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Area forecast discussion 
National Weather Service Des Moines Iowa
1159 PM CDT sun may 24 2015

Short term /tonight/...
issued at 318 PM CDT sun may 24 2015

A couple rounds of moderate to heavy rainfall are expected for the
County Warning Area tonight...with little if any thunder expected except early in
the period mainly across the far southeastern County Warning Area. The 18z WRF
reflectivity summarizes forecast thoughts rather well regarding radar
trends for the short term period of the forecast.

The first round will be from late afternoon into this
conjunction with the mesoscale convective vortex presently lifting northeast through central
Missouri. There will be a brief period across the far southeastern
County Warning Area...where instability will be higher until the mesoscale convective vortex passes later
this evening. Although widespread severe weather is not expected...any storms
that do develop may have to be monitored due to the combination of
elevated instability as well as shear values...again across the far
southeastern County Warning Area. Would not be surprised to see some isolated heavy
rainers from the convection as it lifts northeast.

The second round of moderate to heavy rainfall will be overnight
tonight into Monday conjunction with the mesoscale convective vortex presently
in the arklatex region. Greatest threat for heavy rainfall will be
across central and eastern parts of the County Warning Area...especially in central
and southern Iowa roughly centered on the I-35 corridor given the
precipitation residence time. Precipitable water values are quite impressive...with values
as high as around 1.7 inches and thus exceeding the 90th percentile
and approaching record high values for this time of year. Warm cloud
depths will approach or exceed 12 kft. Although deep-layer
instability will not be high...MUCAPES will be sufficient along with
anomalous moisture to result in a heavy rain threat. Even thunder
will not be needed for efficient rainfall production overnight. Am
not overly concerned about widespread flash flood threat have opted to not issue a Flash Flood Watch. That being
said...some isolated instances of minor flooding is possible...
especially in urban areas or areas with poor drainage.

Only minor tweaks to forecast temperatures tonight...mainly lowering them a
couple degrees in places as highs today did not go as high as

Long term /Monday through Sunday/...
issued at 318 PM CDT sun may 24 2015

Surface low will continue to lift north through the beginning of
the period...and expect ongoing precipitation across much of the
area in the early morning hours...especially the north. This will
lift north...with boundary lingering near Minnesota/Iowa boarder through
the morning hours. Weak trough will push east through the late
morning into central Nebraska. Concerns about precipitation
redeveloping near eastern Nebraska in the afternoon and pushing
east into Iowa late in the afternoon. High res models are trending
towards this solution. Concern will be with severe potential with
storms which may develop...with models indicating cape values in
the late afternoon and early evening across central Iowa near or
above 2000 j/kg with shear increasing along weak
boundary...sufficient to allow for storms which develop to
persist with potential to become severe...with hail and wind the
main threats. Surface low will lift northeast across eastern Iowa
through Tuesday. This will allow for precipitation chances to
persist along boundary draped across Iowa through Tuesday. With
slow moving low...concern becomes for heavy rain potential.
Conditions will remain favorable to allow for rainfall rates to be
heavy at times...though moisture begins to diminish with precipitable water
rates much lower...closer to 1 inch...and warm cloud depths not as
deep. However...efficient rainfall will be possible and cannot
rule out potential localized heavy rain. Will need to monitor for
flash flood and flood potential given previous days rainfall
across the area.

System will finally push south of the area Tuesday night...with a
break in precipitation chances Wednesday before large upper level
low pushes east across northern Canada with associated system
pushing into central Iowa late Thursday bringing another round of
precipitation chances through the extended. Models hang boundary
up in central/southern Iowa through the weekend...with GFS the
most aggressive developing another low across Central Plains
states...and keeping persisting chances for thunderstorms across
Iowa. Have trended towards European model (ecmwf) with precipitation chances
ending from north to south through the weekend. Temperatures will
be generally steady through the week with highs in the 70s and 80s
and lows in the 50s and 60s. However...behind boundary late in the
period temperatures will again be much cooler.


issued at 1159 PM CDT sun may 24 2015

Warm sector has spread across the forecast area this evening and
will continue into the day on Monday. Have seen ceilings across
much of the area climb above MVFR and anticipate much of the area
to be VFR overnight. Some MVFR visiblities may occur in the
northwest near kfod where light winds allow for light fog
development. Generally VFR conditions on Monday with increasing
southwest surface winds. Some convection is expected by Monday
evening which will produce scattered MVFR conditions in and around


issued at 318 PM CDT sun may 24 2015

Although moderate to heavy rainfall is expected overnight tonight in
conjunction with the two rounds of activity...a widespread flash
flood threat is not anticipated...thus Flash Flood Watch was not
issued. Forecast rainfall amounts remain below flash flood guidance
values. Of more concern regarding flash flooding is its potential
late Monday into Monday in conjunction with the activity then.

In terms of river flooding...minor to moderate within-bank rises are
expected at multiple locations especially within the middle to lower
Des Moines River well as the lower Raccoon river basin.
If rainfall over the next 36-48 hours comes in heavier than
expected...then minor flooding could be expected at some


Dmx watches/warnings/advisories...


Short term...zogg
long term...awb

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