123
FXUS63 KDVN 282356
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
656 PM CDT Fri Jun 28 2024

.KEY MESSAGES...

- Isolated showers and storms are possible overnight into early
  Saturday morning. SPC has a Slight Risk for severe storms
  west of a line from Manchester to Cedar Rapids to Kahoka,
  Missouri, and a Marginal Risk to the east.

- Another round of active weather will occur Monday through
  Wednesday with several chances for showers and thunderstorms.
  Heavy rain is possible each day.

- Moderate to Major flooding is expected on several area rivers.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 152 PM CDT Fri Jun 28 2024

At 2 PM, showers continue across eastern Iowa, northwest
Illinois and far northeast Missouri with thunderstorms over
Iowa, Keokuk, Jefferson, Washington and Henry Counties. Clouds
and rain have limited temperatures through the afternoon. At 2
PM, temperatures range from 67 degrees at Freeport to 75 degrees
at Keokuk. The heaviest rainfall amounts have been along and
north of the Highway 30 corridor where rainfall amounts over 1
inch have been reported.

The wave currently moving across the area is forecast to exit
into Illinois by  bringing a break in the rain across the area.
Farther to the west along the Nebraska and Iowa border,
instability has increased where skies have been clear through
the day but is limited the farther east that you go. Models
continue to limit instability to near the cold front which is
forecast to move across the area from overnight into Saturday
morning. This instability will be tapped as a weak wave moving
to our north during the 9 PM to 4 AM timeframe. There has been
little change in the Storm Prediction Center Day 1 Outlook
through the day with a Slight Risk west of a Manchester Iowa to
Kahoka line and a Marginal Risk to the east. Little instability
is needed with 0 to 6 km shear near 45 knots. The HRRR
continues to be aggressive in the development of storms to our
northwest Illinois that moves across the area after 9 PM while
other models are more limited in the convective coverage and
intensity overnight. There remains low confidence in this
forecast but the potential remains in place for severe storms.
Based on current instability and model forecast and the timing
of the front during the overnight hours, think that ant storms
that develop this evening will be in a decaying as they move
across the area overnight. Think that the main threats will be
lightning, hail, and damaging wind gusts. Heavy rain remains a
possible given precipitable water values over 2.00 inches.
Probability match mean for rainfall shows a large spread among
the models in rainfall potential tonight with models having
anywhere between 0.40 to 1.50 inches.

The cold front is forecast to be in the vicinity of the
Mississippi River by 12 UTC Saturday with a continued threat for
showers and storms ahead of the front. Severe storms are not
anticipated. Dry air is slow to advect in behind the front but
dewpoints will be falling into the 60s through the afternoon.
High temperatures on Saturday are forecast to range from the
lower 80s along the Highway 20 corridor to the upper 80s in far
northwest Illinois.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 152 PM CDT Fri Jun 28 2024

This weekend, we return to zonal flow aloft, becoming northwest flow
on Sunday, as a ridge builds over the Central US. Surface high
pressure will slowly traverse through the area during this time
period, exiting through the day on Monday. This timeframe will be
relatively quiet, weather-wise, which is welcomed. Saturday, we are
expecting temperatures to increase into the mid-upper 80s in our
southeastern half of the forecast area, with temperatures trending
near to slightly below normal Sunday and Monday. The warmer
temperatures Saturday will result from the slow-moving cold front
passing through the area that morning, allowing temperatures to warm
ahead of it. There will be a chance for showers and storms earlier
in the day, but as we approach the afternoon hours, we will see
chances drop off. From there, we will remain dry through Sunday and
much of Monday.

Monday night and into Tuesday, we see our first wave that is set to
impact the area this coming week. Much of the action with this seems
to be late Monday night, moreso during Tuesday morning, as the LLJ
takes much of the night to shift east over our area. Although, if
this system speeds up, we may see showers and storms earlier in the
night on Monday. This action will be associated with the leading
shortwave trough, with the bulk of the energy in our northern
forecast area. Thus, this will be the focus for higher
precipitation amounts and thunderstorm potential. It is too soon to
discuss deterministic amounts of rainfall, but we will see the
potential for heavier rainfall. Guidance is highlighting the
potential for high moisture content once again, with PWATs near 2.00-
2.50". Ensemble guidance remains quite low on probabilities for
rainfall, while deterministic guidance comes in quite aggressive
with precipitation. Thus, we will refrain from more details. Rather,
just be mindful that this can be a wet period, especially for those
in our northwest. The parent wave comes through Tuesday into
Wednesday, which will bring the chance for more heavy rain and
thunderstorms. As the cold front approaches that afternoon/evening,
moisture will pool along the boundary, with guidance highlighting
this being the timeframe with the highest PWATs. Thus, an increased
risk for higher rainfall rates.

Beyond that, guidance starts to diverge on the next system, with
large differences in timing and placement. While guidance seems to
favor the Thursday night into Friday timeframe for more precipitation,
will opt to refrain from any more details, as there is plenty of
time for this to change. In either case, it would seem that we will
approach the end of the work week with another round of showers and
storms for the area. All guidance highlights much of the end of the
week and into the weekend as an active period for rainfall.
Unfortunately, all of this rainfall will lead to further
fluctuations on the projected flooding along area rivers. Be sure to
stay up to date on local flood headlines!

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 645 PM CDT Fri Jun 28 2024

Periods of MVFR/IFR are forecast tonight into early Saturday
morning, with the lowest ceilings at CID and DBQ. Isolated
showers and storms will remain possible into Saturday AM, but
confidence on direct impacts to the terminals is low. BRL may
have a slightly higher chance for scattered storms late tonight
into early Saturday AM, but with low confidence on where (or if)
this round of convection develops, left thunder mention out of
the TAFs for now.

&&

.HYDROLOGY...
Issued at 1213 PM CDT Fri Jun 28 2024

Headline Changes:

Issued a flood watch for the Wapsipinicon River near De Witt due
to recent rainfall and QPF in the next 24 hrs. Upgraded Illinois
City LD 16 on the Mississippi from Moderate to Major flood
category.

Discussion:

Higher rainfall fell in the Wapsipinicon River basin than
initially forecast. As a result, the new forecast for the De
Witt gage has the river reaching flood stage in a little over 24
hrs. However, confidence in the placement of QPF tonight
remains too low to issue a warning at this time. Later shifts
will monitor trends and can issue if needed. The Cedar River
forecasts remain on track, with crests likely in the next 24
hours at Palo and Cedar Rapids. A secondary rise with a lower
crest than the 1st one, is now forecast on the Cedar due to the
1-2 inches that fell near the headwaters in the past 24 hours.

On the mainstem Mississippi, rises will continue at all sites
over the next 7 days. Higher rainfall amounts in southern MN
and northern IA in the past 24 hours has resulted in a quicker
forecast to Major flooding for many sites by approx. 36 to 48
hrs earlier, including Rock Island LD 15. Crests along the river
should begin to show up in upcoming forecasts this weekend
beginning with Dubuque LD 11. Barring any more heavy rainfall,
crests are anticipated in the July 4th-10th timeframe.

&&

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

&&

$$

SHORT TERM...Cousins
LONG TERM...Cousins
AVIATION...Uttech
HYDROLOGY...Gross