Area Forecast Discussion
Issued by NWS Des Moines, IA

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242
FXUS63 KDMX 251110
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
610 AM CDT Mon Jul 25 2016

...Updated for 25/12Z Aviation Discussion...

.SHORT TERM.../Today/
Issued at 306 AM CDT Mon Jul 25 2016

Quiet wx expected for the short term. Mainly clear skies expected
across the northern CWA...with some mid clouds across the southern
half especially this morning. CWA will be in a region of little if
any forcing. High pressure will dominate the wx. Have tweaked
temperatures slightly from going fcst. May see some patchy light fog
toward sunrise but should mainly be of the aviation type and will
burn off quickly.

.LONG TERM.../Tonight through Sunday/
Issued at 306 AM CDT Mon Jul 25 2016

Main trends continue on track for most of the week. Tonight and
Tuesday will continue to be dominated by high pressure over the area
with few if any clouds other than some high based cirrus. Gradually
the high will move east of the region by Tuesday morning with light
winds throughout the region. Though wont include in forecast at this
time...there may be some patchy ground fog by Tuesday morning
despite the lower dew points across the region. Not expecting any
real impacts to traffic at this time. Other than that temperatures
will remain warm with afternoon highs still reaching the upper 80s
over the south and in the mid 80s across the north. Overall the
trends with the midweek convection have slowed...with an apparent
start time of mid to late morning for most of the region west of I35
and the better chances remaining over the west half the balance of
the afternoon hours. With cloud cover highs will be cooler on
Wednesday and guidance in the ball park with lower 80s northeast and
mid 80s across the south.

There continues to be divergence in model solutions with regard to
the evolution of the mid to late-week system. The Euro and GEM are
generating a closed surface low with the passage of the next mid
level wave...with the Euro model nearer Iowa while the GEM is
tracking much farther south of the state. The GFS has more of a
diffuse system tracking south of the state. The more organized Euro
generates several inches of rainfall by the end of the week over
Iowa while the GFS keeps the heavier rain south and west of the
state. The difference in the models is arising due to differences in
the development of a Midwest trough aloft and the progression
/evolution of the upper level trough. The GFS is progressive with no
phasing taking place between the two waves as they cross the
Midwest. The Euro on the other hand suggest the first wave slows and
the second wave arrives/phases and deepens the entire trough closer
to Iowa. With better dynamics aloft a surface system would then be
more likely to develop. Though correctness in either solution is
questionable for now...the Euro is generally better at timing the
movement of systems between 3-5 days compared to the GFS. However
...climatology would not generally favor a deepening wave over the
Mississippi River Valley this time of year. For now will continue
trends of increasing PoP from Wednesday through Friday... with
lingering thunder chances even on Friday. The latter portion of the
week looks wetter and cooler in either case...with the Euro having a
wetter forecast at this time. Given the clouds and
precipitation...highs will be held back in the 70s to lower 80s and
lows in the 60s. Late in the period and closer to the weekend
conditions should improve with departure of the system though some
may return toward Saturday night and Sunday... giving the region
only about 24-36 hours of dry weather.

&&

.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 610 AM CDT Mon Jul 25 2016

VFR conditions will prevail through the entire TAF period. Surface
high pressure will slowly drift eastward across Iowa...and will be
centered over eastern Iowa by 12Z Tue.

&&

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

$$

SHORT TERM...Zogg LONG TERM...rev AVIATION...Zogg



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