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Area forecast discussion 
National Weather Service Des Moines Iowa
327 PM CDT Thursday Jul 24 2014

Synopsis...
issued at 316 PM CDT Thursday Jul 24 2014

Low pressure over western South Dakota will move east and be over southern WI by
Saturday evening. Cold front will trail the low and move through
Iowa Saturday night. Low pressure will move northeast along the
front Saturday night. Cool high pressure will build into the
region Sunday through the middle of next week.

&&

Short term /tonight/...
issued at 316 PM CDT Thursday Jul 24 2014

Large area of Theta-E advection ahead of approaching low pressure
system has allowed for area of thunderstorms across northern Iowa
and western portions of the County Warning Area. Models have a poor handling on the
current situation...indicating that precipitation will decrease.
While Storm Prediction Center analysis shows a relatively unfavorable environment for
storms...given ongoing precipitation and strength of Theta-E
advection...anticipate this to continue through the late afternoon
and evening hours. Precipitation appears to be elevated...and will
continue to be with very limited surface based cape. Therefore any
threats for severe weather will primarily be large hail.

As low pressure system approaches...precipitation with shift to the
north/northeast. In addition...low level jet is expected to
increase...impinging on north and northeastern portions of County Warning Area
beginning near 06z. Have therefore increased probability of precipitation beyond 06z. Low level jet is
expected to push south somewhat near 12z...and have brought higher
probability of precipitation further south. Models are a bit slower...and have hung on to
precipitation through 12z. Precipitable water values overnight remain high...over 1
inch...and locally heavy rainfall will be possible with
storms...however dynamics decrease overnight...and anticipate severe
threat will also diminish.

Long term /Friday through Thursday/...
issued at 316 PM CDT Thursday Jul 24 2014

Warm front will lift across the County Warning Area with strong capping moving in
rapidly during the day. 700 mb temperatures will warm to +16 with cin
remaining greater than -50 even during maximum heading. Do not look
for any precipitation in the County Warning Area after early Friday morning through
Friday night..and only low probability of precipitation across the south with the wave
passage Saturday and Saturday night.

A strong push of warm air aloft and quick return to dew points in
the 70s again for Friday. Much of the County Warning Area will not have a chance
to recover enough to reach heat advisory criteria...but the
southwest is likely to reach 105 or better for a couple hours
Friday afternoon. Will hoist a heat advisory for those areas from
17z-00z. Clouds and cooling will keep heat indices below criteria
fro Saturday.

Much of the rest of the forecast period will be dominated by cool
Canadian high pressure. Temperatures will be below normal through the
week. A dry weak is on tap until at least Thursday. Once the high
pressure retreats to the east...return flow will bring a chance
for thunderstorms Wednesday night into Thursday.

&&

Aviation...24/18z
issued at 1228 PM CDT Thursday Jul 24 2014

Low pressure system will begin to affect sites near 00z...with
precipitation chances especially at northern sites
kfod/kmcw/Kalo. Have included only vc mention at this time due to
uncertainties in timing and location of thunderstorms and rain or
rain showers...however...kmcw/Kalo may see thunderstorms and rain...especially after 06z.
Winds will increase through the period...becoming strong and gusty
after 12z. Overall...conditions will remain VFR through periods of
MVFR or lower visibilities and ceilings will be possible within
thunderstorms and rain.



&&

Dmx watches/warnings/advisories...
heat advisory from noon to 7 PM CDT Friday for Adams-Cass-
Ringgold-Taylor-Union.

&&

$$

Synopsis...MS Jul 14
short term forecaster...awb
long term...MS Jul 14
aviation...awb

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