Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 300841
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
341 AM CDT Thu Mar 30 2017

.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 00Z TAFS through 00Z Thursday evening/
Issued at 614 PM CDT Wed Mar 29 2017

IFR conditions will prevail through much of the forecast period
with some improvement expected after 20Z. An Easterly wind at
20G30kts this evening will gradually diminish overnight then
become Northeast at 10-20kts aft 15Z. Some concern for convection
moving into Southern TAF locations. I did include a tempo group
for a few hours mid to late evening in DSM and OTM TAF`s.

&&

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

&&

$$

SHORT TERM...Kotenberg
LONG TERM...Cogil
AVIATION...FAB



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