Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 160815

Area Forecast Discussion
National Weather Service Quad Cities IA IL
315 AM CDT Fri Mar 16 2018

Issued at 310 AM CDT Fri Mar 16 2018

Northeast surface winds have established themselves over the CWA
early today, with thin high clouds over most locations. That is
allowing for a slow drop in temperatures overnight, as we keep the
boundary layer mixed. The winds are increasing as the high pressure
in the Great Lakes remains in place, while low pressure develops in
western KS. This gradient will remain tight through the day as the
low moves east, and will keep dry air feeding in at low levels.


.SHORT TERM...(Today and Tonight)
ISSUED AT 310 AM CDT Fri Mar 16 2018

Today and tonight is a bit of a battle of positive and negative
factors that could come together to bring freezing rain to much of
the northern 1/2 of the area tonight. The dry air feeding in at low
levels, which is already occuring with both allow for the expected
evaporative cooling (below freezing at night) and will also likely
delay precipitiation`s movement northeast today and this evening. In
fact, it may keep our far northeast dry for nearly the entire event.
Much higher confidence in saturation is found in the southwest 1/2
and categorical pops will be maintained there this afternoon and
evening. The delayed precipitation and morning filtered sunshine,
will certainly allow for pavement temperatures in the northeast
2/3rds of the area to climb diurnally, well above freezing. That
should allow for several hours lag in time in all areas for
temperatures dropping near to below freezing, minimizing any ice
accumulation on roads and sidewalks. The low pressure will be
weakening this afternoon and tonight as is moves east across
Missouri. So, despite a near direct hit from the warm advection
rains and dynamics tonight, the forcing will be weakening with
time, while still advecting in very dry low level air. That all
suggest the QPF may be rather low on this event, and our impacts
from any moderate intensity rainfall will be short duration
tonight. That is important, as the narrower the window of moderate
rainfall tonight, the less impact sustained evaporative cooling
and ice accumulation will have. This all said, I am on the fence
on whether an advisory is high enough of a probability to be
issued this a far out. I could see waiting to later today and
having a great knowledge on pavement temperatures at that time
helping identify the exact areal outline of the travel threat. On
the other hand, the minimal impacts of wind shield ice, trees ice,
decking ice could be used to have a very low end advisory as well
tonight. In any case, we`re talking about a 9 PM to 9 AM time
frame. For now, in coordination with surrounding offices, will
issue a lower end freezing rain impacts advisory for counties
between Highway 20 and Highway 30 in Iowa, from Jones county
eastward and into our Illinois counties of Carrol and Whiteside.


.LONG TERM...(Saturday through Thursday)
ISSUED AT 310 AM CDT Fri Mar 16 2018


Wintry mix of freezing rain and wet snow may continue into the mid
morning - mainly over central sections of the forecast area as the
precipitation slowly sinks southward. Precipitation intensity will
decrease through the mid morning as the 500mb vorticity max
is sheared out and low-level deformation wanes. As colder air
wraps in on the northwest side of the surface low, could even have
some wet snow south of I-80 before the precipitation ends. The
potential impacts from this system were discussed in the short
term section (above).

If there are slippery conditions early in the morning, all pavement
should just be wet by the mid morning hours due to effects of the
mid March sun angle. The remainder of the day will be quiet with
highs in the 40s.

Sunday through Thursday

Main storm track is expected to set up over the Southern U.S. and
East Coast, which will keep us dry through this period. On
average, temperatures are forecast to be slightly above normal
into the 40s and 50s. The exception is Tuesday and Wednesday when
a mid-level trough digs into the eastern third of the U.S. The
model blend has highs in the upper 30s to mid 40s for Tuesday, and
a few degrees warmer on Wednesday. Uttech


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1135 PM CDT Thu Mar 15 2018

Expect high clouds overnight with an easterly wind, which will
delay the onset of precip even longer during the day Friday. Much
of the rain now expected to be delayed until midday or after. By
the time precipitation spreads north into KDBQ Friday evening, a
mix of rain and snow is expected. Elsewhere, all rain is forecast
through 06z.


IA...Winter Weather Advisory from 10 PM this evening to 10 AM CDT
     Saturday for Clinton-Jackson-Jones.

IL...Winter Weather Advisory from 10 PM this evening to 10 AM CDT
     Saturday for Carroll-Whiteside.



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