Scientific Forecaster Discussion
fxus63 koax 232356
Area forecast discussion
National Weather Service Omaha/valley NE
656 PM CDT Thu Mar 23 2017
Short term...(tonight through sunday)
issued at 320 PM CDT Thu Mar 23 2017
Forecast concerns in the short term will be shower and
thunderstorms through Saturday with the slow moving storm system.
Where the best potential for severe weather is and what kind of
rainfall amounts may occur.
The ktop/koax 12z soundings from this morning showed moist
conditions through h7 with around 1 inch of pwat and steep 3-6km
lapse rates around 8 deg c/km. H9 winds increased to around 45kts
during the morning and a pocket of strong 0-3km bulk shear across
northeast NE between 15z and 18z...and the lift ahead of the
elevated warm front likely helped spark the thunderstorms and rain with hail that
quickly moved into South Dakota. This initial wave of 700 mb warm air advection
continues to move into Minnesota and Iowa this afternoon.
This afternoon...the latest subjective surface analysis has the
warm front lifting across the forecast area with showers and
thunderstorms ahead of it. There has been a lot of lightning with
the storms and even some grass fires, however not a lot of
precipitation. Temperatures south of the warm front have warmed
into the mid and upper 60s with dewpoints in the 50s.
The large mid-tropospheric trough over Nevada/California is forecast to shift
toward The Four-Corners area then deepen over Colorado/wrn Kansas overnight
into a closed low...slowly tracking across Kansas. Broad surface
low pressure over eastern Colorado further deepens tonight with a
cold front extending into central and northeast Nebraska.
The day1 severe weather outlook tornado probabilities extend from
central Nebraska into western Kansas south through the OK Panhandle
and the Texas Panhandle with an area of hail/wind outlook in this
similar area where thunderstorms will be more focused. Broad upper
level divergence and warm air advection along with pwats around an
inch to 1.25" are progged.
The combination of the the approach of the upper level trough/broad
upper level divergence/waa/mid-level frontogenesis have isolated to
scattered storms this afternoon...becoming more focused from western
Kansas into western and central Nebraska into northeast Nebraska
this evening and tonight where convective available potential energy of 1000-2500 j/kg will be more
prevalent and 0-6km bulk shear is forecast to exceed 60kts. The
rap/hrrr did not have a good handle on the morning convection and
started to pick up on the afternoon convection with the 16z hrrr
the general trend is to increase precipitation coverage from
central Nebraska into northeast Nebraska this evening and
overnight. Will maintain highest pops in northeast Nebraska
through tonight and Friday morning. Another area of showers and
thunderstorms ahead of the dry slot develops from eastern
Oklahoma into eastern Kansas and western Missouri and should make
it into southern Iowa Friday. In between, scattered
showers/thunderstorms will be possible. The day2 Storm Prediction Center outlook
brings the marginal risk toward fnb...however keeps the slight
risk generally from southeast Kansas into southwest MO. Rain/showers
will continue on the northwest side of the storm system across the
outlook area Friday night and Saturday with the slow-moving
Related to the rainfall expected...trimmed back amounts somewhat
with general amounts of a tenth to 0.50 inch. Still have higher
amounts from .75 to 1.75 for parts of northeast Nebraska.
Long term...(sunday night through thursday)
issued at 320 PM CDT Thu Mar 23 2017
Unsettled weather continues with more showers Sunday
night...Tuesday night-Thursday. Highs mostly in the 50s and 60s.
Aviation...(for the 00z tafs through 00z Friday evening)
issued at 606 PM CDT Thu Mar 23 2017
Main concern is deteriorating conditions associated with areal increase
of thunderstorms and rain over ern neb tonight. At this point...expect convection
currently organizing from northwest Kansas into cntrl neb along sfc trof/dry
to move into NE neb later this evening and generally persist into
Friday morning. As for koma/klnk...trends over the last several
hours combined with latest model guidance all suggest very low
chance for seeing ts activity thru the fcst pd.