Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 271831
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
131 PM CDT Mon Mar 27 2017

.SHORT TERM.../Today through Tonight/
Issued at 344 AM CDT Mon Mar 27 2017

The low pressure system that impacted the state over the weekend
has moved northeast into the central Great Lakes region. Another
PV anomaly currently over south central Kansas and into Oklahoma
will be tracking east today. The surface low pressure reflection
is situated east of the upper level features and will move east
through southern Missouri today. Theta-e advection and the low
level jet preceding the system has brought a few showers north
into far southern Iowa. The northward extent of this precipitation
is expected to diminish by mid morning as the LLJ weakens.

Weak surface high pressure riding will move into western Iowa by
this afternoon. Good mid-level drying will occur from north to
south today as the high pressure arrives. Along with the
thinning moisture profile, weak to moderate subsidence will arrive
by the afternoon. So the biggest question is will the clouds
finally begin to erode today from west to east. Some erosion
should occur especially over the west. Elsewhere, the cloud base
will be thinning which will allow for more solar radiation to
penetrate the residual clouds and reach the surface today. This
will result in temperatures warmer than Sunday.

.LONG TERM.../Tuesday through Sunday/
Issued at 344 AM CDT Mon Mar 27 2017

Models have come into much better agreement with the next system
to impact the state Wednesday into Friday. Thus, the 27.00z GFS is
much more in line with the 27.00z ECMWF solution with the surface
low track across Missouri and higher confidence in the cold and
rainy weather Wednesday and Thursday.

Tuesday looks to be fairly pleasant, relatively speaking, with
temperatures rising to around climo for this time of year. Mid-
level stratus will hang around for much of the day as moisture
remains stuck underneath the inversion. The inversion finally
weakens by the afternoon, but by then higher clouds from the
approaching upper level trough are likely to be over much of the
state.

Wednesday into Friday...Large and deep low pressure will
transition out of the southern Rockies across the
Southern/Central Plains throughout the day Wednesday. Several
waves of Theta-E advection and isentropic upglide push into the
state beginning past 06z Wednesday and continue through the day
Wednesday. The surface low moves across Oklahoma into southern
Missouri, placing the forecast area within a decent deformation
zone b/t 00-12z Thursday. Temperatures across northern Iowa look
cold enough for snow to develop as there is moderate lift within
the snow growth region b/t 06-15z Thursday. The GFS BUFR soundings
at MCW suggest a thin warm aloft overnight into Thursday morning
across northern Iowa, but the omega in the DGZ should be strong
enough to overcome this warm layer and cool the column to below
freezing. This goes for the surface temperature as well b/t 06-15z
Thursday. Have snow mentioned across the north during this time
with light amounts attm. Winds on Thursday will be stout out of
the north-northeast keeping temperatures from increasing too
drastically. Tweaked max temperatures down slightly and nudged up
winds Thursday.

The ECMWF is a bit quicker to exit the low pressure system by
early Friday with surface high pressure building into the
region. The high pressure remains across the region into Saturday
providing some relief to the cold and dreary weather pattern. The
ECMWF and GFS try to bring another system into the region by
Saturday night into Sunday providing chances for rain. However,
more confident the surface high will hold off the progression of
the low pressure to the south of the forecast area and may need to
trend drier late in the extended period if models begin to pick
up on this solution.

&&

.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 128 PM CDT Mon Mar 27 2017

General continuation of low ceilings will continue through the TAF
period. Any projected clearing will primarily stay off to the
north and beyond this issuance period. Primarily MVFR ceilings
will prevail, though a period of IFR appears increasingly likely
to return overnight with more limited clearing/lifting. so far
today than initially expected.

&&

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

$$

SHORT TERM...Donavon
LONG TERM...Podrazik
AVIATION...Curtis



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