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Area forecast discussion 
National Weather Service Des Moines Iowa
1231 PM CDT Sat Aug 1 2015

Short term /today/...
issued at 334 am CDT Sat Aug 1 2015

Weak wave associated with earlier evening southwest storms and the
lingering thunderstorms over Lucas/Appanoose/Davis counties in the
southeast between 06-08z now heading out of the area. The main
system today is upstream and associated with a weak surface low near
western South Dakota/ND and eastern Wyoming with a warm front/stationary front
draped east across South Dakota to southern Minnesota at 07z. Features and
surface wind fields rather weak which will have an impact on forecast
later today. This especially true regarding initiation of expected
thunderstorms then into the overnight period. Meanwhile warm airmass
in place with expected return of moisture by middle to late afternoon.
With h850 temperatures 20 to 22c over the area and south-southwest h850 winds of 15 to
25 kts...temperatures will easily mix into the upper 80s to lower 90s by
late afternoon...priming an area of MUCAPE of 1500-2500 j/kg across
the west at the same time. Precipitable waters increase as well...with GFS values
nearing 2 inches over northwest sections at 00z. Various solutions
of mesoscale models...hrrr/nmm show an mesoscale convective system developing from the current
cluster of storms over South Dakota...then moving into eastern
Nebraska/southwest sections by 21z. The synoptic scale models favor
a more northerly track of development from the surface low later this
afternoon near Sioux Falls east/southeast with time through the
evening. The nmm does suggest secondary development over Iowa later in
the evening. Needless to say...low confidence with potential for
several mesoscale convective system through the next 24 hours and mixture of solutions. For
now am favoring the hrrr/nmm solution of storms tracking east-southeast
today...entering far western sections between 21-00z with some
additional development over far northwest sections in the same time
period. We remain outlooked for severe day1...with possibility that
very late in the period today the first batch may occur...better
chances after 00z.

Long term /tonight through Friday/...
issued at 334 am CDT Sat Aug 1 2015

A more active pattern setting up across the area for the middle/long
range beginning tonight. A shortwave trough will continue to push
east/southeast through the region today/tonight...with a frontal
boundary expected to drop through the County Warning Area late tonight and be across
southern Iowa Sunday before dropping south of the state Sunday
night. A warm front is expected to lift north through the state
today...with the County Warning Area in the warm sector by early evening. As the
shortwave trough approaches the region...convective activity
expected to develop across southeast South Dakota with an mesoscale convective system to push east-southeast across the
County Warning Area tonight. NAM/GFS/ec all show more of a northern Route...with the
hi-res models a bit further south. Have gone with a blend of the two
as exact placement still uncertain. Either way...decent shear and
instability in place so severe weather is expected. Precipitable waters around 1.6
to 1.8 inches so decent moisture in place and fz level around 12.4
kft. Therefore could again see some heavy rain...but overall rain
rates not expected to be as high as in recent events earlier in the
week. Some lingering activity expect in vicinity of the front Sunday
morning...with the front dropping south of the area late
Sunday/Sunday night.

Another weak wave may slide by and kick of some precipitation just to the
North/East of the County Warning Area Sunday night...with increasing chances for
additional precipitation late Monday into Monday night as models show
another mesoscale convective system moving across the area. Active pattern will continue
into the end of the week/next weekend with a northwest flow pattern
in place and weak impulses topping the western US ridge. Warm
temperatures expected with humidity creeping up this weekend and
heat indices pushing into the middle to upper 90s. Temperatures to drop back
into the 80s behind the front for Monday into Tuesday...with another
shot of cool air sending temperatures down into the 70s across the state
for highs late next week.

&&

Aviation...01/18z
issued at 1231 PM CDT Sat Aug 1 2015

VFR conditions will prevail through the taf period with the
possible exception of reduced visibilities/ceilings in and near
thunderstorms. Confidence in timing and placement of any storms is
relatively low...but appears best chance will be across the north/NE
after dark tonight and have maintained thunderstorms in the vicinity in that area.
Otherwise...anticipate mainly high clouds and varying SW winds
through the period.

&&

Dmx watches/warnings/advisories...none.

&&

$$

Short term...rev
long term...beerends
aviation...Lee

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