Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 280450
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1150 PM CDT Sat May 27 2017

...Updated for 28/06Z Aviation Discussion...

.SHORT TERM.../Tonight through Sunday/
Issued at 333 PM CDT Sat May 27 2017

The main forecast concern was focused on lingering showers/storms
this afternoon and evening across the eastern portions of the
forecast area. Much of the forcing and any instability has begun
to weaken and thus the current storms/showers look to diminish by
around 00z or sooner.

Another weak shortwave looks to pass through the state tonight
into early Sunday morning providing another round of light showers
looks possible east of I- 80. However, with the secondary trough
moving through tonight, limited moisture and forcing associated
with this system and have very low confidence with any measurable
precipitation tonight. Other concern is breezy weather tomorrow
afternoon with decent mixing and winds atop the mixed layer around
20-25 knots and the majority of the gusts will be realized at the
surface due to the deep dry adiabatic sounding profiles. Thus,
nudged up winds and temperatures slightly tomorrow afternoon.

.LONG TERM.../Sunday night through Saturday/
Issued at 333 PM CDT Sat May 27 2017

Overall, a very inactive long-term fcst period for this time of
year. With westerly to NW flow all week, we should be solidly
locked into near-normal temperatures with highs in the 70s and
lows in the 50s.

Monday into Tuesday... 19z Sat water vapor imagery clearly picking
up on cut-off low over Manitoba slowly dropping to the southeast.
By Monday morning, this low should be positioned near Lake
Superior. Models in decently solid agreement with tracking this
low, so consensus blend appropriate. Timing of trough axis/weak
cold front appears to pass through Iowa Monday morning. If this
timing holds, would need to raise POP/QPF Monday morning and lower
it for Monday afternoon. Monday afternoon looks to be stratus/sc
fest with wrap- around 850mb moisture overspreading much of Iowa,
increasing to the north and east. Could see an isolated shower or
two, but with lack of focusing mechanism, will be difficult for
anything sustained to get going. Fairly similar/persistent day
expected for Tuesday... With Tuesday being less windy as pressure
gradient relaxes with upper low propagating eastward, further away
from Iowa.

Wednesday through Thursday Morning... Iowa stays in NW Flow
regime. With wrap-around moisture east of the area and sfc high
pressure passing through the upper Midwest, expecting decently
sunny day Wednesday. 850mb temps in the +5C to +10C range,
suggesting highs in the upper 60s to mid 70s. With light winds,
should be a decently pleasant time period.

Thursday Afternoon and Beyond... Models diverge on mesoscale (as
expected), but synoptic scale trend generally shows Iowa in return
flow/WAA by Thursday afternoon as sfc high moves into the Ohio
Valley region. 12z Sat GFS picking up on a strong band of theta-e
advection and frontogenetical forcing associated with a warm
front pushing through Iowa Thursday into Friday. Due to model
divergence, confidence not the greatest with this solution... but
have left in token chance POPs for now. Long-range models in
agreement with warming as 850mb temps make it into the +10C to
+15C range...possibly placing Iowa well into the 80s by next
weekend.

&&

.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1150 PM CDT Sat May 27 2017

VFR conditions are expected during the valid TAF period. Surface
winds on Sunday are expected to be higher than those on Saturday due
to deeper mixing within the boundary layer.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...Podrazik
LONG TERM...Kotenberg
AVIATION...Zogg



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