Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 221307
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
807 AM CDT Fri Mar 22 2024

.KEY MESSAGES...

- A Winter Weather Advisory continues for Hwy 30 through Hwy 20
  corridors until 1 PM where a wintry mix to accumulating wet
  snow to provide travel impacts including for the morning
  commute.

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

&&

.UPDATE...
Issued at 804 AM CDT Fri Mar 22 2024

Overnight banded snow has come in with reports of 2-4 inches
from Linn county through Stephenson county this morning With the
ongoing heavy snow with rates of 1+/ hour, and another 4 hours
of that, we`re more confident on a narrow stripe of 6-8" snow
from Linn county through Freeport. This 30-50 mile wide stripe
should be much higher than locations farther north and south,
where advisory impacts remain forecast. A warning has been
issued for the heavy snow band through 1 PM. The southern edge
of the advisory has been pushed one county south as well.

ERVIN

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 345 AM CDT Fri Mar 22 2024

Water Vapor imagery shows a shortwave trough extending from
Minnesota to Colorado. This will continue to move southeast
and pass through the region over the next 12-18 hours.
Ramping H925 to H85 warm air advection is fostering an uptick
in coverage of showers, mainly north of I-80 currently. Have
noted some isolated lightning strikes with this activity with
the increasing ascent and steepening of mid level lapse rates at
or above 7C/km. Will see bands of warm advection precipitation
continue the next few hours focusing mainly north, with what can
best be described as a wintry mix of rain/sleet/snow as thermal
profiles change quickly over time. Persistent elevated
instability will continue to drive a convective nature to the
precipitation with some thunder.

In time, a strengthening mid level frontogenetical band will
lead to a more prevalent convective wintry mix north through
daybreak, that will be followed up by a more robust oriented
NE-SW band of precipitation sweeping southeast across much of
the service area after 12z-14z through 21z along and behind a
passing surface trough. This peak of forcing will be aided by
upper divergence with the passing of the right entrance region
of a jet streak shifting across the Upper Midwest and Great
Lakes, and continued elevated instability. This looks to support
a band of accumulating wet snow in our northern service area
aided by evaporational cooling with temperatures dropping down
near the freezing mark during the peak of the snow. Recent Hi-
res guidance has shifted the main axis of the snow a bit further
south through the Hwy 20 corridor where the 00z HREF guidance
has 70%+ probabilities of snowfall rates of 1" or greater per
hour. Current forecast has 2-5 inches of snow along/north of Hwy
30 with those higher amounts along Hwy 20. Due to the
convective nature can`t rule out some isolated pockets of 6+
inches far north, but the signal in the hi-res guidance looks to
support this being fairly narrow and/or isolated and thus the
limited coverage and confidence leads to a continuation of the
Winter Weather Advisory at this time. In addition, the
convective nature will likely lead to rather variable amounts
over short distances, and in these strong Fgen bands there also
tends to be a sharp cutoff to the snow amounts on the southern
edge.

Further south of Hwy 30 through I-80 expect rain mixed with
sleet, but then extrapolation of the convection over Nebraska
would support some of the more recent Hi-res solutions
indicating a transition to all snow for a time further south
down through the I-80 as the strong bout of forcing sweeps
through mid morning through early PM. Warmer temperatures
should limit accumulations (mainly an inch or less), but could
see some impacts mostly due to lower visibility. Even further
south of I-80 expect mainly rain showers with some thunder, with
a brief transition to a mix of snow not out of the question down
to near Burlington. All of this precipitation should come to an
end from northwest to southeast by late morning through late
afternoon.

After this, expect a mix of clouds and stars for tonight and
colder lows ranging from the teens north to the mid 20s south.
Brisk northerly winds will make it feel even colder and more
like the single digits and teens overnight.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 345 AM CDT Fri Mar 22 2024

Saturday...Upper MS RVR Valley high pressure to maintain a dry but
coolish day through Sat evening with below normal highs in the
mid 30s to mid 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
and Sunday night, with it possibly being wet snow or rain-snow
mix with some snow acumms possible on grassy-elevated sfc`s (WPC
24 hr probabilities of an inch or more of snow ending 12z
Monday is 40-60% northwest of a Vinton to Independence line).

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.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 530 AM CDT Fri Mar 22 2024

Warm advection bands of a wintry mix (rain/sleet/snow) and bouts
of MVFR to IFR conditions to focus primarily at the northern
TAF sites (CID, DBQ) over the next couple of hours before
becoming predominantly a wet snow by 14z and continuing until
18z. Conditions are favorable for moderate to heavy snow with
snowfall rates 1 inch or more per hour at times resulting in
periods of LIFR/VLIFR conditions, likely (70%) at DBQ with a
chance (30-50%) at CID. This could also be accompanied by some
thunder. Accumulations due to the banding and convective nature
could vary greatly over short distances and range from an inch
or less to upwards of 5-6 inches. Still some uncertainty on where
the heavier band sets up.

Elsewhere at MLI and BRL, showers of rain and possibly a mix
with sleet with MVFR to VFR conditions this morning look to
transition to a burst of snow for 1-2+ hours between 16z and
20z before ending. There is a chance (20-40%) for thunder. This
will lead to likely (60-70%) periods of IFR to LIFR
visibilities and minor accumulations on grassy and elevated
surfaces.

Conditions are expected to improve to MVFR and VFR after 23z
through 06z from north to south. Winds will remain gusty at
times at 10-20+ kt during the period shifting from E/NE this
morning to N/NW this afternoon.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory until 1 PM CDT this afternoon for
     IAZ040-041-051-063>066.
     Winter Storm Warning until 1 PM CDT this afternoon for IAZ042-
     052>054.
IL...Winter Weather Advisory until 1 PM CDT this afternoon for
     ILZ009.
     Winter Storm Warning until 1 PM CDT this afternoon for ILZ001-
     002-007.
MO...None.

&&

$$

UPDATE...Ervin
SHORT TERM...McClure
LONG TERM...12
AVIATION...McClure


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