Special Weather Statement, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
654 PM CDT Sun Oct 10 2021

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 310 PM CDT Sun Oct 10 2021

Occluded low pressure along the ND/MN border has a quasi-
stationary frontal boundary draped eastern MN to central IA to
another low in the TX panhandle. Ahead of the front, temperatures
were in the 80s with dewpoints well into the 60s, but only in the
40s under the occluded low in eastern Dakotas.

A band of light rain extended from southern IA to southern WI.

&&

.SHORT TERM...(This Evening through Monday)
ISSUED AT 310 PM CDT Sun Oct 10 2021

Tonight: There may be a few thunderstorms this evening but the
strong forcing arrives after midnight. CAM's consistent on
bringing a widespread rain/embedded thunderstorms spreading
quickly from south to north across the dvn cwa. Surface low
pressure and accompany potent upper level trough will be
responsible for this pcpn. Can't rule out isolated elevated hailers.
In the meantime, the cold front to our west will make progress
into our western cwa switching winds there to the northwest.
Lows should range from the mid to upper 50s west, to the mid 60s east.

Monday (Columbus Day): Compact/potent storm system is then
"crowbarred" northward into Eastern IA due to major trough pushing
eastward into the Rockies (old Henry rule). The ECMWF/GFS take
the surface low northward along the MS River during the afternoon,
while the NAM has low farther west near Independence, IA.
Shear/SRH will be quite strong with the potential for strong to
severe thunderstorms. SPC has for now a slight risk from extreme
eastern IA and points east. While the main threat looks to be
damaging wind due to the strong wind field in the column, can't
rule out a couple of tornadoes with just enough CAPE. The
NAMNEST/HRRR indicate a line of strong to possibly severe storms
in the morning, with another arching line along a dry slot in the
afternoon. This will be interesting to see how this pans out but
one key is amount of sunshine and resulting instability, which
will then determine the strength of the storms. Highs will range
from the mid 60s west to the mid 70s east. South winds will also
be gusting to at least 30 mph especially along and east of the MS River.

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 310 PM CDT Sun Oct 10 2021

Key Messages:

1. There is little change in the forecast through the long term
period.

2. An active pattern will be in place across the Upper Midwest
through Friday with chances of showers and storms about every other
day.

3. Temperatures will be near to slightly above normal through the
period. Temperatures by next weekend will be cooler and near normal
for the middle of October.

The negatively tiled 500 mb shortwave trough from Monday will be
exiting from eastern Iowa and northern Illinois into Wisconsin
Monday night along with its attendant surface low. Scattered showers
and storms will be exiting north of Highway 20 corridor after
midnight. In the wake of this storm system, 500 MB ridging at the
surface and aloft will move across the area for Tuesday. bringing
tranquil weather to the region. Skies will quickly clear from
southwest to northeast prior to sunrise on Tuesday with sunny skies
through the day.

A very dynamic system over the Rockies Tuesday night will begin to
lift northeastward and into eastern North Dakota by 00 UTC Thursday.
This storm system is vertically stacked with the surface low nearly
underneath the upper level closed low. This storm systems will bring
multiple rounds of showers and  thunderstorms to the area Wednesday
into Wednesday night as multiple pieces of vorticity rotating
around this upper level move across the region. Models
have come into better timing of the front to later on Wednesday
evening. The amount of shower and thunderstorm activity early in the
day may work to inhibit and destabilization that would occur and
thus limiting the severe potential. However, models continue to show
a few hundred J/KG of CAPE along with 30 to 40 knots of shear
meaning that some severe storms will be possible in a high shear and
low CAPE environment. In addition to the precipitation, the pressure
gradient will increase as the storm system moves to our northwest
with a broad pressure rise and fall couplet moving across the area
into Wednesday night. This will result in breezy conditions across
the area through the day with winds of 20 to 30 MPH.

The storm system in North Dakota will continue to occlude as it
lifts into southern Manitoba and Ontario Wednesday night into
Thursday as a deep trough moves into the Plains. The base of this
trough digs into New Mexico by 00 UTC Thursday before continuing
eastward. Another shortwave within the trough will eject into
central Missouri and Illinois late Thursday night with the potential
for overrunning rain showers spreading northward across eastern
iowa, northwest Illinois and far northeast Missouri through the day
on Friday before the trough axis shifts to the east on Saturday.

In the wake of this storm system, high pressure is progged to build
into the Southern Plains at the surface with a cooling northwesterly
flow across the Plains with temperatures more typical of the middle
of October with highs in the lower to mid 60s and low temperatures
in the lower to mid 40s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
ISSUED AT 655 PM CDT Sun Oct 10 2021

A gradual reduction in flight categories is expected through the
period as moisture continues to flow into the area. The next 6 to
12 hours is expected to remain VFR with some possible MVFR
showers through daybreak. Slght chance for some thunder as well,
and will be monitoring for potential TEMPOS. Otherwise, expect low
MVFR or IFR by tomorrow late AM.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

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

Hazardous Weather Outlook...CORRECTED
National Weather Service Quad Cities IA IL
1229 PM CDT Sun Oct 10 2021

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-111730-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
1229 PM CDT Sun Oct 10 2021

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...THIS AFTERNOON AND TONIGHT

This afternoon, isolated thunderstorms will bring a risk for
lightning and brief heavy rain.

Tonight: There will be a few thunderstorms this evening, then rain
and embedded scattered thunderstorms are expected after midnight.
Locally heavy rainfall and isolated large hail is possible tonight.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

Monday: There is a slight risk for severe thunderstorms east of a
Galena, Illinois to Kahoka, Missouri line. Several rounds of
thunderstorms are likely, with severe storms possible. The main
risks will be damaging winds and a couple of tornadoes. Frequent
lightning will also accompany some of these storms.

Wednesday: Thunderstorms are possible but it is too early to
determine the risk for severe weather.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is expected on Monday.

Haase

Special Weather Statement
National Weather Service Quad Cities IA/IL
832 PM CDT Sun Oct 10 2021

IAZ076-077-087-110215-
Keokuk IA-Washington IA-Jefferson IA-
832 PM CDT Sun Oct 10 2021

...A strong thunderstorm will impact portions of eastern Keokuk,
northwestern Washington and northwestern Jefferson Counties through
915 PM CDT...

At 831 PM CDT, Doppler radar was tracking a strong thunderstorm near
Sigourney, moving northeast at 40 mph.

HAZARD...Winds in excess of 30 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Harper around 840 PM CDT.
  South English around 845 PM CDT.
  Kinross around 850 PM CDT.

Other locations in the path of this storm include Wellman and Kalona.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4151 9203 4151 9165 4116 9210 4128 9227
TIME...MOT...LOC 0131Z 224DEG 36KT 4129 9212

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...30 MPH

Gibbs