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fxus63 koax 231730 

Area forecast discussion
National Weather Service Omaha/valley NE
1230 PM CDT Mon Apr 23 2018

Short term...(today through wednesday)
issued at 330 am CDT Mon Apr 23 2018

Forecast concerns in the short term will be very high fire danger
today and chance for rain Tuesday/Tuesday night and again

Water vapor satellite imagery shows the h5 trough over Idaho with
some lightning in northern Utah. Over parts of Montana they have
widespread half to one inch precipitation amounts forecast, some
of which will fall as snow. The wave will continue to phase with
the trough from Canada as it swings through the plains. Upper
level divergence persists through the event along with increasing
Omega. The nam12 tends to be a little weaker with the upward
vertical motion and tracks it a little more west than the other
models and this results in the nam12 being drier across the
forecast area. In general, the bulk of the models have come into
a little better agreement with the chance for rain Tuesday and
Tuesday night. The namnest/ec/GFS/UKMET/icon/Canadian all now have
an area of a trace to up to a quarter or a third of an inch of
rain. Not great, but with the very dry conditions this month, any
rain is welcome.

Today's warm temperatures from 70 to 75 and lowest relative
humidity values of 22 to 25 percent will place quite a few
counties in the very high fire danger category across east central
Nebraska into west central Iowa.

Increasing clouds can be expected for tonight with the approach
of the storm system mainly after 06z and between 12-18z Tuesday
the chance for light rain/showers begins to move into parts of
northeast Nebraska. Showers become likely in northeast
Nebraska Tuesday afternoon...spreading southeastward Tuesday
night...with the rain pushing south Wednesday morning. North
winds increase Tuesday night behind the front to 10 to 20 mph as
temperatures drop into the mid 30s north to the mid 40s south.
Did leave an hour or two mention of a mix in the north as several
models showed enough cooling to support this, although the chance
for precipitation decreases markedly by this time. The clouds
decrease from north to south Wednesday with highs in the 60s.

Long term...(wednesday night through sunday)
issued at 330 am CDT Mon Apr 23 2018

Thursday, the longwave trough that is over British Columbia
sweeps eastward across Canada and extends southward into the
Central Plains. The GFS/ec both have the trough dragging a cold
front through with some light rain possible. The current blended
forecast is on the dry side and has 20 to 30 percent pops and quantitative precipitation forecast
of a trace to few tenths of an inch. The front moves through early
enough in the day to limit highs, but still look for highs in the
60s. Steep lapse rates should promote downward mixing of stronger
northwest winds into the 20 to 30 mph category and gusty.

The winds may pick up in the morning Friday, but should die down by
evening as surface high pressure builds in. Mid level ridging and
south flow will boost temperatures for Saturday, although the medium-
range models differ a bit on if the ridge will be over the Central
Plains or the central rockies. These model differences continue for
Sunday as the GFS brings a shortwave into the northern plains with a
few showers in northeast Nebraska, while the ec holds any rain off
until Monday night. Our forecast has some spotty showers in for
Sunday with a chance for rain Monday night. Temperatures in the 60s
Friday moderate further into the 70s Saturday and remain in the 70s
for the rest of the extended.

With the warm temperatures and dry April, for those locations with
crp grass areas, fire weather conditions will be elevated Friday
into Monday.


Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1230 PM CDT Mon Apr 23 2018

High pressure will prevail over the area in advance of an
approaching cold front and upper trough. VFR conditions are
expected through the period with light winds.


issued at 330 am CDT Mon Apr 23 2018

Some locations may pick up a tenth to a third of an inch of
rainfall Tuesday/Tuesday night. Here are the dry record statistics
for April.

Driest April precipitation records

Location April to date record year other information
Lincoln 0.11" 0.02" 1910 to be in top 5 0.36"
Omaha 0.10" 0.23" 1936 to be in top 5 0.38"
Norfolk 1.00" 0.11" 1928 to be in top 20 1.04"


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