Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 212013
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
313 PM CDT Thu Mar 21 2024

.KEY MESSAGES...

- A winter weather advisory continues for the Highway 20
  corridor for 1 AM to 1 PM Friday.

- A wintry mix and accumulating snow is expected late tonight
  through Friday north of Highway 30. Snow amounts of 2 to 5
  inches are expected along and especially north of Highway 20.
  Snowfall rates of 1 to 2 inches per hour are expected between
  8 and 11 AM, creating slick spots on roads and sidewalks
  during the morning commute. A mix of rain, sleet and snow
  will be possible between Highway 30 and Highway 20.

- Rain is expected south of Highway 30 tonight through Friday
  AM, with surface and road temperatures remaining above
  freezing.

- Active weather is expected again Sunday through Tuesday
  morning, with widespread precipitation and strong winds.


&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 226 PM CDT Thu Mar 21 2024

Tonight, the strong clipper system is still on track to move
into the central Plains late this evening. It will quickly move
east across Iowa and northern Illinois overnight and Friday
morning. A warm advection wing of precipitation is expected to
track along the Highway 20 corridor, mainly snow, about 10 PM
to 2 AM as has been indicated by the HRRR over past several
runs. After a bit of a lull, stronger forcing along with upper
level support is expected to move across the area after 3 or 4
AM with a mix and snow dropping south into the CWA. It will
quickly change to all snow along the highway 20 corridor. The
snow rates may be 1 to 2 inches an hour briefly for an hour or
two along Highway 20 during the 7 am to 11 am time. The rain
snow mix will be between highway 30 and highway 20, with just
rain south. Snowfall accumulations of 2 to 4 inches are expected
along Highway 20 with the higher totals north. The bulk of the
precipitation will fall during the morning hours. It will
gradually end from northwest to southeast during the late
morning and through the afternoon hours. Through collaboration,
lowered SLRs a bit into the 6:1 to 9:1 range. This will be a
heavier wet snow with potential for heavy snow rates as well.
The liquid totals for this event will range from around a third
of an inch to near 0.6 inches northwest of a line from
Sigourney, IA to Mt Carroll, IL. To the SE of that line amounts
quickly taper off to a tenth to a quarter inch. Lows tonight
will be in the upper 20s to mid 30s, with highs Friday getting
into the upper 30s and low 40s north to the mid 40s to low 50s
south of I 80 and even some mid and upper 50s in the far
southeast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 226 PM CDT Thu Mar 21 2024

Saturday...Upper MS RVR Valley high pressure to maintain a dry but
coolish day through Sat evening with sub-normal highs in the 30s to
low 40s. The first wing of elevated return flow/WAA aloft still on
track to sweep acrs the CWA with southwesterly LLJ flow Sat night
into early Sunday morning. This wing will look to produce a band of
light snow that may do a dusting up to half inch of snowfall acumms
acrs the northwest third to half of the DVN CWA.

Sunday...Increasing pressure gradient to the northeast of southwest
plains cyclogenesis to lee of the approaching upper L/W trof axis to
induce windy conditions acrs the area. Southeast fetch will lead to
a slightly warmer day than Saturday, with precip and top-down
saturation robbing from the warm up potential. More of an organized
elevated warm air advection(WAA) surge should drive some precip acrs
western and northern portions of the fcst area by Sunday afternoon,
with it possibly being wet snow or rain-snow mix with some snow
acumms possible on grassy-elevated sfc`s(Ensemble 50-60th
percentile) has 1-3 inches of wet accum acrs the northwest third or
so of the CWA by Sunday evening. Impressive warm moist conveyor
signal still there as the upper trof shears acrs the northern plains
and MO RVR Valley through Tuesday morning. But the models continue
to slow the progress of such a large synoptic scale feature, with
Sunday night now appearing to be windy, warming(not much temp drop-
off) with isolated to sctrd showers and possibly a thunderstorm
racing north acrs the area into Monday morning.

Monday and Tuesday...With current ensemble timing of the medium
range models, the pre-trof conveyor of showers with even a little
embedded thunder should be realized Monday acrs the area by midday.
Strong south to southeasterly LLVL wind fields and shear, along with
ambient temps in the 50s and 60s with sfc Dpts upper 40s to low
50s may be enough for at least a limited severe storm risk. It may
have to wait until the arrival of the in-wrapping dry slot into the
back of the system Monday afternoon or evening for a wing/line of
low-topped supercells scenario. A lot of timing and evolution
uncertainty at this juncture still with this potential. The higher
rainfall axis`s now may lay out northwest and off to the east of the
local fcst area, but warm moist conveyor feed up off the Gulf still
could produce significant rainfall close to home by Tuesday.
Tuesday still looking like a mainly dry slot windy cooling day in
the wake of the occluding cyclone complex acrs the northwestern GRT
LKS.

Wednesday and Thursday...Between system`s upper ridging will look to
bring about a bit of a mid week reprieve with moderating temps, but
another eastern Pacific upper low will look to make strides inland
and eventually approach the Midwest somewhere  by late week into the
start of next weekend.    ..12..

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1255 PM CDT Thu Mar 21 2024

Mid deck with some embedded non-consequential flurries this
afternoon with east winds of 5-10 KTs. Tonight, still a
challenging fcst walking in a rather vigorous clipper system
with an associated precip shield. The precip may not make it to
MLI and BRL until mid Friday morning...mainly rain and MVFR
conditions at BRL and possible rain-snow-sleet mix at MLI after
10 AM. The DBQ site will look to be the most impacted with a
wintry mix changing over to a heavy wet snow by 12-13z or so.
The most intense snowfall rates at over an inch and hour and
doing accumulation/low VSBY restrictions will look to occur
from around 8 AM to 1100 AM or so Friday morning. Sharp snowfall
gradient to the south and CID may only experience light snow or
rain-snow mix getting more widespread from 11-12z Fri and on
into the morning. Another factor to complicate things, is enough
elevated instability to produce some isolated lightning
flashes/thunder acrs much of the area late tonight and
especially on Friday.   ..12..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory from 1 AM to 1 PM CDT Friday for
     IAZ040>042.
IL...Winter Weather Advisory from 1 AM to 1 PM CDT Friday for
     ILZ001-002.
MO...None.

&&

$$

SHORT TERM...14
LONG TERM...12
AVIATION...12


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