Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 221128

Area Forecast Discussion
National Weather Service Quad Cities IA IL
628 AM CDT Thu Mar 22 2018


Issued at 345 AM CDT Thu Mar 22 2018

At 3 AM CDT, the region is under clear skies with clouds and some scattered
light rain and snow now moving east into Central Iowa. Temperatures
with light winds and weak high pressure have fallen mostly into the
20s with isolated upper teens noted. Satellite supports radar and observations
of some clouds to arrive later this AM with some light rain and possibly
mixed this AM with wet snow in SW sections of the forecast area with
little or no accumulations. A disturbance moving into California will
arrive Friday and Saturday with significant amounts of snow and rain
with a watch being hoisted over the northern 2/3 of the area.


.SHORT TERM...(Today and Tonight)
ISSUED AT 345 AM CDT Thu Mar 22 2018

Short term forecast confidence assessment...good or above average with
minor sensible weather issues. Any light precipitation amounts should
be mostly rain or mixed wet snow with no accumulations. Temperatures
today and tonight should be mostly within 3 degrees of forecast with
clouds making for warmer lows then tonight.

Today...increasing clouds with mostly cloudy skies and scattered light
rain and possibly rain/wet snow with mostly trace to a few hundredths
of an inch expected in SW 1/3 of the area. High today should be in the
upper 40s to lower 50s with light winds.

Tonight...mostly cloudy SW to partly/mostly clear NE with mins mostly
25 NE to around 35 SW and possibly few degrees higher or lower depending
on cloud cover tonight. Winds should become light northeasterly.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 345 AM CDT Thu Mar 22 2018

Friday and Saturday

Issued a Winter Storm Watch for Friday Night through early
Saturday afternoon for part of the northern and central forecast
area. Heavy wet snow with snowfall rates peaking between 1-2
inches per hour combined with easterly wind gusts of 30-35 mph
will make for very dangerous travel conditions. Please refer to
the Winter Storm Watch text for location specific details. Decided
not to include Stephenson County in the Watch at this time
because I have lower confidence on heavy precipitation reaching
that part of the CWA.

Marginal surface temperatures (near freezing) and a sharp heavy
to light precipitation gradient will cause snowfall amounts to
vary considerably - even over individual counties. The current
forecast has a broad swath of 5 to 8 inches of snow, but a narrow
band of 8-10 inches is certainly possible. The most recent NAM has
around 12 inches within the heaviest band - do not have the
confidence to go that high right now. Models are starting to show
elevated instability in the form of low MUCAPE, so later shifts
will have to reassess convective potential.

Setup and Confidence:

A slow moving, neutrally tilted trough will exit the Four Corners
region on Friday, pulling anomalously high PWATs of around 1 inch
into Iowa and Illinois. Low-level mass fields depict an
impressive connection to the Western Gulf, which is corroborated
by model forecasts of significant northward 850mb WV transport.
Although the surface low is not expected to be very strong (above
1000mb), deep tropospheric moisture coupled with moderate to
locally strong forcing will result in widespread precipitation.
The aforementioned moisture and ascent driven by a coupled jet and
eventually convergence/frontogenetic response from a 850-700mb
TROWAL feature, increases confidence for significant precipitation
across parts of the CWA with up to 1 to 1.5 inches locally.

Potential Impacts:

Main concerns are very hazardous travel conditions and possibility
for sporadic power outages if the weight of the wet snow combined
with the strong wind gusts were to bring down tree branches.

Sunday on

The remainder of the extended forecast largely follows the model
blend. Active weather is expected into early next week with good
chances for rain. Uttech


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
ISSUED AT 626 AM CDT Thu Mar 22 2018

VFR conditions to prevail through the period with mostly fair
skies early becoming mostly cloudy by afternoon with mid to high
clouds. Winds will be light and favor the north this morning
becoming easterly this afternoon and tonight.


IA...Winter Storm Watch from Friday evening through Saturday
     afternoon for Benton-Buchanan-Cedar-Clinton-Delaware-

     Winter Storm Watch from Friday evening through Saturday
     afternoon for Johnson-Muscatine.

IL...Winter Storm Watch from Friday evening through Saturday
     afternoon for Bureau-Carroll-Henry IL-Jo Daviess-Putnam-
     Rock Island-Whiteside.




LONG TERM...Uttech
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