Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Omaha/valley NE
643 PM CDT sun Jul 5 2015

Short term...(tonight through wednesday)
issued at 307 PM CDT sun Jul 5 2015

Forecast concerns in the short term will be if any thunderstorms
can form early this evening...and then thunderstorms that develop
with the cold front/severe and heavy rain potential with this
weather system through Monday.

At 12z...500 mb low pressure was centered over northern Manitoba
Canada with a broad trough trailing southwest into the northern U.S.
700 mb moisture was pooled ahead of the 700 mb trough with 2 to 4 degree 700 mb
dewpoints. 12z 850 mb dewpoints had risen to 12 to 14 degree c across
the state. Morning convection with a weak shortwave trough dissipated
by early afternoon...with most of the lingering clouds in
southwest Iowa. There were a few spots that received over an inch
of rain. Temperatures are warming into the upper 80s and lower
90s. Water vapor satellite imagery shows plenty of moisture from
the Pacific and across Mexico into The Rockies.

Storm Prediction Center mesoanalysis Page show highest MLCAPE torward Fairbury and
Lincoln and the weakest cap is in this area. Meanwhile...the
warmest middle-level temperatures are building in to northeast
Nebraska. The short-term hires models are mainly dry this
evening. The rap and Storm Prediction Center hrrr do show some isolated storms
possible in this high cape/weak cap area. Will include low probability of precipitation
this evening. This will need to be monitored as if storms break
the cap...the could quickly become severe.

Tonight...there is upper level support with upper level divergence
in the right rear entrance region of the jet and Omega with the
middle level trough. Warm advection/Theta-E advection increases with
these features...and showers and thunderstorms become more
widespread along the front. Storms should increase in northeast
Nebraska remaining west of Norfolk through 03z...then spread into
the rest of northeast Nebraska with the cold front. Through
12z...a pre- frontal trough and thunderstorms will continue to push
southeast...meanwhile deep layer shear increases in northeast
Nebraska. Cape of 2000-4000 j/kg is forecast. Do mention severe
potential in the zone for northeast Nebraska overnight. During the
morning...another push with the middle level trough will continue
showers and thunderstorms across the forecast area during the
morning. The storms may weaken though by the time they make it to
far southeast Nebraska and southwest Iowa. Thunderstorms shift
southward and re-generate Monday afternoon across the rest of the
forecast area...ending Monday evening.

Heavy rain is a concern with the high precipitable waters . Precipitable waters increase to 1.8
to 2.2 inches through Monday evening. The nam20 even has a rare 3
inch bullseye for precipitable water near fnb at 00z Monday evening. Training
and locally heavy rain area possible. The storms are progressive
through tonight. Monday afternoon the storm motions do drop down
to around 15kts...so this will need to be monitored.

Mainly dry and cooler weather is on tap for the rest of the short
term.

Long term...(wednesday night through sunday)
issued at 307 PM CDT sun Jul 5 2015

Cooler and unsettled weather continues into the extended with a
ridge and warmer conditions for Saturday and Sunday.

&&

Aviation...(00z tafs for kofk...klnk and koma.)
Issued at 639 PM CDT sun Jul 5 2015

VFR conditions are expected through the evening with gusty
southerly surface winds. Scattered showers and thunderstorms could move
toward kofk by 04-06z but confidence is fairly low. A cold front
will approach kofk by 10-12z and a better chance for showers and
thunderstorms will be along this boundary. The front will continue
to slide southeast through the afternoon bringing increasing
chances for showers and thunderstorms to koma and klnk by
afternoon.

&&

Oax watches/warnings/advisories...
NE...none.
Iowa...none.
&&

$$

Short term...zapotocny
long term...zapotocny
aviation...Kern

National Weather Service Glossary of Abbreviations