ia discuss
Office: DMX
FXUS63 KDMX 260344
AFDDMX
Area Forecast Discussion
National Weather Service Des Moines IA
1044 PM CDT Fri Jul 25 2025
...Updated for the 06z Aviation Discussion...
.KEY MESSAGES...
- Showers and storms will develop over southern Iowa this
afternoon and expand northward through the evening and
overnight. Heavy rainfall will be the main concern, and could
lead to increased flash flooding and river flooding concerns.
- Additional isolated showers and storms are possible southeast
tomorrow afternoon and evening. Some storms could be strong
with gusty winds and small hail the main concerns.
- Hot and humid conditions develop Sunday into Monday with heat
indices over 105 possible both days.
&&
.DISCUSSION...
Issued at 247 PM CDT Fri Jul 25 2025
Showers and isolated thunder over southern Iowa are the first of
what will be intermittent shower and thunderstorm chances lasting
through the evening. These chances will spread northeastward through
the evening bringing the potential for more heavy rainfall to the
area. Fortunately most of the rain last evening stayed outside the
forecast area so soils aren't as primed as what was anticipated this
time yesterday. However, still anticipating some potential for flash
flood impacts over southern Iowa, primarily in urban areas should
prolonged heavy rain occur over the same area. Rainfall amounts will
generally be around 1 to 3 inches, with isolated pockets of 4 inches
or more certainly possible in some locations over southern into
southeastern Iowa.
Of similar concern will be a lower confidence but potentially
impactful secondary band that develops slightly farther north in a
few of the short range models. This would put a line of slow moving,
training storms over central into north central Iowa, which is an
area that received heavy rainfall earlier in the week. Likewise,
rivers in these areas are already running at increased flows as
water continues to route southward from rain this week. Should this
band of 1 to 3 inch rain fall over one of these basins, the
additional runoff could exacerbate conditions on the rivers, as well
as lead to localized flash flooding as the water works it's way
through the system. Similarly, any heavy rainfall over urban areas
could cause flash flooding and ponding on roadways. Again, this is a
lower confidence scenario as most of guidance keeps the heaviest
rain over southern Iowa where rivers are less aggravated, but
certainly something to keep a close eye on. If this band displaces
even farther north where flood warnings and watches are already
ongoing, particularly on the Iowa and Cedar Rivers. The Des Moines
River basin is also running at increased flow and could be impacted.
Beyond the heavy rainfall and flash flooding risk, there remains a
low chance for a few stronger storms, particularly in southern Iowa.
The main threat with these storms will be strong winds as rain falls
and the downward mass flux produces increased outflow from the
storms. The storm prediction center currently has a marginal
risk for severe weather just south of the forecast area and
barely clipping our southeastern counties, but gusty winds are
possible farther north of this area as well. Precipitation
lingers into Saturday morning but should mostly wrap up through
mid-day. Some guidance suggests isolated redevelopment in the
southeast Saturday afternoon, but this will be fairly sporadic.
The next hazard on deck is the hot and humid conditions that develop
Sunday into Monday as thermal ridging/warm temperatures aloft leak
eastward into the forecast area. Highs Sunday and Monday will be in
the low to mid 90s, with dewpoints pushing the upper 70s to near 80
in some locations. This would push heat indices into the 105 to 110
range, likely warranting heat headlines on Sunday and Monday. Monday
is currently forecast to be the warmest day, however, guidance has
begun to key in on a shortwave dropping southward into the forecast
which could impact high temperatures on Monday. This wave may also
bring some severe potential to the area, with SPC pulling the
marginal risk for severe weather.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1040 PM CDT Fri Jul 25 2025
Showers and thunderstorms will continue to lift northeast from
Missouri and Kansas after 06z. KDSM and KOTM are the primary two
sites that may be impacted by this activity. Less confidence in
precipitation chances after 14z and have opted to keep mention
out at this time. MVFR to IFR stratus may also develop at all
sites tonight into Saturday morning. Cigs will gradually improve
then late morning and into the afternoon. VFR conditions are
anticipated to end the period. Light wind through most of the
period.
&&
.HYDROLOGY...
Issued at 247 PM CDT Fri Jul 25 2025
With upcoming heavy rainfall in the south this evening, and the
potential for a secondary band of heavier rainfall slightly farther
north in the area, there will be a risk for additional impacts on
area rivers this evening into Saturday. Basins of greatest concern
will be the Iowa and Cedar River basins, which already have multiple
sites approaching minor flood stage. Additional heavy rainfall of 1
to 3 inches within these basins could compound with the already
elevated river levels and exacerbate flood concerns. Similarly, the
Des Moines River basin is running at elevated levels, although no
sites are currently expected to approach flood. This could change if
the heavier band occurs. The Cedar River basin is at a lower risk of
being directly impacted by this band, but is only slightly displaced
from the expected area. The Iowa River basin and Des Moines River
basins being farther south will be at a greater risk for being
impacted by this band, which could push sites into flood stage that
weren't previously expected, especially those between the Highway 30
and Interstate 80 corridors. Urban areas will also be at risk for
flash flooding, especially as runoff routes into already elevated
streams. &&
.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday morning for IAZ059>062-071>075-
081>086-092>097.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday morning for IAZ059>062-071>075-
081>086-092>097.
&&
$$
DISCUSSION...Dodson
AVIATION...Donavon
HYDROLOGY...Dodson
Office: DVN
FXUS63 KDVN 260521
AFDDVN
Area Forecast Discussion
National Weather Service Quad Cities IA IL
1221 AM CDT Sat Jul 26 2025
...Updated for 06z Aviation...
.KEY MESSAGES...
- Chance of showers and storms today mainly south of Hwy 20,
increasing coverage tonight into Saturday AM with heavy
rainfall and localized flooding potential particularly in
counties along and south of I-80. Gusty winds are also
possible with a Marginal Risk or level 1 of 5 for severe
weather for parts of the area.
- Heat builds back in Sunday through Tuesday, potentially
dangerous, but there will also be episodes of storms making
for a challenging temperature forecast and low confidence on
the spatial extent and magnitude of the heat (day to day
evaluation needed).
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 145 PM CDT Fri Jul 25 2025
GOES visible satellite imagery showed several compact cyclonic
circulations (MCVs) in a corridor stretching from southeast
Iowa into northern Kansas. These low/mid-level impulses were
positioned atop a weak quasi-stationary front as analyzed by
WPC, extending from the Lower Great Lakes back to the southwest
into the Central Plains.
Not a big air mass difference on either side of the boundary
with very humid conditions over the region (dewpoints in the
low/mid 70s). SPC mesoanalysis does show a rather tight north
to south gradient in PWATs from ~1.25" across the north to 2.25"
in the central to southern forecast area. This enhanced
corridor of deep moisture is forecast to gradually shift
northward through tonight into Saturday AM, ahead of the
approaching MCVs. With the anomalously moist air mass -- near
the 98-99th percentile per the NAEFS climatology -- and
expectation for slow storm motions around 10-20 mph at times per
MBE vectors, some locally very heavy rainfall is possible over
the next ~24 hours. Additionally, high freezing levels of 15-16
kft will promote efficient warm rain processes with potential
for peak hourly rain rates around 2-2.5" in the strongest
storms.
Forecasting the most likely placement of the heaviest rain is a
bit tricky, but based on a CAM model consensus counties along
and especially south of I-80 appear to have the highest chances.
The latest HREF LPMM QPF does show potential for localized
bullseyes of 3-4" with 0.5 - 1.5" amounts being more common, and
then a rapid drop off in amounts along/north of Highway 30.
Decided to issue a Flood Watch for counties along/south of I-80
due to the potential for localized flash flooding with 3 hr FFG
values in the 1.5 to 2.5" range. Of course the thick
vegetation/mature crops can handle a lot of water this time of
year, so areas most susceptible will be urban locations and
other low-lying flood prone areas.
For timing, scattered convection is anticipated to develop with
the lead MCV this afternoon and evening, likely to track
through the central portion of the outlook area. More widespread
slow moving showers and storms are then expected tonight, again
with the highest chances south of Highway 30. This activity
will likely linger into Saturday AM and it's possible scattered
storms redevelop during the afternoon. SPC has continued with
the Marginal Risk (level 1 of 5) for severe storms, mainly for
locally damaging winds. And WPC has a Slight Risk (level 2 of 4)
for flash flooding.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 320 AM CDT Fri Jul 25 2025
Saturday night and Sunday models support some amplification of the
upper ridge overhead. The building heights aloft and lack of
any appreciable forcing may limit storm coverage and support
more diurnally induced widely scattered activity. This upper
ridge and increasing heights aloft will also bring a return of the
heat. With corn sweat in prime-time, we'll see some very humid
to oppressive conditions with dew points likely in the mid/upper
70s and possibly 80 in spots. This will bring the potential for
dangerous heat index readings exceeding 100 to around 105 degrees
across much of the area, provided convection and cloud cover stay
limited to allow highs to top out in the upper 80s to around 90.
Monday through Wednesday, the pattern looks to become quite
conducive for periodic storm complexes with an attendant heavy rain
and severe weather threat, as the ridge is suppressed further
to the south allowing our region to reside in the action zone or
'ring of fire' with main belt of westerlies strengthening and
shifting southward through the Northern Plains and Upper Midwest.
This timeframe will also hold the potential for a continuation
of dangerous heat and humidity, but this will likely be a day to
day evaluation because of the uncertainty with temperatures given
the active pattern and potential for rounds of convection.
Beyond mid-week though there are signs pointing to a cooler and
somewhat drier pattern for late next week, as we see a bout
of northwest flow attendant to an eastern Canada low.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1205 AM CDT Sat Jul 26 2025
The forecast in general is expected to be predominantly VFR
through 09z, then after 09z becoming predominantly MVFR to IFR
with increasing precipitation chances through 17z, then
gradually returning to VFR after 17z through 21z.
We appear to be in a bit of a lull in-between waves and as such,
the next few hours will likely predominantly VFR with low
chances for a brief shower along with some patchy MVFR possible
particularly at DBQ and CID. After 09z, much of the guidance is
pessimistic with developing lower CIGs particularly at DBQ and
CID with low MVFR to IFR and even the potential for pockets of
LIFR, along with some fog. Some concerns with this due to the
amount of cloudiness, but with the abundant moisture and light
wind any breaks should allow for some lower conditions to
develop. Also, expecting a burgeoning of showers and storms
toward dawn and through late morning (11z-17z) ahead of the
next wave lifting up from NE Kansas. Highest precipitation
probabilities during this time appear to be at MLI and BRL, and
have gone with prevailing mention while also hitting
visibilities harder with low end IFR due to expected high
rainfall rates. Probabilities are lower at CID, but still high
enough certainty to warrant TEMPO mention. Meanwhile at DBQ,
confidence is lower to warrant just PROB30 mention for
precipitation. Sat afternoon is expected to trend back to mainly
VFR, with an isolated storm possible but confidence too low for
any mention at this time.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch through this evening for IAZ063>068-076>078-
087>089-098-099.
IL...Flood Watch through this evening for ILZ009-015>018-024>026-
034-035.
MO...Flood Watch through this evening for MOZ009-010.
&&
$$
SHORT TERM...Uttech
LONG TERM...McClure
AVIATION...McClure
