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Area forecast discussion 
National Weather Service Des Moines Iowa
1150 PM CDT Wednesday Apr 1 2015

Update...
issued at 1116 PM CDT Wednesday Apr 1 2015

A line of showers and thunderstorms will continue to move through
central Iowa overnight along and ahead of a cold front sweeping
through the state. Overall the severe threat has greatly
diminished with any chance of even an isolated severe storm
relegated to the far southern County Warning Area at this time. This chance is
even marginal given the better instability and deep layer shear is
situated off to the south and west of the County Warning Area.

&&

Short term /tonight/...
issued at 352 PM CDT Wednesday Apr 1 2015

Strong south winds and very dry conditions continue this afternoon
and the Wind Advisory and red flag warning will be maintained until
23z and 00z...respectively...as scheduled. As winds diminish with
sunset conditions will improve and these hazards should be allowed
to expire. For tonight...all eyes remain on the approaching cold
front and the associated convection expected to develop. In terms of
initiation...a trend toward slightly later and further northwest
continues and it appears that precipitation will not enter our
northwest corner until shortly after 00z this evening. Probability of precipitation have
been further delayed appropriately...but even so once the storms do
form they will move southeast with the front and produce rain across
most or all of the area...aided by a developing low level jet
overnight which will enhance convergence along the cold
front/leading edge of the convection. Thus categorical probability of precipitation have
been maintained across most of the forecast area. The delay in onset
time in our northwest has also decreased the threat of severe
weather somewhat as the intensity of the storms will gradually
diminish after dark...but a slight risk for severe hail/wind remains
from about Atlantic up to Algona and northwestward. There is also a
possibility of locally heavy rainfall...but given the very dry
atmospheric conditions and relatively limited moisture available
within the column no significant impacts are anticipated.

Long term /Thursday through Wednesday/...
issued at 352 PM CDT Wednesday Apr 1 2015

Two primary windows of concern through the period...at onset with
what will likely be departing mesoscale convective system overnight and another early next
week. Convection should be decaying by daybreak with minimal MUCAPES
in place. However large scale synoptic forcing will remain with
phased lift in right entrace region of Minnesota/Ontario jet...DPVA
ahead of upper MS valley short wave...and sloped cold front aloft
rise/fall couplet. Any significant precipitation should be quite short
lived however with aforementioned 1-3km thermodynamic forcing well
into MO and Illinois by 18z which is supported by most hi res models.
Considered another round of fire weather headlines into Thursday with
decent mixing and low level drying behind the system...especially
over northern Iowa. However most deterministic and ensemble quantitative precipitation forecast solutions
suggest at least a half inch of rainfall over these locations so
opted to omit for now. This will need to be watched if forecasted
precipitation amounts do not develop however. The question into Friday will
be lingering precipitation potential with middle level forcing continuing
well behind the surface features but potentially offset by low
level dry air and the lack of lift below 3km. Thus have some token
low end chances late Thursday night and Friday south.

The pattern will remain fairly similar through the remainder of the
forecast with somewhat low amplitude flow keeping forecast somewhat
inactive into early next week...and temperatures seasonal. The only
precipitation potential over the weekend appears to be Sat night NE with
warm front developing over northern Iowa and weak wave rippling along
weak baroclinic zone. This front and system will remain in place
in some form but may not activate appreciably until early in the
next work week as the surface features mature. Confidence is not
great in this timing however with GFS much faster...around
18hrs...than the European model (ecmwf) so have broad brushed chances for Monday and
Tuesday for the time being.

&&

Aviation...02/06z
issued at 1150 PM CDT Wednesday Apr 1 2015

Line of showers and thunderstorms will push through the eastern
and southern taf sites through the early morning hours. Have gone
with mainly thunderstorms in the vicinity as expect storms to weaken with time. Dry and VFR
conditions then expected for the remainder of Thursday into
Thursday night. Southerly winds to shift around to the northest
behind the cold front and line of storms...with some gustiness
possible Thursday.

&&

Dmx watches/warnings/advisories...none.

&&

$$

Update...beerends
short term...Lee/Curtis
long term...small
aviation...beerends

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