377 
FXUS63 KOAX 291738
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1238 PM CDT Tue Sep 29 2020

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 353 AM CDT Tue Sep 29 2020

Forecast Summary:

One day of above-normal temperatures today will be followed by 
cooler-than-normal temps through the weekend as a couple of shots of 
cooler air plunge through the Plains. The coldest day of the week 
should be Thursday, with temperatures dropping well into the 30s 
Thursday night when our first real shot of widespread frost and 
spotty freezing temperatures are likely. Saturday brings the only 
substantial chance for precipitation through early next week.

Today through Friday:

Upper flow pattern features a strong ridge in the West from 
northwest Mexico into the Pacific Northwest, and a deep trough to 
our east extending from the Great Lakes into East Texas. Strong 
northerly flow resides in between these features, with a 120-140kt 
300mb jet extending from southern Manitoba into eastern Nebraska. A 
slight eastward shift of trough and jet is forecast today, allowing 
mid level heights to rise and promote a nice warm advection pattern 
at the surface. Westerly low level flow and warmer 850 temps suggest 
highs rising well into the 70s in eastern Nebraska, and likely just 
above 70 in western Iowa.

West to northwest winds are likely to gust to around 35 mph or 
higher this afternoon as deep mixing occurs. Wind profilers suggest 
speeds are a bit higher than models indicate now, so have increased 
speeds through much of the day all areas. The strong winds combined 
with mixing induced low humidities suggest very high fire danger in 
some spots across eastern Nebraska this afternoon. Current fuel 
status indicates widespread uncontrollable fires are not likely, so 
will refrain from any fire weather headlines at the moment.

A wind shift will drop through the area later tonight as a mid level 
shortwave rotates into the southern Great Lakes. Highs Wednesday 
will swing to just below normal as cold advection continues through 
the day. And that cool advection is accelerated Thursday when 850 
temperatures drop below 4C. Highs may not reach 60 in much of our 
area on Thursday.

Winds diminish under mainly clear skies for Friday morning when 
surface high pressure settles over the Mid Missouri Valley. Decent 
radiational cooling should allow for some spots to drop into the 
lower 30s, and perhaps lower, with areas of frost likely most of 
eastern Nebraska and southwest Iowa. Winds turn southerly rather 
quickly Friday as surface high slides east. A nice 30-degree warmup 
from morning lows should put most spots back into the 60s.

Saturday through Monday:

A significant shortwave will induce surface cyclogenesis in the 
western Plains on Saturday. Only modest-at-best moisture return is 
expected, but strength of system suggests areas of showers and even 
isolated thunderstorms are a good bet. ECMWF is most bullish in 
showing widespread rains across eastern Nebraska and southwest Iowa, 
but most other mid-range models have a decent precipitation signal 
in or close to our area as well. Currently have rather low precip 
chances in the forecast, but confidence is increasing for rain on 
Saturday.

A brief cooldown will follow this system for Sunday, with a return 
to warm advection to start next week. Have highs in the 60s this 
weekend, then closer to the lower 70s on Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1234 PM CDT Tue Sep 29 2020

VFR conditions to prevail for the TAF period. Wind speeds are
beginning to increase across the area as wind gusts near 20 kts
have been observed at several sites. Wind gust should peak near 25
kts. Winds will rotate over the afternoon from westerly to
northwesterly. By 23Z, wind gusts should begin to diminish. After
01Z, winds should settle to less than 10 kts.


&&

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

$$

DISCUSSION...Dergan
AVIATION...Fajman