Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 180825

Area Forecast Discussion
National Weather Service Des Moines IA
325 AM CDT Sun Jun 18 2017

.SHORT TERM.../Today through Tonight/
Issued at 321 AM CDT Sun Jun 18 2017

Confidence: High

Finally the significant trough has pushed the high thetae air south
of the area for a couple of days...and any severe concerns along
with Today...however we will be dealing with the northern stream.
it. H850 subjective analysis shows approaching cold front/trough
which will swing into the north later this morning and afternoon.
Steepening lapse rates and sufficient vorticity will combine to
build cumulus/showers and isolated thunderstorms across the area
during the afternoon hours. Though severe weather should not
occur...wind gusts may approach 35 to 45 mph with some of the storms
northeast due to a layer of drier air nearer the sfc/boundary layer.
Hires/convective allowing models suggest some lingering activity
beyond 00z to about 01z as leftover energy from the day contributes
to some convective elements into sunset. Highs today will be much
more comfortable...10C north to 12C southwest. With cloud cover
highs will only reach the lower 70s north and the upper 70s over the
central and south. Tonight skies will become partly cloudy with
lows in the 50s.  Expect a pleasant northwest wind at around 10 mph.

.LONG TERM.../Monday through Saturday/
Issued at 321 AM CDT Sun Jun 18 2017

Summary...Gradual temperature rise through the week, approaching
upper 80s to 90 by Wed/Thur before cooling back to 70s/low 80s by
the Weekend.  Storm opportunities throughout a fair amount of the
forecast, especially Wed-Fri.

Monday through Tuesday...Northwest upper level flow will dominate
the period, but not quite as quiet as forecast a day or two previous
anticipated. GFS/Euro continue to push a vort max a bit further SW
for Mon, which should have little issue sparking a few storms, and
possibly small to near-severe hail, in an environment of 500-1250
J/kg MUCAPE or so. Additionally, temps by afternoon look to
reach/approach convective temps, further supporting scattered
storm development as if the vort max would not be sufficient. On
Tue, another large vort max will move through the flow as the
upper level trough pivots through, but should keep any
showers/storms NE of the CWA.

Tuesday Night through Saturday...Upper level trough finishes
pivoting through Tue night and zonal flow will set in through most
of the week. The weather will generally be unsettled, highlighted by
waves of WAA and passing weak boundaries as shortwaves and surface
reflections move through the flow. Difficult to pick out any real
quiet periods with storms depicted each day Tue night on into Fri
ahead of a trough/cold front moving through Sat. A window for severe
storms, hailers, may be Wed afternoon/evening with depictions of
CAPE values in excess of 4000 J/kg, but effective shear only around
20-25 kts. Certainly a lot can change between now and then given 4
days out, but interesting nonetheless. Temps may be difficult to
pinpoint to an extent given some level of uncertainty in convective
timing and extent, but should have little issue rising back well
into the 80s by Wed/Thur. Temps then fall back into the 70s/low 80s
by Sat with the trough/cold frontal passage.


.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1151 PM CDT Sat Jun 17 2017

VFR forecast for much of the duration with only some MVFR ceilings
at very beginning of forecast in northern Iowa. Surface winds will
be west to northwest and gusty by midday Sunday into Sunday




LONG TERM...Curtis
AVIATION...Cogil is the U.S. government's official web portal to all federal, state and local government web resources and services.