Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 221148

Area Forecast Discussion
National Weather Service Des Moines IA
648 AM CDT Thu Mar 22 2018

.SHORT TERM.../Today through Tonight/
Issued at 417 AM CDT Thu Mar 22 2018

Confidence: Medium to High

Weak surface warm front and warm air advection aloft continue to
result in a narrow band of light precipitation from west central
Iowa southeast to near Lamoni at 0645z. Surface temperatures near
the precip indicate that most will fall as light sprinkles/rain but
on the leading edge the precipitation may be mixed as light
rain/snow as it translates east through 13z.  After 13z temperatures
will begin to warm enough to change all of the light precipitation
over to light rain/sprinkles. Very light amounts of qpf are
anticipated and most likely no impacts from the precipitation. Will
monitor for any possible light freezing precip if temperatures on
the leading edge of the cloud cover dont warm fast enough.  If any
notice is needed...a SPS would suffice.  Temperatures immediately
behind the warm front continue to warm into the mid to upper 30s
already this morning...and gradual warming through the day today
will push afternoon highs into the mid to upper 40s northeast with
lower to mid 50s from central to southwest Iowa. As the stronger
warm air advection exits the southeast later this afternoon the
light precipitation will come to an end in the afternoon hours.
Tonight clouds will remain over the region with weak warm air
advection continuing into the frontal zone. Cloud coverage may be a
bit less extensive...but enough to remain mostly cloudy.
Temperatures tonight will be warmer with east winds increasing
during the night.

.LONG TERM.../Friday through Wednesday/
Issued at 417 AM CDT Thu Mar 22 2018

The focus for this forecast period revolves around Friday through
Saturday. Models continue to be consistent in their solutions of a
potent shortwave breaking down the upper ridge as it moves across
the area. Meanwhile a strong surface low is forecast to move out
of the Rockies and western Plains across central and southern
Missouri. Ample moisture will be brought up with this system as
well as some decent instability across far southern Iowa. Rain
with isolated thunderstorms is possible Friday and Friday night.
Moderate to heavy rainfall is possible during this period which
may pose a hydrology threat as area streams could have rapid
rises. By Saturday the rain should end from west into central Iowa
by late morning.

Further north...cold air will be drawn down across MN into
northern Iowa during the early evening hours Friday. This will
change the rain over to a wet and heavy snow. Several inches of
snow is possible over northeast Iowa with the heaviest band
setting up along or east of a Mason City to Tama line. In
addition, winds will increase across the area Saturday morning
with advisory or near advisory wind gusts possible. The snow north
will change back over to rain in the afternoon before ending as
the system quickly scoots to the east.

Sunday looks dry at this point but a strong low enters the Pacific
Northwest and digs a trough across the western U.S. Another strong
surface low quickly develops over the Rockies in response to the
digging of the upper trough drawing moisture back into the region
and by Monday a frontal boundary will set up somewhere between
southwest Iowa into northern Missouri. Widespread instability will
develop across Iowa and showers with possible some thunderstorms
will move back into the area. This system will have to be watched
for potential rainfall given the amount of rain we are expecting
for Friday/Saturday. Additional moderate to heavy
rainfall...especially if it falls over areas that received
moderate rainfall over the weekend, could see additional
hydrology concerns. Some flooding could occur if things line up
with respect to repeated moderate rainfall over an area. That
system will then push off by mid day Tuesday but then the
aforementioned upper trough moves over the Upper Midwest keeping
cool and cloudy conditions in place for Iowa.


.AVIATION.../For the 12Z TAFS through 12Z Friday morning/
Issued at 647 AM CDT Thu Mar 22 2018

Thin band of light rain possibly mixed with a frozen mix moving
across IA through 19z associated with warm air advection. Mid
level clouds will remain through the period though a few breaks in
the cloud cover will be possible. Winds remain generally east
through the period as well and under 12kts. Major changes on the
way for Friday 03/23...especially aft 18z. Those concerns will be
address in next few packages. /rev


Winter Storm Watch from Friday evening through Saturday
afternoon for IAZ006-007-016-017-026>028-038-039-050.



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