Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 180938
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
338 AM CST Sat Nov 18 2017

.SYNOPSIS...
Issued at 330 AM CST Sat Nov 18 2017

Patchy light rain continued across the area overnight, while
a few showers and thunderstorms occurred in parts of western and
central Illinois. Low clouds and light fog persisted overnight,
but an increasing north breeze helped keep dense fog from
developing. Early morning temperatures ranged from the upper 30s
near U.S. Highway 20, to the low 50s in the Keokuk and Macomb
areas.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CST Sat Nov 18 2017

Precipitation types/amounts, isolated storms, and strong
northwest winds are the main forecast challenges in the short term
period.

The far southern counties are in the SPC day 1 marginal risk area,
with marginally severe hail this morning the main threat given
the steep mid level lapse rates and sufficient deep layer shear.

A band of strong frontogenetical forcing will sweep eastward
through the forecast area today. This system has a similar look to
the recent event, which resulted in brief periods of heavy
dendritic snow and minor accumulations on grass and elevated
surfaces. Snow growth/Fgen diagnostics and Bufr soundings support
a 1-2 hour period with sufficient dynamic cooling to result in a
change over to all snow across areas along/north of Interstate 80.
The complicating factor with this event will be an increasing
northwest wind gusting over 35 mph, which will contribute to brief
periods of lower visibilities. Will continue to highlight this
potential in the Hazardous Weather Outlook and later shifts can
elevate messaging as needed. Fortunately, road temperatures
remain too warm for any significant accumulations. Sustained wind
speeds and gusts are expected to remain slightly below advisory
criteria.

Tonight, expect a clearing sky and a gusty northwest wind. Lows
will dip into the 20s, with wind chill values dropping into the
single digits and teens after midnight.

.LONG TERM...(Sunday through Friday)
ISSUED AT 330 AM CST Sat Nov 18 2017

Generally dry in the longer term with variable temperatures.
Sunday and Monday, dry northwest flow aloft will dominate the
central US. Warm low level advection Monday will push highs back
into the 50s. Tuesday, a dry cold front will bring another surge
of cold air, dropping highs back down in the 30s by Wednesday.

Next weather-maker is late Friday into Saturday as a cold front with
decent forcing crosses the midwest.  Have increased temperatures
Friday above guidance due to progged warm air aloft and strong warm
advection ahead of the front.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
ISSUED AT 1115 PM CST Fri Nov 17 2017

A passing cold front will keep mostly IFR/LIFR conditions through 18/16Z
with episodes of rain, drizzle, and fog and light northeast to north
winds increasing to 10 to 20 mph by 18/10Z. After 18/15Z, the rain
may mix with or briefly change to a wet snow at DBQ/CID/MLI terminals
until 18/18Z. Skies will clear by 18/20Z with VFR conditions and
windy NW winds of 20 to 30+ mph.

&&

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

$$

SYNOPSIS...RP Kinney
SHORT TERM...RP Kinney
LONG TERM...DMD
AVIATION...Nichols



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