Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 062141
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
341 PM CST Tue Dec 6 2016

.SYNOPSIS...
Issued at 338 PM CST Tue Dec 6 2016

Cold front has pushed east of the dvn cwa with sunny skies and brisk
northwest winds gusting to 30 mph behind the front. There was an
area of stratus grazing Highway 20 but this was moving eastward
with the bulk of the clouds remaining north of the cwa. 3 pm
temperatures ranged from the upper 20s to mid 30s.

Elsewhere, a secondary cold front was pushing towards nw IA with
readings only in the single digits in the northern Plains and
northern Rockies. Deepening upper low was located in northern MN
with snow falling in ND and MN.

&&

.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 338 PM CST Tue Dec 6 2016

Forecast focus on clouds and temperatures.

Tonight: Cold air advection well underway with colder temperatures
being funneled southeast around the strong low pressure situated
in northern MN. Skies should be clear to partly cloudy with
northwest to west winds remaining at 10 to 15 mph most of the
night. Clouds should increase later overnight as a weak disturbance
pushes into the central Plains. Minimum temperatures will drop
into the teens along and northwest of a Dubuque to Cedar Rapids
line. Elsewhere, lows should be in the 20 to 25 range. Wind chills
will fall into the single digits north to teens south.

Wednesday: Storm system tracks into the northern Great Lakes with
continued cold air advection, with 850 mb temperatures falling to
-10c. GFS/ECMWF streak a band of light snow or flurries in weak
warm air advection across KS and into central and southern MO.
While the dvn cwa is expected to remain dry there should be a
continued increase in cloud cover. Mid/high level clouds should
spread northward over the cwa from the system to our south, with
the potential for stratus pushing southward from the Great Lakes
system. The end result is a mostly cloudy/cloudy and cold day with
highs only in the 20s across most of the cwa, with some lower 30s
in our far southern counties. Wind chills for much of the day will
range from the single digits and teens north to the lower 20s south.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 338 PM CST Tue Dec 6 2016

Wednesday Night:

NW 850mb flow and cold air advection continue the steady temperature
fall to the -10 to -12 C range (at 850mb). Greatest sensible weather
impact is going to be the cold wind chills near 0 F. Ambient temps
are forecast in the lower to middle teens.

Thursday and Friday:

We`ve lost most of the snow cover across the CWA over the past few
days, if we had not, it would probably end up being 5-10 F degrees
colder. Nonetheless, coldest daytime highs of the season (so far)
are forecast with upper teens to mid 20s. 850mb temps are progged
near -14 C and 1000-500mb thicknesses between 510-516 dam. Similar
to Wednesday night, min overnight/early morning wind chills near 0 F
will feel quite cold.

Flurries or Light Snow Showers Possible on Thursday: Cyclonic mid-
level flow, steep low-level lapse rates, and with vorticity maxima
rotating through, could have periods of convective-like flurries or
light snow showers. Model time-height sections indicate saturation
above the -10 C isotherm, so should not have a problem introducing
in-cloud ice crystals. Added mention of flurries to the grids for
now.

Friday Night:

Deep warm air advection/isentropic lift could initiate a band of
light snow in or near the DVN CWA. POPs are low in the 20-30% range,
favoring our north half. Overall, moisture is limited in the models
for this period.

Saturday and Sunday:

Another shortwave is likely to impact the Midwest. The GFS/GFS
ensemble mean/Canadian are cold enough for mainly snow, the ECMWF is
the outlier maintaining a system which is less phased. The GFS
deterministic track of the sfc low is in good agreement with its
ensemble mean, taking it across E Iowa. Stay tuned to future updates
as a lot can change with respect to strength/timing/impacts. Model
blend temps warm into upper 20s to mid 30s by Sunday.

Monday and Tuesday:

Temps trend below average and there are periodic snow chances. There
is a large spread in temperatures on Tuesday between the ECMWF and
GFS tied to the strength of an arctic front forecast to plunge into
the Midwest. The ECWMF is not as cold as the GFS. If there is
widespread snow cover across the Upper Mississippi Valley by this
time, it will be easier for the arctic air to advect in with more of
a punch. Certainly potential for our first sub-zero overnight lows
for portions of the CWA from Tuesday night through the week. Uttech

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
ISSUED AT 1149 AM CST Tue Dec 6 2016

VFR conds through the taf cycle as high pressure builds into the
mid MS Valley. Northwest winds around 15 knots with gusts to 25
knots this afternoon then west around 10 knots tonight into
Wednesday morning.

&&

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

$$

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


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