Scientific Forecaster Discussion
fxus63 kdmx 162333
Area forecast discussion
National Weather Service Des Moines Iowa
633 PM CDT Wed Oct 16 2019
.. updated for 00z aviation...
Discussion.../tonight through Wednesday/
issued at 344 PM CDT Wed Oct 16 2019
Today, stratocu and stratus hung across much of the region through a
good part of the day. There were some occasional holes in the cloud
shield but in general those holes filled in with stratocu before too
long. Clearing occurred across the southwest into west central
during the early afternoon but this did little to help temps.
Tonight the clearing trend will continue although clouds will linger
north and east for a fair part of the evening. Forecast lows
tonight do reflect the expected clearing although if clouds hang
around, temps will not fall off as far as expected.
Thursday a ridge of high pressure aloft will shift east through the
day with the ridge axis over central Iowa by 00z Friday. At the
surface, high pressure will move east allowing for surface winds to
become southerly by mid to late morning. With sunshine and warmer
air pushing up, Thursday will be a nice day with mid 50s to mid 60s
expected for highs.
Friday the upper ridge moves off into the Great Lakes region with a
large trough pushing into The Rockies and Western Plains. A surface
low will develop over the northern plains with a cold front into the
plains. Strong southerly winds will develop ahead of the cold front
which will enter the state in the late afternoon or early evening.
Friday will be warmer still but will be breezy. Strong lift will
spread into the state late day and especially Friday evening and
should be enough to develop showers and a few storms along the
frontal boundary. Moisture is questionable so the coverage may not
be widespread but southern and eastern Iowa should see at least
isolated to scattered showers/storms.
This system pushes east on Saturday with precip ending in the
morning hours. Saturday and Sunday should be mild with increasing
winds on Sunday ahead of a stronger system to impact the state.
Sunday afternoon a deep trough in the Western Plains shifts east as
a strong surface low and front develops across the plains. Sunday
evening through Monday morning this system intensifies as it lifts
into western Iowa. Instability of 500 j/kg develops over southern
and western Iowa along with strong shear will bring a window of
opportunity for some strong with possibly severe storms Sunday
Models vary on the position of the surface low by Monday but the
consensus is that precip will be east of the forecast area between
18z and 00z. It will be very windy Monday into Tuesday and models
are not handling the wind very well. Winds at this point were
increased at least 10 mph sustained with higher gusts. Given the
strength of this system this is likely still not enough but given
the discrepancies between location of the low it should serve as a
decent starting point. Colder air will spill in behind this system
for Monday night and Tuesday but any lingering precip is in
question. The Euro drops some wrap around precip into northwest
Iowa while other models wrap the low up and push it into the Great
Lakes leaving Iowa dry...cool and breezy.
Aviation.../for the 00z tafs through 00z Thursday evening/
issued at 632 PM CDT Wed Oct 16 2019
VFR conditions are expected through the taf period. Northwest
winds will become variable overnight before switching around to
southerly by Thursday afternoon, increasing to around 10 knots.