Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 161704

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1204 PM CDT Mon Apr 16 2018



Issued at 330 AM CDT Mon Apr 16 2018

Large cut-off upper low complex will continue to slow-roll east acrs
the GRT LKS today, while omega block ridge sets up acrs the north-
south stretch of the plains. Well below normal temp regime to
continue well into this week, with a piece of wave energy ejecting
out of western upper TROF and being another potentially significant
weather maker acrs the upper Midwest by mid-week.


.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Mon Apr 16 2018

Today...Cold blustery raw day today on the western flank of western
GRT LKS large cyclone complex and lingering cyclonic flow. Bands of
light to moderate snow currently pivoting and rotating southeastward
around backside of this system will look to start to move out of the
area/decease by mid to late morning. until then, will continue to
cover more enhanced bands of moderate to locally heavy snow with
special wx statements and graphicasts...localized quick
accumulations possible up to an inch through 12-14z this morning.
Other areas just light snow and flurries through late morning.
embedded flurries in wrap-around stratocu probably to last well into
the afternoon, but will not mention measurable POPs after 18z. But
can`t rule out isolated to sctrd snow showers in the east and
northeastern CWA through late afternoon/early evening. Steep lapse
rates under enhanced higher based H65 MB inversion and rather tight
ongoing cyclonic pressure gradient, to continue to drive gusty
northwest winds of 15 to 25 MPH and gusts to at least 30 MPH today.
wind chills in the teens well into the mid to late morning period.
Will play the cooler side of guidance highs today with most areas
staying in the 30s...the southwestern CWA best chance of some 40s if
breaks in the cloud cover remain and don`t "CU" back up.

Tonight...Gradual clearing from the southwest into the overnight
hours. Sfc winds may be a bit gusty during the evening, but then
expect a late night drop-off to 5-10 MPH toward dawn Tue morning.
With eventual clear out and sfc wind decease, lows will drop into
the low to mid 20s acrs much of the CWA and be not all that far away
from record cold territory for a few climate sites for April the.

.LONG TERM...(Tuesday through next Sunday)
ISSUED AT 330 AM CDT Mon Apr 16 2018

A very active and cool pattern persists through the long term. The
main focus is with the next dynamic early spring system to impact
the area midweek.

Potent Pacific trough digging toward the California Coast this AM
will take on a negative tilt as it emerges over the High Plains
Tuesday night. Then expect a transition to a positive tilt system
/closed low/ as it moves across the Upper Midwest Wednesday and
Wednesday night eventually occluding or becoming near vertically
stacked with both surface and mid/upper level lows passing over the
region. Expect the brunt of the precipitation with this system to
focus on the northwest or cold side, and it should be rather heavy
as well given the tremendous forcing aided by strong positive
vorticity advection, frontogenetic forcing and upper level divergence.
I would expect to see a wing of WAA induced precipitation lift
across portions of the area late Tuesday night and early Wednesday
AM, with the main focus for this band generally north of I-80
where currently consensus shows best deep layer saturation within
area of strong elevated moisture flux convergence. As we`ve seen
with these dynamic early spring storms, there will likely be some
precipitation type challenges on both sides of the system related to
surface temps, ice cloud microphysics and evolution of TROWAL (Trough
of Warm Air Aloft). Bottom line is a brief bout of a wintry mix is
possible in this initial WAA band late Tuesday night and Wednesday AM
before going to rain. Can`t rule out even some embedded thunder with
this WAA band given advection of mid level instability/steep lapse
rates, which if occurs could further wreak havoc on precip type and
likely introduce more potential for brief period of sleet and/or snow.
Then cooling of vertical thermal structure aided by dynamic processes
via large scale ascent will likely result in rain changing over to snow
Wednesday afternoon into evening. Could see several inches of snow
accumulation before all is said and done by Thursday AM, with areas
roughly along/north of I-80 most favored for the snow accums right now.
Snow could be heavy at times for a little while as well with strong
omegas overlapping dendritic growth zone. The other component of this
system will likely be strong gusty winds, which could exceed advisory
criteria Wednesday in the transitory warm sector and Wednesday night in
the cold sector with momentum transfer aided by strong cold advection.

To summarize, watching another dynamic spring storm likely to impact the
region late Tuesday night through Wednesday night with a variety of
weather including a wintry mix, thunder, rain, winds and yes more snow
with the potential for accumulations. Confidence is fairly high on the
system impacting the region. However, this system is still just offshore
so confidence in the details is low. Nonetheless, stay tuned especially
if you have any travel plans near and north/west of the area midweek.

Beyond, there is another system suggested for the weekend. Model
trends have generally been to slow system down and track further south,
as fairly typical for these SW systems. Thus for now it appears that
any impacts will be well to our south, and region will largely be
governed by Great Lakes high and cold northeast fetch enhanced by Lake


.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
ISSUED AT 1201 PM CDT Mon Apr 16 2018

MVFR CIGS will continue in stratus rotating around an upper level
low pressure near Lake Michigan today. The back edge of this will
reach local TAF sites between 18z and 21z today. After this
stratus clears out, VFR clear conditions with gradually decreasing
northwest winds are forecast through Tuesday afternoon.


Issued at 1201 PM CDT Mon Apr 16 2018

Routed flow forecasts remain low confidence on the
Iowa/Cedar/Wapsipinicon rivers. The high water upstream retains a
sharp rise fall with the crest, with little forecast attenuation,
but that seems incorrect as local creeks and wetland back fill
space is available for high water. Thus, no watches or warnings
have been issued for the Iowa/Cedar/Wapsi at this time.


ISSUED AT 330 AM CDT Mon Apr 16 2018

Record Lows for April 17...

Moline.........18 in 1875
Cedar Rapids...22 in 1997
Dubuque........16 in 1875
Burlington.....23 in 1907




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