Area Forecast Discussion
Issued by NWS Des Moines, IA

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602
FXUS63 KDMX 240458
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
1158 PM CDT Fri Sep 23 2016

.SHORT TERM.../Tonight/
Issued at 335 PM CDT Fri Sep 23 2016

Tonight we will see a lull in the rather active weather we`ve been
having. Low pressure develops over the Plains and slowly shifts
East...reaching Eastern Nebraska and the Dakota`s by Saturday
morning. Storms will develop in these areas as a low level jet
increases again tonight and focuses into this area and interacts
with a frontal boundary. The storms should stay out of the
forecast area through tonight.  The only forecast problem tonight
will be the continuation of low level moisture trapped beneath a
ridge and North of a very slow moving warn front across central
Iowa which kept low clouds and reduced visibilities in fog.

.LONG TERM.../Saturday through Friday/
Issued at 335 PM CDT Fri Sep 23 2016

Models deepen an upper trough/low over the rockies and the surface
low that develops across the Plains will shift North as the cold
front associated with it slowly gets dragged across the state
through Sunday afternoon. Storms are expected to slowly move into
Western Iowa through the morning hours and into central Iowa by
late afternoon. The front will slowly lift Northeast across the
state Sunday. Instability is not great but sufficient. The
question will be how far the warm front lifts overnight and how
expansive the cloud cover will be over the state from the
convection out West. Extensive cloud cover will limit the amount
of instability we realize. Having said that though there is
sufficient shear for these storms to become supercells...at least
initially with large hail and damaging wind at least possible. The
bigger threat will be the heavy rain potential with PWAT`s
approaching an inch and three quarters over areas that hammered
the last couple of days.

By mid day Sunday the front exits to the East and the upper trough
will be over central Iowa to precip should be ending across the
area. Following the rain will be much cooler temps and pretty
breezy conditions for Sunday night and Monday. Temps may be too
warm for this period as some of the models are suggesting low 60s
for high Monday. For the remainder of the week a large ridge
slowly shifts across the area providing a dry several days for
Monday through Thursday. The models drive a shortwave against the
ridge Thursday into Friday but it will not have moisture to work
with and the Euro is much slower with it so with low confidence I
removed pops from the Thursday timeframe.

&&

.AVIATION.../For the 06Z TAFS through 06Z Saturday night/
Issued at 1159 PM CDT Fri Sep 23 2016

IFR conditions due to stratus were still over much of north
central IA at 05z with a few MVFR and LIFR spots as well. This
stratus is expected to remain fairly steady state through the
early morning hours until lifting northward and/or dissipating shortly
after sunrise. There is some potential for further development
south toward KDSM but confidence is not high enough for
inclusion. VFR conditions are then anticipated through much of the
day until convection increases west to east into the evening.
Confidence in location and timing is not great enough for any
mention beyond VCSH as of yet however.

&&

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

&&

$$

SHORT TERM...FAB
LONG TERM...FAB
AVIATION...Small



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