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Forecast Discussion
NWS Omaha/Valley, NE

FXUS63 KOAX 171736

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1236 PM CDT Tue May 17 2022

...Updated Aviation Forecast Discussion...

Issued at 400 AM CDT Tue May 17 2022

At 400 AM, delinquent anvils from overnight convection in western
and central Nebraska were bringing mostly cloudy skies to our
region. Radar indicated a couple echos over northeast Nebraska,
most of which likely were not reaching the ground. Elsewhere dry
conditions prevailed. WAA, from light southerly winds, was
keeping temperatures warmer than recent mornings (mid to upper
60s for most).

Thunderstorm Threat Today and Tonight:

The main forecast concern through the next 24 hours is the
potential for severe thunderstorms. Numerous forecast challenges
exist, including the affects of any ongoing convection prior to
the main event (before 3 PM), timing of convective initiation this
evening and the evolution of hazards as storms progress southward

A weak shortwave moving through Nebraska will produce widely
scattered shower and thunderstorm activity across the region
through 3 PM. This activity should be largely elevated and severe
weather is not anticipated prior to 3 PM. This said, any
convection in the time window could still modify the local
environment and impact how convection develops later this evening.

The main show should begin during the 4 PM to 7 PM window as a
second shortwave approaches and convergence increases along a
stationary boundary in northeast Nebraska. CAMs (HRRR, ARW, FV3 &
NAM NEST) are in better agreement with the placement and timing of
convective initiation (compared to previous runs), and this was
reflected in the 40 dBZ paintball analysis from the 00Z HREF. As
such confidence in convective initiation during the 4 PM to 7 PM
window is high (70%). Environmental parameters suggest a 1 to 3
hour window for possible isolated supercell activity after storms
initiate, then convection should grow upscale into an MCS with the
potential for bowing segments or embedded supercells. Thus the
initial hazards (4 PM to 9 PM time window) look to be a mix of
large hail (to the size of ping pong balls) and downburst winds
(gusts to 65 mph). As the likely MCS matures after 9 PM, the
primary hazard should be damaging wind gusts of 60 to 75 mph. The
hail threat could linger with any embedded supercells, and with
better instability (CAPE >2500 j/kg) south of Interstate 80 there
is a potential for golf ball or larger hail. An isolated flash
flood risk may also develop across southeast Nebraska and
southwest Iowa between 10 PM and 2 AM. HREF guidance indicates the
potential for localized rain totals of 1.5 to 3 inches south of
Interstate 80 during this window, which would be flirting with
current 3 Hour Flash Flood Guidance (FFG). A couple tornadoes
can`t be ruled out during this event if we can get a an isolated
supercell going or a line segment favorably aligned with the 0-3
KM shear. Overall though the tornado potential is lower than the
damaging hail or wind threat. The most likely time window for
storm activity in the Omaha and Lincoln Metros is 8 PM to 11 PM

Storms May Return Thursday Evening:

A warm front should lift north across the region Thursday morning
as the next significant trough advances into the Northern Plains.
This should set the stage for warmer conditions Thursday afternoon
(high temps in the upper 80s) and bring limited moisture return
by the afternoon. Thunderstorms are possible Thursday evening as
a well defined cold front surges through the region. Though the
greatest risk for severe weather looks like it will be over
southern Minnesota, Wisconsin and northern Iowa, there is some
potential for severe weather in our region (see the SPC Day 3

Cooler Over the Weekend:

A broad area of surface high pressure should settle into the
Northern and Central Plains over the weekend. As this occurs a
noticeably cooler airmass will overspread the region, sending our
temperatures back below seasonal averages. The coolest
temperatures are expected Saturday, when afternoon highs may be
limited to the lower 60s region wide and morning lows may dip
into the 30s across northeast Nebraska. A few light rain showers
are possible Saturday morning, but otherwise the weekend should be


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1230 PM CDT Tue May 17 2022

A messy aviation forecast is in place for the 18z TAF issuance,
with ongoing convection just now exiting the KOFK area, and newer
convection bubbling up west of KOMA and just north of KLNK. These
current storms are expected to come before another set of storms
later this evening after 02z from the northwest, with not a ton of
confidence on the exact timing of storms this evening but they
should push through rather than linger for long periods of time.
After storms have pushed through the area, MVFR and potentially
IFR ceilings could develop after midnight and persist through the





NWS OAX Office Area Forecast Discussion

Forecast Discussion
NWS Hastings, NE

FXUS63 KGID 171751

National Weather Service Hastings NE
1251 PM CDT Tue May 17 2022

.DISCUSSION...(Today through Monday)
Issued at 343 AM CDT Tue May 17 2022

The primary forecast concern will center around the enhanced risk
for severe weather this evening, which currently appears to be our
best chance at precipitation through the week ahead. Our next
chance for precipitation will be with a strong cold front late
Thursday afternoon and evening, but the better chances with this
next system should be northeast of our forecast area. Most areas
should be dry Friday through the weekend, with just a slight
chance for showers Friday night. Temperatures will be warmer than
normal through Thursday with the warmest day being 90s on
Thursday. Then a cold front will send highs back down into the 60s
for the weekend before we climb back into the lower 70s early next

Today and Tonight...
At just before 4 AM we have a few showers and thunderstorms
trying to develop and forecast models indicate this activity may
increase over the next several hours before sliding east of our
area by mid to late morning. There should then be a prolonged lull
in precipitation with mostly sunny skies from late morning
through late afternoon for most locations. This will allow the
atmosphere to destabilize and then thunderstorms will form along a
northeast to southwest oriented cold front this evening primarily
after 6 PM. Thunderstorms should really increase across the
coverage area this evening between 6-10 PM and then slide east
southeast. Forecast models have been coming into better agreement
in that this will likely be a fairly widespread and appreciable
precipitation event across our forecast area with many locations
having a shot at 0.50 to 1.5 inches of rainfall. Would not be
surprised in a few isolated 2 to 3 inch rainfall amounts where
stronger storms train over the same area. Severe thunderstorms
could impact the area through 1 AM before most of them pass
southeast of our forecast area.

MUCAPE values based on several different models will likely
average between 2500-3500 J/KG with 0-6km deep layer shear values
of 30-40 kts, which would support higher end severe weather. At
this time large hail to golf ball size, maybe larger, and wind
gusts to 70 mph seem likely in at least some of the stronger
storms. The storms will likely quickly form into a line and can
not rule out a weak QLCS tornado or two, but the low level wind
shear is not very impressive until well after dark when storms
will probably begin to become more elevated by that point.

This will be a quiet weather day between systems with zonal flow to
perhaps a slight upper ridge leading to dry conditions and highs
around 80.

The large upper trough will take a far northern track across the
northern plains. This is not a good track for us to see a lot of
precipitation as most of the dynamic energy with this system will
be well to our north. However, the strong cold front and plenty of
instability just ahead of the front could be enough to generate a
strong line of thunderstorms primarily during the evening hours,
but hard to tell how far southwest along the front the storms will
form this far out. Right now the best chance for thunderstorms
will be across our northeastern zones and points northeast from
there, but this could change. It will certainly be warm and moist
ahead of the front with highs in generally in the 90s. The SPC
slight risk area is northeast of our forecast area where the
coverage of storms should be greater. Confidence in storms across
our area is still fairly low.

Friday through Sunday...
For the most part we`ll dry out as we get into dry and cooler
northwesterly upper level flow on the back side of the departing
storm system. However, we do have just a slight chance for some
light rain Friday night in association with the upper trough, but
most folks will probably see little to no precipitation. This
will send highs back down into the 60s for Friday and Saturday,
possibly getting back close to 70 again by Sunday. We may have to
watch out for a slight chance of a light frost Saturday morning
May 21st across our northwestern zones, right now our lows are
forecast to be in the mid to upper 30s in Ord and lexington so it
could be close.

We have a slight chance for precipitation with a weak passing
shortwave. Highs should begin to warm back up and possibly into
the 70s for most areas.


.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Wednesday)
Issued at 1240 PM CDT Tue May 17 2022

VFR conditions persist at both terminals through the rest of this
afternoon. Southerly winds are expected to continue, becoming
slightly south-southwest by mid-afternoon as the remnants of
decaying thunderstorms move through the area.

Heading into late this afternoon into evening, a cold front is
expected to cross the region, kicking off showers and
thunderstorms. A few of these may become strong to severe with
hail and strong winds being the main threats. Have put vicinity
storms in the forecast for now as there remains some uncertainty
on where the front will be located this evening. Conditions are
expected to be VFR/MVFR through this time with thunderstorms
bringing short periods of reduced visibility. Conditions improve
after midnight with northerly winds 5-10kts expected through the
remainder of the forecast period.





NWS GID Office Area Forecast Discussion