Newton, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

012
FXUS63 KDMX 101118
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
618 AM CDT Tue Jun 10 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Areas of smoke to persist tonight

- Noticeably warmer Wednesday

- Next chance (60-70 percent) for more organized, widespread
  precipitation Wednesday afternoon, Wednesday night & into
  Thursday

&&

.UPDATE...
Issued at 202 AM CDT Tue Jun 10 2025

No substantive changes to the forecast through Wednesday
morning, with quiet and increasingly mild conditions during that
time. All eyes are on thunderstorm and severe weather chances
from Wednesday afternoon onward as we enter a considerably more
active weather period. The overall set-up will be typical for
the season, with a warm/stationary surface front underlying
moderate zonal flow aloft, instability pooling south of the
boundary, interactions with mid-level shortwave impulses and/or
the nocturnal low-level jet providing forcing mechanisms for
convection, and the resulting storms influencing the location of
the front and degree of instability in subsequent rounds of
potential initiation. In such situations, predictability is
normally highest with the initial round and decreases
incrementally thereafter. For tonight`s update have only focused
on the first round of storms late Wednesday.

By midday Wednesday the surface warm/stationary front will be
draped from west-to-east across northern Iowa, likely somewhere
between Highway 30 and Highway 18. To the south of the boundary,
southwesterly surface flow and relatively deep mixing will
induce temperatures to climb to their highest levels of the year
so far, with highs in the lower 90s and dewpoints in the
mid-60s. This will feel sweltering given our recent persistent
spate of cooler than normal weather. It will also cause
instability to pool against the front, with MUCAPEs in the
2000-3000 J/kg range by mid-afternoon. A mid-level impulse
approaching from South Dakota will arrive coincident with peak
heating/destabilization and initiate strong convection somewhere
over northwestern/northern Iowa in the mid-to-late afternoon,
with a cluster of storms moving eastward along the front and
perhaps southeastward into the pool of instability. Farther
south, toward central and even southern Iowa, some new CAM runs
are generating storms and soundings do show an uncapped and very
unstable airmass, however there appears to be no forcing/focus
mechanism for such storms and have kept POPs low in those
areas.

In terms of a severe weather threat, certainly instability will
be more than sufficient, at least along and south of the front.
However, shear will be modest with 0-6 km Bulk Shear values
around 30-35 KT along the boundary, and less to the south. 0-1
km is even less impressive, with relatively light and
unidirectional near-surface flow resulting in values of only
5-10 KT. In this scenario, the most likely mode for severe
weather will be large hail, though there is some potential for
strong winds as well given the large CAPE profiles, especially
if an organized group of storms can establish a cold pool and
become forward-propagating. In addition to severe thunderstorm
threats, heavy rain is also a distinct possibility, especially
heating into the overnight Wednesday night as additional
thunderstorms may fire north of the boundary and train over the
same areas to some extent. However, with less forcing for ascent
overnight it appears QPF may not be as robust as it looked like
it could be a couple nights ago, and in addition our northern
counties have good capacity given the antecedent conditions.
Still, it is certainly a threat worth monitoring and we will be
watching the Wednesday afternoon-night timeframe closely as it
approaches.

&&

.DISCUSSION...
Issued at 232 PM CDT Sun Jun 8 2025

Main forecast concern today centers on the mid to late week
system.

Upper low is finally departing across the Great Lakes, with the
pattern adjusting to a more zonal flow over the midwest. As the
surface ridge slides off to the south and east Tuesday, a warm
front sets up in its wake over northern Iowa. This front will
provide the initial focus for storms Wednesday. Given the
available instability near and especially south of the boundary,
thunderstorms are likely. Given the instability, could see some
embedded severe storms as well. The front is expected to linger
in the vicinity of northern Iowa/southern Minnesota through
Thursday, keeping the rain chances around through the period.
The details for Thursday depend largely on the position of the
front and any remnant outflow boundaries from convection the
day/night before. Given the zonal flow aloft along the boundary
and available moisture, areas near the front and aforementioned
boundaries will need careful monitoring for heavy rain and
flooding potential.

Meanwhile, energy currently over southern California is
forecast to meander across the southern US and potentially
interact with the northern stream by late week. Lots of spread
in the model solutions however, so confidence remains low at
this time on this evolution.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 618 AM CDT Tue Jun 10 2025

VFR conditions are expected through the TAF period, with no
aviation impacts.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

UPDATE...Lee
DISCUSSION...DMD
AVIATION...Lee