Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 301746
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1246 PM CDT Thu Mar 30 2017

...UPDATE and 18z AVIATION...
Issued at 1245 PM CDT Thu Mar 30 2017

1730z visible satellite imagery shows extensive stratus clouds
over Iowa. Elevated clouds above this stratus deck are rotating
counter-clockwise around low pressure near the Kansas/Missouri
border. Have lowered PoPs over much of northern Iowa while keeping
or raising over far southern Iowa and eastern part of the CWA
given current radar trends and hires guidance. Otherwise, ongoing
forecast appears on track with clouds persisting and highs ranging
from near 40 across the north to upper 40s near the Missouri
border.

&&

.SHORT TERM.../Today through Tonight/
Issued at 341 AM CDT Thu Mar 30 2017

Message of the Day: Rain and clouds continue...Though less rain
today than yesterday.
Hazards: Minimal chance of thunder possible south, river rises
Forecast Confidence: Medium-High

Synoptics... 08z Thu water vapor imagery easily picking up upper
level low spinning over northeastern Kansas and slowly propagating
to the northeast. Additionally, water vapor imagery picking up on a
longwave trough coming onshore along the Pacific coast and digging
its way through California. This trough is progged to strengthen
into a closed low by Thursday night and will help push our Kansas
upper low east of the region. Model consensus generally good to
follow, with a lean towards the ECMWF solution which has been more
consistent run-to-run with the evolution of this system.

Mesoscale... Best moisture transport already east of the DMX CWA as
western edge of the LLJ out of Iowa by 15z Thu. Subsequently, best
instability and isentropic/adiabatic lift also east of the CWA. This
will lead to much less precip Today than yesterday. By 12z-15z Thu,
models trying to pick up a band of vorticity/frontogenetical forcing
oriented SW to NE moving across the CWA from west to
east...primarily impacting our northern counties. Fcst soundings
support saturation, with cloud depths upwards of 7 kft. This
suggests light rain as this band traverses eastward. As the core of
the low propagates across north-central Missouri, best band of 950-
800mb frontogenetical forcing and instability axis will remain in
Missouri, perhaps barely clipping our far southern/SE CWA between
15z and 18z today. Thus have isolated thunder mention, but
confidence is low in thunder occurrence. Temperatures today should
be close to where they were yesterday. No major changes in terms of
CAA or WAA. See no reason to break up the st deck, meaning another
grey day across Iowa with a heavy lean to persistence.

.LONG TERM.../Friday through Wednesday/
Issued at 341 AM CDT Thu Mar 30 2017

Iowa will be in-between systems on Friday with subsidence as
brief upper ridging slides through the Midwest. This will likely
be the best day to see a little sunshine in some locations across
the state, most likely the north where drier air will be deeper.
However, warm advection begins to intensify on Friday night into
Saturday ahead of next system dropping into the central Plains.
Isentropic lift strengthens into Saturday with clouds thickening
and some light rain possible by afternoon, especially in western
Iowa where deeper saturation will occur after midday. The better
surge of moisture arrives Saturday night with light rain becoming
widespread across much of central Iowa. Southern Iowa will see the
best shot of precipitation and QPF amounts where forcing will be
maximized north of the surface low track. The system is expected
to depart on Sunday afternoon with strong subsidence spreading
across the state by Sunday night.

Quiet weather is expected on Monday with subsidence and drier air
overspreading the state. Surface ridge axis will slide overhead on
Monday night, however clouds are expected to increase quickly on
the backside of the ridge with warm advection taking off early
Tuesday. While a few showers will be possible into Tuesday, dry
low level air will tend to limit the overall threat. Deeper and
stronger forcing arrives with upper system on Tuesday night into
Wednesday and this will be the best chance of precipitation into
the middle of next week. With surface low tracking close to the
Iowa/Missouri border, much of the forecast area will be in the
`cool` sector with steadier rainfall, however convective
instability will be close to southern Iowa and a few thunderstorms
cannot be ruled out at this point.

&&

.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1245 PM CDT Thu Mar 30 2017

Stratus clouds prevail over the state as low pressure spins near
the Kansas/Missouri border with elevated clouds circulating around
this low. IFR/LIFR ceilings will continue over southern Iowa with
some drizzle at times while IFR and low MVFR ceilings will be
over northern Iowa through this afternoon. Showers have been
quite limited and only have a mention at KALO and KOTM at this
time. Overnight, IFR and low MVFR ceilings will persist and last
into Friday morning. Drier air will finally begin to push into the
state later tomorrow morning, which should finally allow for
ceilings to begin to lift over the northern TAF sites toward the
end of the TAF period.

&&

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

$$

UPDATE...Ansorge
SHORT TERM...Kotenberg
LONG TERM...Cogil
AVIATION...Ansorge



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