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Area forecast discussion 
National Weather Service Des Moines Iowa
623 PM CDT Monday Jul 6 2015

Short term /tonight/...
issued at 320 PM CDT Monday Jul 6 2015

Initial main concern is with convection ahead of boundary pushing
through central Iowa. Much of the area has been overcast today
from ongoing rounds of showers and storms. This has limited
instability ahead of the front in most locations except for areas
near the Missouri border. Any chance to see severe weather will
come from storms that form in this airmass near the border
although shear is marginal at this point. Damaging winds will be
the main threat with secondary from large hail as warm layer depth
will be quite deep this evening. However...given this deep warm
layer and precipitable waters of 2+ inches...heavy rainfall will be likely with
any storm. While overall storms should remain progressive...there
may be isolated instances of flash flooding in far southern Iowa
prior to boundary arrival later this evening. This area did miss
much of the heavy rain from this morning and has had around two
weeks to recover from previous heavy rain events...therefore there
is some storage capacity. The boundary will pass through the
entire area by later this evening with cooler and drier Canadian
airmass pushing into the state. There has been some visibility
restrictions in this airmass as smoke from Canadian Forest fires
has been advected into the area as well. Therefore...there should
be hazy conditions into the overnight from this smoke over much of
the state and likely into the morning. Temperatures will be much
cooler overnight as dewpoints drop into the upper 40s to 50s
across the forecast area.

Long term /Tuesday through Monday/...
issued at 320 PM CDT Monday Jul 6 2015

Surface high pressure will push south from Canada into Iowa for
Tuesday and begin pushing east Wednesday. This will keep
conditions cool and dry. Have kept temperatures near going...and
below normal...but may be too warm if smoke from Canadian wild
fires pushes into Iowa...though models keep most of this north and
west. As high pushes east low begins to lift northeast through
Oklahoma and Missouri...which may affect southern Iowa Wednesday.
There is still uncertainty in the northern extent of this low
with influence of high. GFS keeps system south of Iowa with Gem
and NAM bringing it well into southern Iowa. Believe these models
are under doing the amount of middle level dry air...and have
therefore trended towards the European model (ecmwf) which is more of a blend of
these two solutions for Wednesday and Wednesday night.

Next concern will become rain chances Thursday night as ridge
begins to build into Southern Plains and boundary pushes north
into Iowa. Models are in fairly good agreement with placement of
system. Concern will become potential for heavy rainfall across
the south with precipitable water values again near 2 inches. As ridge builds
system will continue to push north...with an active pattern for
the end of the period...with chances for thunderstorms off and on
through the weekend. Expect to see breaks in the chances with best
forcing to the west Friday...and the north Sunday though diurnal
development cannot be ruled out at this time....with the best chances
Saturday. Chances for severe thunderstorms will increase in this
time with instability increasing...though at this time models indicating
more limited shear...though at this temporal length will need to
continue to be monitored for severe potential. Temperatures will
warm through the end of the period as well with ridge building in.
Guidance brings highs into the 90s for the weekend...though have
kept temperatures under at this time with some uncertainties in
convective trends as well as how strong ridge will be with low
pressure expected to push south through the weekend.


issued at 623 PM CDT Monday Jul 6 2015

Rain showers/thunderstorms and rain and low clouds are clearing off to the southeast...and
may affect kdsm/kotm intermittently in the next couple of hours
but thereafter will be of no concern. However...a broad swath of
smoke from Canadian wild fires has lowered to the surface across
much of northwestern Iowa and neighboring states and will produce
MVFR to briefly IFR visibilities tonight. It is difficult to predict when
these visibilities will improve...but current thinking is that it will
not be until at least late tonight and possibly not until late
tomorrow. Have trended this way in the 00z tafs...but amendments
may be necessary.


Dmx watches/warnings/advisories...none.



Short term...cogil
long term...awb

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