Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 080905
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
305 AM CST Thu Dec 8 2016

.SYNOPSIS...
Issued at 300 AM CST Thu Dec 8 2016

At 2 AM CST...generally partly cloudy to mostly cloudy skies in lower
clouds with blustery northwest winds of 15 to 25+ MPH high pressure
from the northern plains continues to slide slowly southeast. Isolated
flakes are occurring mainly north of I-80 corridor. Temperatures are
mostly in the teens to near 20 degrees southeast sections.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 300 AM CST Thu Dec 8 2016

Short term forecast confidence assessment...good or above average. Main
issues are isolated flurries or flakes and sky coverage with intervals
of clouds suggested next 24 hours.

Today...minor changes. Intervals of clouds and some sun with less clouds
south 1/3 and more clouds than sun north 1/3 to 1/2. Blustery and cold
with highs mainly 20 to 25 degrees on northwest winds of 15 to 25 MPH.

Tonight...little change from the day in terms of clouds and wind except
have removed isolated flurries. Lows mostly in the 12 to 17 degree range.
Once again low wind chills approaching zero toward daybreak.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 300 AM CST Thu Dec 8 2016

Long term forecast still has considerable uncertainty as an active
flow regime will continue across the central United States. Guidance
continues to focus on two things, a winter weather event this
weekend and cold air for next week with a series of waves in the
dynamic pattern.  Each of these waves will bring with a chance for
snow.  Overall pattern remains unchanged run to run as a strong jet
remains across the central US with little poleward variability. This
sets us up for the possibility of multiple systems affecting the
area.  However, due to the nature of the environment, guidance will
likely be all over the place until we get closer to each event.

This weekend, Friday should be a quiet day before the chance of snow
returns to the area for the weekend.  Guidance consensus is that a
warm advection band of precip will move across the northern CWA.
Have increased pops over the blend because confidence in this event
occurring has increased.  The GEM is further south than the
consensus and trends in the models.  Regardless, snow ratios will be
close to 17:1 across the north in the cold air.  This with QPF
brings a swath of 2 to 4 inches across the northern zones.  Two
concerns with this event.  1st, the QPF, the GFS is much more moist
than the ensemble means and other guidance.  If the GFS is correct
then a lot more snow could occur in this band.  The other is the
placement of this band.  Snow will likely fall in a narrow swath
that may be a moving target until it shows up on radar.  As a
result, expect fine tuning through the next 48 - 72 hours.

Sunday into Monday, another more robust system is prog in the
guidance.  Confidence is low in many of the solutions as the models
have been all over the place in the last 24 hours. One thing seems
to be clear, low pressure is forecast to pass south of the CWA,
putting us on the cold side of the system.  Any precip that would
fall is expected to be snow.  The GEM, the most aggressive for our
CWA mimics the 12z ECMWF from 12/7.  However, the 00z ECMWF has
backed off on that solution this run.  Therefore, I find it hard to
really but much confidence in many solutions this far out.  The H5
wave for this system is still off the west coast and not sampled by
any RAOBs.  Believe that this energy will be on shore Saturday
afternoon. As a result, this will prove to be a difficult forecast
with much uncertainty, with the possibility of a clear forecast not
being available until later Saturday.  As previously mentioned, it
would be prudent to stay abreast of the forecasts for this weekend
as there is potential for much change that could significantly
change impacts from any event.

Next week,  cold snap with series of waves through the flow still
advertised.  However, recent ECMWF has backed off on the cold H85
temps for midweek.  A good rule for this period could be, model
discrepancies run to run should not lead to major shifts in the
forecast until these `changes` look more like trends.  Models have
suggested cold temps for a few runs, if other models start
gravitating towards the 00z ECMWF, then that should be discussed.
Regardless, with this flow, cold air and chances for snow are
favored.   Gibbs

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
ISSUED AT 1139 PM CST Wed Dec 7 2016

Strong cold advection will bring bouts of low clouds with generally lower
VFR and MVFR cigs 1500-3500ft agl, brisk w/nw winds 15-25 kts, and
occasional flurries and possibly pockets of light snow showers over the
next 24 hrs.

&&

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

&&

$$

SYNOPSIS...Nichols
SHORT TERM...Nichols
LONG TERM...Gibbs
AVIATION...McClure


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