Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 130835

Area Forecast Discussion
National Weather Service Des Moines IA
335 AM CDT Tue Mar 13 2018

.SHORT TERM.../Today through Tonight/
Issued at 335 AM CDT Tue Mar 13 2018

A surface high pressure area currently draped across the Dakotas
will slide southeastward today and tonight, reaching the Ozarks by
sunrise Wednesday. This will result in dry and quiet weather, with
mostly clear skies and fairly cool temperatures several degrees
below normal for the season. There is some question as to how low
temperatures will radiate late tonight, but with the high moving by
so quickly it appears the window of opportunity for calm winds is
brief, so have only lowered temperatures a degree or two in our
southwest, nearer to the center of the high and coincident with the
Nish valley.

.LONG TERM.../Wednesday through Monday/
Issued at 335 AM CDT Tue Mar 13 2018

Relatively quiet weather from Wednesday into Thursday with upper
ridging gradually sliding into the Missouri River Valley by the
later Thursday. Warm advection will be underway at the beginning
of the period and with relatively sunny conditions on Wednesday
with a southwest to west surface winds, temperatures should warm
quickly. Model soundings indicate a relatively well mixed layer
and temperatures approaching 60 are expected in the southwest and
into the DSM metro area. Temperatures will be cooler across the
north where a cold front will arrive by midday limiting overall
heating by afternoon but readings will still be above normal. The
thermal profile will be a bit cooler into Thursday with the front
through the state and some increased clouds in the south.
Anticipate highs 5 to 10 degrees cooler than Wednesday as the
colder airmass oozes into the state.

A relatively strong shortwave will be undercutting the ridge by
later Thursday into Friday with renewed warm advection into the
Plains and Iowa by Thursday night into Friday. Isentropic lift
will gradually strengthen into Thursday night with clouds
thickening in southern Iowa. Some light precipitation is expected
to develop after midnight in the south where deeper saturation
occurs, but this will be fighting a dry easterly flow near the
surface. Sounding profiles do suggest some threat of
freezing/frozen precip types overnight into mid morning Friday and
have included mention in the zones. However, the drier air
advecting in from the east should limit QPF amounts during this
time with little glazing/accums expected. The forcing persist into
Friday and Friday night gradually expanding northeast but
generally holding from Highway 20 southward. This will be mainly
liquid both Friday into Friday evening although some transition to
snow on the backside/northern fringes will remain possible. The
influence of this system is expected to quickly wane into Saturday
with quiet weather for much of the weekend as surface ridging
passes through the Midwest. Pattern remains relatively active into
early next week with another threat of light precipitation into
Monday/Monday night as the next system ejects from broad western


.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1129 PM CDT Mon Mar 12 2018

High confidence in VFR conditions prevailing at all terminals
through the TAF period. Winds from the north-northwest and
northwest will increase mid to late morning before subsiding
Tuesday evening.





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