Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 160530

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1130 PM CST Thu Feb 15 2018


Issued at 330 PM CST Thu Feb 15 2018

Latest sfc analysis was indicating initial front and wave pushing
acrs the far southeastern CWA ATTM...with the real cold push and
north-northwest wind surge noted further off to the northwest acrs
central NE, up along the IA/MN border and then toward Green Bay.
This system to eventually scour out the clouds and moisture by
Friday, with a chill down for the end of the week. Then a passing
trof may produce a minor snow event for Saturday, before
southwesterly pattern amplification acrs the mid CONUS may bring
about an unseaonably moisture surge from the south by early in the
week fueling rain and possible thunderstorms.


.SHORT TERM...(This Evening through Friday)
ISSUED AT 330 PM CST Thu Feb 15 2018

Tonight...The secondary and main cold front noted above will surge
down through the region this evening, leading to brisk north-
northwesterly 15 to 25 MPH sfc winds overnight. Extent of cold air
advection by this cooling/deepening LLVL flow to bring about a large
range/gradient of low temps acrs eroded snow cover by Fri morning
from NW-to-SE, generally from upper single digits to low 20s. The
race will be on for northwest winds to dry pavement made wet by
recent snow melt, before it freezes again making for some localized
slick spots. Think there will still be some lingering puddles and
wet areas that freeze up later tonight and may mention this in the
HWO. Steering west-southwesterlies aloft over incoming southeastern
flank of sfc ridge, will continue to advect high clouds acrs much of
the area overnight until clearing from the northwest toward dawn.
How much elevated moisture it will have to work with at question,
but embedded short wave trof in this flow aloft will propagate right
acrs the CWA from 06z-12z Fri. Depending on deepening post-frontal
northerly llvl flow, this wave may produce a band of light snow or
flurries acrs at least the southern third of the DVN CWA after
midnight into early Fri morning. Currently expect at worst a
dusting, and much of it may have trouble reaching the surface.

Friday...Continued clearing, brisk and colder this day as high
pressure gradient continues build down acrs the area. Despite
increasing sunshine and eroded snow cover in spots, Friday afternoon
highs may not recover all that much from morning lows, many areas
ranging from the mid 20s to near 30. The lingering deeper snow cover
areas of the north may have trouble getting out of the low to mid
20s. The sfc winds will look to relax by mid afternoon though, as
the upstream ridge center slides right acrs the CWA.  ..12..

.LONG TERM...(Friday Night through next Thursday)
ISSUED AT 330 PM CST Thu Feb 15 2018

The main forecast issues in the short term period are a minor
precipitation event on Saturday, followed by a more potent system
early next week.

Friday night: Questions linger as to the remaining snow cover after
a recent warm period. Given today`s snow depth data and forecast
temperatures through Friday, the north will be favored for single
digit readings, with teens to low 20s south of I-80 where any
snowpack will be negligible.

Saturday: A weak trough will traverse the forecast area, bringing
some light snow or a rain/snow mix to portions of the area.
Accumulating snow, from a light dusting to around an inch, is
favored north of Interstate 80, with little or no snow along and
south of I-80.

Sunday: Strong WAA will return, boosting afternoon highs into the
40s and low 50s and setting the stage for a period of active weather.

Sunday night through Monday: The initial wave of WAA precipitation,
mainly in the form of rain will spread into the area late Sunday
night. Synoptic scale models still show some differences in the
storm path/timing on Monday, but there are enough similarities to
raise some red flags concerning the potential for pockets of heavy
rain and thunderstorms. Blended temperature guidance call for highs
into the 60s across the south as the warm sector advances well into
the forecast area. The GFS indicated PWAT values over 1 inch.
Rainfall amounts approaching an inch over frozen ground could result
in substantial runoff and some flooding concerns. Both the GFS and
ECMWF would be problematic in terms of thunderstorms interacting
with a warm front with sufficient deep layer shear and some weak
surface based instability. The probability for ingredients to gel
just right for severe storms in late February is low, but we will
need to watch the potential closely through the weekend. By Monday
night, snow may be favored in eastern Iowa, with continued rain in
northwest Illinois.

Tuesday: The ECMWF continues to hold up the boundary compared to the
faster GFS and would favor additional accumulations along/west of
the Mississippi. Confidence in forecast details for the period is
still relatively low. Right now, the balance tips toward locally
heavy rain and thunderstorms rather than significant snow, but that
could change.

Wednesday and Thursday: Expect mainly dry conditions and seasonal


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1121 PM CST Thu Feb 15 2018

A period of MVFR ceilings of 1500-3000ft agl is likely at CID, DBQ
and BRL overnight, and possible at MLI but too much uncertainty
to include. Some flurries may also accompany the low clouds. VFR
conditions will then return late tonight and early Friday, and
remain through the rest of the TAF cycle as high pressure builds in.
Gusty NW winds 15-25 kts will diminish to below 10 kts during the
afternoon, then turn southerly Friday evening as the high begins to
move away.




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