Harper, Iowa Weather Forecast Discussion

170
FXUS63 KDVN 221058
AFDDVN
Area Forecast Discussion
National Weather Service Quad Cities IA IL
558 AM CDT Mon Sep 22 2025
.KEY MESSAGES...
- Off and on chances of showers and a few thunderstorms continue through
  Thursday before a drier weather pattern develops by Friday
  into the upcoming weekend
- Strong to severe storms remain possible this evening across
  the northwestern portions of the CWA
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 303 AM CDT Mon Sep 22 2025
The work week begins with generally quiet conditions through this
afternoon. Early this morning, there are some areas of fog that have
developed under an area of mostly clear skies. While we`re not
expecting fog as thick or dense as it was Sunday morning, reductions
in visibilities will be possible for the AM commute. Any headlines
appear unlikely, but we will continue to monitor. Anyone traveling
this morning should prepare to encounter fog in spots.
As one mid-level shortwave moves off to the east this morning, a
second one is slated to move into the area from the west, currently
over western Nebraska per latest GOES-East mid-level water vapor
satellite imagery. This wave is progged to cross central Iowa by
this evening. Ahead of this, a surface cold front is also progged to
dive southward over northern Iowa this evening, which most of the
CAMs suggest a line of convection to develop along the boundary.
Looking at the convective parameter space, shear appears to be quite
weak (deep-layer and 0-3km shear both under 20-25 knots), but
instability looks slightly more favorable with MLCAPE values around
500-1500 J/kg per the global models and HREF ensemble. Mid-level
lapse rates are still looking fairly modest (6-7 C/km), but ample
moisture ahead of the boundary with dew points in the lower/mid 60s
and a seasonably cool profile aloft should support a wind threat via
cold pool generation, especially if convection grows upscale like
what some of the CAMs are suggesting. There has been no change from
SPC for the convective outlook, keeping a Marginal Risk (level 1 of
5) of severe weather to locations along and north of a line from
Millersburg, IA to Freeport, IL. Locally strong winds and hail are
the main threats. Any storms that develop this evening over our
northwestern CWA should continue to track southward, but decay with
time after midnight tonight as convective inhibition increases.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 303 AM CDT Mon Sep 22 2025
The long-term period remains active to start, but a pattern shift by
the end of the work week will bring drier and more pleasant
conditions to the area.
First, let`s talk Tuesday. We will continue to be under a longwave
upper-level trough that will expand as far southwest as the Four
Corners region. A large embedded wave along the base of the trough
will translate across the central Plains towards Missouri by Tuesday
morning, and bring large-scale forcing for ascent to the Corn Belt.
The cold front that will sweep through the area tonight should
become stationary over our area for a time, helping to focus
additional chances (20-50%) of showers and storms. Along the
boundary, both instability and shear should fall quite a bit, along
with pretty meager lapse rates, so we`re not expecting any strong to
severe storms Tuesday. Convection will be most likely during the
afternoon/early evening hours during peak daytime
heating/instability.
Wednesday and Thursday: the aforementioned upper trough will slowly
pivot across the central CONUS, making slow progress eastward, so we
will continue to see a few more of these embedded shortwaves
sweeping through the area. Low to medium chances (20-40%) of showers
and isolated storms will continue to linger over the area, most
likely across our southeast. A slight cooldown is expected these
days, with highs warming to the lower 70s area-wide.
Friday into the upcoming weekend: big changes come during this time
frame as upper-level ridging over the western CONUS develops and
kicks out the persistent trough to the east. The result will be dry
conditions for our region with temperatures increasing to slightly
above normal (upper 70s to lower 80s), so for those that have
outdoor plans this weekend, weather is looking quite pleasant! In
fact, the global models and LREF cluster analysis indicate a rex
block developing over the western US, which could persist into the
early part of next week. For us, that would mean a period of dry
conditions continuing beyond the weekend into early next week.
&&
.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 558 AM CDT Mon Sep 22 2025
Visibility reductions due to fog, along with scattered low
stratus clouds, were observed over the area early this morning.
Some locations are seeing IFR to LIFR conditions, but so far
this morning, they haven`t lasted long and conditions have
improved, such as DBQ and CID. Some amendments to the TAFs are
possible if the observations warrant it.
Eventually, conditions will improve to VFR by late this morning
into the afternoon hours. Generally light southerly winds
will continue, increasing only to around 5 to 10 knots during
the daylight hours today.
Tonight, a cold front dives southward across the northern
forecast area, supporting increasing chances of thunderstorms.
Uncertainty remains on the exact timing due to differences among
the high-res models, so we`ve used PROB30 groups for now to
highlight the most likely timing.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Schultz

NWS DVN Office Area Forecast Discussion