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fxus63 kdmx 192055 
afddmx

Area forecast discussion
National Weather Service Des Moines Iowa
355 PM CDT Fri Jul 19 2019

Discussion.../tonight through Friday/
issued at 353 PM CDT Fri Jul 19 2019

Very warm and humid conditions are in place across all of Iowa this
afternoon. Dew points at several ASOS sites are in the 79 to 80
degree range. The high dew points combined with temperatures in the
low to mid 90s have push heat index values into the 105 to 110
degree range. Surface low pressure over west central Minnesota with
a boundary to the east towards Twin Cities. Vigorous convection has
developed to the north of this boundary and east of the surface low.
The boundary will sag south overnight as everything translates
eastward into Wisconsin and will move into northern Iowa by Saturday
morning. The boundary will undercut the existing elevated mixed
layer which will continue to provide a capping inversion to
convective development. It is possible that existing storms could
move into far northern Iowa and augment the environment but
confidence is low on how far south convection will get during the
day Saturday as the cap slowly erodes. Latest cam solutions suggest
that convective development will be delayed until mid to late
afternoon until a short wave arrives. The initial development would
be Post surface boundary and over northern Iowa. A better potential
for surface based convection will exist into central and southern
Iowa where afternoon heating will erode the eml. The excessive heat
warning remains in effect for a large portion of the state Saturday,
however, expect the headline will be shaved back towards Highway 30
to Interstate 80 tonight when a better grasp of where the surface
boundary is Saturday morning.

A few severe storms will be possible late Saturday and Saturday
night with the main threat being damaging wind gusts. The more
significant threat will be the potential for heavy rainfall with
deep warm cloud depths and precipitable water values in excess of two inches as
the an increasing low level jet feeds into the boundary. The
greatest potential for heavy rainfall Saturday night will be south
of Interstate 80. The boundary will remain over northern Missouri on
Sunday with another round of moisture lifting over the boundary into
Iowa. This will keep a shower and thunderstorm threat going into
southern Iowa during the day. Otherwise, much cooler conditions
Sunday with highs in the 70s to low 80s.

High pressure will build into the region on Monday and will dominate
the weather into the mid portion of the week. Much cooler conditions
and dry weather is expected during this period. Have maintained a
dry forecast through Thursday and Friday though some signals that a
few chances for precipitation may arrive by the end of the week.

&&

Aviation.../for the 18z tafs through 18z Saturday afternoon/
issued at 1223 PM CDT Fri Jul 19 2019

VFR conditions are expected through much of the period. Breezy
conditions this afternoon will diminish overnight. A boundary
will drop south into northern Iowa by early Saturday. At this
time, confidence is low on how far south this boundary will extend
by 18z Saturday.

&&

Dmx watches/warnings/advisories...
excessive heat warning until 7 PM CDT Saturday for iaz023>028-
033>039-044>050-057>062-070>075-081>086-092>097.

Excessive heat warning until 10 PM CDT this evening for
iaz004>007-015>017.

&&

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