Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 310837

Area Forecast Discussion
National Weather Service Des Moines IA
337 AM CDT Sun Jul 31 2016

.SHORT TERM.../Today/
Issued at 308 AM CDT Sun Jul 31 2016

Convective trends will be the primary concern today. 07Z surface
analysis shows a warm front well to our south and west from the High
Plains through the Ohio Valley, but the more elevated baroclinic
zone  farther northeast continues to drive MCSs from SD into KS. 5-
7kft ceilings have also recently blossomed in the warm/theta-e
advection zone and 0-2km moisture convergence axis in the vicinity
of the NE/IA border so would not be surprised to see weaker
elevated convection develop soon over western portions of our
forecast area or just to the west. Thus have added PoPs to western
sections toward 12z which is supported by both several high res
models. Both WRF cores, HRRR and RAP all either develop fresh warm
advection precip and/or eventually bring the SD/NE MCS into IA.
Although MLCapes will be higher than the past several days, there
is little signal that sufficient convergence and reduced CINs will
come together to support additional surface based development by
afternoon. Have low end pops extended into the afternoon south,
but this is more to account for MCS remnants than new development.
Expect the intensity of anything that reaches IA to wane with
typical warm advection cycle min during the day, but both
instability and shear will be higher than the past several days so
any appreciable convection could be severe at times supporting the
Marginal outlook.

Much like the past several days confidence in high temps is not that
great. No stratus this morning, but residual convective debris or
precip could hold highs back so again stayed closer to a guidance

.LONG TERM.../Tonight through Saturday/
Issued at 308 AM CDT Sun Jul 31 2016

The long term looks very unsettled with precip chances just about
every day...mainly late afternoon or evening thorugh the
overnight. Fro tonight...a surface low over the Dakota`s and
Nebraska will have a warm front extending from it into Missouri.
Aloft a short wave will be riding atop a building ridge. Much
stronger theta-e advection and forcing will occur over central
Iowa than we have seen in some time. The result will be
thunderstorms that will spread across the forecast area during the
overnight and persist into Monday morning. A few storms could be
severe initially with wind being the main threat then turning
into a heavy rain threat overnight.

Monday into Tuesday we have a similar set up only during this
period the ridge builds more into Iowa and the shortwave coming
across will be more across the Northern Plains/MN and impacting
Northern Iowa more than Southern Iowa but we will have even
stronger forcing in place and while we may have the usual lull in
the late afternoon or early evening through the
overnight we will see storms fire once again an roll across
central Iowa...especially Northern portions. Similarly...a severe
threat would exist initially with wind the main threat then
becoming more of a heavy rain threat overnight...just further
North from the previous night.

Tuesday night the ridge builds well into MN and with no apparent
shortwaves or boundaries around there should be a break in precip
and we should be quite muggy and warm through Wednesday. Highs
should be into the lower 90s across the South with mid to upper
80s North both Tuesday and Wednesday. The caveat to this is that
another strong system will be nosing into the Northern Plains
which will dampen the ridge and shift the ridge axis East. In any
event...this warm up will not be like the past one. It will be
shorter lived and there will be more clouds and storms around
which...if that occurs...will knock temps back and we may not get
very warm.

Wednesday night and Thursday a strong cold front will push across
the forecast area knocking highs back into the 70s and 80s. The
front will lie across much of the region from the Great Lakes back
into the Rockies so there should be quite a broad area of
potential for thunderstorms across the area from Wednesday night
into Friday. Some of these storms could be strong to severe.

This pattern repeats for the weekend with an upper ridge building
into the region and shortwaves topping the ridge bringing periodic
thunderstorm chances.


.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1146 PM CDT Sat Jul 30 2016

Some mid clouds hanging around KMCW and some high clouds expected
to stream across the state tonight. Fog potential still at KALO
and KOTM mainly, so only have those sites reaching MVFR VSBYS.
Light and variably winds becoming southeast around 5 to 10 Sunday.




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