665
FXUS63 KDVN 121617
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1017 AM CST Wed Feb 12 2025

.KEY MESSAGES...

- No headline changes are planned with this forecast issuance.
  Impactful snow is on track to fall across the area into
  Wednesday night. Widespread snowfall totals of 4 to 6 inches
  across the area with totals over 6 inches possible northwest
  of a Iowa City to Dubuque line. In addition to the snow, gusty
  winds will cause some blowing and drifting snow through
  Wednesday night.

- Another storm system is forecast to impact the area Friday
  night into Saturday and bring wintry precipitation to the
  area.

- An active weather pattern continues across the region through next
  week.

&&

.UPDATE...
Issued at 1017 AM CST Wed Feb 12 2025

Ongoing snow storm expected to continue through the day. Band of
snow ahead of 12z today dropped more snow than expected from
Iowa City up through Bellevue, IA. Upwards of 4 inches of snow
was reported from this band. This morning, increased forcing
lead to snow overspreading the entire area. Soundings depict a
very deep DGZ, 2600m according to the SPC mesoanalysis. This
deep DGZ is leading to dendritic snow fall. Under the heaviest
band, 1/4sm was reported with snowfall rates around 1.5 inches
an hour. This band has currently weakened as transient FGEN has
moved out of the area this morning. The deep DGZ is the name of
the game for this event. Wherever it intersects with forcing we
will see good dendritic snow and rapid snowfall accumulations.

The rest of today, it appears that we loose forcing in the DGZ
around lunchtime, especially along and south of I-80. Snowfall
rates should drop. North of I-80 periods of heavy snow will
continue, while more transient in nature. This will give the
false impression of the event coming to an end. However, what
we expect is more forcing to move into the area this afternoon.
The deep DGZ remains through the afternoon as the forcing
increases. This will lead to heavy snow like this morning across
most of the area. This will be timed well to affect the evening
commute across most of the area.

Overall, additional snowfall totals of 4 to 8 inches are
possible from Iowa City to Freeport. Elsewhere could see 2 to 5
more inches. In the heaviest band, overall snowfall totals over
10 inches seem likely. This looks to be from Freeport, IL
through Iowa City.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 221 AM CST Wed Feb 12 2025

Regional radar shows snow across eastern Iowa and northwest
Illinois early this morning with an almost continues band
stretching from MOunt Carroll southwestward to Des Moines then
into central Nebraska. Snowfall amounts up to 1 inch are
possible through sunrise across the area with the highest
amounts along northwest of line from Cedar Rapids northeastward
to Mt Carroll.

A large area of snow is developing across Kansas associated with a
shortwave moving into western kansas and Oklahoma at this time.
Models continue to show the associated vort lobe moving
northeastward this morning and into eastern Iowa by 12 UTC with
the onset of widespread light to at times moderate snowfall
across the region. This snow is expected to continue into
Wednesday night before coming to an end from west to east by 9
UTC or 3 AM. The SREF has backed off on snowfall rates through
the event with rates peaking at around a half an inch an hour.
Model generated liquid precipitation has decreased to roughly
0.20 to 0.40 inches across the area with the highest amounts
north of Highway 30. Model sounding profiles especially in the
NAM have warmed for KBRL and KMLI making them less efficient at
producing snow crystals and lowering the snow to liquid ratios
south of Interstate 80. However SLRs across the area remain in a
14:1 to roughly 18:1 from south to north. This will still be a
dry snow across the area. This has worked to reduce snowfall
totals slightly from previous forecast across the southern part
of he forecast area. The highest probabilities for snow
accumulations remain in the 4 to 6 inch range across most of the
area with slightly lower totals in west central Illinois and
higher totals northwest of a Iowa City to Dubuque line were
totals may be closer to 6 inches with higher amounts over 7
inches possible. It will be breezy through the day with
sustained speeds of 10 to 15 MPH and gusts up to 20 MPH that
will increase to 25 MPH this evening. This will lead to some
blowing and drifting snow especially in open area.

Skies are slower to clear once precipitation comes to an end but it
will still be cold across the area on Thursday morning. Low
temperatures Thursday morning will be in the single digits above
zero with a chance for below zero lows west of a Cedar Rapids to
Manchester line. Winds will remain breezy through sunrise Thursday
with wind chills in the teens below zero  west of a Fairfield
to Tipton to Dubuque line. Have decided to not issue a Cold
Weather Advisory at this time but it will still be very cold
Thursday morning.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 221 AM CST Wed Feb 12 2025

Thursday through Friday morning: Arctic high pressure will settle
across Iowa and Illinois bringing mostly clear and dry conditions.
However, temperatures will be very cold (given the fresh snow
cover!) with highs struggling to reach the teens and lows in the
single digits below and above zero. Wind gusts up to 25 MPH
will linger into Thursday morning across eastern Iowa producing
wind chills in the teens below zero west of the Mississippi
River.

Friday afternoon though Saturday night: By Friday afternoon the high
pressure will slip into the Ohio Valley with moisture returning on
the backside of the high. Meanwhile, a deep trough will progress out
of the Rockies and into the Midwest. Deterministic models track a
strengthening surface low from the southern Plains to the Ohio
Valley. This will spread at least shovelable snow of several inches
across the entire forecast area during this time-frame. Exact
amounts and location of the heaviest snow still to be determined as
this is still several days out. Temperatures will be warmer with
highs in the upper 20s to lower 30s. The warmer temperatures
Friday night into Saturday may lead to periods of a snow,
freezing rain or sleet mix.

Sunday through Tuesday: Global models indicate a persistent deep
trough in the middle of the country with a ridge along the West
Coast.  This fits with the teleconnections as the Arctic Oscillation
(AO) goes sharply negative while the Pacific-North American (PNA)
goes somewhat positive. This will keep the arctic air mass locked in
place across our area. Highs will be in the single digits and teens
with lows around 10 below to the single digits below. Once again,
these readings may not be cold enough depending on how deep the snow
pack will be at the time. The pattern remains active next week but
low confidence in the track of potential winter storms.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 523 AM CST Wed Feb 12 2025

A storm system will continue to bring light to moderate snow to
eastern Iowa TAF sites through at least 03 UTC on Thursday.
Conditions are currently VFR at KDBQ, KMLI, and KBRL with MVFR
ceilings at KCID with IFR visibilities in light snow.
Conditions are forecast to quickly deteriorate at all TAF sites
through 15 UTC as snow develops across eastern Iowa. MVFR to
IFR ceilings are forecast with IFR visibilities to periods LIFR
visibilities in moderate snow through the morning hours. Snow
will come to an end from west to east after 06 UTC at all TAF
sites. Expect north winds of 10 to 15 knots continue through the
TAF period with gusts up to 25 knots possible after 00 UTC
through the end of the period.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Storm Warning until 3 AM CST Thursday for IAZ040>042-
     051>054-063>068-076>078-087>089-098-099.
IL...Winter Storm Warning until 3 AM CST Thursday for ILZ001-002-
     007-009-015>018-024>026-034-035.
     Winter Weather Advisory until 3 AM CST Thursday for ILZ002.
MO...Winter Storm Warning until 3 AM CST Thursday for MOZ009-010.

&&

$$

UPDATE...Gibbs
SHORT TERM...Cousins
LONG TERM...Haase
AVIATION...Cousins