Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 112301
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
501 PM CST Wed Jan 11 2017

.UPDATE...
Issued at 500 PM CST Wed Jan 11 2017

Have expanded the dense fog advisory to include Whiteside, Henry,
Mercer and Warren counties in west central and northwest Illinois
based on obs and reports.

&&

.SYNOPSIS...
Issued at 312 PM CST Wed Jan 11 2017

Low pressure has moved into central MO with 3 hr pressure falls
of 6 mb in northeast MO/western IL. 4 mb rises were noted in KS. This
indicates the surface low to track into western IL by this
evening. The arctic front has sagged southeast and early this
afternoon extended from southern WI to near the Quad Cities and
into KS. Precipitation was increasing across the dvn cwa and the
low levels were finally saturating.

A warm front was moving northward along I-70 in MO with temperatures
to the south in the 60s and 70s with dewpoints well into the 50s.
To the north of the arctic front readings were in the single digits
above and below zero. There is almost a 100 degree temperature
difference with the mid 80s in sw TX and 12 below zero in northern
MT! Closer to home temperatures ranged from the upper 20s at
Independence to the lower 50s in our far southern cwa.

&&

.SHORT TERM...(This Evening through Thursday)
ISSUED AT 312 PM CST Wed Jan 11 2017

Headlines: Freezing rain advisory and dense fog advisory in effect
until 9 pm. There is the potential if freezing drizzle develops overnight
the advisory may need to be expanded southward and extended into
the overnight hours. Will pass concerns to the evening shift to
monitor precipitation trends.

Tonight: Rain or freezing rain will gradually end from southwest
to northeast this evening as the forcing lifts to our northeast.
The arctic front will continue to sag southward allowing the
colder/drier air to filter into the cwa overnight. Forecast
soundings indicate the potential for some freezing drizzle in
portions of the cwa overnight as we lose the mid/high level
moisture. Will let the evening shift monitor trends. As this
arctic airmass builds deeper into the cwa the dense fog in our far
eastern cwa should also dissipate later this evening. The surface
low should quickly move into OH by 12z (6 am). Minimum
temperatures will range from 11 at Independence to the mid 20s
from Macomb to Princeton, IL.

Thursday: Any lingering mixed precipitation should end in the
morning but forecast soundings indicate a strong inversion at
around 850 mb trapping low level moisture below. This should keep
our skies cloudy or mostly cloudy but temperatures will be quite
cold. Highs will range from the upper teens at Independence to the
upper 20s from Macomb to Princeton, IL.

.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 312 PM CST Wed Jan 11 2017

Active and unsettled weather to continue to the end of this week
and into next week. Challenging forecast in extended primarily due
to precip type issues Sunday.

Thursday night-Friday...strong 1045+ mb high to slide across the
upper Midwest, keeping the CWA dry. Friday lows to be in single
digits to lower teens. RH progs suggest high clouds early Friday,
but still may see some thinning of clouds. Wind chills also will be
between -5 and -15 degrees Friday morning, especially north of
highway 30.  All 12z solutions continue to show cut off upper low
rotating over the SW CONUS with a weak 500mb wave moving east over
the northern Plains. This wave may be able to generate enough lift
for flurries north of highway 20 although it will be moisture
starved. Rest of area to remain dry Friday.

Friday night-Monday...extremely challenging time frame with main
issue being precip type.  The track of surface low will be key as to
what type of precipitation, amounts, and when it will fall. 12z GFS
shows low track from northern TX to northern MO by 00z Tues whereas
the ECMWF has the low a little further east, tracking right over the
Quad Cities by 06z Tues. These solutions are further east than their
previous runs and the GFS Ensemble Mean is also further east than
its deterministic run. Thus have sided closer to the ECMWF track
with this forecast. Plenty of moisture will be advected north ahead
of this low, with 12z NAEFS showing anonymously high PWs (up to 2
standard deviations) for the middle of January. There will be two
main waves of energy that will move through the foreacst area
during this time frame. The first weaker wave will bring a light
glaze of ice to areas generally south of a Fairfield to Galesburg
line Sat night-Sun morning. The second wave will bring
precipitation to the south as early as Sunday afternoon, spreading over
the entire area Sunday night, and continue through the day on
Monday. Due to the complexity of this system, continued model run-
to-run differences, and that it is still 4 days away, have tried
to keep the weather grids simple with a chance of rain or freezing
rain on Sunday changing to all rain on Monday as forecast
soundings depict a quick changeover to all rain from southeast to
northwest over CWA, as temperatures warm aloft. Monday will be the
day where most of the QPF falls.

Looking further ahead, upper low lifts northeast over the area
Tuesday, with dry conditions and temperatures remaining above normal
through the middle part of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1201 PM CST Wed Jan 11 2017

VFR conds becoming MVFR this afternoon as an arctic front sags
southward across the taf sites. Light rain will spread across the
KBRL/KMLI tafs this afternoon ahead of the front, then a few
hours of freezing drizzle at KDBQ/KMLI at the tail end of the
precipitation shield. MVFR/lcl IFR conds expected tonight into
Thursday morning. South winds ahead of the front then northerly
behind the front with wind speeds of 10 to 20 knots.


&&

.HYDROLOGY...
Issued at 312 PM CST Wed Jan 11 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 with high water upstream to Keithsburg, IL.
This situation is expected to persist for the remainder of the week.

Another ice jam has formed just downstream of Joslin that is
causing minor flooding upstream.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Freezing Rain Advisory until 9 PM CST this evening for Jackson.

IL...Freezing Rain Advisory until 9 PM CST this evening for Carroll-
     Jo Daviess-Stephenson.

     Dense Fog Advisory until 9 PM CST this evening for Bureau-Henry
     IL-Mercer-Putnam-Warren-Whiteside.

MO...NONE.
&&

$$

UPDATE...McClure
SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Gross/Uttech
AVIATION...Haase
HYDROLOGY...Gross/Uttech



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