Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 221732

Area Forecast Discussion
National Weather Service Des Moines IA
1232 PM CDT Fri Mar 22 2019

...Updated for 18z Aviation...

.DISCUSSION.../Today through Thursday/
Issued at 332 AM CDT Fri Mar 22 2019

Quiet weather is expected today with surface and upper level
ridging in vicinity of Iowa. Temperatures will be similar to
Thursday albeit slightly cooler in the north and east where some
weak cold advection will be occurring. Otherwise, relatively
seasonal weather through tonight. An upper low crossing the
Rockies tonight will pass into the Plains on Saturday. This will
lead to increasing warm advection by Saturday with the
strengthening southerly flow also bringing moisture back toward
Iowa. As isentropic lift increases through the day, clouds will
rapidly overspread central Iowa with light rain developing into
southwest Iowa by midday. This initial surge of theta-e advection
is expected to push northeast into the afternoon with light rain
moving across the southwest half of the forecast area by sunset on
Saturday. Precipitation amounts will be relatively light
initially as forcing passes quickly.

More substantial forcing will arrive late Saturday night into
Sunday morning with the main upper low as decent Q-convergence
pushes across central and southern Iowa. The associated lift will
produce widespread rainfall across much of the forecast area but
mainly across the southern half of the state. Elevated instability
does graze far southern Iowa and a clap of thunder or two is not
out of the question near the Missouri border. Rainfall of up to a
half an inch or so is expected near the I80 corridor as the rain
continues through Sunday morning. The precipitation should begin
to taper off by midday Sunday and into the afternoon as increasing
subsidence spread from west to east into Iowa. Cooler air will
arrive Sunday night into Monday with below normal readings during
this time.

The upper trof across the central Conus will shift east on Monday
into Tuesday with a low amplitude ridge building into the central
US by midweek. Warm advection will intensify by Tuesday into
Wednesday with temperatures rebounding. Moisture will also be
drawn back north and will have to watch for the possible
development of stratus during this time as well. Both Euro and GFS
indicate a decent threat of precipitation toward the end of next
work week with a boundary across Iowa. Instability will also be
higher with this system with the potential from stronger
thunderstorms as the upper system approaches. Concerns for heavier
rainfall somewhere in the state will also need to be considered
and monitored.


.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1228 PM CDT Fri Mar 22 2019

VFR conditions are expected throughout the period. Light north
winds will gradually shift from northerly this afternoon to
easterly through tomorrow.





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