Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 221847
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
125 PM CDT Fri Jul 22 2016

.SHORT TERM.../Today/
Issued at 343 AM CDT Fri Jul 22 2016

A large MCS that moved across Wisconsin and Illinois on Thursday
evening generated an outflow boundary that has steadily progressed
southwestward and is now reaching central Iowa. There is also what
could be described as a very weak warm front stretching from
northern Nebraska across northern Iowa but it has largely washed
out. With hot and humid conditions continuing through today and
boundaries lingering across the area, it is expected that showers
and thunderstorms will develop at times and most prognostic models
pick up on this with a smattering of QPF though there is very little
predictability/consistency between them. A lack of organized forcing
and light low-level flow preclude anything organized and it is
believed that most convection will occur either during the morning
hours, tied into the nocturnal maximum and low-level jet, or during
the late afternoon/evening peak heating time. Forecasting the
location of any such activity is very uncertain so will maintain
broad-brushed low POPs for much of the day to account for it.
Otherwise, while temperatures across much of the area will be
slightly less hot today than yesterday, dewpoints will remain very
high and much lighter winds will add to discomfort. Given the
duration of this event and warm overnight temperatures, will
maintain the excessive heat warning areawide through today.

.LONG TERM.../Tonight through Thursday/
Issued at 343 AM CDT Fri Jul 22 2016

Corrected...Little changes with the going forecast from the
previous forecast. Chances for precipitation to increase late
tonight into Saturday with theta-e advection picking up along the
boundary in place across the CWA as it lifts northward. Heat to
remain in place across the south to the south of the boundary
across the CWA. Moisture pooling along and south of the boundary
will keep dewpoints high and thus very high heat indices again.
Therefore no changes planned to the current heat headline across
the southern portion of the area into Saturday. Stronger upper
level trough to push eastward through the northern plains/southern
prairie provinces of Canada with an associated cold front sweeping
southward across the CWA into Sunday. Will have some additional
chances for precipitation with this frontal passage which stalls
out across the south Sunday night and pushes into MO for Monday.
This will finally bring some relief from the heat for Sunday into
early next week.

Upper ridging to then build across the western US with ring of
fire scenario setting up and the waves to track east southeastward
across the region into the middle of next week. This will set up
several chances of storms again toward Wednesday through the end
of the week. Temperatures will remain seasonal with highs in the
80s and lows in the 60s.

&&

.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 125 PM CDT Fri Jul 22 2016

General instability, an outflow boundary from last night`s
convection and diurnal heating will all be causes for convection.
General VFR conditions are expected but like yesterday...areas of
MVFR cigs around the periphery of an upper level high will impact
kmcw, kalo and possibly kotm.  Weak storms will be possible across
the North where a weak boundary lies, and across the South where
remnant outflow boundaries from last night are sitting.  After 06z
the boundary will remain across the North but a disturbance moving
across the South may be the bigger focus for storms.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 7 PM CDT Saturday for Adair-Adams-
Appanoose-Boone-Clarke-Dallas-Davis-Decatur-Guthrie-Jasper-Lucas-
Madison-Mahaska-Marion-Marshall-Monroe-Polk-Poweshiek-Ringgold-
Story-Tama-Taylor-Union-Wapello-Warren-Wayne.

Excessive Heat Warning until 7 PM CDT this evening for Audubon-
Black Hawk-Bremer-Butler-Calhoun-Carroll-Cass-Cerro Gordo-
Crawford-Emmet-Franklin-Greene-Grundy-Hamilton-Hancock-Hardin-
Humboldt-Kossuth-Palo Alto-Pocahontas-Sac-Webster-Winnebago-
Worth-Wright.

&&

$$

SHORT TERM...Lee
LONG TERM...Beerends
AVIATION...FAB



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