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000
FXUS63 KDVN 201124
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
624 AM CDT Tue Apr 20 2021

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 217 AM CDT Tue Apr 20 2021

At 3 AM, yesterdays cold front is well south of the area along
the Missouri and Arkansas border. Mid level water vapor imagery
shows a shortwave moving into eastern Kansas. Regional radar
shows snow blossoming ahead of this shortwave across northern
Missouri into southeastern Iowa. At this time, weak returns on
the KDVN radar are mid level clouds with ceilings lowering across
the area. A frost advisory is in effect across the area along and
north of a line from Williamsburg Iowa to Mount Carroll Illinois.
Temperatures are in the 30s across the area this morning with the
coldest temperatures in the lower 30s along and north of a Cedar
Rapids to Clinton Iowa line.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 217 AM CDT Tue Apr 20 2021

The primary focus of the forecast are chances of precipitation
and type as well as temperatures. Models continue to trend to the
south and east with the better lift and moisture with Interstate
80 on the far northern end of the snow this morning.

Models continue to show increasing saturation south of a Fairfield
Iowa to Galesburg Illinois line this morning with snow
overspreading this area between now and 12 UTC. Lower confidence
in northern extent of precipitation this morning as precipitation
falls into a dry layer. Precipitation will begin as all snow this
morning or a rain and snow mix in west central Illinois and then
quickly change over to all snow. Snowfall amounts will be light
with around an inch of snow south of the Iowa/Missouri border with
totals quickly decreasing with a dusting along the Interstate 80
corridor. Precipitation will transition to a rain/snow mix along
interstate 80 by mid morning and then the rest of the CWA by 18
UTC. Rain showers are possible this afternoon with steep mid level
lapse rates overhead as the 500 mb trough swings across the area.
Precipitation will quickly come to an end this evening with some
lingering rain/snow mix in Bureau and Putnam Counties.

Attention then shifts to the freeze warning for Tuesday night into
Wednesday morning. One concern for the freeze warning going
forwardis the potential for lingering cloud cover across the
area which may limit temperatures from dropping to much in the
wake of todays storm system. Model guidance still has low
temperatures below freezing Wednesday morning and the current
forecast has low temperatures in the upper 20s which is 2 to 3
degrees of record low temperatures at KBRL(27, 1904), KDBQ 26,
1982 and other years), and KMLI (27, 1953 and other years).

.LONG TERM...(Wednesday through Monday)
ISSUED AT 217 AM CDT Tue Apr 20 2021

Key Messages:

*A widespread freeze is expected again Wednesday night into Thursday
morning.

*Much warmer temperatures are forecast by early next week.

Wednesday

After a cold start in the 20s and a widespread freeze, temperatures
will warm into the 40s for the afternoon. Diurnally driven
stratocumulus will quickly increase in coverage through the morning
as the boundary layer warms beneath very cold temps aloft (-20 C at
700mb). While the lower atmosphere will be very dry with dewpoints
in the 20s and teens, forecast soundings have up to a few hundred
J/kg of SBCAPE in the afternoon which will support isolated pop-up
showers.

The dry sub-cloud layer will greatly limit QPF potential. Areas that
have showers may only realize trace to a few hundredths of liquid.
Cold surface wetbulb temps could support a rain/snow mix or briefly
all snow within the strongest showers, even if ambient temps are in
the low/mid 40s prior to the arrival of a shower.

Cloud cover will rapidly decrease Wednesday evening and night as
high pressure sets up over the Midwest. The dry air mass, clearing
skies, and light winds will allow temps to drop back into the mid
20s to lower 30s overnight, resulting in another widespread freeze.
We`ll likely need freeze headlines for Wednesday night into Thursday
morning.

Thursday through Sunday

A persistent zonal flow is forecast through the upcoming weekend,
leading to slightly below normal temps in the 50s to lower 60s. The
next chance for rain (highest south of I-80) is from Friday
afternoon into Saturday morning as a cut-off 500mb low tracks from
Missouri into the Ohio Valley. At this juncture, models keep the
greatest moisture return and heavier rain south of the area.

Monday

A strong area of low pressure emerging out of the Central Rockies
into the Plains will bring breezy southerly flow to the Midwest,
ushering in much warmer temperatures. NBM highs are in the low 60s
in the northeast to low 70s southwest. Uttech

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
ISSUED AT 619 AM CDT Tue Apr 20 2021

IFR expected at BRL early this morning with steady light snow
dropping visibilities to around 1 mile and ceilings to the
MVFR/IFR threshold. A return to MVFR is forecast by this afternoon
as ceilings gradually improve and the precip shifts to the east.
At the other terminals, VFR will prevail today and tonight.

&&

.CLIMATE...
ISSUED AT 417 AM CDT Tue Apr 20 2021

Record Lows for April 21...

Moline.........27 in 1953
Cedar Rapids...23 in 1934
Dubuque........26 in 1982
Burlington.....27 in 1986

Record Lows for April 22...

Moline.........28 in 1986
Cedar Rapids...22 in 1986
Dubuque........25 in 1986
Burlington.....27 in 1986

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Frost Advisory until 8 AM CDT this morning for Benton-Buchanan-
     Cedar-Clinton-Delaware-Dubuque-Iowa-Jackson-Johnson-Jones-
     Linn.

     Freeze Warning from midnight tonight to 9 AM CDT Wednesday for
     Benton-Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-
     Henry IA-Iowa-Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-
     Linn-Louisa-Muscatine-Scott-Van Buren-Washington.

IL...Frost Advisory until 8 AM CDT this morning for Carroll-Jo
     Daviess-Stephenson.

     Freeze Warning from midnight tonight to 9 AM CDT Wednesday for
     Bureau-Carroll-Hancock-Henderson-Henry IL-Jo Daviess-
     McDonough-Mercer-Putnam-Rock Island-Stephenson-Warren-
     Whiteside.

MO...Freeze Warning from midnight tonight to 9 AM CDT Wednesday for
     Clark-Scotland.

&&

$$

SYNOPSIS...Cousins
SHORT TERM...Cousins
LONG TERM...Uttech
AVIATION...Uttech
CLIMATE...Cousins