Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 230817

Area Forecast Discussion
National Weather Service Quad Cities IA IL
317 AM CDT Fri Mar 23 2018

Issued at 315 AM CDT Fri Mar 23 2018

1044 mb high was centered at the southern end of Hudson Bay ridging
into the Upper MS Valley and Great Lakes region. Early morning
temperatures were in the 20s in those areas, with readings in the
dvn cwa ranging from the mid 20s north to the upper 30s south.

Meanwhile, low pressure was organizing in the central Rockies with a
stationary front that extended across northern KS into sw MO.
Dewpoints were in the 50s across Texas with a stiff south wind.


.SHORT TERM...(Today)
ISSUED AT 315 AM CDT Fri Mar 23 2018

Forecast focus on rain spreading into our southern cwa this

Today: Dry this morning but rain should spread eastward into the sw
half of the cwa during the afternoon. This will be occurring as low
pressure moves into western KS with a strengthening southwest LLJ.
This is expected to bring stronger forcing/isentropic upglide and
increasing moisture into the cwa. Forecast soundings indicate PWAT`s
increasing to nearly one inch by the end of the day in our southern
counties. Rainfall amounts should be less than 1/4 inch for today.
Highs will range from the mid 40s to lower 50s.

.LONG TERM...(Tonight through Thursday)
ISSUED AT 315 AM CDT Fri Mar 23 2018

Extremely dynamic, strong, early spring winter storm, a very
challenging forecast tonight and Saturday with heavy snow a
certainty with exact locations still an issue.

Long Term Forecast Assessment...average to below average with near
to below average confidence due to very strong evaporative cooling
expected to occur with this storm.  This will likely make many
locations snow totals off by 3 plus inches depending on snow
changeover. Thunder-snow very likely with accumulation rates well
over an inch an hour at times. Heavy snowfall rates will also result
on snow covered adn slushy roads with risk of heavier snow access
maybe 30 plus miles further south for later shift to reassess.

Tonight...bands of rain to mix with and change to snow over most of
the northern 1/2 or more of the region in the evening hours. As
mentioned above, the locations for heavy snow will be a major
challenge with large dendritic growth in strong forcing and thunder-
snow almost guaranteed up to I-80 suggested. Half dollar sized
flakes will be not uncommon with snowfall accumulation rates of a
half inch to well over an inch an hour.  Locations along and north
of I-80 should have mostly 2 to 7 inches of snow by daybreak with
east winds of 20 to 30+ mph. Limited blowing snow suggested due to
low snow ratios of 7 to 10 to 1. Mins tonight around 30F north to
upper 30s far south.

Saturday...Snow line to slide further south with evaporative cooling
continued heavy snow rates and again risk of thunder-snow into late
morning hours. Additional snow totals of 2 to 6 inches suggested,
mostly before 3 PM. Again gusty easterly winds of 20 to 30+ mph and
some drifting of heavy wet snow to be likely with roads poor due to
intense snowfall rates of slush and snow. Very possible the highway
34 corridor in Iowa and south may need at least an advisory for
later shifts to monitor. Highs will be in the mid to upper 30s with
roads likely improving with diminishing snow by late afternoon.
Forcing tools suggest widespread 6 to 12 inches of snow in warning
locations with isolated 15 plus inches a real possibility. The
heaviest snow axis is currently suggested to be between Independence
Iowa to Clinton Iowa to Princeton but local forcing tools again with
strong evaporative cooling suggest this axis could move further
south by 30 miles or maybe even more.

Saturday night...becoming fair and cold with lows in the 20s with
likely mins in the teens and maybe even colder in areas that receive
5 plus inches of snow for later shifts to reassess.

Sunday...fair and seasonably cold with highs and lows mostly in the
40s and 20s.

Monday and Tuesday...risk of some mixed precipitation early,
becoming all rain with good southerly winds. Highs mostly in the 50s
and lows in the 40s.

Wednesday through Friday...near seasonal temperatures and dry
which is highs upper 40s to mid 50s and lows upper 20s to mid 30s.


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1135 PM CDT Thu Mar 22 2018

VFR conditions to persist into Friday afternoon, with light and variable
winds shifting from E/NE and increasing to around 10 kts. Friday afternoon
and evening will start to see precipitation make gradual inroads into
the terminals ahead of an approaching system. Drier air and slowing
of the system will likely bring arrival by mid to late afternoon
at CID and BRL and evening at MLI with DBQ quite possibly staying
dry until very late in the TAF period. Expecting precipitation to
be rain at BRL where potentially more showery with low potential
of thunder, thus conditions likely varying between VFR to bouts of
MVFR/IFR in the stronger showers. At CID and MLI, evaporational
cooling on strengthening easterly flow should allow for the rain
to mix or change to snow by late evening with conditions becoming
MVFR to IFR. Winds by Friday evening will be easterly and gusty at
15-25 kts.


IA...Winter Storm Warning from 7 PM this evening to 7 PM CDT Saturday
     for Benton-Buchanan-Cedar-Clinton-Delaware-Dubuque-Jackson-

     Winter Weather Advisory from 10 PM this evening to 7 PM CDT
     Saturday for Iowa-Johnson-Louisa-Muscatine.

IL...Winter Storm Warning from 7 PM this evening to 7 PM CDT Saturday
     for Bureau-Carroll-Henry IL-Jo Daviess-Putnam-Rock Island-

     Winter Weather Advisory from 7 PM this evening to 7 PM CDT
     Saturday for Stephenson.

     Winter Weather Advisory from 10 PM this evening to 7 PM CDT
     Saturday for Mercer.



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