Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 220843
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
343 AM 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

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 Tuesday through the end of
the week. Temperatures will remain seasonal with highs in the 80s
and lows in the 60s.

&&

.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1217 AM CDT Fri Jul 22 2016

Primary concerns are fog developing north and eventually trends of
eastern Iowa convection. Confidence is not great in either
regard. 05z surface analysis shows the front has just sagged into
NW Iowa and will continue to drift south through the morning.
Temp/dewpoint spreads are already very low so expect at least MVFR
fog and/or ceilings to develop. Have only included thunder mention
at KOTM, the most likely location for now. Certainly potential
elsewhere as well, even later today near the front, but
confidence is not great enough to include as of yet.


&&

.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...Small


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