872
FXUS63 KDVN 280741
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
241 AM CDT Fri Jun 28 2024

.KEY MESSAGES...

- Off and on rain today with embedded thunderstorms. Question of
  whether or not we see strong to severe storms later due to
  slow returning instability.

- After a brief period of quiet weather this weekend, an active
  pattern sets up once again next week, with plenty of chances
  for showers and storms. Heavy rain is possible, but it is too
  soon to determine the severe threat.

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

.SHORT TERM /THROUGH SATURDAY/...
Issued at 241 AM CDT Fri Jun 28 2024

A closed upper level low over Montana will drift southeast
towards the area today behind a quick moving shortwave this
morning. At the surface, high pressure will move east of the
area. This high helped to decrease deep moisture across the area
yesterday and early this morning. The leading shortwave, with an
attendant 30-35kt LLJ, is leading to widespread showers moving
into the area this morning. This jet is expected to continue in
some form this morning until the wave moves east of the area.
With limited CAPE, robust thunderstorms are not expected,
however, some rumbles of thunder are possible. This shower
activity is expected to continue during the morning hours
before gradually decreasing in coverage. Remarkably, the CAMs
are in good agreement in shower coverage and timing through the
morning, leading to a higher confidence forecast through at
least 18z.

In the afternoon, the stronger wave approaches the area. Deep
moisture return doesn`t occur til later in the afternoon. With
the showers from this AM, think cloud cover will keep the area
rather cool. As a result, think that CAPE will not be all that
impressive this afternoon and into the early evening.
Currently, think severe risk is very low across the area. That
said, deep layer shear is 30-40kts. If the forecast CAPE is
higher, and DMC occurs, there could be a chance for a strong to
severe storm as SPC depicts across our far west. The main thing
is CAPE, when does it get here, how warm do we get? We eventually
see MUCAPE build after sunset. The better chance for strong to
severe storms looks to be overnight, when shear increasing to
40-45 kts and CAPE moves into the area. Even then, we could have
so many small cores from the forcing that the severe risk could
be low. The main concern I see is heavy rainfall. Do not think
there is a flash flood threat. The main thing to me is what does
this additional rainfall do to the crest forecasts on area
rivers the next few days.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 241 AM 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 /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1242 AM CDT Fri Jun 28 2024

Rain showers will gradually overspread the area tonight and last
through most of the TAF period. CIGs will begin to lower later
to MVFR. There is a slight chance for some sporadic lightning
strikes and thunder through the period as well. With the
sporadic nature have decided to leave out of the TAFs at this
time.

&&

.HYDROLOGY...
Issued at 202 PM CDT Thu Jun 27 2024

Change:

The Mississippi River at Rock Island: A flood warning for MAJOR
flood category is in effect until further notice. The river is
expected to continue to rise to 18.0 ft on July 4th. However,
additional rises thereafter are likely.

Rainfall potential: Several storm systems may bring heavy rainfall
to the Midwest, which may aggravate the flooding or delay any crests.
There is additional showers and thunderstorms this Friday and Friday
night, again early next week, and another system towards the end of
next week. Stay tuned!

Outlook...

The overall weather pattern looks to remain quite active through
Independence Day and potentially into the middle of July. The Madden-
Julian Oscillation (MJO) which has been weak to non-existent for
much of June is forecast to strengthen over the next 10 days and is
forecast to move from phase 2 to phase 4 over the next two weeks.
Phase 3 and 4 of the MJO climatologically correlates to above normal
rainfall for the upper Midwest and Mid-Mississippi Valley. Indeed
the Climate Prediction Center has a 40-50 percent probability of
above normal rainfall July 4-10.

&&




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

&&

$$

SHORT TERM...Gibbs
LONG TERM...Gunkel
AVIATION...Gibbs
HYDROLOGY...Haase