Area Forecast Discussion
Issued by NWS Des Moines, IA

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157
FXUS63 KDMX 221056
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
556 AM CDT Sun Apr 22 2018

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

.SHORT TERM.../Today through Tonight/
Issued at 325 AM CDT Sun Apr 22 2018

Bottom Line Up Front...
No hazardous weather impacts expected today through tonight.

08z GOES-R water vapor imagery clearly picking up on upper low
spinning over southeastern Kansas. Adding IR imagery, mid to high
level clouds associated with this low have overspread Iowa,
lowering in cloud base towards the south as one would expect.
These clouds have helped mitigate radiational cooling as
temperatures have only fallen 5 to 10 degrees off their max highs
from yesterday. Water vapor imagery also picking up on a weak
shortwave coming onshore to the pacific NW that will bring very
minor impacts to the Midwest on Tuesday.

For today, the upper low over Kansas will continue to gradually propagate
southeastward, taking the ongoing mid-level clouds with it. 850mb
temps should be several degrees warmer today than they were
yesterday. Coupled with expectations for more sunshine than
yesterday as well, a 5 to 10 degree 24-hr warmup in temperatures
seems prudent. Tonight, with light winds few clouds in northern
Iowa, another night of sub-freezing temperatures is likely.

.LONG TERM.../Monday through Saturday/
Issued at 325 AM CDT Sun Apr 22 2018

Bottom Line Up Front...
Slight rain chances Tuesday and Thursday should bring no hazardous
impacts to Iowa in what will be a quiet week ahead.

Monday should be a quiet day as a 1020mb sfc high positioned over
northern Wisconsin advects dry air into Iowa. 850mb temps should
make it to +5C to +8C, which is a few degrees warmer than Sunday.
Added sunshine makes it easy to bump temps up 5 to 10 degrees on
Monday vs Sunday.

The weak upper low coming onshore to the Pacific NW as described
above should make it into the Midwest by Tuesday. The operational GFS
remains a stubborn outlier in its easterly track of the
shortwave. The remaining medium and long-range models...and even
the GFS ensemble to a fair extent... continue to keep agreement
with tracking the shortwave through Nebraska and Kansas, with
suitable dynamics passing south and west of Iowa. Given run-to-run
consistency, have begun to buy into non-GFS consensus blend and
have, subsequently, begun trend of lowering precip chances/QPF
for Tuesday into Wednesday. Clouds still seem like a decent
likelihood, so temperatures may need to be dropped a few degrees.

To end the week, long-range models have been consistent with
bringing an upper low from Alberta through Wisconsin and towards
the Great Lakes. The GFS has been notably deeper/colder and
stronger with this low, whereas the 00z Sun ECMWF has weakened
this to more of a relatively warmer, open wave pattern.
Ultimately, am not very excited about precip chances with this.
This could be cool enough to bring one last shot of sub-freezing
temperatures to Iowa, but there is a lot of time between now and
next weekend. If the ECMWF is correct, would expect to see trend
of increasing temperatures to begin. Overall, near to slightly
below normal temperatures expected this week.

&&

.AVIATION.../For the 12Z TAFS through 12Z Monday morning/
Issued at 554 AM CDT Sun Apr 22 2018

Medium-High confidence in VFR throughout TAF period. Small, non-
zero chance of fog impacts at KMCW tonight. Otherwise KOTM will be
breezy at times today, with winds diminishing to under 10 kts
after sunset.

&&

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

$$

SHORT TERM...Kotenberg
LONG TERM...Kotenberg
AVIATION...Kotenberg



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