Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 232346
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
646 PM CDT Sat Jul 23 2016

...Updated Aviation Discussion...

.SHORT TERM.../Tonight/
Issued at 355 PM CDT Sat Jul 23 2016

Thunderstorms ongoing mainly across far Northeast Iowa as outflow
from morning convection moves into greater instability with diurnal
heating. Main activity has activated near strong instability and
convergence and will be moving east of the forecast area shortly.
Surface cold front is well to the west currently extending from the
Central Dakotas and through Western Nebraska and will not arrive to
Northwest IA until late tonight. A capping inversion above the
incoming cold front will limit convective potential associated with
the boundary. The best potential for storms will be over North
Central Iowa with any storms that may drop southeast from Minnesota
however the main forcing will remain north of the state.  That said
with PWATS hovering near 2 inches, any storm could produce heavy
rainfall.

Heat headlines will remain in effect until 7 pm. It will remain
warm and humid into this evening however, conditions by 7 pm
will fall below criteria and cooler temperatures arriving on
Sunday will allow for the expiration of the warning.

.LONG TERM.../Sunday through Saturday/
Issued at 343 PM CDT Sat Jul 23 2016

Cold frontal boundary will be sliding through the central and
southern CWA at the onset of the period in response to an upper
level trough currently over the Pacific NW swinging through the
northern plains. NAM/GFS forecast soundings during the period of
the frontal passage depict a pronounced +26 C H850 cap and little
in the way of kinematic support or deep shear to support
convection. Have thus trended dry through the morning hours with
slight chance POPs in the south for Sunday afternoon to account
for the possibility of elevated convection during peak heating
along the decaying boundary aloft.

Southern plains ridge will flatten over the course of the week as
multiple shortwaves propagate through the flow, which will bring
more seasonable weather to the region for next week. GFS has come
in line with the EC in taking the surface boundary well into
Missouri late Sunday into Monday and have kept Monday dry as
surface high pressure passes through. Trended back pops for
Tuesday with the GFS/EC both slowing the progression of the next
H300 wave that will affect the state midweek. Model solutions
diverge on the placement and timing of the mid to late week waves,
necessitating continued chance POPs during this period.

&&

.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 646 PM CDT Sat Jul 23 2016

VFR conditions look to prevail throughout the entire TAF period.
The latest HRRR suggests a bit more scattered thunderstorms later
tonight into the overnight hours across central Iowa than
previously forecast. Slightly more confident for storms to develop
over northern Iowa and have VCTS mentioned at MCW/ALO. Otherwise,
the main cold front will swing across the state towards sunrise
Sunday and bring a wind shift to the northwest.

&&

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

&&

$$

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



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