Area forecast discussion
National Weather Service Des Moines Iowa
638 am CDT Wednesday Jun 19 2013
Short term.../today/...
issued at 339 am CDT Wednesday Jun 19 2013
High pressure ridge moving off to the east now with warm air advection beginning to
move into western Iowa. Sat pictures show an increase in clods from decaying
blowoff clouds. Deeper moisture convergence moving into southwestern Iowa
will bring at least isolated thunderstorms and rain this morning as warm air advection arc lifts
northeast across the County Warning Area. Kept the precipitation to the west half however.
Combination of namdng5 and hrrr gives a reasonable presentation of
expected outcome. Temperatures today very dependent on cloud cover. Feel
there will be enough breaks to get highs a little above MOS guidance and
warmer than yesterday in most locations.
Long term.../tonight through Tuesday/...
issued at 339 am CDT Wednesday Jun 19 2013
Complicated forecast for extended...with many periods of
probability of precipitation...and somewhat low confidence in timing...with breaks in
precipitation chances from time to time through the remainder of the
week. Large upper level low will be driver for precipitation
chances trough much of the period. Low will remain primarily over
Pacific northwest...and is beginning to slowly push inland at this time. Models have
significant discrepancies over placement of low...but should come
into better agreement as low pushes inland. Ridge remains over
Iowa through much of period...with shortwaves pushing through
sparking convection chances.
Models have significantly slowed down short waves propagation
eastward...with focus for development in central NE pushing into
Iowa late overnight. Have therefore slowed probability of precipitation for
overnight...though could see some development ahead of main precipitation
band with Theta-E advection. System is slow moving...with precipitation
through Thursday. Strong shortwave set to track across northern
plains late Thursday. This will likely be the focus for severe
weather across the Dakotas...and may form into mesoscale convective system pushing across
Iowa...with northern Iowa most likely location overnight Thursday.
Severe weather will be possible with this system. Shortwave
expected to track across southern South Dakota/Minnesota and heaviest precipitation may
stay north. Numerous shortwaves continue to track east as upper
level low remains across northwestern US. As low pushes
eastward...tracks of waves will likely go north of County Warning Area...but may
see development further south...and have kept probability of precipitation across the
north. Somewhat stronger wave pushes through flow for the
weekend...though upper level low will push eastward and surface
low in Western Plains will also lift NE at this time...and timing
and location for precipitation chances over the weekend is very
muddled. As upper level low pushes east front will drop across
Iowa with prolonged precipitation chance for late in the period.
Temperatures will warm significantly under the ridge...with
surface southerly flow. Have bumped temperatures up with warm air advection for
early in the period...though mixing may be somewhat limited.
Overall...temperatures will warm with Summer like readings.
&&
Aviation...19/12z
issued at 632 am CDT Wednesday Jun 19 2013
A southeasterly flow of will bring moisture north into the state and result
in isolated rain showers over the western taf sites this morning. VFR
conditions will hold through the taf period with middle and high
level ceilings. Thunderstorms and rain will move into western a tonight...but at this time
thinking is that the thunderstorms and rain will remain mainly west of the taf sites
with only a small chance of them reaching kfod and kdsm by 12z.
&&
Dmx watches/warnings/advisories...
none.
&&
$$
Short term...MS Jun 13
long term...awb
aviation...MS Jun 13
