Forecast Discussion
NWS Omaha/Valley, NE

273
FXUS63 KOAX 170538
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1238 AM CDT Sun May 17 2026

.KEY MESSAGES...

- The ongoing round of severe storms ending early Sunday
  morning. The rest of the morning hours will be cool and
  breezy, but become warm and muggy later Sunday

- Severe storms will develop again on Sunday afternoon. Very
  large hail, damaging downburst winds, and tornadoes will be
  possible. The greatest severe potential will be northwest of a
  Lincoln to Harlan line.

- A final round of severe storms develops on Monday afternoon.
  Very large hail, damaging downburst winds, and tornadoes are
  once again possible, particularly southeast of a Seward to
  Onawa line.

- Much cooler conditions are expected for the rest of the work
  week.

&&

.DISCUSSION...
Issued at 1141 PM CDT Sat May 16 2026

Overview:

A volatile severe weather setup will affect the local forecast area
through Monday, with multiple rounds of severe storms likely each
day, and significant severe weather at times, including very large
hail and tornadoes.

Early Sunday:

Widespread thunderstorms have been very efficient in eating up
instability late Saturday evening into early Sunday morning. This
will be capped off by a broad arc of surging severe thunderstorms
working along the Nebraska/Kansas state line. This bow echo will
push off to the east of the forecast area by around 3 AM, give
or take with a broad stable region overspreading the area and
pushing south into KS. Currently believe that the stable airmass
will spread 40 to 70 miles south of the KS/NE border. Normally
would suspect it would dive farther south, but the 0-3 km shear
vectors are favoring ENE gusting segments with this main bow,
and the overall flow pattern with an incoming strong short wave
with negative tilt and developing surface low will quickly draw
the unstable airmass back north. All this to say that the area
is set up for a pretty pleasant morning on Sunday after a rainy
Saturday night. But that will change over the course of the day.

Sunday afternoon into Sunday night:

The center of the upper trough axis will remain well to the west on
Sunday but an embedded lead short wave trough and attendant jet
streak will eject from eastern CO into eastern NE during the day. An
elongated trough of surface low pressure will extend from the main
surface low in southeast CO up through south central NE and into
southeast SD. Expect this to be a zone of persistent strong deep
moist convergence through the afternoon. Additionally, there is a
strong model signal for a narrow dryline surge into central NE and
central KS during the afternoon. East of this, in the warm sector,
middle to upper 60s dewpoints will surge back north during the day.
This will set up very strong instability with MLCAPE likely in the
3000-4000 J/kg range. It is worth noting that even amidst this
highly unstable environment, there is a slight weakness in the mid-
level winds, so forecast parameters such as the 0-6 km shear vector
are not particularly impressive. However, one look at hodographs
tells a story of ample cyclonic curvature in the lowest portions of
the hodograph with what is likely enough of a wind difference to
keep the updrafts relatively clean of downdrafts. Model guidance is
consistent in destabilizing sufficiently for initiation by 4 PM, and
would not be surprised if it`s slightly earlier. That initial
convective initiation will likely extend on a north-south line
from Knox County down through Boone County, and due south from
there. This is where things get especially interesting. The
strength of the forcing will play a significant role in whether
storm mode becomes linear or remains largely cellular. The deep
shear vectors, while not large in magnitude, are largely
perpendicular to the line, so as long as the forcing isn`t
overwhelming, convection is likely to remain cellular. The
significant speed and directional shear in the lowest levels,
impressive at initiation and increasing notably into the early
evening hours, point to the potential of quick organization into
a line of supercells with tornado, hail, and downburst
potential. Any longer-lived supercell features that can persist
into the intensifying environmental shear conditions will have a
chance to produce strong tornadoes. With that said, the storm
mode is not a simple forecast with this event, and will have
some dependency upon those mid-level winds, timing of convective
onset, and intensity of linear forcing.

Monday:

The primary trough and strongest jet streak eject across Nebraska on
Monday. Sunday`s convection looks to clear the area very early
Monday morning, and once again expect a robust early-day recharge of
moisture and instability north into Nebraska and Iowa. There are
question marks regarding just how far north and east this will
extend, but a majority of 00Z model guidance brings it well north,
perhaps extending as far as a Hebron to Wahoo to Onawa line by
early to mid afternoon. Warm sector instability will once again
be quite strong. Deep layer wind shear will be sufficient for
supercells storm mode to be dominant. Storm motion may take
these storms slightly more parallel to the initiating boundary
which may complicate storm mode, but most all signs point to a
broken line of supercells, potentially training over some areas,
with favorable hodographs for sustained supercells, very large
hail, downdrafts, and tornadoes. Also see potential for strong
tornadoes particularly in long-lived, more isolated supercells.
The question is not necessarily the available ingredients for
severe weather on Monday, but the locations in which they will
be present...how far north and west. And we may not know that
with great confidence until Monday morning.

After Monday:

Temperatures cool sharply with highs in the 50s and 60s at mid week
and even some potential for frost on a couple of mornings. Then
another slow warmup expected by the weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1238 AM CDT Sun May 17 2026

A line of strong to severe storms is observed south of KLNK this
morning, and should continue to track east away from the TAF
site. Model guidance hints at some potential for storm
redevelopment that may impact terminals through at least 09z so
have introduced TEMPO mentions with this issuance. The bulk of
showers and storms should exit after 12z. Some guidance also
indicates a potential lowering of ceilings to MVFR after 12z,
particularly at KOFK. By the late morning into the afternoon,
will see gusty southeasterly winds overspread terminals with
gusts of 30 to 35 kts at times. More showers and storms are
forecast to develop toward the late afternoon and evening hours,
and these will once again have the potential to become severe
with large hail, damaging winds, and a tornado.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch until 5 AM CDT early this morning for NEZ050>053-
     065>068-078-088>093.
IA...Flood Watch until 5 AM CDT early this morning for IAZ069-079-
     080-090-091.

&&

$$

DISCUSSION...Barjenbruch
AVIATION...Castillo

NWS OAX Office Area Forecast Discussion

Forecast Discussion
NWS Hastings, NE

489
FXUS63 KGID 170533
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1233 AM CDT Sun May 17 2026

.KEY MESSAGES...

- Enhanced risk of severe weather (level 3 of 5) during the
  evening and overnight hours today and again Sunday. Organized
  damaging wind, very large hail, and tornadoes are possible.

- Dangerous fire weather conditions are becoming an increasing
  concern for Sunday afternoon along and behind a surging dry
  line. Areas along and south of the state line have been placed
  under a Fire Weather Watch.

- Monday`s severe weather potential is highly uncertain for our
  local area, as latest trends are shifting the main threat
  corridor along and ahead of a front a bit further E.

- Relatively quiet remainder of the forecast.

&&

.UPDATE...
Issued at 1233 AM CDT Sun May 17 2026

The Severe Thunderstorm Watch has been cancelled. A few weaker
storms will trail along the NE/KS border into the late night
hours. Also could see redevelopment of weaker thunderstorms
north of I-80 later tonight, and there are already signs of
this happening near North Platte.


Issued at 643 PM CDT Sat May 16 2026

A Severe Thunderstorm Watch is in effect until 1 AM. Several
supercells have developed along the warm front along and north
of I-80. Other than the increased coverage of supercells early
this evening, the convective forecast is unfolding as expected.

&&

.DISCUSSION...
Issued at 327 PM CDT Sat May 16 2026

Short discussion here as we transition to severe weather ops.

Two main convective regimes for the short term:
1) isolated supercells along a retreating warm front over mainly
south central Nebraska late this afternoon and evening. All
modes of severe will be possible given potent combination of
instability and shear. Already seeing signs of this along I-80
corridor.

2) larger complex of storms is forecast to move in from the W
later this evening. This activity would have an organized with
threat with it, as well as potential for QLCS tornadoes. This is
concerning considering the late time of day and difficult to
spot them. Could also see some large hail, but would be a
secondary threat. Can`t rule out a few swaths of wind driven
hail. Isolated gusts up to 80 MPH will be possible in the
strongest cores. This batch favors south central Nebraska more
than Kansas, but KS zones by no means in the clear.

Severe threat should end by around 09Z.

Focus then turns to Sunday`s severe weather and fire weather
potential. Will all depend on where the dry line sets up, but
trends have been to shift this further E and bring more of the
dry surge and fire weather into play. Will need to seem how
things settle from today...but anywhere along and ahead of the
dry line could see significant severe weather, including intense
supercells with very large hail, damaging wind gusts, and
tornadoes. The greatest tornado threat looks to be along and
E/NE of the Hwy 81 corridor. Late afternoon and early evening is
the main time frame of concern for dry line storms. Another
batch of severe storms with mainly a large hail and wind threat
could move in from the NW along the primary cold front late
Sunday evening and into the overnight.

Fire weather discussion will be included below shortly.

Exactly how things unfold Sunday will determine frontal location
for Monday. As mentioned above, this is trending further E/SE
such that most of out area could be on the cool side of the
front by midday. In fact, far N/NW zones could struggle to get
out of the 50s while far S/SE zones push 90F. A strong spring
front, indeed, that is bound to spark off widespread severe
weather...just a question of if it`s here or just E/SE.

Not much time spent in the extended periods as it appears fairly
quiet.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1233 AM CDT Sun May 17 2026

For KGRI/KEAR Airports:

The threat for thunderstorms tonight has now greatly diminished.
Some lingering light showers could continue through the night.
A period of MVFR ceilings are forecast from around 09-10Z to
17-18Z.

Winds could remain gusty out of varying directions as the main
complex of thunderstorms departs to the east, but expect a
return to prevailing easterly winds around 10-15 kts overnight,
gradually turning southerly by early Sunday afternoon, then
shifting to northerly late Sunday afternoon.

There is a low chance for thunderstorms developing late Sunday
afternoon. Chances for this are relatively higher at KGRI, where
a PROB30 has been included. Any storms that develop late Sunday
afternoon could also be severe.

&&

.FIRE WEATHER...
Issued at 643 PM CDT Sat May 16 2026

Dangerous fire weather conditions are possible along and south of
the Nebraska-Kansas state line Sunday afternoon and evening. This
roughly includes areas along and between Highways 183 and 281, and
along and south of Highway 136. Winds will turn from southeast to
south Sunday morning and increase to 20 to 30 mph with gusts up to
40 mph in the afternoon. Relative humidity is forecast to fall as
low as 10 to 15 percent. Near critical fire weather conditions
could extend north along and to the east of the Highway 281
corridor, where winds will be similar but humidity slightly
higher.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Fire Weather Watch from this afternoon through this evening
     for NEZ083>085.
KS...Fire Weather Watch from this afternoon through this evening
     for KSZ005>007-017>019.

&&

$$

UPDATE...NWS Bismarck
DISCUSSION...Thies
AVIATION...NWS Bismarck
FIRE WEATHER...NWS Bismarck

NWS GID Office Area Forecast Discussion