Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 282020

Area Forecast Discussion
National Weather Service Des Moines IA
320 PM CDT Thu Jul 28 2016

.SHORT TERM.../Tonight/
Issued at 321 PM CDT Thu Jul 28 2016

Main concern will be with cloudiness and temperatures overnight as
upper system slowly drifts through the region. Low clouds remained
extensive this afternoon although became more cellular with
daytime heating. A few light showers were occurring across the far
northeast near surface trof axis. The activity will continue for a
few more hours but should die off quickly with the approach of
sunset. Otherwise...short term models continue to indicate the
broad area of cloudiness to persist overnight and expand across
the central Iowa in an area of weak cold advection. The cloudiness
will keep temperatures slightly warmer than otherwise would be the
case with the airmass that`s in place.

.LONG TERM.../Friday through Thursday/
Issued at 321 PM CDT Thu Jul 28 2016

Relatively quiet conditions are expected on Friday with subsidence
across most of the area. However, the backside of the upper low a
cool temps aloft may lead to a few isolated showers across the
eastern portion of the forecast area and have continued a low
chance in those areas. Temperatures will remain below normal with
thermal trof nearby along extensive cloudiness. The quiet weather
will persist into Saturday with surface ridging hold firm over the
state. Warm advection will begin to intensify Saturday night into
Sunday as ridging slides east and southeast flow strengthens. By
Sunday night, theta-e advection will pass through central Iowa on
nose of low level jet with convection likely to expand across the
state, possibly persisting into Monday morning. Thereafter,
thermal ridging will expand into much of Iowa with temperatures
rising into the 90s for many areas by Tuesday into Wednesday. It
is likely heat index values of around 100 and possibly higher will
occur on Tuesday and Wednesday and will continue to monitor for
possible headlines. Otherwise, only other concern will be the
proximity of the westerlies just north of the state which may
allow for convection to creep into the state on these days, which
may keep temperatures cooler than expected.


.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1239 PM CDT Thu Jul 28 2016

Low ceilings will continue to be problematic during the forecast
period as upper low gradually drifts southeast. MVFR to IFR
ceilings will be common in northern IA today and spread southward
tonight along with MVFR visibilities. Little improvement is seen
until toward the end of the period with surface winds remaining
light from the north.





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