596 
FXUS63 KOAX 261130
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
630 AM CDT Tue Oct 26 2021

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 419 AM CDT Tue Oct 26 2021

Latest water vapor imagery shows upper level ridging overhead this
morning with a deep western trough extending across the CA/AZ/NV 
border. This deepening trough is forecast to quickly move into 
the High Plains towards 00z this evening. Ahead of this, rapid 
lee surface cyclogenesis will take place with the center of the
surface low over northwest Kansas by 00z tonight. Ahead of this, 
strong low-level moist advection is expected with surface 
dewpoints reaching the lower to mid 50s across much of the 
southern half of the CWA by 00z. A thickening stratus deck within 
the warm-air advection regime may begin to produce widespread 
drizzle by late afternoon which would likely continue into the
evening.

While the bulk of better severe weather ingredients will remain 
to our south across the central/southern Plains, a nose of MUCAPE 
on the order of 1000-2000 J/kg does extend into south-central 
Nebraska and eventually spreads east across our CWA late this 
evening into the early morning hours of Wednesday. This elevated 
instability will remain above a fairly thick stable layer per 
point forecast soundings. Severe potential appears limited as 
effective shear above this stable layer remains meager. A few of 
the earliest storms could be capable of large hail and/or damaging
wind if we can mix through the stable layer across our far 
southwestern CWA. Otherwise, generally sub-severe thunderstorms 
are likely through the overnight across much of the CWA with 
locally heavy rainfall the primary hazard ahead of the eastward 
moving cold front.

Rain chances, heavy at times, continue through much of Wednesday 
as the main trough and associated surface cold front slowly move 
eastward through the area. Overall rainfall amounts through 
Wednesday night range from around 0.75' in our northwest to 
1.75-2.0" in our southeast, which happens to be the same area that
received a widespread 2-3" over the weekend. With already 
saturated soils, some localized flash flooding is possible within
the areas of the higher rainfall rates. Area rivers were quick to
recover behind this past weekend heavy rain so there remains 
plenty of room for runoff. As the system departs the region, a 
tightening surface gradient in addition to strong momentum 
transfer to the surface could push wind gusts up towards 30-40+ 
kts into Thursday.

Weak upper level ridging is expected to move overhead on Saturday.
Warmer temperatures under this ridge should allow highs on 
Saturday to reach into the low 60s before a strong cold front 
slides through the region late on Saturday. Strong cold air 
advection behind this front will send temperatures falling with 
most areas sub-freezing by Monday morning depending on cloud 
cover. Model guidance is coming into good agreement at a swath of 
precipitation extending west to east across Nebraska within a weak
frontal circulation. Precipitation types could be mixed depending
on how temperature profiles end up. Precipitation amounts 
associated with this still look fairly light.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 623 AM CDT Tue Oct 26 2021

IFR conditions are in place at all three terminals this morning,
with pockets of mist and an occasional dips into LIFR ceilings in
a few surrounding airport locations. The current bank of clouds 
are expected to move west and lift slightly to MVFR levels late
this morning, with KOMA just outside the eastern edge of the 
lower cloud cover after 16z. Strong sustained wind speeds out of 
the southeast are expected throughout the period, with gusts 
reaching over 30 kt this evening. Low-level wind shear will also 
develop after sunset, with wind speeds approaching 50 kts out of
the SSE at FL014. Thunderstorms are expected to overspread the 
area around 07 to 09z from the west, with exact timing and 
location of these chances becoming clearer as the day goes.

&&

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

$$

DISCUSSION...Kern
AVIATION...Petersen