Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 292350

National Weather Service Des Moines IA
650 PM CDT Thu Sep 29 2016

...Updated Aviation Discussion...

.SHORT TERM.../This evening through Friday/
Issued at 334 PM CDT Thu Sep 29 2016

Little of concern tonight outside of possible fog redevelopment. The
Ohio Valley upper low should remain nearly stationary with clear
skies across Iowa. The broad low level cyclonic flow continues to
drawn in some lower humidities, especially east, however the latest
RAP shows somewhat higher 0-500m RH north and west. This is also
where early morning stratus and fog lingered so have introduced some
patchy fog wording there early in the morning with clear skies and
light wind.

.LONG TERM.../Friday night through Thursday/
Issued at 334 PM CDT Thu Sep 29 2016

The more likely window for sensible weather through this period will
be toward the middle of next week, although the current Ohio Valley
upper low may just brush Iowa with light precip over the weekend.
The models are in good agreement drifting the system back to
southern Lake Michigan by late Saturday. The forcing will be neutral
or subsident but increasing moisture 3km and below may be sufficient
to squeeze out some light showers east. The system should finally
depart to end the weekend as the western CONUS trough advances.
This will increase temps and moisture somewhat as return flow
begins and ridging enters Iowa. The GFS and ECMWF are now fairly
consistent and suggest deep forcing increasing west to east
Tuesday Night into Wednesday. Timing is still somewhat suspect
however with the ECMWF frontal passage much faster, so while the
best window appears to be around Wednesday have lingered some low
PoPs east into Thursday. Instability looks weak regardless of the
solution, but both deep and shallow shear are quite high. This
suggests somewhat of a weak, subtle fall QLCS tornado threat if
diurnal timing is favorable due to the high shear values 3km and


.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 650 PM CDT Thu Sep 29 2016

VFR conditions will prevail through the entire forecast period.
Fog is possible by Friday morning and may impact FOD and MCW, but
low confidence in mentioning attm.





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