Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 182318

Area Forecast Discussion
National Weather Service Omaha/Valley NE
618 PM CDT Fri Aug 18 2017

.SHORT TERM...(Tonight through Monday)
Issued at 225 PM CDT Fri Aug 18 2017

Storms have developed this afternoon, in northwest MO, moving
southeast away from our area. There is another ares of towering
cumulus in extreme northeast NE, however Highres HRRR/Rap don`t
want to develop this area at all. Thus will keep the late
afternoon forecast dry. Then beautiful, typical mid summer
weather tonight into Saturday with high pressure overhead. Lows
tonight in the upper 50s to lower 60s. Highs Saturday in the mid
80s to lower 90s.

Storms develop Saturday afternoon across the central part of NE,
as a weak wave moves out of the central Rockies. The greatest
chance of storms moves into especially eastern NE Saturday evening,
and then across southeast NE and eventually northeast KS a
convective complex slides east southeast.

Sunday could see a small chance of showers/storms southeastern
part of the forecast area in the morning as system departs to our
southeast. Unsure of additional convective development Sunday
afternoon. The Nam remains generally dry, but the GFS/EC/Canadian
all hint at another very weak upper wave meandering through the
mid MO valley region that could spark additional isolated afternoon
storms, especially along/ south of I80. Sunday is another warm
day with highs in the upper 90s to lower 90s. Dewpoints are
forecast to begin nudging back into the upper 60s to lower 70s,
which results in afternoon heat index values in the lower to mid
90s for a few hours in the afternoon.

Eclipse Weather Outlook

With a relatively weak, fast zonal flow aloft, models typically
have a hard time discerning weak perturbations that move out of
the Rockies. The bulk of the models are suggesting that there
remains a small chance of thunderstorm development Sunday night
somewhere on the Plains, which includes portions of NE/KS.
However, the models remain consistently inconsistent with previous
runs, with the EC showing possible development further north of
I80, but other models developing spotty convection along and
south. Thus, model consensus blends still give us 20-40% chance of
thunderstorms Sunday night, but the threat may diminish through
Monday morning. Questions remain about associated cloud cover and
how much clearing will take place by eclipse totality time at 1
pm. Nam model is the most optimistic in clearing the clouds, but
GFS and EC both remain pretty pessimistic for especially southeast
NE. Even if the lower convective clouds clear Monday morning,
there may still be quite a bit mid and high clouds streaming in
from the southwest which may lead to more fuzzy than clear views
unfortunately. As suggested yesterday, defining cloud coverage in
a less than clean weather pattern for a 5 minute window remains a
significant challenge. Have knocked down model blend max forecast
temps 2-3 degrees due to cooling effects of the eclipse. We
should still reach mid 80s to low 90s temps, and again, when
combined with typical summer dewpoints, afternoon heat index
values post eclipse reach the lower to mid 90s.

.LONG TERM...(Monday night through Friday)
Issued at 225 PM CDT Fri Aug 18 2017

Models bring a cold front into the region Monday night, thus have
40-70% Pops Monday night, with a lingering chance of shower/storms
south of I80 Tuesday morning. Tuesday night and Wednesday look dry
and pleasant. Highs Wednesday in the lower 80s. There is a weak
wave moving into the area on northwest flow Wednesday night which
could bring small pops to the area. Forecast confidence beyond then
is somewhat low, but generally dry.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 609 PM CDT Fri Aug 18 2017

VFR conditions will prevail thru the fcst pd.




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