Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 271155
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
655 AM CDT FRI MAY 27 2016

...Updated Aviation Discussion...

.SHORT TERM.../Today/
Issued at 409 AM CDT Fri May 27 2016

Some light shower activity continues to develop along a weak
outflow boundary slowly moving southward across the central
portion of the forecast area. Other than the diminishing LLJ,
there is very little upper level support evident via the IR
satellite trends. Plus, there is minimal mucape and effective
shear available, so not anticipating these showers to persist much
past 12z this morning. Further south, showers and even an isolated
thunderstorm look to advance northward on the nose of the LLJ, but
again, the activity is moving into a more stable environment and
expect this activity to diminish after sunrise.

Models continue to not handle current radar/precipitation trends
well, and thus low confidence with leaning one way or the other
towards one specific model. The two `best` solutions seem to be the
03z HopWRF and the 00z 4.0km WRF-NMM for initial conditions and
precipitation trends throughout the day. The 27.06z Experimental
HRRR is not far off as well. Likely to see a break in the
precipitation later this morning into the early afternoon hours,
before redevelopment occurs towards the end of the period. The
atmosphere will have a difficult time recharging today with the
abundant cloud cover remaining in place, so confidence is high in
the low probability for widespread severe weather. The GFS and NAM,
and the SREF hinting on a weak shortwave embedded in the southwest
flow aloft to enter the southern portions of the forecast area late
this afternoon. The parent upper level low pressure looks to be over
western Kansas by 00z Saturday with no discernible surface low to
develop near the forecast area. With the aforementioned hi-res
models solutions depicting storms to develop after 22z today, have
pops increasing past from south to north during this time.

For temperatures, went a little cooler across the southwest where
ongoing showers continue and also expecting redevelopment to occur
late this afternoon.

.LONG TERM.../Tonight through Thursday/
Issued at 409 AM CDT Fri May 27 2016

Upper system will continue its slow progress through the Midwest
into the first half of the weekend with unsettled weather
continuing until its passage. Main concern for tonight will be
from heavy rainfall (reference hydro discussion below) as
generally weak shear will limit the severe potential tonight.
Saturday will see a gradual decrease in the precipitation threat
across the state as the upper low lift north through the region.
Focus for precipitation on Saturday will be in the northwest third
of Iowa near baroclinic zone. Meanwhile, subsidence will spread
northward into the state during the day. The threat will become
more limited on Saturday night as the system pulls away from the
state and subsidence continues to overspread Iowa. Sunday appears
to be the best chance of dry conditions across all of central iowa
with weak shortwave ridging building into the upper Midwest.
Temperatures will remain warm on backside of system as little cool
air is associated with the departing low.

The next threat of precipitation arrives late Sunday night into
Monday as shortwave passes across the northern Rockies. Moisture
transport will increase from the south with destabilization and
weak forcing leading to a few storms during this time. However,
the main bulk of forcing arrives on Tuesday ahead of surface
boundary with the best coverage of showers and storms during this
time. With good shear and sufficient instability, severe weather
will be possible during this time although the extent is not yet
known. Temperatures will remain warm until frontal passage by
midweek at which time readings are expected to drop below normal
by the end of next work week.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 654 AM CDT Fri May 27 2016

MVFR ceilings look to continue to impact DSM and OTM through the
morning hours. Lower confidence to mention further north and left
out mention of IFR/MVFR ceilings until tonight. With the
rain/storms spreading across central Iowa this evening, introduced
MVFR to IFR visibility towards the end of the period. Ceilings are
likely to be around 1000 feet or a bit lower during the overnight
period.

&&

.HYDROLOGY...
Issued at 409 AM CDT Fri May 27 2016

Rainfall this week across central iowa has averaged around an inch
to inch an a half with highest amounts across the west with
southeast much drier. Confidence in QPF placement remains
relatively low late today into tonight although central and
eastern Iowa seem most likely as low level flow will be focused
more into that area along with PWATS approaching 1.5 inches. The
Euro, however keeps its heaviest pcpn farther west which would be
more problematic as this is where conditions are most moist. Given
low confidence at this time, will forego any headlines and let the
next forecast cycle reassess the potential.

&&

.DMX Watches/Warnings/Advisories...None.

&&

$$

SHORT TERM...Podrazik
LONG TERM...Cogil
AVIATION...Podrazik
HYDROLOGY...Cogil



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