Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 282036

Area Forecast Discussion
National Weather Service Des Moines IA
336 PM CDT SAT MAY 28 2016

.SHORT TERM.../Tonight/
Issued at 335 PM CDT Sat May 28 2016

Main challenge will be lingering thunderstorms/showers. Upper level
system on track to move east this evening with lessening CAPE during
the evening hours. Will continue thunder through mid evening and
then showers until 10z northeast. Otherwise...gradual diminishment
of convection. Brief heavy downpours and potential for severe will
linger over the northeast this evening. Clouds will also dissipate
through the evening over the south/southwest with cloud cover
lingering northeast. Otherwise expect lows to drop to upper 50s to
lower 60s as slightly cooler air moves in following a weak
trough/cool front. Some concerns for patchy fog toward dawn but with
slightly drier air moving in and winds remaining at 7 to 10kt
overnight...will leave out of forecast for now. Some ground fog is

.LONG TERM.../Sunday through Saturday/
Issued at 335 PM CDT Sat May 28 2016

Weak upper level shortwave ridge will build behind our departing
wave for Sunday. Despite the rising heights and a surface high, a
few stray afternoon showers and thunderstorms may still develop
across the southwest with steep low to mid-level lapse rates and
MLCAPE values of 1500 to 2000 J/kg as depicted by the NAM. Deep
shear profiles are weak, however, and any convection that does
manage to develop will be poorly organized. Expanded the slight
chance POPs into the SW CWA to cover this possibility. Low level
return flow will set up early Monday morning as the ridge slide

Confidence in the timing and placement of precipitation during
the day on Monday is low. Weak mid-level theta-e advection will
work through a relatively dry airmass, and despite substantial
POPs/QPF being generated by the GFS/EC, model BUFR soundings
remain quite dry and devoid of MUCAPE, especially in the north.
Trimmed back POP categories and coverage based on this
uncertainty. The better threat for thunderstorms will be on
Tuesday as a sharp H300 shortwave dives south out of the Northern
Plains and an attendant cold front shifts across the CWA during
peak heating on Tuesday. After the passage of this system,
northwesterly flow will settle in place downstream of a western
CONUS ridge, helping to bring drier conditions and seasonable
temperatures for the latter half of the week.


.AVIATION.../For the 18Z TAFS through 18Z Sunday afternoon/
Issued at 1247 PM CDT Sat May 28 2016

Main challenge will be thunder coverage and lowering cigs with
thunder through 01z...-shra and cigs through 12z northeast where
lower cigs of MVFR/IFR briefly may occur as upper level low pulls
east. Sites KMCW and KALO most likely to see lower cigs this
period while the remainder of sites will briefly hit MVFR as
thunder rolls through. Have not hit BR or FG much aft 06z...but
may need to monitor with next package for valley area concerns.


.DMX Watches/Warnings/Advisories...


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