Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 200421

National Weather Service Des Moines IA
1120 PM CDT Wed Oct 19 2016

.SHORT TERM.../This evening through Thursday/
Issued at 334 PM CDT Wed Oct 19 2016

A quiet night is in store across the forecast area with high
pressure building in from the northwest. Thick high clouds early
tonight will begin to clear out late, and modest north northwest
breezes will push cooler air into Iowa with temperatures dipping
into the mid 30s across the north. A few sprinkles are expected at
times, mainly northwest and southeast, but will have no impact.

.LONG TERM.../Thursday night through Wednesday/
Issued at 334 PM CDT Wed Oct 19 2016

The primary sensible weather concern will not occur until late in
the forecast period with only temperature swings until then. Mid
level kinematic forcing/DPVA will remain over Iowa into Thursday
morning but precip is not expected with subsidence and cold
advection below 3km. The current northern Plains ridge will also
usher in cooler air behind the departing OH Valley front with highs
only reaching the 50s Thursday. Lows into Friday morning will
approach the freezing mark again with frost possible north and east.

Dry, higher amplitude NW flow will persist as this system reaches
the eastern CONUS keeping our forecast dry into early next week.
There is a surge of warm/theta-e advection starting our temp rebound
late Friday, but moisture seems insufficient for any precip beyond
virga or sprinkles not worth a mention at this time. After a very
weak frontal/trough passage around Sunday, this will eventually
transition to upper level ridging through the MO Valley by Monday
and then SW flow to some degree into midweek. This will allow for
increased PoPs started by token amounts into Tuesday in theta-e
advection and then higher into Tuesday Night and Wednesday. There is
a fairly wide spread in short wave strength through GFS/ECMWF
deterministic and ensemble runs so while the confidence in details
is not great, it has increased that precip will manifest itself to
some degree. The strength and track of the surface low is in
question but thunder will likely come back into play and even
possibly a minimal severe threat, especially if the convection could
become surface based with enhanced shear along and ahead of whatever
form the surface low and warm front take.


.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1120 PM CDT Wed Oct 19 2016

VFR conditions are expected through the TAF period. Winds will
become NNW with speeds generally below 12 knots but increase some
after 16Z. Only high clouds and perhaps a few sprinkles are
anticipated with the passage of an upper level trough axis tonight.
The concern of low clouds is somewhat less as satellite imagery
showed low clouds diminishing instead of expanding.





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