099
FXUS63 KDMX 172341
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
641 PM CDT Sat Aug 17 2024

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Isolated diurnal driven showers in the north will diminish
  after sunset.

- Mostly dry on Sunday, although a low chance (< 20%) of high
 based showers or sprinkles in the far west.

- Mostly dry with seasonal conditions mid-late week.

&&

.DISCUSSION...
Issued at 226 PM CDT Sat Aug 17 2024

This evening through Sunday...

Stacked low pressure system continues to sit and spin over the Great
Lakes vicinity this afternoon. Broad cyclonic flow remains anchored
over the upper Midwest along with a corresponding shield of pesky
low clouds, once again pivoting through the region. Regional radars
showing isolated to widely scattered showers moving s/sewd across
the northern sections pf Iowa and expect these to continue through
sunset, before dying with loss of heating. Any rainfall amounts will
be minimal.

Overnight, the sfc high will make a stronger push to build swd out
of the northern Plains. Hence, expecting skies to gradually clear
and winds becoming light/variable. The guidance continues to trend a
bit more aggressive with fog formation overnight. The 12z HREF is
showing a patchwork of higher probabilities (20-50%) of vsbys < 1/2
mile, with the MAV/MET guidance indicating a few of the more fog
prone sites (e.g. KEST/KMCW) could crash to 1/4 mile. As we know,
fog forecasting is fickle, but continued the trend of mentioning
patchy/areas of fog in the north for now, and will have future
shifts monitor trends this evening.

On Sunday, any morning fog should dissipate fairly quickly with a
mostly sunny start.  However, diurnal cumulus will develop again as
heating commences. In the upper levels, a weak shortwave is expected
to dive sewd on the east flank of the developing upper ridge during
the afternoon hours. The best upper lift and low level moisture
convergence should remain west of our forecast area, generally along
and west of the Missouri River.  However, the various ensemble and
CAM solutions have trended eastward with the precipitation axis for
tomorrow afternoon.  At this time, soundings/X-sections in this
forecast area indicate that the low levels will remain quite dry,
and not supportive for precipitation, although a few high based
sprinkles are possible. However, have trended sky cover higher due
to increasing confidence of mid/high level cloudiness. Highs on
Sunday should still be in the low to mid 80s.

Monday through late week...

Early next week, the models remain in good agreement showing the
upper ridge expanding eastward into the Corn Belt. This is expected
to result in mostly dry conditions, with a slow warming trend. Highs
will range from the upper 70s to mid 80s, with mid to upper 80s
likely by weeks end.  Lows will be seasonal in the 60s.  Precip
chances are relegated to low chance /20-30%/ PoPs on Tuesday night,
and again late on Friday.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 641 PM CDT Sat Aug 17 2024

Ceilings will dissipate this evening with widespread VFR
conditions overnight into Sunday. Surface winds remain northwest
but become light overnight and remain modest into Sunday. Some
patchy fog may occur in northern Iowa around sunrise with local
MVFR visibilities.

&&

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

&&

$$

DISCUSSION...Fowle
AVIATION...Cogil