Area forecast discussion
National Weather Service Omaha/valley NE
252 PM CDT Friday may 24 2013
Discussion...
Timing of best precipitation chances through Memorial Day weekend
and beyond main challenge and confidence of skill beyond
climatology...I.E. Highest probability of precipitation at night...not the highest.
18z surface + 12z upper air analysis had surface to 850 moist
axis and subjectively placed warm front from scntrl Kansas into southwestern
nebr. Although a few high based showers developing NE of boundary
in scntrl nebr and other possible higher based activity across
northern/northestern zones early will have to be monitored...main action over
the forecast area will probably be from late this evening through
overnight hours. Any convection that increases through this
evening western High Plains will be aided by decent Theta advection
into boundary as low level jet strengthens. 12z GFS was probably
suffering feedback issues by 12z Sat in southern placement of mesoscale convective system.
However...some southern extension of an mesoscale convective system could make it into far
southwestern zones early tonight thus likely probability of precipitation all of western zones just
after 06z with any activity then focusing more across northestern zones Sat
morning before expected decline.
After tonight deeper moisture will overspread much of the
forecast area with much higher than normal precipitable water
values generally locked in till much of the energy from western U.S.
Trough ejects late next week. With moisture/instability in place
and some sort of warm front or convectively enhanced boundary
possibly remaining over or near area...strengthening nocturnal low
level jet plus any disturbances lifting out of western trough could
keep active pattern in place...especially through Holiday weekend
and then again by next Thursday. Although did try to diurnally
decrease chances from SW to NE across area on Saturday...after that
made little changes to probability of precipitation through Monday...with likely probability of precipitation
generally reserved for nighttime with decreased daytime probability of precipitation in
Tuesday/Wednesday period.
Overnight/early Saturday convection could reinforce boundary
across forecast area Saturday...thus kept temperatures closer to a 00z
European model (ecmwf)/12z NAM compromise northern areas with any 80+ mention confined
to southern zones. After moisture becomes more uniform over the
area beyond Saturday...better surface thermal gradient may shift NE
of area thus providing more uniform temperatures although 00z European model (ecmwf) kept
some boundary/slightly cooler temperatures over area through Monday.
Chermok
&&
Aviation...
18z tafs for koma...klnk and kofk.
VFR conditions will prevail at least through early this evening.
Thereafter...expect scattered thunderstorms and rain development in central Nebraska with
activity pushing into eastern Nebraska toward midnight. Occasional strong
thunderstorms and rain will be possible in response to strengthening low level jet. Early
Sat morning...influx of low level moisture will result in IFR ceilings
settling in over eastern Nebraska through most of the morning hours.
Dee
&&
Oax watches/warnings/advisories...
NE...none.
Iowa...none.
&&
$$
99/99
