Area forecast discussion
National Weather Service Omaha/valley NE
608 am CDT Wednesday Jun 19 2013
Aviation...
12z tafs for kofk...koma and klnk.
Isolated thunderstorms are possible across eastern Nebraska this
morning with chances increasing later today...especially
overnight. Due to the apparent minimal coverage and low confidence
west/respect to timing...no mention was made at tafs expect at kofk
late tonight when low level jet may have more Success in bringing
a bit more widespread activity toward that area. Outside of any
convection...VFR conditions are expected.
Chermok
&&
Previous discussion... /issued 337 am CDT Wednesday Jun 19 2013/
Discussion...
Although we are not expecting a continuous period of showers and
thunderstorms over the next 48 hours...it really is difficult to
discern any period in that time that should not warrant at least
a slight chance pop. Therefore...we will be carrying a small pop
for portions of the County Warning Area through this time with great uncertainty
on timing/location. Model guidance has performed rather poorly on
weak convective events in the past couple days and so forecaster
confidence remains low.
Upper air analysis and water vapor imagery show a large trough off the
Pacific coast with the low pressure centered just off the
Oregon/Washington coasts. Out ahead of this is a weak ridge of
high pressure extending from the Southern Plains into the western
Dakotas. Several weak impulses are embedded within the southwest
flow in between the main features. The first shortwave of concern
is currently located over the Nebraska Panhandle. Latest regional
radar mosiac shows a convective complex slowly drifting east and
weakening across western Nebraska while another moves slowly
northeast across northwest Kansas and weakens. Latest rap brings
a hint of this activity into the forecast area throughout the
morning and am going to tweek probability of precipitation accordingly. Broad scale lift
associated with the middle level impulse will still be present into
the afternoon and as instability increases with daytime
heating...feel thunderstorms have a chance to continue across the
forecast area in a broad low level warm air advection regime.
Low level jet will veer slightly overnight and could sustain
convective activity...therefore will continue a pop through the
overnight. By Thursday...the upper ridge axis will be directly
overhead and extend into the eastern Dakotas. In addition...a surface
cold front will extend south across the central Dakotas and into
northwest Nebraska which will likely be the focus for thunderstorm
development. Very strong instability will exist in our northern
County Warning Area however a quite Stout cap will also be in place which may
prohibit the eastward expansion of thunderstorms. Storm Prediction Center has included our
north in the swody2 for any mesoscale convective system activity moving southeast from northern
plains convection. This will be aided by a veering southwest low
level jet and so have higher probability of precipitation going in our north.
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 main surface boundary will remain to our
north leaving the region in the warm sector. Highs will likely top
out in the low 90s.
As the upper low moves toward the northern plains by Sunday...the
surface front will drop south into the area and be the potential focus
for thunderstorms.
Kern
&&
Oax watches/warnings/advisories...
NE...none.
Iowa...none.
&&
$$
