Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 231048
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
548 AM CDT Mon Apr 23 2018

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

.SHORT TERM.../Today through Tonight/
Issued at 359 AM CDT Mon Apr 23 2018

Bottom Line up Front...
Quiet, persistent short term forecast as no hazardous weather
expected.

08z Mon GOES-R water vapor imagery picking up on large upper low
spinning over the Ozarks. This upper low should continue to
gradually propagate eastward. Iowa impacts from this low are mid to
upper clouds from southern to central Iowa. As the low moves
eastward, these clouds should depart as well, setting Iowa up for
another sunny day today. 850mb temps warm up around 2 or so degrees
today versus yesterday. Ultimately, starting with persistence a
great start, followed by warming up temperatures a few degrees.

.LONG TERM.../Tuesday through Sunday/
Issued at 359 AM CDT Mon Apr 23 2018

Bottom Line up Front...
Quiet long term, with very slight possibilitiy of thunder
Thursday evening as only potential hazard.

Tuesday into Wednesday...
Well-advertised shortwave still slated to impact the Midwest
Tuesday into Wednesday. Timing has been slightly delayed, so
precip now lingers into Wednesday morning. Track of the shortwave
has been forecast focus the past few discussions, and spaghetti
plots finally starting to tighten around a solution in tracking
the upper low through southeastern Nebraska into
northern/northeastern Kansas. This has effectively been the non-
GFS track (the GFS has been an easterly outlier), though the 00z
Mon ECMWF did nudge slightly farther east. Overall, lack of
moisture continues to be biggest inhibitor to this system. With
broad low-level cyclonic flow over the Deep South, Gulf of Mexico
moisture access completely shut off.

Behind this system, a broad, weak 1020 mb sfc high will race
eastward across the center of the country, serving to bring dry air
entrainment and sunshine into Iowa by Wednesday afternoon.

Thursday into Friday...
Long-range models have been showing good run-to-run consistency
in bringing an upper low across Manitoba into Ontario, with an
attendant cold front draping southwestward though Iowa. Sfc
reflection low should be over the Northwoods of Wisconsin by 00z
Fri, with the fropa reaching the eastern edge of the DMX CWA.
Temperatures will be very tricky for Thursday... if the front is
accelerated a few hours, clouds and light precip will blanket most
of the CWA through peak heating, which would lower temps about 5
to 10 degrees from going forecast. Similar to the Tuesday system,
there will be cyclonic flow over the Deep South as the fropa is
going through Iowa, so Gulf of Mexico moisture access will be shut
off once again. Enough frontogenetical forcing and ascent
processes in play with fropa to generate light precip.

Overall, near normal temperatures for this week. Interestingly, a
very quiet forecast in terms of winds. Behind the front on
Thursday into Friday may be the only day of the week where winds
get appreciably above 10 or so mph. Hints into early next week of
intermountain thermal ridge making it into Iowa... if this does,
cannot rule out 80s for Sundayish-Tuesadyish time period.
Obviously a lot of time for change between now and then though.

&&

.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 547 AM CDT Mon Apr 23 2018

High confidence in VFR flight conditions throughout TAF period.
Mid to high-level clouds expected, with winds at or below 10 kts.

&&

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

$$

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



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