Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 020545
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1145 PM CST Thu Dec 1 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 320 PM CST Thu Dec 1 2016

Large upper low centered north of Lake Huron providing extensive
low stratus across the northern Plains/Midwest/Great Lakes regions.
Welcome to meteorological winter! Afternoon temperatures across
the dvn cwa were in the mid 30s to 40 degrees.

&&

.SHORT TERM...(This Evening through Friday)
ISSUED AT 320 PM CST Thu Dec 1 2016

Forecast focus on cloudy skies and temperatures near normal for
early December in the short term.

Clouds:

Little change in the airmass as upper level trough will remain
across the Great Lakes region. This will keep much of the dvn cwa
in a moist cyclonic flow with a stratus deck stuck in place through
Friday. The exception will be in far northeast MO on Friday where
clouds should decrease as that area will be closer to high pressure
sliding eastward into the mid Mississippi Valley.

Temperatures:

With the cloud cover and enough of a northwest wind this will
prevent much of a diurnal swing in temperatures. Lows tonight will
be in the lower to mid 30s with highs on Friday in the mid 30s to
lower 40s.

.LONG TERM...(Friday Night through Thursday)
ISSUED AT 320 PM CST Thu Dec 1 2016

Overview: Quiet and near average temperatures to start this extended
forecast period. Then, becoming increasingly active from Saturday
night into next week with several separate rounds of precipitation
possible. Temperatures will trend below average by the end of next
week making it feel like winter.

Friday Night and Saturday:

Dry weather continues before a weak system moves in late Saturday
night. Forecast lows for Friday night are in the 20s. On Saturday,
partly to mostly cloudy skies will hold temps in the 30s to lower
40s - near normal for early December.

Saturday Night through Sunday Night:

First decent chance for light precipitation is from late Saturday
night into midday Sunday. Fast moving, low amplitude trough progged
to force a zone of warm air advection and DCVA through E Iowa/NW
Illinois.

Potential for Light Snow...

Moisture is limited because closed low along the Western Gulf Coast
will restrict northward advection of moisture. Locally, 850mb temps
of -2 to -4 C appear cold enough for all light snow; however, sfc-
925mb ambient temps and sfc wet-bulb temps are warmer making either
rain or a rain/snow mix more likely along/south of a Vinton, IA to
Monmouth, IL line. Best chance for light accumulations of a trace to
just under 1 inch are NE of an Anamosa, IA to Princeton, IL line,
highest furthest to the NE. Majority of accumulation should be on
grassy and elevated surfaces with less on roadways. For these
reasons and since sfc temps will be rising Sunday morning with
southerly sfc winds, not anticipating much in the way of travel
impacts.

Monday Night through Tuesday:

Next system has more Gulf moisture associated with it as it pulls
northeastward out of Texas. 850mb temps, max wetbulb temps aloft,
and sfc wetbulb temps all favor mainly a rain event. This could
change some in future model runs if there is more dry air than the
models are currently resolving.

Tuesday Night on:

Forecast confidence remains low in progressive and complex upper
pattern with anomalously strong +150 kt Pacific jet impinging on the
contiguous U.S. As expected at this lead time, run-to-run intra and
inter-model consistency is lacking.

Not much can be said about the details this far out except that
there is potential for a strong, rapidly deepening low in the
Midwest next week if key phasing of 2 or 3 separate 500mb vort.
maxima can occur (the ECMWF and several GFS ensemble members are
hinting at this). On the other end of the spectrum, if phasing does
not occur, E Iowa/NW Illinois could be largely missed by significant
precipitation. The track/strength will likely remain uncertain
through this weekend as the models continue to jump around with the
evolution and positioning of key kinematic features.

What does look probable is a change to much colder, below average,
temperatures by the end of the week. Uttech

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1141 PM CST Thu Dec 1 2016

Wraparound low clouds to continue with mostly MVFR and isolated sprinkles
or flurries until 12/09Z. Clouds will continue with slow improvement
to mostly low end VFR conditions by Friday afternoon into evening. Winds
to remain west to northwest at 5 to 15 MPH.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Uttech
AVIATION...Nichols



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