000
FXUS63 KDVN 160603
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
103 AM CDT Tue Apr 16 2024

.KEY MESSAGES...

1) Well above normal temperatures can be expected through the middle
of this week, with temperatures increasing into the upper 70s to 80s!

2) Chance for strong to severe storms Monday night into Tuesday
morning, as well as Tuesday afternoon through the night. All hazards
will be possible.

3) Cooldown expected after the Tuesday system, bringing us closer to
seasonal norms at the end of the week. CPC favors below normal
temperatures after the middle of this week.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 232 PM CDT Mon Apr 15 2024

Tonight...

Tonight, a strong surface low develops in the Western Plains and
pushes east through the night. Warm front develops and stretches
east, well ahead of the surface low. It will move south-north into
our area tonight. This feature has continued to slow down over the
last few runs, with latest guidance hinting that this will stall
over our northern half of the forecast area tomorrow morning. We
will see a strong LLJ develop west of the area tonight, shifting
east as we head towards Tuesday AM. The slower eastward progression
of the LLJ will lead to limitations in the severe potential tonight.
With this pattern in mind, we may see isolated-scattered
showers/storms tonight, but confidence in the severe threat is
decreasing. Timing will also be after midnight, if we see storms.
Ingredients all come together closer to sunrise tomorrow, which
would highlight the best chance to see strong/severe storms.

The SPC continues to highlight areas along/south of a line from
Belle Plaine IA to Macomb IL in a Marginal Risk for severe weather,
level 1/5. Main hazards will be large hail and lightning.

Tuesday...

Later in the day Tuesday, our forecast area will fall under the warm
sector of the advancing surface low, with the warm front draped over
the north. In the warm sector, we should see CAPE values increase to
the 1500-2500 J/kg range, with higher possible if we get increased
surface heating. Given moderate-high shear, steep lapse rates, and
sufficient instability, organized convection is favored. Currently,
guidance is showing the chance to get a line of severe storms, with
the environment favoring embedded supercell structures. Some leading
supercells are possible, but confidence is low on this. Confidence
is higher on the arcing line of convection Tuesday afternoon and
evening. Timing has moved up a little compared to yesterday,
resulting from the lack of storms overnight and Tuesday morning.
Without these clouds present, we could see more surface heating,
making the environment even more favorable for severe convection.
Thus, mid-afternoon, we may see the first line of convection
approach our area, and push through late afternoon and through the
evening. While some differences exist amongst guidance, there is a
general consensus on seeing at least one round of storms. Some short
term guidance also hints at a secondary line of potentially severe
storms coming in shortly behind the first. This would bring another
threat for wind and tornadoes. Although, confidence lowers on the
secondary line of convection.

Gusty southeast winds will be seen through the day as well, with
sustained winds between 20-30 mph and gusts upwards to 40 mph. No
headlines are currently out, but will be evaluated this evening and
tonight.

The SPC continues to highlight our whole area in a Slight Risk for
severe weather (level 2/5), with the expansion of the Enhanced Risk
(level 3/5) for areas along/south of a line from Dubuque Iowa
through Galva Illinois. All hazards will be on the table, with an
increasing tornado and wind threat.

Tuesday Night...

Latest trends in guidance have hinted at a possible third line of
convection coming through late Tuesday night and Wednesday morning.
Confidence is low on this as well, but this line of convection would
bring along the wind and tornado threat again, especially after
midnight. This will be a quick hitting line of convection, if it
develops, traveling along the cold front associated with the low.
Surprisingly, the environment is favorable for this line, as we will
have several hours between rounds of convection for the boundary
layer to recover. While it will be nighttime, guidance is hinting at
the potential for surface-based convection near daybreak, rather
than elevated, hence the wind/tornado threat. If the storms stay
elevated, then there would be an increased risk for hail. Have those
weather radios and cell phones ready, just in case!

Event Rainfall...

Heavy rainfall can be expected with any storms that push through,
especially through the morning/afternoon on Tuesday. PWATS will
range between 1.25-1.50"+, which is well above the daily max
locally. Diving into probabilities, areas along and north of
Interstate 80 have a 90-100% chance of seeing at least 0.50" of
rain, with the chances for 1.00" or more ranging between 70-90%.
Much of the rainfall forecast remains similar to the recent
days, but areas south of Interstate 80 have trended slightly
downward on totals. Although, it is still looking like those
areas in our south should see at least 0.50" of rain, with areas
in our north still seeing between 1.00-2.00". This heavy
rainfall will be widespread and may lead to rises in local
streams, as some are already higher than normal. We also have a
Marginal Risk for Excessive Rainfall, which indicates the
potential for localized flash flooding, especially in urban
areas.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 232 PM CDT Mon Apr 15 2024

A weak wave, along with a band of FGEN will move into the area
from the NW into Thursday. All guidance has some QPF with this
system, however, there is a large spread in precip amount. A
look at the 24 hr accum 25th-75th range from the NBM runs from
0.04 inches to 0.63 inches. At this time, it looks mainly like
rain showers and maybe a rumble of thunder as it moves through
the area. Not expecting many impacts from this system.

After this, a chillier weekend with temps in the 50s are
expected, but with quiet weather.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 102 AM CDT Tue Apr 16 2024

A strong low pressure system will track into western Iowa today
lifting a warm front northward through the area. It will move
into SE MN tonight with a cold front pushing eastward through
the region. Strong ESE winds will be seen this morning with
gusts increasing to 30 to 35 kts. Some showers will be possible
closer to sunrise, especially near BRL. Showers and
thunderstorms are expected to work east across the area from
late morning through late afternoon/early evening along with the
cold front. Some of the storms could be strong to severe with
damaging winds, large hail and tornadoes all possible. These are
currently expected to impact the terminals from 2pm to 6pm when
MVFR or IFR visibilities and ceilings will be seen with the
storms along with variable gusts around 35 to 40 kts. After the
storms move through, winds will become southerly but will remain
gusty.

&&

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

&&

$$

SHORT TERM...Gunkel
LONG TERM...Gibbs
AVIATION...14