Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 212346

Area Forecast Discussion
National Weather Service Des Moines IA
646 PM CDT Wed Jun 21 2017

...Updated Aviation Discussion...

.SHORT TERM.../Tonight through Thursday/
Issued at 318 PM CDT Wed Jun 21 2017

Strong warm advection and moisture transport will persist this
evening into tonight with the main areas lifting northeast of
Iowa during the night. Scattered convection is expected across
northern Iowa late this afternoon and evening as this area lifts
north. Given the increasing CAPE and decent wind profiles, severe
storms will remain possible this evening. The low level jet axis
will persist across Iowa during the overnight with isolated to
scattered convection persisting near the axis as it veers into the
early morning. Strong to severe wind gusts will remain possible
with any of the stronger storms given the potential transport of
some of the LLJ momentum to the surface. Temperatures will be
warm overnight with modest surface winds and the warm sector over
much of the state.

Some left over convection is expected into Thursday across the far
north and east but should be on the wane as the LLJ decreases.
Focus will then turn to the approaching shortwave and convection
by Thursday afternoon into the evening. Moisture transport and
convergence will be focused into the area near or just north of
the Iowa/Minnesota border by early afternoon. Strong instability
will be in place south of a boundary which should be located in
near the northern Iowa border. Convection is expected to expand by
afternoon near the border and move to the east southeast into the
evening. Severe wind and hail will be possible with this
convection given the strong bulk shear values and an isolated
tornado or two near the boundary with localized backed winds.

.LONG TERM.../Thursday night through Wednesday/
Issued at 318 PM CDT Wed Jun 21 2017

Front will push through the state on Thursday night with
convection sliding southeast across central Iowa. The severe
potential will remain with winds and hail continuing to be the
primary threat. Otherwise, a much cooler and stable airmass will
overspread the state by Friday morning and remain in place for
much of the weekend. The threat of showers on Saturday is looking
less likely as models continue to evolve toward little
precipitation during the day. A few showers will remain possible
as a weak wave passes near the state, but most locations can
expect little if any rainfall. There will also be the threat for
isolated shra/tsra on Sunday afternoon as well with cool
temperatures aloft as upper system passes northeast of the state,
however these should dissipate quickly with loss of daytime
heating. However, much of the weekend will be dry with cool

Early next week will see warm advection returning by Monday and
persisting into the middle of the week. Moisture will eventually
work back into the region along with instability with the next
threat of storms arriving late Tuesday into Wednesday.


.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 643 PM CDT Wed Jun 21 2017

VFR conditions are likely to prevail throughout much of the TAF
period. Some lingering visibility restrictions anticipated at ALO
through around 02z at the latest from a diminishing thunderstorm.
Additional thunderstorms are possible overnight tonight and again
tomorrow afternoon, but low confidence in the coverage and
duration and thus left out mention of any thunder for OTM, DSM and
FOD and have mention of VCTS for ALO and MCW overnight as
convection may redevelop in this location.





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