Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Omaha/valley NE
322 PM CDT Sat Jul 12 2014
Short term...(tonight through tuesday)
issued at 247 PM CDT Sat Jul 12 2014
Forecast concerns in the short term will be thunderstorm re-
development and potential for locally heavy rain...severe weather.
This morning/S oax sounding had 1.71 in precipitable water and a warm cloud layer
of over 10k feet. Closed 500 mb low pressure was centered over Manitoba
and extended into the northern Continental U.S. With the strong shortwave
over Wisconsin/southern Minnesota. 700 mb moisture of 6deg c was pooled
over northern Nebraska...but were 2 to 3 degree c lower than
forecast by the NAM Friday. Warm 700 mb temperatures +10c covered much
of scentral and southern Nebraska. 850 mb dewpoints were also pooled
in northern Nebraska with 14-16deg c.
At midday...the bulk of the convection was closer to the cold front
over southern Minnesota...another boundary was near i80.
In between...it was cloudy with areas of sprinkles/showers. This
afternoon/evening...500 mb shortwave trough energy will swing through
and strengthen from Iowa into southern Nebraska...then shift
southward out of the area after 09z. At 20z...the surface front
had pushed through most of the metropolitan area and was near lnk. Can
see the front on the WSR-88D with not much in the way of echoes.
Should see an increase in the coverage of storms this evening
with the heating and convergence along the front and increased
upper level support. The hrrr/rap do have some isolated to scattered
convection...then increase coverage especially in the 03z-06z time
period south of the metropolitan areas in southeast Nebraska and
southwest Iowa. Have only isolated/scattered coverage in the forecast through
03z...then increase to likely coverage in southeast Nebraska and
southwest Iowa. The low level jet should focus more to our
east...but may mention locally heavy rain for a few hours in
southeast Nebraska and southwest Iowa.
Severe storms cannot be ruled out with moderate instability and
sufficient shear. Seems like heavy rain would be more of a
concern due to the precipitable waters available and high efficiency. 850 mb
convergence appears weaker in our area and stronger farther east
into Iowa...so this may temper severe potential. The Storm
Prediction Center does have our area in the slight risk for
severe storms. The wpc excessive rainfall forecasts do mention
southeast Nebraska and far southwest Iowa through
tonight...however afternoon update shrunk the area for the
excessive rainfall though and now is just clipping our area.
The moisture does not clear out cleanly and there is some middle
level warm air advection with cyclonic flow around the storm
system to the northeast through Monday. Isolated showers/thunderstorms
will be possible Sunday through Monday morning.
Surface high pressure builds in for Monday night and Tuesday with
near record lows Monday morning and highs in the 70s Tuesday about
15 degrees below normal.
Long term...(tuesday night through saturday)
issued at 247 PM CDT Sat Jul 12 2014
Surface high pressure will dominate the weather pattern Tuesday
through Saturday. Look for below normal highs in the 70s.
Wednesday and Thursday...then highs in the 80s Friday and
Saturday. Will keep mainly dry and may need to add probability of precipitation for
Saturday with a front moving into the area.
Aviation...(18z tafs for kofk...klnk and koma.)
Issued at 1232 PM CDT Sat Jul 12 2014
MVFR ceilings and isolated showers behind a cold front will gradually
dissipate in the kofk area early in the taf period. Otherwise
mainly VFR conditions are forecast. Light south winds will turn
northerly as the front moves through...and there could be isolated
thunderstorms near koma and klnk between 00z and 06z.