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Forecast Discussion
NWS Omaha/Valley, NE

FXUS63 KOAX 030812

Area Forecast Discussion
National Weather Service Omaha/Valley NE
312 AM CDT Tue Aug 3 2021

...Updated Forecast Discussion...

Issued at 312 AM CDT Tue Aug 3 2021

Another cool and quiet night across the region under
northwesterly flow aloft, with high pressure in control at the
surface. Mostly clear skies and little to no wind has led to
temperatures dropping into the upper 50s to lower 60s as of 3
AM...almost 10 degrees cooler than average lows this time of year.

For today, expect a very similar day to yesterday though with
maybe a touch more wind (on either side of 10 mph out of the
south/southeast). Like past days, the main concern will be smoke
in the area as latest HRRR guidance shows smoke currently over
eastern Kansas sliding northward as winds increase this morning.
Near- surface smoke concentrations are once again progged to
decrease toward mid-day, though should be enough aloft to keep
temperatures from getting higher than the lower to mid 80s.

Southerly winds will strengthen further heading into Wednesday as
a shortwave trough and surface low pressure approach from the
west. This should keep near-surface smoke concentrations lower
than previous days. In addition, said features could bring some
showers and storms to the area as they pass through Wednesday
night, though model soundings suggest some low level dry air that
will need to be overcome, so would expect amounts and coverage to
be on the lower side.

Heat will then start building heading into the weekend as
southerly flow persists and the amplified upper level pattern
(ridging west, troughing east) starts to break down allowing the
warm air over the western CONUS to creep into the area. By
Saturday, NAEFS guidance suggests 850 hPa temperatures exceeding
the 90th percentile of climatology, followed by the 99th+
percentile over a good chunk of the area Sunday. This is largely
influenced by extremely warm GEFS guidance, which suggests highs
well into the 100s for the weekend. In contrast, the EPS is much
more subdued, with mean high temperatures in the mid to upper 90s.
Given poor performance of GEFS guidance for the heat in late
July, tend to think the EPS is much more reasonable. Even with the
"cooler" solution, heat advisory criteria look like they`ll be
met for a good chunk of the area Sunday.

Regarding precip chances beyond Wednesday night, several
additional weak shortwaves look to move through bringing periodic
low chances for showers and storms. The strongest shortwave would
likely move through Saturday, with the strongest forcing largely
remaining north of the area, but guidance differs greatly on
southern extent of heaviest associated precipitation (which could
in turn greatly impact temperatures).


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1122 PM CDT Mon Aug 2 2021

MVFR vsbys in smoke/fog remain the primary forecast concern
through mid to late Tuesday morning. Have included restrictions
for several hours at all sites, though KOFK may see the lowest
vsbys as they have the last couple of nights. Otherwise, south to
southeast 5 to 15kt return Tuesday, with mainly scattered mid and
high level clouds.





NWS OAX Office Area Forecast Discussion

Forecast Discussion
NWS Hastings, NE

FXUS63 KGID 030953

National Weather Service Hastings NE
453 AM CDT Tue Aug 3 2021

.DISCUSSION...(Today through Monday)
Issued at 453 AM CDT Tue Aug 3 2021

As of 330 am satellite shows some mid level clouds (around 9K-10K
ft) developing across the western half of the CWA. This alto cu is
expected to continue developing over the next several hours and into
the morning. If there happens to be any elevated instability around
we could pop a surprise sprinkle or two around morning (though we
very well may be too dry and too stable). Expecting winds to be
breezier today and tomorrow with a tightening surface pressure
gradient, as we sit wedged between the departed surface high and and
an approaching surface low. Aloft we remain in north-northwest flow
as the ridge to the west begins to deamplify with a couple of
shortwaves over the coming days. With regards to smoke, there will
still certainly be plenty of upper level haze as long as we remain
in this pattern of north and northwest flow. At the surface however,
we should see an improvement today with even less haze than
yesterday for most places. The continued presence of the upper level
haze though could keep our temperatures down a tad. So, continued
the trend from yesterday and went on the slightly cooler side of
guidance (though not by much), especially since we struggled to
achieve yesterday.

As mentioned above, a couple of shortwaves will pass over the ridge
in the coming days. This first wave will bring our next chance for
precip as early as Wednesday afternoon. All the models have this
upper level wave diving south across the area Wednesday afternoon
and evening and generating a surface low with a front that will pass
through the area Wednesday evening and overnight. Have convection
starting up Wednesday afternoon for the far western portions of the
CWA and then expanding eastward during the evening and then
lingering in the eastern half overnight. The NAM shows a few areas
with around 1,000-2,000 J/kg of MUCAPE, but only around 25 kts of
bulk shear. This could still be enough for a few stronger storms,
but nothing severe is expected at this time. Convection could also
potentially linger into Thursday morning. A note about Thursday
though: the GFS and the NAM both generate some spotty afternoon
showers that look most likely diurnally driven for Thursday. While
there are no official PoPs on Thursday at this time, this could be
something to watch for.

Behind this wave the upper level ridge will continue to deamplify
and will shift east slightly, positioning the axis just to our west
by Friday afternoon. This is when we will start to really see
temperatures climb back up again. NBM seems to be catching on to the
warmer temperatures, though still went with the 50/50 blend with
CONSALL for Friday and Saturday. Friday evening also brings some
PoPs back into the forecast that last through the daytime on
Saturday. A second upper level shortwave is approaching from the
west on Friday and the midlevel wave looks to be just ahead of it.
While PoPs are officially in the forecast as early as 00Z Saturday,
both the EC and the GFS are generating more of a QPF signal on
Saturday morning, 12Z. There also appears to be a surface front to
the west stemming from the surface low over ND that will move
through Saturday afternoon and evening and could support continued

Sunday looks to be the warmest day of the forecast, and so went with
the model certainty 75th percentile for highs. This brings temps up
into the 100s for a few places. Southerly flow at the surface all
week will also help to advect in higher dewpoints which means we
could be looking at a similar kind of heat and humidity that we just
saw last week (though likely not as severe). After a dry weekend,
Monday evening brings back some brief PoPs with a quick perturbation
aloft and a weak surface front.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Wednesday)
Issued at 1220 AM CDT Tue Aug 3 2021

Smoke and haze forecasting continues to be rather difficult. The
HRRR Smoke indicates a period of little to no near sfc smoke
tonight and into tomorrow morning, then a swath of sfc smoke looks
to be advected northward into the area around mid-morning and
through the afternoon. This could bring visibilities down into the
5 SM range and possibly lower. Otherwise VFR conditions are

Winds will pick up to being breezy and out of the south and
southeast tomorrow during the day. This will be thanks to a
tightening of the sfc pressure gradient as we are wedged between a
sfc low to the northwest and the recently departed sfc high to the





NWS GID Office Area Forecast Discussion