Area Forecast Discussion
Issued by NWS Des Moines, IA

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269
FXUS63 KDMX 240445
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1145 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 06Z TAFS through 06Z Sunday night/
Issued at 1144 PM CDT Sat Jul 23 2016

Some LIFR ceilings have developed over MCW and look to diminish by
around 07z as it is on the southern fringe of the this pesky
stratus deck. Otherwise, the cold front will swing across the
state and bring a wind shift. VFR conditions throughout the TAF
period for all other TAF sites.

&&

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

&&

$$

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



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