Area forecast discussion
National Weather Service Des Moines Iowa
640 am CDT Wednesday may 22 2013
Short term.../today /...
issued at 325 am CDT Wednesday may 22 2013
Upper low will drift slowly southeast through the state today with
comma head/deformation area sliding overhead. Recent radar trends
in South Dakota and southern Minnesota have shown an increase in returns
and anticipate this precipitation entering the north during the
morning. Have gone likely to categorical across the far north for
expected light rainfall with quantitative precipitation forecast generally quite light. Farther
south...the precipitation will be more scattered in nature with probability of precipitation
tapering off toward Missouri border to just isolated wording.
Otherwise... cloudiness will be widespread with sounding saturated
in the lower levels along with cold advection. This combination
will keep daytime highs from climbing much and readings are
expected to be stuck in the 50s across the northwest with lower 60s
southeast.
Long term.../tonight through Tuesday/...
issued at 325 am CDT Wednesday may 22 2013
Light showers will slowly diminish and push off to the east with
the upper low pressure system tonight. Any additional rainfall
amounts will be very light...but have held onto likely probability of precipitation
through about midnight as sprinkles and light showers will be
fairly widespread across our northeast and east close to the low.
From Thursday into Friday a deep layer ridge will build across the
central U.S. While at the surface a high pressure area from Canada
will slide down into Wisconsin. This will result in cool and dry
weather across Iowa on Thursday and Friday...and in fact early on
Friday morning a few stations in the northeast could drop into the
upper 30s if winds go calm and dewpoints are low enough. At this
time however lower 40s are more likely and the frost threat
appears low.
From Friday night through early next week a more active weather
pattern will set up...as the 500 mb ridge axis remains nearby and
is repeatedly overtopped and flattened by impulses moving through
the flow. At the surface a broad low pressure area will develop
and persist in the Lee of The Rockies...with a pseudo warm front
setting up somewhere around southern Iowa/northern Missouri and
remaining roughly stationary for several days. This will result in
several rounds of thunderstorms associated with the middle level
impulses...however the timing of these features and the location
of the frontal zone remain uncertain at this time. Thus have
grudgingly maintained blanket chance probability of precipitation from Friday night
through the end of the forecast period. Despite this duration of
probability of precipitation there should be at least a couple of relatively dry periods
during that span...but as of this writing such periods cannot be
predicted. All in all the weekend and early next week will be
fairly wet and active with some severe weather possible at times.
&&
Aviation...22/12z
issued at 640 am CDT Wednesday may 22 2013
Upper low will pass through Iowa today with ample low level
moisture. This is forecast to produce widespread light
rain/drizzle across northern Iowa with more scattered light shower
activity in the south. Ceilings and visibilities will be MVFR with
localized IFR conditions. Some improvement will occur by afternoon
but with nightfall and cooling. Ceilings will likely begin to
lower once again. Surface winds will become north to northwest
across the entire area by later this afternoon as the surface low
passes to the east.
&&
Dmx watches/warnings/advisories...none.
&&
$$
Short term...cogil
long term...Lee
aviation...cogil
