Norfolk, Nebraska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

384
FXUS63 KOAX 142322
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
622 PM CDT Wed May 14 2025

.KEY MESSAGES...

- Shower and storm chances increase this evening through early Thursday
  morning (50-80%), mainly along and north of Highway 20. A
  slight risk of severe weather exists across this area, with
  large hail and damaging winds the main threats. Storms exit
  early Thursday.

- Windy conditions are expected for Thursday with a Wind
  Advisory in effect from 10 am to 8 pm along a line from Butler
  toward Harrison counties and points northward. Fire danger
  should be mitigated by Wednesday`s rainfall. Some showers
  (15-30% chance) may linger across our far north.

- Windy conditions may linger into Friday, with another chance
  (30- 40%) of some light showers over our far northern
  counties. Wet pattern takes shape for the start of the
  upcoming work week with several chances for storms.

&&

.DISCUSSION...
Issued at 330 PM CDT Wed May 14 2025

.SHORT TERM.../Today through Thursday Night/

20z 500 mb RAP objective analysis shows the longwave trough across
the western US with the base and associated vorticity maximum over
the Four Corners area. The feature has already induced a closed 850
mb low based over northwest Kansas and western Nebraska, with the
baroclinic zone/warm front draped over central Kansas. RAP sfc
analysis also shows two main sfc low features, one associated with
the 850 mb disturbance over north central Kansas and a secondary low
across south central North Dakota, with a frontal boundary
essentially connecting these two features. Just ahead of the warm
front in central Kansas, do see a ~20 kt LLJ pumping in some
moisture which is increasing our sfc dewpoints today. A tightening
pressure gradient from the sfc low over north central Kansas and
boundary layer mixing tapping into the aforementioned LLJ is
resulting in the continued windy conditions from the southeast this
afternoon. Increasing moisture will result in increasing cloud cover
ahead of the approaching system today with highs reaching the upper
80s to low 90s.

The main concerns for the short term forecast continue to be the
severe weather risk later this evening into the early morning hours
Thursday. Forcing overspreads the forecast area late this afternoon
into the evening hours as the sfc low feature and frontal boundaries
slowly progress to the east. At this time, mid level forcing looks
to remain the strongest across our far north. The forcing coupled
with 500 mb height falls and increased moisture transport will aid
in steepening lapse rates resulting in an unstable airmass across
the area with anywhere from 1,500 to 3,000 J/kg of MLCAPE by the
early evening hours, but with MLCIN present. 0-6 km bulk shear is
also reasonable at 30 to 40 kts so could definitely see some
severe weather. Much of the instability becomes elevated as we
head into the late evening into early Thursday morning.

CAMs continue to show a QLCS/linear feature forming along the
frontal boundary by 00z over the North Platte forecast area
extending southward toward the Hastings area. Some uncertainty is
seen however, with southward extent depending on which CAM solution
you look at, most likely due to capping issues. The NAM Nest tries
to develop a few supercells over the Hastings forecast area which
then congeal into a messy linear segment by the 5-6z timeframe over
the northern half of the OAX CWA during which the LLJ begins to ramp
up. A secondary linear feature associated with the main cold front
then swings through northeast Nebraska during the early morning
hours. Meanwhile, the HRRR, ARW cores and FV3 HiRes simulations seem
to have better agreement amongst each other that a QLCS will
develop over north central/central Nebraska around the 23-00z
timeframe and track east northeast throughout the evening into
early Thursday morning through northeast Nebraska. The HRRR also
hints at a few prefrontal convective elements/supercells this
evening across eastern Nebraska which we will need to keep an
eye on.

The linear mode of these storms suggests that damaging winds and
large hail will be the primary threats with these storms. BUFKIT
soundings show a decent amount of dry air in the mid levels, and the
resulting DCAPE values of ~1,500 J/kg add confidence in the damaging
wind threat. Hodographs show decent low level curvature this
evening, so if any discrete cells are able to form ahead of the
baroclinic zone/warm front over eastern Nebraska and become sfc
based, could potentially see a tornado or two. Soundings show
some of this capping eroding or weakening, but what remains
uncertain is if enough forcing will exist ahead of the
baroclinic zone to be able to generate any prefrontal
convection. With the QLCS feature, will need to pay attention to
the orientation of the ~30 kt 0-3 km shear vector which, if
aligned normal to the line, could result in a brief spin up.

These severe weather concerns are addressed well by the Storm
Prediction Center`s Day 1 Convective Outlook, as northeast Nebraska
is in a slight risk of severe weather, with a marginal risk
extending down to the I-80 corridor. PoPs peak at 50-80%, primarily
along and north of Highway 20. The strong storms should exit the
forecast area by the 10-12z timeframe. We could see a few lingering
showers/non-severe storms mainly over northeast Nebraska on
Thursday. Highs Thursday will be in the mid 60s north to low 80s
across our far south with partly to mostly cloudy skies.

Winds will be on the increase as well aided by the large scale
subsidence expected behind the frontal feature and the tightening
pressure gradient as the sfc low deepens to an impressive 985 mb
over northeast SD. These 25-35 mph sustained winds with some
isolated gusts up to 45-50 mph have resulted in a Wind Advisory from
10 am to 8 pm Thursday along a line from Butler toward Harrison
counties and points northward. Fire danger concerns are possible as
well over our far northwest counties, but QPF amounts (anywhere from
0.25 inches along a line from Albion to Wayne, with amounts closer
to an inch near the South Dakota border) could help suppress these
concerns.

.LONG TERM.../Friday through Tuesday/

Friday will see the 500 mb closed low swirl around the
Minnesota/Wisconsin area with OAX being influenced by cyclonic flow.
Thus we could see a few light rain showers, with the best chances
(30-40%) across our counties bordering South Dakota. Breezy
conditions are still expected Friday as the sfc low moves toward the
Ontario region, with fire danger concerns also possible. Saturday
should be less breezy with partly to mostly sunny skies as a sfc
ridge of high pressure moves over the forecast area.

PoP chances (anywhere from 30 to as much as 90%) return Sunday
through Tuesday as a series of 500 mb waves eject out of the
Colorado and western US area. Strong to severe storms are certainly
plausible, as several GEFS and Euro based machine learning
algorithms highlight severe probabilities across the CWA during
this timeframe. Heavy rainfall is certainly plausible as well.
However, much can change during the extended period, so we
recommend that you continue to monitor the latest forecasts and
updates as we get closer to this timeframe.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 622 PM CDT Wed May 14 2025

VFR conditions to start the TAF period at all the terminals but
storms are developing out west. Storms are looking more likely
to develop south of KOFK around 00Z this evening, moving north
into the terminal around 02Z. Have introduced this round of
storms into the TAFs, but there`s still a 20% chance these
storms never develop. We have highest confidence in the next
round of storms impacting northeast Nebraska around 06-10Z as a
line of storms moves from west to east. Farther south, we could
potentially see a storm or two develop this evening impacting
KLNK or KOMA, but potential is lower, around 30% chance. Timing
of these storms would be between 02-05Z. After 05Z, storm
activity should stay contained north of these two terminals.

Once the storms move through, models show a period MVFR cigs
developing at KOFK before the winds turn fully westerly and ramp
up quickly. As these winds ramp up, low cigs should clear
around 13-14Z. The front moving across eastern Nebraska will
shift winds to westerly by morning at all the terminals with
strong winds developing, gusting 35 to 40 kt at KOFK and 30 to
35 kt at KOMA and KLNK. KOFK will be near the edge of the cloud
cover toward the South Dakota state line, but KOMA and KLNK
should be mostly clear through the day on Thursday.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Wind Advisory from 10 AM to 8 PM CDT Thursday for NEZ011-012-
     015>018-030>034-042>045-050-051.
IA...Wind Advisory from 10 AM to 8 PM CDT Thursday for IAZ043-055.

&&

$$

DISCUSSION...Castillo
AVIATION...McCoy