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Area forecast discussion 
National Weather Service Omaha/valley NE
1148 PM CDT Friday Apr 18 2014

issued at 943 PM CDT Friday Apr 18 2014

Going forecast is in good shape tonight...but we did update to
increase overnight lows...mainly in the western 2/3rd of the forecast area. A
good deal of high cirrus along with winds staying up overnight may
make it tough for temperatures to fall much.


Short term...(tonight through monday)
issued at 324 PM CDT Friday Apr 18 2014

Thunderstorm chances beginning Saturday into Sunday night are the
primary forecast concerns.

Flat upper ridging was over the plains this morning...ahead of mean
trough extending from southern British Columbia into the northern
Baja California. Upper low ejecting from northern Idaho this afternoon will
track along the Canadian border through Saturday morning before
lifting toward hundson Bay on Sunday. This feature will nudge a
surface cold front into the plains...reaching northeast Nebraska by
Saturday afternoon. Meanwhile...southern part of western trough will
push through the southern rockies Saturday night and eventually east
of the central and Southern Plains by Monday. So net result of these
features will be for Saturday cold front to stall over our area
Saturday and remain quasi-stationary until southern part of the
trough moves east late Sunday night or Monday. Thus continued
chances for thunderstorms will remain in the forecast.

Surface winds were beginning to kick up this afternoon as high
pressure slides east and pressures lower in the High Plains.
Winds should help mix out some of the higher particulate
concentrations from smoke and dust that were trapped under strong
morning inversion. Those winds will continue overnight and
Saturday until cold front approaches Saturday afternoon. Low level
moisture is relatively low this afternoon...with dew points only
in the 40s from central Nebraska to the Red River. However a plume
of 50s dew points is forecast to surge north from central Texas
into eastern Nebraska by late Saturday afternoon. Temperatures
ahead of the front will likely approach 80...but relatively mild
air aloft will keep surface based convective available potential energy well below 1000 j/kg.
0-6km bulk shear is also limited to 20-25kt late Saturday
afternoon. But convergence along front combined with subtle
cooling aloft from weak shortwave ejecting from the southwest
suggests showers and thunderstorms will be likely Saturday
night...but severe threat appears limited at best. This wave will
eject to our northeast Sunday it looks like a lull in
activity then.

Another round of thunderstorms is expected Sunday afternoon with
approach of southern upper wave. Cold front should set up
northwest of Interstate 80 in the afternoon...with continued
influx of low level moisture pushing surface dew points toward
60f. Temperatures aloft will also be cooler as trough
approaches...and with surface temperatures in the 70s...surface-
based convective available potential energy should top out in the 1500-2000 j/kg range. Upper flow
is relatively again shear is minimal with 0-6km bulk
shear near 20kt. Severe threat again looks minimal...but maybe a
little better than Saturday. Precipitation chances will continue
into Sunday night...ending from northwest to southeast with
time...and only in southeast Nebraska and southwest Iowa will
there be lingering chances Monday morning. Northwest flow then
will clear skies and cool temperatures slightly...but should still
see highs well into the 60s Monday afternoon.

Long term...(monday night through friday)
issued at 324 PM CDT Friday Apr 18 2014

Middle level ridging will build into the region Monday night and
Tuesday as strong middle level trough develops over the Pacific
northwest. By Wednesday...upper low will move into the northern
rockies and eventually track across the northern plains Thursday and
Friday. Warmer temperatures should result Tuesday into Wednesday
when highs in the 70s if not some 80s will rule.

Upper level diffluence will increase markedly on
concert with strong warm advection regime in the lower half of the
atmosphere. Could see elevated warm advection convection late
Tuesday night and during the day Wednesday...however better
chances should come Wednesday night when upper trough begins to
move into the plains and shoves surface low/cold front/dryline
into eastern Nebraska. Surface dew points again should approach 60
with cooling aloft. Strong shear is forecast as low level jet
kicks up...with GFS forecasting 50kt of 0-6km bulk shear.
Instability and shear certainly look sufficient for severe hail
Wednesday night...with timing and position of surface features
still in question for location of potentially stronger severe

Storms will likely linger into Thursday morning before front sweeps
to the east. Somewhat cooler temperatures behind this system
Thursday...and even cooler Friday as core of cold air settles south.


Aviation...(06z tafs for kofk...klnk and koma.)
Issued at 1143 PM CDT Friday Apr 18 2014

VFR conditions are generally expected through the period.
Marginal-low level wind shear is still expected overnight. On
Saturday a cold front will approach kofk around 00z but will
likely not make it to koma/klnk until after this taf period. Scattered
rain showers or possibly an isolated thunderstorms and rain or two are likely to develop along
the boundary by 00z sun. These are expected to become more
numerous near the end of the taf period...but given the
uncertainly in coverage through 06z will not include any precipitation
mention at this time.


Oax watches/warnings/advisories...


short term...dergan
long term...dergan