Area Forecast Discussion
Issued by NWS Des Moines, IA

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207
FXUS63 KDMX 181748
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1248 PM CDT Mon Jul 18 2016

.SHORT TERM.../Today/
Issued at 440 AM CDT Mon Jul 18 2016

Ongoing convection will continue to produce heavy rain over
portions of central to southern Iowa. Training looks to continue
over the DSM Metro and more heavy rain in the southwest. Rainfall
rates look to persist at 1 to near 4 inches per hour at times. LLJ
continues to feed good moisture transport into southwest Iowa
resulting in very deep moisture convergence in this location.
PWATs over 2.0 inches in southwest Iowa with very subtle Corfidi
vectors resulting in the potential for continuous training heavy
rain along and south of Interstate 80. The last several runs of
the HRRR and RAP along with the NSSL WRF, persist the convection
through at least 12z to 14z this morning until the LLJ relaxes.
Convection extends west back into Nebraska from just north of
Columbus to the southeast portions of the state, all training
eastward into southwest Iowa this morning. Confident the heavy
rain will persist through the morning rush hour. The radar looks
to be overestimating rainfall amounts near the radar, while
further away such as in southwest Iowa, it is leaning slightly
toward underestimating the rainfall amounts. Regardless, the
rainfall rates are the main concern as these storms are efficient
rain producers and likley to see several reports over 3 inches by
morning.

.LONG TERM.../Tonight through Sunday/
Issued at 440 AM CDT Mon Jul 18 2016

Tonight into Tuesday, the forecast area remains in the ring of
fire with the large upper level ridge holding in place over the
south central CONUS. A strong shortwave riding the ridge moves
into the state overnight tonight into Tuesday morning. Storms
look to quickly develop along a boundary extending from northwest
to southeast Iowa as the LLJ increases past 06z Tuesday. Decent
moisture transport into central to northern Iowa and with the
strong shortwave to finally reach the forecast area between
09-15z Tuesday, expecting widespread heavy rain across much of
northern Iowa. Likely will need a flash flood watch as heavy rain
fell in this location Saturday night. Good theta-E advection and
PWATs of 1.5 to 2.0 inches over much of Iowa tonight. Widespread
rainfall totals could exceed 2 inches over northern Iowa by
midday Tuesday and thus increased QPF amounts.

Wednesday through Friday, hot and humid conditions build into the
state during this time with all three days rising well into the
90s. Surface dew points range in the lower to middle 70s and
tweaked them up slightly during this period. The overnight lows
Wednesday night are likley to stay warmer as the dew points
remain steady in the middle 70s. Certainly will need a heat
headline over the course of the next couple of forecast packages,
but felt the need to hold off until after the heavy rain tonight
into Tuesday.

Saturday into Sunday, some relief by the weekend as a front moves
through Saturday morning. Not much deep moisture to work with
attm and have only slight pops going on Saturday.

&&

.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 1246 PM CDT Mon Jul 18 2016

Some cumulus is expected to develop this afternoon in the 2500 to
3500 ft layer with localized MVFR possible. Thunderstorm chances
will return overnight into early Tuesday with the potential again
for gusty winds, lowering cigs and vsbys.

&&

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

$$

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



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