Area forecast discussion
National Weather Service Omaha/valley NE
606 am CDT Thursday Jun 20 2013
Aviation...
12z tafs for kofk...koma and klnk.
Although thunderstorms are possible today...no mention was made in
taf forecasts during daylight hours due to the apparent small
probability and low confidence. A prob30 was carried at kofk later
tonight as convection developing later today works around upper
ridge possibly clipping northestern nebr. Otherwise...an area of low
clouds with ceilings around 1k feet above ground level +/- expanding over S central
nebr/northern Kansas should mix out this morning before bringing ceilings to
klnk/kofk. However...trends will need watching for possible
amendments. Low clouds could again develop toward Friday morning
and this will need assessing in later forecasts.
Chermok
&&
Previous discussion... /issued 332 am CDT Thursday Jun 20 2013/
Discussion...
Water vapor imagery shows middle/upper level troughing over the
western Continental U.S. With weak ridging over the central states. At the
surface...a broad area of low pressure in response to the middle/upper
trough extends from eastern Montana through eastern Colorado. Strong
warm air advection regime is in place across the Central Plains in
addition to low level moist advection.
00z NAM did not perform well regarding its depiction of convection
across Nebraska early this morning so am not putting much weight
into this solution in the near term. Latest rap/hrrr have been
latching onto convection initiating early this morning across
northeast Kansas where altocumulus castellanus field resides. If this activity gets
going it could likely spread north into southeast Nebraska/southwest
Iowa as slightly veered low level jet axis shifts east. If
activity does develop...it could linger through much of the
morning. Additional development is possible later this afternoon.
A surface front is forecast to extend from the Dakotas southwest into
central Nebraska and to low pressure centered over northwest Kansas
this afternoon. Moderate instability and steep middle level lapse
rates would favor thunderstorms initiating near the frontal
boundary and potentially spreading east early this evening. In
addition...an mesoscale convective system is expected to develop over the eastern Dakotas
tonight and could spread south- southeast into our northern County Warning Area
sustained by increasing nocturnal low level jet.
The area is dominated by southwest flow aloft into the weekend with
the main upper low moving across the Pacific northwest and toward
the northern plains. The surface frontal boundary will remain to our
north leaving the region in the warm sector. Highs will likely top
out in the low to possibly middle 90s by Saturday.
As the upper low moves toward the northern plains Sunday...the surface
front will drop south into the forecast area and depending on cap
strength...could be the focus for more thunderstorms.
Kern
&&
Oax watches/warnings/advisories...
NE...none.
Iowa...none.
&&
$$
