Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 202318
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
618 PM CDT Sat Apr 20 2019

.DISCUSSION.../Tonight through Saturday/
Issued at 245 PM CDT Sat Apr 20 2019

Tonight into Sunday...
Relatively quiet conditions are expected during this time ahead of
approaching system. Thermal ridging will slide across the state
late tonight into Sunday with readings well above normal. Will
begin to see low level moisture increase into Sunday as well with
sustained southerly flow into the state. However, substantial cap
will limit the threat of any precipitation into Sunday evening.

Sunday night into Monday night...
Surface low will approach western Iowa late Sunday night and cross
the state on Monday before exiting to the northeast on Monday
evening. The aforementioned cap will persist into Sunday night but
convection is forecast to develop in Nebraska/South Dakota, some
of which will cross into Iowa later Sunday night. Organization
doesnt appear to be substantial given the relatively benign flow
seen on the soundings and anticipate most activity to be scattered
at most. The light shower/storm activity will persist, mainly
north and central into Monday with some reinvigorated convection
by afternoon into the far northeast in proximity of the surface
low. However, flow continues to be rather modest along with
instability and severe convection is not anticipated. Much of the
activity is expected to pass to the north and east on Monday
night with subsidence increasing across much of the area
overnight.

Tuesday through Saturday...
There may be a lingering threat of showers in the extreme
southeast portion of the forecast area on Tuesday, but most
guidance would suggest any activity remains southeast of the
state. Otherwise, weak surface ridging builds into the state later
Tuesday into Tuesday night with quiet and seasonable conditions.
Warm advection intensifies into Wednesday ahead of the next
boundary. The approach of this next boundary is handled
differently by the longer term models with the main forcing and
pcpn farther north with the GFS. The Euro does bring some very
light shower activity across the state and amounts would be
rather paltry. In either case, it should have limited impacts on
most activities. Both GFS and Euro show stronger warm advection
into Friday and Saturday with a surge of theta-e advection during
this time. This will likely lead to some shower and thunderstorm
activity in the Friday night/Saturday timeframe.

&&

.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 616 PM CDT Sat Apr 20 2019

VFR conditions will persist through the period. South wind at 7 to
10 kts overnight will be gusty by Sunday afternoon with a few
gusts over 25 kts expected.

&&

.FIRE WEATHER...
Issued at 245 PM CDT Sat Apr 20 2019

Elevated fire danger will continue into Sunday with strong and
gusty winds into the afternoon. Soundings in southern Iowa show
winds at top of mixed layer approaching 40kts for a few hours in
the afternoon with around 30kts in central to northeast portions
of the forecast area. Therefore, gusts of 35 to 40 mph seem
reasonable and possibly on the low end. Mixing will be good but
there will be advection of low level moisture into the state which
will limit the drop of relative humidity values to around 35
percent or so by mid afternoon. Overall, not quite red flag
conditions but certainly some elevated fire concerns during the
afternoon on Sunday.

&&

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

$$

DISCUSSION...Cogil
AVIATION...Donavon
FIRE WEATHER...Cogil


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