Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 271144
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
644 AM CDT Sat Aug 27 2016

.SHORT TERM.../Today/
Issued at 359 AM CDT Sat Aug 27 2016

Drier air has been moving into central and western Iowa overnight
with the bulk of the precipitation now moving into the far eastern
portion of the state. A few additional showers have redeveloped
along and north of Highway 20 over the north ahead of an upper
short wave energy and in the region where deeper moisture is more
prevalent. This activity over northern Iowa should expand in areal
coverage over the next few hours but precipitation will decrease
by mid morning. A complex of storms is moving across northeast
Kansas and into southeast Nebraska. Expect this system to affect
parts of southern Iowa this morning. A few additional showers or
thunderstorms may occur over southeast Iowa this afternoon.

Cloud cover is the other forecast challenge today. Low stratus and
some fog is spreading over southwest and south central Iowa. Cloud
bases are beginning to drop below 500 ft and vsbys in a few sites
dropping to one mile or less. This area of clouds extends back well
into eastern Nebraska. With a lack of good flow and subsidence, it
may be very difficult to get rid of the clouds today and may just be
a raising of cloud bases due to some diurnal heating. That said,
clouds again may limit high temperatures today. There may be
localized drizzle associated with these clouds. For now, expect
there should be a few breaks in the clouds central and south but may
remain over northern Iowa through the day.

.LONG TERM.../Tonight through Friday/
Issued at 359 AM CDT Sat Aug 27 2016

Main forecast concern was focused on rain chances Monday into
Tuesday and then trended towards a drier forecast mid to late
next week. Leaned toward the 27.00z ECMWF for much of the
extended.

Tonight into Tuesday...Generally zonal to northwest flow aloft
settles in over the region with surface high pressure building into
the state tonight. The surface high looks to shift east enough
Sunday night into Monday allowing a boundary to lift northward into
southern Iowa. This boundary remains the focus for thunderstorm
develop Monday into early Tuesday before a weak trough/cold front
transitions south through the state. Forcing with this system is
weak and unorganized as well as any type of shear, but there is a
decent amount of instability that builds over the state Monday.
Thus with the CAPE available and some vorticity and
frontogenetical forcing present, cannot rule some thunderstorm
potential until the aforementioned trough moves through the state
by Tuesday. However, any severe threat remains very low.

Wednesday through Friday...trended toward a much drier forecast than
previous forecast as the latest ECMWF and even some of the GFS
are trending that way as well. Mainly due to large surface high
building into the region which wards off any kind of significant
moisture and thus any shortwave that transitions across the upper
level ridge will have little to work with. More confident to go
completely dry for much of the extended next week than to blanket
each period with low chance pops.

&&

.AVIATION.../For the 12Z TAFS through 12Z Sunday morning/
Issued at 644 AM CDT Sat Aug 27 2016

Widespread IFR to LIFR cigs this morning across much of the area.
Areas of fog may impact KDSM/KOTM also this morning. Cigs will
gradually rise later this morning and into the afternoon.
Confidence is not high on timing of return to VFR but should begin
to occur over the southern sites this afternoon but may be delayed
across the north until later afternoon or evening.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Donavon
LONG TERM...Podrazik
AVIATION...Donavon



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