Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 171110
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
610 AM CDT Wed Apr 17 2024

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

.KEY MESSAGES...

- Gusty winds this morning with precipitation ending.
  Diminishing wind and clearing from west to east by this
  afternoon.

- Widespread showers and a few storms arrive tonight into
  Thursday.

- Colder with Frost/freeze headlines possible at the end of the
  week and into the weekend.

&&

.DISCUSSION...
Issued at 321 AM CDT Wed Apr 17 2024

Upper low pressure has moved into southwest Minnesota this morning
with the surface reflection centered over north central Iowa. An
area of lingering wrap around showers is ongoing, mainly over north
central Iowa though some very light activity does extend south to
near Interstate 80. The surface pressure rises are beginning to move
into western Iowa and these are in close proximity of the strongest
pressure gradient over Iowa, thus will have increased winds and
gusts as this translates east across the state today as the surface
low departs. The wind could briefly approach wind advisory criteria
in some areas but generally, northwest winds of 20-25 mph with gusts
over 35 mph are expected before a default high pressure ridge
arrives by this afternoon and relaxes the gradient. Therefore, no
headlines are anticipated at this time.

A broad area of stratus does remain upstream over the central and
eastern Dakotas and Nebraska. How quickly the stratus begins to
clear from west to east across Iowa today is a little less certain.
Cloud level steering will be from the west/northwest and add in some
drying with the arrival of the ridge and the stratus should begin
clearing over the west by mid to late morning and much of the rest
of the area this afternoon. It is possible, it could linger through
most of the afternoon near Mason City and Waterloo and points
northeast, which will keep temperatures down there.

Precipitation chances return quickly to Iowa tonight into Thursday
and this is due to two systems converging over the state. The first
is just ahead of colder air that will arrive over the region later
this week. A short wave along with a plume of Pacific moisture will
aid in the development of showers over northwest Nebraska later
today that will spread quickly east overnight and into the northwest
half of Iowa by around 06z tonight. The other area is a strong surge
of Gulf moisture lifting north towards the Iowa/Missouri border,
also by around 06z. The low level jet and strong theta-e advection
lifting into southern Iowa in addition to isentropic lift and
overrunning further north, will lead to showers and thunderstorm
development into southern Iowa. These two areas of precipitation
will move east/southeast across Iowa into the day on Thursday with
precipitation ending from northwest to southeast through the day.
Some uncertainty remains on if there will remain a gap or area of
less precipitation between these two systems somewhere across
central Iowa or if it will be more merged. Suspect the will be a
minimized area of precipitation but it may be narrow. Precipitation
amounts of 0.25 to 0.75 inch are possible along with some higher
amounts. A few strong storms could occur near the Iowa/Missouri
border late tonight into early Thursday pending if the instability
does indeed reach the area and if it does, how much of the 1000+
J/kg MUCAPE can be realized pending the lift point of parcels.

The first round of the cooler air will fill in behind the system
followed by a stronger push of colder air Friday night and into
Saturday. This will result in high temperatures mainly in the 50s
Thursday and Friday, though should clouds remain Thursday, some
areas may remain in the 40s. Freezing temperatures may arrive by
Friday morning and again Friday and Saturday nights. Given the early
growing season, this may require Frost or Freeze headlines.
Temperatures will begin to rebound early next week. Precipitation
chances will also return with the warmer weather.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 606 AM CDT Wed Apr 17 2024

Widespread MVFR to local IFR stratus is across Iowa this
morning. The stratus will begin to clear from west to east and
bases should gradually lift with diurnal heating. Gusty
west/northwest wind this morning could gust to 35 kts before
starting to diminish this afternoon. A period of VFR conditions
will follow through early this evening. Widespread showers and
isolated thunderstorms arrive overnight along with MVFR cigs.

&&

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

&&

$$

MESOSCALE...Jimenez
DISCUSSION...Donavon
AVIATION...Donavon


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