Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kdmx 141051 
afddmx

Area forecast discussion
National Weather Service Des Moines Iowa
551 am CDT Mon Oct 14 2019

Discussion.../today through Sunday/
issued at 416 am CDT Mon Oct 14 2019

Ridge of high pressure is situated across much of Iowa early this
morning. The broad area of stratus that covered the area on Sunday
has nearly all dissipated leaving mostly clear skies across the
state. The clear skies and light winds have setup near peak
radiational cooling with temperatures dropping into the upper 20s
to low 30s common early this morning. The light winds along with
temperature and dew point spreads near 3 degrees or less will also
lead to the first widespread frost this morning. Recall the first
freeze had stronger winds thus a lack of frost with the previous
cold temperatures early Saturday.

The high pressure ridge will push east today with warm advection
developing by mid to late morning from west to east. The
atmosphere this morning is starting off quite dry with precipitable water values
around 0.30". Moisture will be lacking much of the day therefore
expected plentiful sun much of the daytime with a few periods of
filtered sun with passing cirrus. A stronger push of Theta-E
advection arrives as the low level jet increases to 45 kts this
evening. In addition, increasing kinematic forcing will be
arriving overnight ahead of a vigorous upper low that will be
dropping into the northern plains late tonight into Monday.
Despite the forcing, only a few isolated thunderstorms are
possible over far eastern Iowa, mainly after midnight. Otherwise
not expecting much if any precipitation elsewhere with moisture
still lacking. The more significant impact with be the increasing
northwest winds in the wake of a cold front that will move across
the state. Differential cold advection initially will lead to a
well mixed boundary layer with the cold advection leading to good
momentum transport of mixed layer winds to the surface. Mixed
layer winds may reach 35-40 kts during the afternoon coincident
with the peak pressure gradient of 25 ubars/km and peak subsidence
behind the upper short wave. Expect Wind Advisory headlines may be
required for much of the area Tuesday. Temperatures will be steady
to falling during the afternoon hours. A few flurries also
possible far north though the primary moisture plume is below the
dendritic growth zone.

High pressure arrives once again on Wednesday followed by another
round of warm advection on Thursday. Upper level southwest flow
develops by Friday leading to increasing chances for showers and
thunderstorms late Friday and into the weekend. The greatest
chances for precipitation will be Friday night and then Sunday. At
this time, the primary upper level will lift northeast out of the
long wave trough on Monday with strong cyclogenesis occurring and
leading to active weather somewhere across the Midwest. Low
confidence tracking placement this system though at this time.

&&

Aviation.../for the 12z tafs through 12z Tuesday morning/
issued at 549 am CDT Mon Oct 14 2019

Aviation forecast is wind direction and low level wind shear driven for the
period. Light and variable wind today will become southeasterly
during the day then gradually southwest overnight. An increasing
low level jet will create low level wind shear overnight tonight. Isolated
thunderstorms are possible vicinity kmcw/Kalo late.

&&

Dmx watches/warnings/advisories...
none.

&&

National Weather Service Glossary of Abbreviations