Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 180909
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
409 AM CDT Wed Apr 18 2018

.SYNOPSIS...
Issued at 330 AM CDT Wed Apr 18 2018

Sub-999 MB sfc low rolling east-northeastward acrs far northeastern
KS ATTM, with inverted trof jutting north of it up the MO RVR
valley. MSAS indicating strong pressure fall bullseyes to the lee of
these features in NW IA and toward the KS City areas. Very strong
elevated F-Gen band and H85 MB convergent zone driving a wing of
elevated thunderstorms acrs west central IA which are currently
prolific lightning producers. Current winter headlines to continue
for today with passing vigorous storm system, then dry and
moderating weather into the weekend.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Wed Apr 18 2018

Intense elevated Frontogenetical forced band/convergent H85 MB flow
zone, mentioned above driving wing of thunderstorms, being handled
by NAM40 lift tool which sweeps it acrs the northern third of the
DVN CWA this morning. In general this wing to enter the northwestern
CWA mainly along and north of Hwy 30 between 11-12z, and move east
along an north of Hwy 30 through late morning...weakening somewhat
along the way. Still lightning and at least small hail to be
produced by these storms. Some isolated storms possible further
south to I80 or even further south as well this morning, looking at
wing of 200-800 j/kg elevated plume of MUCAPES through 15-16z before
shifting east and waning. The incoming showers/rain to produce some
freezing rain at the sfc, with increasing easterly sfc flow and
lower WBZ feed. The icing may be more prevalent on wind blown
elevated surfaces, but current pavement temps indicated in the upper
20s to low 30s north of I80 suggest some untreated roads may become
ice glazed as well. See a quick transition to freezing rain-sleet
mix, with sleet becoming more prevalent and may accumulate some. But
then the ongoing very strong lift(Omegas over 20 microbars/sec) and
dynamical cooling machine to transition the column to mainly a wet
snow producer from west-to-east as the morning progresses...probably
faster than what the models give this process credit for.

Expect banded heavy snowfall swaths of convective nature developing
in ongoing warning areas, and northern advisory areas as well. 1-2+
inch per hour snowfall rates very possible under these bands as they
set up and then progress eastward. thunder snow possible this
morning thru midday north of I80. Assessing several parameters from
the latest run models, including HiRes solutions, the Hwy 20
corridor-especially from Dubuque on westward, still looks like the
prime area of strong forcing combined with earlier snow switch over
for higher accumulations of 4-7+ inches by mid afternoon. Most of
this to fall before 18z. The Hwy 20 corridor east of DBQ should
range from 2-5 inches by late afternoon. Sharp snow accums gradient
to the south toward I80, with less than an inch along that
interstate corridor. But there may be banded and very localized
higher swaths of snow acumms even in these more southern areas
toward I80. Some lingering light snow in this systems wrap around
after 00z through 03z with additional light accumulations possible
east of the MS RVR. All in All, will let the headlines ride as they
are, but the southern sections of both the Warning areas, and the
Advisory areas may be marginal for their respective threat hazards
(snow and ice glaze amounts).

.LONG TERM...(Thursday through next Tuesday)
ISSUED AT 330 AM CDT Wed Apr 18 2018

Quick look at the longer range, still looks mainly dry with
moderating temps back closer to normal into the weekend, as Rex
block and precip-making wave, rolls to the south of the area.
Temps may push 70 degrees by Monday in the south. A frontal system
may then bring the next chance of rain by Late Tuesday into next
Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1241 AM CDT Wed Apr 18 2018

A fast moving area of a wintry mix of moderate to locally heavy
rain, freezing rain, sleet and snow with embedded thunder will
sweep through the region after 12z through 16z, with conditions
deteriorating rapidly to IFR/LIFR. Greatest impacts expected at
CID and DBQ terminals where freezing rain/sleet should quickly
switch to snow within 1-2 hours after precipitation onset, with
snow then persisting through the afternoon before tapering off
into the early evening. Sleet and snow accumulations of at least
1 to 2 inches are expected on pavement. At MLI and BRL expecting
rain and sleet for a few hours by mid morning before transitioning
to bouts of snow by afternoon with minor accumulation possible on
pavement at MLI during any bouts of heavier snow.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory from 8 AM this morning to 7 PM CDT this
     evening for Cedar-Clinton-Muscatine-Scott.

     Winter Storm Warning from 8 AM this morning to 7 PM CDT this
     evening for Dubuque-Jackson-Jones.

     Winter Weather Advisory until 7 PM CDT this evening for Iowa-
     Johnson.

     Winter Storm Warning until 7 PM CDT this evening for Benton-
     Buchanan-Delaware-Linn.

IL...Winter Weather Advisory from 8 AM this morning to 7 PM CDT this
     evening for Carroll-Rock Island-Stephenson-Whiteside.

     Winter Storm Warning from 8 AM this morning to 7 PM CDT this
     evening for Jo Daviess.

MO...NONE.
&&

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...12
AVIATION...McClure



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