Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Omaha/valley NE
847 PM CDT Tuesday Jun 2 2015
issued at 837 PM CDT Tuesday Jun 2 2015
Remnants of an mesoscale convective vortex is currently moving through southwest Iowa with
a few lingering showers that will end in the next couple of hours.
Meanwhile...the stronger wave is moving through western NE/South Dakota with
a large cluster of strong and occasionally severe storms...but
still well west of the region.
00z upper air data revealed neutral heights across the plains.
Ample 850 mb moisture was in place with +12 to +14 dewpoints. +12 to
+16 h70 temperatures exist...and this may limit additional development
across the western High Plains south of existing development.
Extremely unstable conditions also exist with klbf sounding
containing about 3800 j/kg of cape.
Convective cluster should continue to move east toward our
forecast area...but it will probably still take several more
hours...and likely hold off until after midnight...thus will
adjust ongoing for a little later development. Meanwhile...a
strengthening low level jet will develop...and we may see best
chance for additional development ahead of the convective cluster
along the Missouri River corridor and north and east...similar to
latest hrrr depiction. Southeast Nebraska will probably have the
lowest chance of any development overnight.
Short term...(tonight through friday)
issued at 325 PM CDT Tuesday Jun 2 2015
Forecast challenges in the short term will continue to be
timing/placement of thunderstorms...heavy rain potential...and
The latest subjective surface analysis had surface low pressure
stretching from the Dakotas into northeast Colorado. Warm...moist
air with dewpoints in the middle 50s to middle 60s streaming northward
across the plains. A weak shortwave trough is moving across the
area and enough lift to produce some isolated showers/thunderstorms in the
metropolitan this afternoon. The main area of convection are closer to
the advancing upper level trough and the fronts.
Tonight...isolated showers may linger into early evening for parts
of southeast Nebraska and southwest Iowa. Thunderstorms are
forecast to develop over the High Plains tonight and move
southeast into northeast Nebraska. These storms should continue to
spread southeast on the periphery of the warm temperatures aloft
and in the moist and unstable air over the forecast area with the
progress of a shortwave trough and the aid of the strengthening low
level jet. Some isolated storms may try to develop ahead of the
main area of storms so have this mentioned...then trend to likely
probability of precipitation especially along and north of i80.
Wednesday morning the shortwave will be pushing into western Iowa
an the mesoscale convective system should also be pushing southeast . Surface low pressure
remains over western Kansas with the moist unstable airmass in
place. Warm air advection continue through the day...so additional storms
may try to re-form...however there appears to be a better chance
for this during the afternoon and evening hours with the next
shortwave and heating during the afternoon. The thermal ridge does
extend into the southern forecast area and if sunshine is
realized...temperatures will try to warm well into the 80s.
Uncertain how much the clouds will linger Wednesday...so have
highs from 78 to 84 degrees. With the steep lapse rates/unstable
air (3000j/kg) in place and the shortwave Wednesday
afternoon/evening and a front in the area...the area is
highlighted in the Storm Prediction Center day2 outlook for a slight risk of severe
storms. Precipitable water values range from 1.3 inches to 1.7 inches over the
next several days. The storms through the period will be capable
of putting down heavy rain. This afternoon we were added to the
day 2 excessive rain outlook for the Wednesday and Wednesday night
The real warm temperatures stay to the south and the forecast area
remains uncapped and ripe for convection. The active weather
continues Thursday and Thursday night with more storms and the
potential for heavy rain. There appears to be less coverage for
storms on Friday. Highs each day should mainly be from 76 to 82.
Long term...(friday night through tuesday)
issued at 325 PM CDT Tuesday Jun 2 2015
Thunderstorm chances increase again Friday night and shift east
during the day Saturday with more storms Saturday night. Finally
the front pushes south and drier air moves in for Sunday and
Monday...however storm chances return for Tuesday.
Aviation...(00z tafs for kofk...klnk and koma.)
Issued at 614 PM CDT Tuesday Jun 2 2015
VFR and dry conditions early in the period. Could see southeast
gusty winds for a few hours this evening...but gusts diminish by
02-04z. Thunderstorms may move into the area later tonight...and
could affect kofk 07-10z. May see a brief period of MVFR ceilings
at kofk after the rain. Rain chances increase at klnk/koma 10-14z.
Thunderstorms chances again Wednesday afternoon 19-24z.