609 
FXUS63 KOAX 301039
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
539 AM CDT Wed Sep 30 2020

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 322 AM CDT Wed Sep 30 2020

Forecast Summary: 

Gusty north to northwest winds today will usher in much cooler air 
which will remain in the area through the weekend. In fact, freezing 
temperatures and areas of frost are likely Friday morning. The only 
real chance for precipitation comes Saturday. A rebound in 
temperatures still looks probable early next week.

Today:

Strong northwest mid level flow remained overhead this morning, in 
between pronounced ridge in the West and trough from eastern Canada 
through the Appalachians and into the northeast Gulf. A broad area 
of mid level clouds from eastern South Dakota into northeast 
Nebraska and much of Iowa was the result of mid level warm advection 
ahead of a shortwave diving southeast. As that shortwave passes 
through today, strong cold advection will follow this morning and 
afternoon. 850 temperatures are forecast to drop a good 10C from 
the mid and upper teens early this morning to near 8C this 
afternoon. After morning cloud cover in our north spreads east, more 
sunshine is expected for the afternoon, offering some help to offset 
strong cool advection. Expect highs only to rebound into the 60s 
north and lower 70s south today. 

Strong northwest winds are also forecast given tight pressure 
gradient and potent pressure rises behind cold front, generally in 
the 20 to 35 mph range across much of eastern Nebraska and western 
Iowa. And despite cooler temperatures than Tuesday, lower dew points 
will still result in minimum afternoon humidities between 20 and 25 
percent. This dry air combined with the strong winds will result in 
near-critical fire weather conditions. Our fire weather fuels status 
remains non-critical overall, but given the prolonged drought in 
northeast Nebraska and west central Iowa, there are likely pockets 
of grasses that could support erratic fire behavior if starts occur. 

The strong winds should diminish rather quickly early this evening 
with loss of daytime heating and cool advection subsides.

Thursday through Sunday:

Another reinforcing shot of cooler air is scheduled to arrive 
between midnight and sunrise Thursday. 850 temps will likely drop 
below 0C in our north by Thursday morning with that cold airmass 
overhead through Thursday night. Temperatures Thursday afternoon may 
not reach 60 in much of our area. Then diminishing winds and mainly 
clear skies should allow for radiational cooling regime overnight. 
There may be a few more high clouds than our forecast suggests, 
which may limit cooling somewhat. Still we should see widespread 
frost Friday morning, with some spots dropping to or below freezing.

Southerly winds return on Friday as surface high slides east and 
pressures fall to our west with the approach of a potent shortwave 
dropping through the Northern Plains. We will likely gain a few 
degrees over Thursday's highs for Friday afternoon, but still well 
below normal.

Moisture profiles are rather paltry for the arrival of strong 
shortwave scheduled Saturday morning. Models in general have backed 
off a bit on extent of potential precipitation Saturday, but most 
all guidance produces some precipitation. Therefore, will maintain 
our chances for showers on Saturday under mainly cloudy skies and 
cool east to northeast winds. Cool temperatures remain overhead for 
Sunday behind exiting shortwave, with Sunday's highs in the 50s.

Monday and Tuesday:

We should see a nice warming trend to begin next week as mid level 
heights rise behind exiting shortwave. A couple of weak shortwaves 
riding through west to northwest mid level flow Monday and Tuesday 
will bring short bouts of warm then cool advection, but overall the 
warm advection pattern will win out. Expect highs back into the 70s 
by Tuesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 537 AM CDT Wed Sep 30 2020

Strong and gusty northwest winds 20 to 32kt are expected to
develop between 14Z and 17Z at all eastern Nebraska TAF sites as a
cold front sweeps through the region. Expect those winds to
continue through 00Z before settling back to under 12kt by 02Z.
Only scattered to briefly broken mid level clouds near FL120 are
forecast through 18Z, then clear skies are expected.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

DISCUSSION...Dergan
AVIATION...Dergan