Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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799
FXUS63 KDVN 160533
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1133 PM CST Sun Jan 15 2017

...AVIATION UPDATE...

.UPDATE...
Issued at 928 PM CST Sun Jan 15 2017

Evening update continued the day shift trend of trending down
sleet/snow accumulations in favor of a bit more freezing rain,
especially across the northwest quarter of the forecast area. Also
believe the warm-up Monday morning will result in a bit less ice
across the far south. Parts of the northwest could approach the
quarter inch warning criteria, and much will depend on the timing
of the change over to rain Monday morning into early afternoon.
Confidence level is not high enough to go with an upgrade at this
time and later shifts will have a better handle on short term
trends and impacts.

&&

.SYNOPSIS...
Issued at 316 PM CST Sun Jan 15 2017

Scattered rain showers continue well south of I-80 this afternoon.
There have been reports of light icing on elevated surfaces.
So far, roads have been mainly wet with sfc pavement temps in the
mid 30s.

&&

.SHORT TERM...(This Evening through Monday)
ISSUED AT 316 PM CST Sun Jan 15 2017

This Evening through Monday Afternoon:

Winter Weather Advisories are either in effect or have been issued
from the entire CWA with the primary impact period being tonight
into Monday morning for a tenth to a quarter inch of ice. Please
see advisory products for county specific beginning and ending
times and expected wintry precip amounts.

Trend in the models today is similar to past several - slower
northward push of the precip.

Precipitation Type and Amounts:

Freezing rain is the main winter p-type of concern before the
eventual changeover to rain occurs from south to north from the
early/mid morning into the afternoon on Monday. Max wetbulb temps
aloft associated with initial bout of mid-level isentropic lift
this evening and early tonight are between 1-3 C. Thus, this is
the best chance to have some sleet mix in with the FZRA. But think
FZRA will be dominant p-type.

Later on tonight, moisture and temperature advection in the
925-700mb layer becomes very strong over the southern CWA during
which time 850mb temps are warming to above 5 C. Hi-res models are
hinting at a fairly quick changeover from FZRA to rain in this
area. Conceptually this makes sense. The strongest forcing is
forecast to occur when the p-type is mainly rain. The 700mb omega
max attendant to this advective and frontogenetic forcing will
work northward through the morning into the afternoon, eventually
reaching the far northern CWA. Would not be surprised if we end up
with widespread QPF amounts of 0.75 inches to ~1 inch with PWATS
in the same territory.

Impacts:

Be prepared for slippery roadways and other paved surfaces mostly
from freezing rain.

Thinking the greatest impacts will be across the northern CWA
where p-type remains as FZRA for the longest duration. There is
some potential for icing amounts exceeding a quarter inch over
the far north, but low confidence on this occurring based on
latest data. Conditions should improve rapidly from along I-80 and
south Monday morning. Uttech

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 316 PM CST Sun Jan 15 2017

Widespread rain, thunderstorms and potentially dense fog will likely
be over the area at the onset Monday night, as the long-advertised
winter storm system lifts through the region. The rest of the week
will be dominated by much above normal temperatures with additional
systems lifting out of the south and southwest possibly bringing
rain chances Friday and again Sunday.

A near consensus of operational models has the surface low lifting
northeast across southeast IA and northern IL Monday night. Low
level convergence and strong upper forcing ahead of a compact mid
level shortwave along with a jet level entrance and exit region
couplet, will provide plenty of deep lift to squeeze out the deep
and unseasonably moist airmass. A developing feed of Gulf moisture
induced by the intense upper low over the TX panhandle this morning
was spreading 850 mb dewpoints of 10 C plus into the SE TX and
precipitable water values greater than 1 inch into SW MO. Model
indicated PW values of .75 to near 1 inch, or over 300 percent of
normal for KDVN, thus do not look unreasonable as this spreads
northeast with the moisture plume along and E-NE of the surface low
track.

Thus, widespread rain will be underway Monday evening, decreasing to
light rain or drizzle from west to east as the low exits toward
morning. Thermal profiles suggest a mix of freezing rain may be
possible late in the far northwest, but this should not be
appreciable as temperatures only begin to drop in the NW just as
moisture moves out. Will continue to mention at least a slight
chance of thunderstorms as supported by elevated steep lapse rates
and thetae lapse rates, especially in the strong lift just in
advance of the upper level shortwave. Widespread quarter to half
inch rainfall will be possible overnight, and model-based storm
total QPF amounts of .75 to 1.25 look reasonable. Introduced areas
of fog overnight, especially in the southeast as winds become light
and convergent with saturated air over the cold ground. Temperatures
will be nearly steady through most of the night from just above
freezing northwest to the upper 30s and lower 40s southeast.

Tuesday...Light precipitation in the form of light rain or drizzle
will exit from west to east as the system lifts out with a lack of
cold air and temperatures recovering to highs in the mid and upper
30s eliminating any significant threat of freezing precipitation.
All models now have the secondary shortwave in the NW flow quickly
following, but moisture is limited in the layer of forcing, thus
precipitation does not look likely.

An upper level ridge passes through the region Wed and Thu for dry
weather with high temperatures in the 40s and lows in the 20s and
30s, well above Jan normals. An active pattern follows, sending
a surface low and upper level wave into the Central U.S.
for rain chances Fri into Fri night, followed by another wave and
rain chances Sat night into Sunday. As is typical in this type of
pattern, there is poor model agreement with these features this far
out in the forecast and thus pops were limited to only chance
category. Will keep temperatures well above normal with
precipitation mentioned as rain for now as air sufficiently cold for
snow appears to be lacking.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
ISSUED AT 1127 PM CST Sun Jan 15 2017

FZRA, possibly mixed with PL to gradually spread north overnight
and change over to all FZRA. Conditions will deteriorate to IFR
and potentially LIFR Monday morning. Precip will change over to
all rain Monday morning into early afternoon from south to north.
There is some potential for isolated TSRA at KBRL toward 00z but
with low predictability have not included in the 06z TAF.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory from 3 AM to noon CST Monday for Clinton-
     Jackson-Jones.

     Winter Weather Advisory until 9 AM CST Monday for Des Moines-
     Henry IA-Jefferson-Keokuk-Lee-Van Buren-Washington.

     Winter Weather Advisory until noon CST Monday for Benton-Cedar-
     Iowa-Johnson-Linn-Louisa-Muscatine-Scott.

     Winter Weather Advisory from 3 AM to 3 PM CST Monday for
     Buchanan-Delaware-Dubuque.

IL...Winter Weather Advisory from 3 AM to noon CST Monday for Carroll-
     Whiteside.

     Winter Weather Advisory until 9 AM CST Monday for Hancock-
     Henderson-McDonough-Warren.

     Winter Weather Advisory until noon CST Monday for Bureau-Henry
     IL-Mercer-Putnam-Rock Island.

     Winter Weather Advisory from 3 AM to 3 PM CST Monday for Jo
     Daviess-Stephenson.

MO...Winter Weather Advisory until 9 AM CST Monday for Clark-Scotland.

&&

$$

UPDATE...RP Kinney
SYNOPSIS...Uttech
SHORT TERM...Uttech
LONG TERM...Sheets
AVIATION...RP Kinney



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