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Area forecast discussion 
National Weather Service Omaha/valley NE
1147 PM CDT Thursday Jul 30 2015

Update...
issued at 1138 PM CDT Thursday Jul 30 2015

Updated the forecast earlier to include some isolated thunder mention
down to about i80 overnight. Evening upper air analysis indicated
a ribbon of 850 mb moisture from western Kansas into northeast Nebraska.
Models indicate that some increase in the low level jet is
expected overnight created some convergence over this moisture as
this band drops to the south through the night. Lifting a parcel
between 850 and 700 mb yields around 1500 j/kg and only around
30-40 j/kg of mucin. Thus some isolated activity appears possible
overnight...as latest regional radar mosaic indicates as well. We
expect this activity to be pretty isolated though with a fairly weak
low level jet and a lack of any larger-scale support.

&&

Short term...(tonight through sunday)
issued at 308 PM CDT Thursday Jul 30 2015

Warm and drier weather continues...but periods of showers and
thunderstorms may develop tomorrow into the weekend. Subjective 12z
upper air analysis indicates upper-level trough starting to show
itself in eastern Canada into the Great Lakes...with ridging
developing over the Great Basin...and west to west-northwest flow
across the central US. Upper-level jet streak of up to 95kt was
noted across Nebraska/Iowa into the Great Lakes. Drier airmass has
persisted...with 850mb high centered over eastern Nebraska/eastern
Kansas...and 8c+ dewpoints suppressed south of an area from northwest to
southeast Kansas and northern Arkansas. Return flow was nosing into the High
Plains...feeding convective development this afternoon in northeast
Colorado. Visible satellite imagery indicated a few cumulus from north central to
western Nebraska...with otherwise mainly clear skies across the area.

Main forecast concerns are potential for
showers/storms...particularly on Friday afternoon/evening/night and
again Saturday afternoon/evening/night. Models generally keep
convective development today/tonight in central/western Nebraska and not
in the County Warning Area...so have kept probability of precipitation out for tonight. Increasing middle-
level moisture on Friday should be more supportive of afternoon
shower/thunderstorm development in central to eastern Nebraska. Despite
just a weak ripple in the northwesterly upper-level flow...and weak
surface convergence...models develop fairly robust convection in
central to eastern Nebraska on Friday afternoon...growing upscale into an
mesoscale convective system that dives into Kansas in the evening/overnight and with some
showers/storms redeveloping on its outflow in southern Iowa to central
Nebraska through morning. Have reflected some of this timing/placement
in refining probability of precipitation. After a bit of recovery time...almost the same
pattern appears...with an eastward shift...as convection develops in
eastern Nebraska/western Iowa...grows upscale into an mesoscale convective system...then drops
south/southeastward into MO overnight. Instability and shear on
both days would be sufficient for at least a marginal risk of severe
weather...though moisture is still somewhat limited. With weak
surface winds...low-level shear would be a non-factor. Temperatures
should warm through Saturday...assuming that the Friday night mesoscale convective system
clears with ample time for recovery...but am less confident about
recovery and warming on Sunday given continued northwest upper-
levle flow but also some return flow sneaking into the western County Warning Area.

Long term...(sunday night through thursday)
issued at 308 PM CDT Thursday Jul 30 2015

Intermittent chances for showers and thunderstorms continue next
work week. Upper-level northwesterly flow should transition to more
zonal flow as ridge slides a bit eastward out of The Rockies...and
models indicate a few waves topping the ridge. Any of those waves
could generate showers/thunderstorms across the area...as well as
reinforce slightly cooler 850mb temperatures as gradient hangs up
near the County Warning Area. All in all...have several periods of precipitation
mentioned...with temperatures lingering below normal...but have low
confidence on any given day.

&&

Aviation...(06z tafs for kofk...klnk and koma.)
Issued at 1138 PM CDT Thursday Jul 30 2015

Isolated rain showers/thunderstorms and rain have developed between koma/kofk this evening...but it
appears unlikely either taf site will be impacted overnight other
than an increase in middle-level clouds. A weak boundary is still
expected to drop southward through the taf sites through the day on Friday and
we will likely see some rain showers/thunderstorms and rain development alng this boundary by
middle afternoon on Friday likely affecting koma and especially
klnk...but south of kofk. We may see some MVFR visby in this
activity. Any rain showers activity should end by early evening Friday at the
tafs.

&&

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

&&

$$

Update...boustead
short term...Mayes
long term...Mayes
aviation...boustead

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