Flash Flood and Damaging Winds in Iowa, August 10, 2016

Area Forecast Discussion
National Weather Service Des Moines IA
1232 PM CDT Wed Aug 10 2016

.SHORT TERM.../Today/
Issued at 323 AM CDT Wed Aug 10 2016

WAA to continue across the area today ahead of a developing low
pressure system along the western high plains. This area of low
pressure associated with upper level troughing shifting slightly
east across the northern Rockies. Low level moisture to increase
across the state today as well, with theta-e advection aloft and a
meandering flow off the gulf. Continued the slight chance pops
toward mid/late day with area of theta-e advection pushing across.
Otherwise better chances expected late tonight as the LLJ kicks in.

Temperatures to warm today as the heat builds in aloft and dewpoints
increase. This will push heat index values to around 100 across much
of the CWA. Overall though expect values to remain below advisory
criteria of 105. Also chance of clouds/precip could cause temps to
not warm quite as much as currently forecast as well.

.LONG TERM.../Tonight through Tuesday/
Issued at 323 AM CDT Wed Aug 10 2016

Overview...After a few scattered showers/storms Wed night/Thur
morning, heat and humidity will continue through Thursday with heat
index values approaching 105 before a cold front ushers in heavy
rainfall potential, cooler temperatures, and drier conditions
through the weekend and into next week.

Wednesday Night through Thursday...Two items of note in this short
period.  First, models have come into decent agreement with the
progression of a more robust shortwave in the 06z-18z window
Thursday. With an added boost from the low level jet, have
introduced chance POPs. Second, heat and humidity will continue
Thursday with temperatures into the low 90s possible and dew points
into the mid 70s, resulting in heat index values in the 100-105
range. Of concern though, will be coverage of morning precipitation
and lingering cloud cover possibly squashing highs a bit. With that
in mind, am not considering heat advisory at this time.

Thursday Evening through Friday...Main concerns reside in this
period, associated with a cold front that will progress through the
state from northwest to southeast. The question becomes not if
showers/storms will develop, but what to expect from them given the
ample forcing. Severe weather continues to be of little concern with
unsupportive shear profiles, though a brief severe storm cannot be
completely ruled out. Instead, the main concern continues to be
heavy rainfall potential with warm cloud layer depths around 1300kft
and PWats in excess of 2 inches likely as moisture pools along/ahead
of the front. With storm motions oriented more parallel to the
front, training storms will be of concern as well. Would not be
overly surprising to see amounts in excess of 2-3 inches in some
locations as a result. Fortunately, antecedent conditions are such
that flooding should not be of much concern outside of urban areas.

Saturday and Onward...After frontal passage Friday, conditions
become quite pleasant with highs in the upper 70s to mid 80s and
dry conditions dominating through the weekend and into the new
work week.

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1232 PM CDT Wed Aug 10 2016

Local areas of MVFR over the east this afternoon. Some potential
for scattered thunderstorms this afternoon then again late
tonight into Thursday morning. Have not included in the forecast
yet but may need to include if confidence increases. Some fog
potential over northeast Iowa however coverage will be less than
this morning.

&&

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

SHORT TERM...Beerends
LONG TERM...Curtis
AVIATION...Donavon

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
343 AM CDT WED AUG 10 2016

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-110845-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-
CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-
APPANOOSE-DAVIS-
343 AM CDT WED AUG 10 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

LOW END CHANCES FOR THUNDERSTORMS WILL EXIST THIS AFTERNOON...WITH
BETTER CHANCES THIS EVENING. SEVERE WEATHER IS NOT EXPECTED.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

HEAT INDEX VALUES MAY REACH INTO THE 100 TO 105 DEGREE RANGE
THURSDAY AHEAD OF IMPENDING COLD FRONT.

WIDESPREAD THUNDERSTORMS WILL BE LIKELY ACROSS THE STATE THURSDAY
EVENING AND INTO FRIDAY AS A COLD FRONT PROGRESSES THROUGH. WHILE
HEAVY RAINFALL IS THE PRIMARY CONCERN...AN ISOLATED STRONG TO
SEVERE THUNDERSTORM OR TWO MAY BE POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

CURTIS