ia discuss
Office: DMX
FXUS63 KDMX 152013
AFDDMX
Area Forecast Discussion
National Weather Service Des Moines IA
313 PM CDT Tue Jul 15 2025
.KEY MESSAGES...
- Warm and humid conditions continue today, cooler temperatures
in the 70s on Thursday.
- Storm chances return to western Iowa late tonight (overnight)
into Wednesday morning. A few strong storms possible with
gusty winds the primary threat. Conditional threat for
additional strong storms later Wednesday into Wednesday night,
especially south, but will depend on morning activity.
- Drier to end the week before additional storm chances return
at times into the weekend.
&&
.DISCUSSION...
Issued at 256 PM CDT Tue Jul 15 2025
Another warm and humid afternoon is ongoing with temperatures in the
80s and dew points in the 60s to 70s resulting in heat indicies in
the upper 80s to upper 90s across the area. Flow out of the south to
southwest will continue to bring in moisture off the Gulf into
Wednesday morning ahead of the approaching low-level low which will
be moving through southern MN through the daytime Wednesday dragging
a cold front with it through the state into Wednesday evening.
Attention first is on the developing convection in Nebraska this
afternoon into evening which will progress eastward towards the
Missouri River into late tonight, maintained in NE by a 30-40 knot
LLJ. The overall parameter space into our far western CWA will make
it difficult for storms to stay in balance with current thinking in
line with previous and recent CAM trends of decaying convection
moving into western Iowa near to after midnight before any lingering
activity continues to push eastward into early Wednesday morning.
Although can't completely rule out a strong storm as the line
initially enters our far western CWA, overall expecting any storms
to be sub-severe. For any strong storms that can maintain into
western Iowa, strong wind gusts are the primary threat followed by
locally heavy rain, though activity should be progressive enough to
limit the hydro threat overall, especially after several dry days
now.
What remains uncertain is the coverage and timing of the decaying
storm activity into central Iowa and beyond which has significant
implications on the any storm development later in the day
Wednesday. The aforementioned cold front will be drifting southward
through the area through the day and setting up somewhere near the
IA/MO border into Wednesday afternoon. Pending any other lingering
outflow boundaries/mesoscale details after the morning activity,
this is likely where additional development will occur during the
afternoon to evening but this boundary in CAMs is anywhere from
south central Iowa into northern Missouri making it difficult to
pinpoint at this range where the better storm threat is. As noted
yesterday, the better shear lags behind the boundary even though
instability blossoms in the warm sector south of the front. There
remains enough of a favorable environment for a few strong to severe
storms develop in the afternoon to evening, especially over southern
Iowa, if not further south, but at this point remains conditional on
frontal location, amount of early day clearing, and any other
mesoscale details. The primary threat will remain strong wind gusts
and locally heavy rainfall once again, though the potential
placement of rain over southern Iowa is also the area which can take
the most amount of rain given antecedent conditions and continuing
maturing crops. The LLJ is not as robust on Wednesday night into
Thursday, but may help maintain some rain/storms over far southern
Iowa into the night before clearing into Thursday morning.
High pressure drifts into and through the area later Thursday into
Friday with cooler temperatures moving in behind the frontal passage
as well. This will bring some pleasant days to end the week with
temperatures in the 70s to low 80s. Active weather returns late
Friday into the weekend, however, with multiple additional chances
for showers and storms at times. Details remain uncertain at this
range, but will continue to monitor trends.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1242 PM CDT Tue Jul 15 2025
VFR conditions ongoing and expected to continue through much of
the night. Scattered diurnal cu will diminish tonight but clouds
will be on the increase west to east late tonight into early
Wednesday. Shower/storm chances also increase in western Iowa
near to after 06Z but confidence in showers/storms maintaining
to most sites too low at this time to include any precip
mentions overnight except at KFOD. Started with shower mentions
for KFOD with uncertainty as well in strength of activity as it
reaches the terminal. Additional showers/storms possible after
the overnight activity into Wednesday morning (and again
afternoon/evening) but coverage and timing remain far too
uncertain to address at this time. Some gusty winds out of the
south this afternoon will decrease tonight with winds shifting
to be out of the west to northwest ahead to behind the passing
boundary Wednesday.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...05
AVIATION...05
Office: DVN
FXUS63 KDVN 151922
AFDDVN
Area Forecast Discussion
National Weather Service Quad Cities IA IL
222 PM CDT Tue Jul 15 2025
.KEY MESSAGES...
- There is a Slight (level 2 out of 5) Risk for severe storms
and excessive rainfall Wednesday afternoon and evening.
Damaging winds, heavy rain, and a low risk for tornadoes are
the primary threats.
- Hot weather Wednesday, with afternoon heat indices near or
just above 100 degrees along and south of I-80.
- Active weather pattern expected late week and into the weekend
with periodic chances of showers and storms.
- Extreme heat possible next week, with heat indices over 100
degrees at times.
&&
.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 219 PM CDT Tue Jul 15 2025
Widespread diurnal cumulus has somewhat inhibited today's high
temperatures this afternoon, and as of 1 PM, we're mainly in the
lower to mid 80s, and seem on target for the upper 80s in most
spots. This is good, since the dew point of 70 to 75 is quite muggy
outside, and heat index readings are 90 to 95 vs something near 100
if the cumulus had not been so widespread.
Looking through our region, we're in weak southerly flow at the
moment over Iowa and Illinois, with a weakness in the upper ridge
moving through southern Illinois today. To our northwest, a cold
front is advancing southeastward through Minnesota and South Dakota,
with scattered thunderstorms along it, and cool, smokey air behind
it as winds are from the north to northeast. This frontal boundary
will be moving towards our CWA over the next 24 hours, resulting in
a thunderstorm chance Wednesday afternoon and early evening.
After a dry night tonight, with warm advection, lows in the upper
60s to lower 70s are expected, with fog limited by south winds of 5-
10 mph. By morning, a low chance for shower and thunderstorms will
be seen in our northwest corner counties. This will be from a
decaying area of storms which is expected to form along the Missouri
river tonight. While these storms are expected to be dissipating
or decayed on arrival, they may provide the trigger for
thunderstorms within our area tomorrow.
An MCV, or mesocale convective vortex is possible within the high
PWAT air mass over Midwest from tonight's storms out west. If that
forms, we will see enhanced forcing for storms along and ahead of
the cold front tomorrow. That trigger is uncertain. That trigger is
also the main source for low level shear over our area. If that does
not form, then the shear profile will be weak for Iowa and Illinois.
What is not uncertain tomorrow is instability! A hot and humid air
mass is in place, and with favorable diurnal timing for high CAPE,
instability for storms is strongly supportive.
The combination of an uncertain trigger and high instability for
storms fits the SPC forecast of Level 1-2, with low probability for
severe storms west to somewhat higher chances farther east. Damaging
winds are by far the main concern tomorrow, with both discreet
and any line organization, but should the MCV bring southeast
winds to our area tomorrow, tornadoes would also be a concern.
Given the weak flow aloft and modest mid level lapse rates
around 6-7 deg/KM, these would tend to be weak tornadoes.
PWATs (atmospheric moisture content), around 2 inches is expected
tomorrow, which could allow for intense rainfall rates, and a quick
1 inch of rain as storms pass by, but little if any repeating storms
is expected, and this progressive nature should limit any widespread
heavy rainfall.
By mid evening tomorrow, these progressive storms are expected to
exit our eastern counties, with any lingering overnight
showers/storms in our far southern counties which could continue
into Thursday morning.
Highs Wednesday with increasing cloud are forecast to be a bit
cooler northwest than today, and just as warm if not warmer
southeast. This could approach heat advisory levels in the afternoon
in the southeast, but given the marginal heat and messaging on
storms, we're opting to keep this message secondary.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 219 PM CDT Tue Jul 15 2025
Thursday, much cooler weather is in store! Highs in the lower
70s north to mid 70s south are expected, with some lingering
showers possible in the far south. While I have not included
smoke in the forecast at this time, we'll have watch how the
evolves in the next couple days, as there's plenty of smoke
behind the front today.
Friday-Monday...an active pattern remains likely with a
strong upper level ridge setting up shop across the southeastern
CONUS. This will put the local area on the edge of the main
storm track with several shortwaves rounding the ridge every
36-48 hrs. Not every day will see rainfall, but warm and humid
conditions will bring a continued risk for afternoon storms. The
next best chance (40-55%) of storms appears to occur this
Saturday and Sunday with heavy rainfall possible given the high
PWAT and favorable pattern for MCS/repeating storms.
Tuesday Onward...some longer range guidance and the latest CPC
8-14 Hazards Outlook shows a building strong upper ridge
developing across the central CONUS pushing the storm track
further north, but unfortunately bringing even warmer air into
the region. Extreme heat may be a growing concern as we enter
next week.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1215 PM CDT Tue Jul 15 2025
The rest of today will see diurnal cumulus gradually rising to
VFR bases, which at this point is already VFR except for CID,
where this process may take another hour or two. Otherwise,
expect south winds through 18Z Wednesday along with VFR
conditions. A cold front, with scattered thunderstorms will be
expected to arrive Wednesday afternoon after 18Z. These storms
may be strong, but are after the TAF period for the moment.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
SHORT TERM...Ervin
LONG TERM...Ervin/Gross
AVIATION...Ervin
