Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 242344
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
544 PM CST Wed Feb 24 2021

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

.DISCUSSION.../Tonight through Wednesday/
Issued at 253 PM CST Wed Feb 24 2021

Take Home Points:

*Snow melt continues
*Temperature roller coaster, with mostly above freezing highs
*Periodic light precipitation chances

Discussion:

While it was a markedly cooler day across the state, it remained
hard to complain too much about considering the bitter cold only a
few days in our rear view mirror. Reinforcing CAA and lingering
stratus kept temperatures predominantly stagnant up through mid
afternoon, in the 30s. A subtle mid-level shortwave continues to
trigger nuisance light precipitation within hi-res guidance this
evening. Confidence is still somewhat limited in the precipitation
potential due to low level dry air, but have low end PoPs across NW/
N Iowa this evening. Otherwise mostly quiet conditions will continue
overnight and Thursday as surface high pressure moves into the area.
That too will keep Thursday highs similar to today with little
opportunity to advect in any appreciably warmer or colder air
masses. Just off to our west/northwest on Thursday though will be
another downsloping event, allowing temperatures to rise into the
50s for large portions of South Dakota.

Back closer to home, Friday will be a breezy day across the area and
especially NW Iowa as surface low development in the Canadian plains
works to tighten the surface pressure gradient locally and increase
S/SW winds as our surface high departs. At this point, pressure
gradient and soundings continue to suggest sub-advisory winds as the
most likely outcome across NW/N Iowa through the afternoon Friday.
Temperatures too will see a nice boost with WAA resulting in a
return to widespread highs in the upper 30s to 40s. Areas of
southern Iowa may be able to overachieve current forecast highs as
the snowpack continues to recede northward as well. Did go with 90th
percentile temperatures for the day with the NBM tending to be under
done during similar setups. Strong WAA and moisture return, coupled
with the upper level shortwave passage will yield precipitation
opportunities Friday evening and into the overnight, largely from
Interstate 80 on eastward. The NBM had continued to look woefully
underdone compared to ensemble guidance, therefore coordinated
increasing and pulling PoPs westward, back to roughly Interstate 35.
Expect rain prevailing south to snow north and a possible mix in
between, but should not be too consequential with only light amounts
expected. Saturday will be a few degrees warmer as another wave of
WAA slides through and periods of sunshine look to prevail,
resulting in possible low to mid 50s across southern Iowa.

Saturday night/early Sunday precipitation chances continue to be
difficult to pin down with much of the moisture shunted over the
southern US by this time. Ensemble guidance continues to show a
handful of members with QPF over the area as a frontal boundary sags
southward, but the majority remain dry at this point in time. As a
result, have only made minor changes to the inherited NBM, remaining
mostly in slight chances for light rain and snow. The primary
consequence looks to be cooler temperatures Sunday and Monday, back
into the upper 20s to 30s for highs for most of the area. A
generally split flow pattern across the CONUS to start the week will
keep us mostly quiet with best/strongest systems remaining north and
south of the region. Temperatures will also look to rebound/warm
again with an opportunity for widespread upper 40s to low 50s by mid-
week.

&&

.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 544 PM CST Wed Feb 24 2021

The remaining clouds are over southern Iowa with SCT025 ceilings
for a few more hours as conditions will be VFR this evening.
However, a fast moving system will enter the state after midnight
and bring lowering ceilings into MVFR most likely over northern
Iowa. Confidence is not great on any light precipitation at MCW,
but have maintained VCSH. Otherwise, concern will be for fog
development after midnight as winds drop off tonight. Current
favored location will be around the South Skunk River and Iowa
River with visibility restrictions possible at AMW, BNW, MIW, TNU,
and GGI.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Curtis
AVIATION...Ansorge



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