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Area forecast discussion 
National Weather Service Des Moines Iowa
312 PM CDT Wednesday Jul 23 2014

Short term /tonight/...
issued at 242 PM CDT Wednesday Jul 23 2014

High pressure will continue to push southeast into Great Lakes
region overnight. This will help to keep conditions dry throughout
the overnight...with clouds mostly decreasing after sunset. As high
pushes east winds will become more southerly late in the
period...with increase warm air advection across the west. Have warmed lows slightly
given amount of warming in the afternoon and warm air advection and increasing
clouds...especially in the west. Approaching system will reach
western Iowa by early morning...though best forcing does not arrive
into County Warning Area until after 12z. Given relatively dry conditions...have
therefore opted for a dry forecast through the period...though may
be too dry in the west in the early morning hours.

Long term /Thursday through Wednesday/...
issued at 242 PM CDT Wednesday Jul 23 2014

Thursday through Friday night...
surface high to propagate east of Iowa by late Thursday morning.
County Warning Area to return to southerly flow...but high should be close enough
to hold more notable warm air advection off until Friday. 700 mb
temperatures forecast to be near +11c which would cap off most
convection...especially east of I-35. Additional problem Thursday
in the dmx County Warning Area will be a notable lack of moisture. Surface trough to
pass through the Dakotas and into southern Minnesota/northern Iowa
Thursday and Thursday night. Strong southwesterly winds of 40 to
45 kts at 850 mb will support decent slug of moisture transport
into western Iowa by 06z and Interstate 35 by 12z...bringing precipitable water
values up to +1 to +2 Standard dev. Tight gradient of Theta-E advection
to move across County Warning Area from west to East. Cape values Friday morning not
significant so no severe weather threat. Forecast soundings show
decent warm cloud depth...so expect decent precipitation
efficiency. Shear profile sufficient to sustain storms as they
propagate eastward...pushing east of the County Warning Area by 18z. Forecast
issue will be if there will be afternoon convection associated
with daytime heating. Models showing axis of moisture convergence
oriented north-S to move across County Warning Area during the day. However...h850
temperatures pushing +25c and h750 mb temperatures pushing +15c will create
formidable cap. Best forcing to be east of County Warning Area with morning
system. With no apparent triggers or forcing mechanisms to help
break cap...so will confine Friday PM probability of precipitation to eastern parts of
County Warning Area. Regardless of probability of precipitation...am confident that heat index values will
range from 95 to 105 for central to southwestern parts of County Warning Area.

Saturday through Wednesday...an unseasonably strong upper trough is
forecast to be along the US/Canadian border at 12z Saturday. The
12z models are in decent agreement with the overall theme of
amplifying the upper trough over the Great Lakes and eastern US and
a ridge over the western Continental U.S.. unseasonably cool air will
dominate the weather patter over Iowa from Sunday through the
extended. Temperatures in forecast may not capture the coolest
temperatures and will need to be adjusted. There will be a few
precipitation chances during this time frame...but the weather
should be mainly dry. Surface ridge should be east of Iowa by
Wednesday and temperatures will likely warm beyond the forecast
period.

&&

Aviation...23/18z
issued at 1223 PM CDT Wednesday Jul 23 2014

Conditions will remain VFR through period...winds will shift to
the south ahead of approaching system. May see thunderstorms and rain/thunderstorms in the vicinity at
western and northern sites...kfod/kmcw...near end of period and
beyond period.



&&

Dmx watches/warnings/advisories...
none.
&&

$$

Short term...awb
long term...kotenberg/Johnson
aviation...awb

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