper level shortwave and weakening surface low
pass across central IL into IN by afternoon. Forecast soundings and
surface temperatures project light freezing rain and possible sleet
perhaps transitioning to a period of light snow north of I-80, while
mainly rain is expected to the south. With forcing rapidly exiting,
only a few hundredths of an inch precipitation is expected, with
higher amounts along and south of the I-80 corridor in IL and over
southeast IA. This may lead to an additional light glazing of ice
and dusting of snow accumulating mainly on non-paved surfaces along
and north of the I-80 corridor. Our current winter weather advisory
is in effect until 10 am to cover this possibility. By afternoon,
thinning clouds may yield at least partial sunshine, helping
temperatures warm into the 40s.

Surface and upper level ridging provide dry weather with seasonable
temperatures Saturday night through Sunday night.

Another similar system emerges from the southwest, likely passing
through MO into far southern IL Monday into Monday night. Forecast
model consistency remains poor with this system and thus forecast
confidence is below average. Will have high pops for rain Monday
afternoon across the south, which may change to snow as the system
exits late Monday night.  This system is expected to dig into a
longwave trough over the eastern U.S. by midweek, with a resulting
northwest flow pulling down cold air and below normal temperatures
Tue and Wed. An incoming upper level ridge then brings warmer
temperatures Thu into Fri. Model consensus has warm advection rain
developing Friday ahead of a strong low pressure system developing
over the plains.


.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
ISSUED AT 650 PM CDT Fri Mar 16 2018

A wintry mix of precipitation will impact all TAF sites but KBRL
overnight into Saturday morning. Expect periods of light
snow/sleet/freezing rain before the precipitation ends by late
Saturday morning. Ceilings and visibilities will drop to MVFR
tonight, then eventually maily IFR before some improvement late
Saturday morning.


IA...Winter Weather Advisory from 10 PM this evening to 10 AM CDT
     Saturday for Benton-Buchanan-Cedar-Clinton-Delaware-Dubuque-

IL...Winter Weather Advisory from 10 PM this evening to 10 AM CDT
     Saturday for Bureau-Carroll-Henry IL-Jo Daviess-Putnam-Rock



LONG TERM...Sheets
AVIATION...RP Kinney is the U.S. government's official web portal to all federal, state and local government web resources and services.