Hail and Damaging Winds in Iowa, May 7, 2024

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1242 AM CDT Tue May 7 2024

.KEY MESSAGES...

- An organized line of storms is expected to move through the
  outlook area late tonight between 1 AM to 7 AM (west to east
  through the area). This system will pose a risk for damaging
  winds and isolated tornadoes.

- For Tonight: The Storm Prediction Center has a Slight Risk
  for severe storms to the south and west of the Quad Cities
  with a Marginal Risk covering the rest of the area.

- Isolated storms may redevelop Tuesday afternoon and evening, a
  few of which could be strong.

- Scattered showers and storms remain possible on Wednesday
  before temperatures cool off late in the week. There is a
  Slight Risk for severe storms across the south on Wednesday
  with a Marginal Risk to the north.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 245 PM CDT Mon May 6 2024

Tonight into Tuesday Morning

The forecast remains on track with a squall line expected to
track through eastern Iowa, northeast Missouri, and northwest
Illinois late tonight into early Tuesday AM. This complex of
storms will cover a large spatial area so rain chances are high
at 90-100% across the outlook area. The convection will
initially develop across Kansas this afternoon/evening before
growing upscale and tracking to the ENE into Missouri, Iowa, and
Illinois tonight.

Confidence has increased on the line of storms still packing a
punch as it reaches the western to even central counties of the
outlook area. While forecast MLCAPE is on the low side
(250-1000 J/kg), low-level shear is high with 25+ kts in the
lowest 1 km and 30-35 kts for 0-3 km. The strong environmental
shear will help to balance the gust front on the leading edge of
the convection, creating more concentrated lift and enhancing
the potential for stronger storms.

As for timing, the QLCS should reach the western counties
between roughly 1 to 2 AM, central areas (near the Quad Cities)
between 2 - 4 AM, and far eastern counties between 5 - 7 AM.

SPC has expanded the Slight Risk for severe storms to the NE,
now encompassing areas to the south and west of the Quad Cities,
with a Marginal Risk for the rest of the forecast area. The
primary threats are scattered damaging wind gusts around 60 mph,
with a low potential for a few higher gusts over the far
southwest counties. There is also an isolated QLCS tornado
risk (5% within 25 miles of a point), highest in the
aforementioned Slight Risk area.

PWAT values near 1.25" are forecast with strong WAA forcing.
Thus, rainfall on the order of 0.50" to 1" is likely for much of
the area. Scattered showers and isolated storms could develop
mid to late morning on Tuesday behind the departing QLCS, but
these are not anticipated to pose a severe risk at this time.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 245 PM CDT Mon May 6 2024

The Upper Midwest is forecast to remain under general troughing or
cyclonic flow aloft through the period. Flow aloft will be
southwesterly a 500 MB through Wed/Thurs it becomes more
northwesterly as the current storm system departs. This will allow a
series of troughs and ridges in the northwest to move across the
area into early next week. The trend for chances of showers and
storms continues about every 24 to 36 hours. There will be periods
of quiet weather in between. Timing on rain chances will likely vary
over the next few days. Temperatures are trending below normal
Friday through Sunday.

The long term period begins Tuesday/Tuesday night with a closed 500
MB low over the northern PLains. At the surface, a cold front wiil
move eastward across Iowa and Illinois through 00 UTC on Wednesday.
A decaying MCS will likely be moving across our northwest Illinois
counties at 12 UTC on Tuesday and exiting the area. Models show
skies clearing quickly and do show some instability across the area
ahead of or right behind the front which will lead to the risk of
showers and storms during the afternoon. There could be some
isolated severe storms with CAPE of 500 to 1000 J/KG and about 20
knots of 0 to 6 km shear. The main threats will be hail and damaging
wind gusts. The amount of instability will depend on how quickly
skies clear.

On Wednesday, the closed 500 mb low will transition to an open wave
with a positive tilt as it moves across the area.  At the surface, a
low is forecast to lift east northeastward from northwest Missouri
into northeast Illinois or northern Indiana by 12 UTC Wednesday.
This would bring the surface low and warm and cold fronts across the
area during peak heating on Wednesday. SPC has a slight or level 2
out of 5 risk of severe storms on Wednesday for the area along and
south of a Keosauqua to Iowa to Princeton Illinois with a Marginal
or level 1 out of 5 risk for severe storms north of that line.
Current model guidance shows the potentail for a high shear low CAPE
event but it will depend on the track of the surface low and how
much instability moves this far north.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1240 AM CDT Tue May 7 2024

A large complex of showers and thunderstorms remains on track to
impact the terminals late tonight, with timing favored between
around 08Z to 12Z. This will lead to periods of MVFR/IFR due to
lower ceilings and reduced visibilities in heavier rain. The
strongest cells could produce wind gusts near 50 kts from the
WSW.

There remains a low chance (20-30%) of a shower or storm
developing Tuesday afternoon ahead of a front across eastern
Iowa. However, latest CAMs are not in agreement on location of
development or timing so have left a mention out of the TAF at
this time.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

SHORT TERM...Uttech
LONG TERM...Cousins
AVIATION...Haase

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
1223 PM CDT Mon May 6 2024

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-071730-
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-
1223 PM CDT Mon May 6 2024

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

Late tonight, after midnight, a line of thunderstorms will move
into eastern Iowa and northeast Missouri. These storms may be
capable of producing wind gusts up to 60 mph, isolated tornadoes,
and heavy rain. By 4 AM Tuesday, these storms will continue to
move northeast across all of Illinois. The Storm Prediction
Center is forecasting a Slight Risk for severe storms, level 2 of
5, for areas west of a Iowa City, Iowa to Galesburg, Illinois
line. A Marginal Risk covers the remainder of the outlook area.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A marginal, level 1 of 5, risk for severe storms continues to be
forecast for locations mainly along and east of the Mississippi
River Tuesday. This is primarily for this same line of storms
affecting our area late tonight and Tuesday morning.

Another chance for thunderstorms will be possible Wednesday, with
another marginal risk over much of Iowa and Illinois, and a
slight risk found in northeast Missouri and west central Illinois.
Large hail, and damaging winds are the primary risks Wednesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed tonight.

GENERAL STORM MOTION OF THE DAY:

50 MPH to the northeast.

Ervin/Uttech