Gretna, Nebraska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

653
FXUS63 KOAX 141818
AFDOAX

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

.KEY MESSAGES...

- One more warm day, followed by a return to more seasonal
  temperatures from Thursday into early next week.

- Thunderstorm chances increase tonight (maximum PoPs of
  40-90%), especially north of US 20. Some severe weather is
  possible.

- Windy Thursday and Friday, potentially leading to some fire
  weather concerns.

- Additional shower and thunderstorm chances Sunday through
  Tuesday. Some severe weather is possible.

&&

.DISCUSSION...
Issued at 246 AM CDT Wed May 14 2025

Today through Thursday:

Early morning water vapor imagery reveals a mid-level trough
from the northern Intermountain Region into the Great Basin,
slowly moving east. A vorticity maximum and associated
mid/upper-level wind maxima currently rounding the base of the
broader trough over the lower CO Valley will progress into the
central and southern Rockies by this evening, before
accelerating northeast through the mid MO Valley and
surrounding areas on Thursday. In the low levels, a deepening
lee cyclone over northeast CO will drift east along the NE-KS
border today with an attendant front advancing east through
western parts of the Dakotas, NE, and KS. The surface low and
frontal system are projected to reach central NE by midnight,
and the NE-IA border by 7 AM Thursday, before accelerating
north-northeast into MN later in the day Thursday.

Gusty southeast winds ahead of the surface low and frontal
system will advect an increasingly moist air mass into the
region today, supporting an increase in cloudiness by this
afternoon. The moisture will combine with above-normal
temperatures in the upper 80s to low 90s to yield a moderately
unstable, but capped air mass by late afternoon.

Latest CAM output indicates thunderstorm development by early
to mid afternoon along the front over western/central SD into
north-central NE. Those models are in fairly good agreement in
depicting upscale growth of the initial storms into a QLCS,
which eventually moves into northeast NE after 9 or 10 PM. That
activity is expected to continue northeast overnight, with the
strongest storms moving out of our area by 4 or 5 AM Thursday.
There is some model variability in how far south the storms
develop in our area, with the general consensus suggesting the
best thunderstorm and severe weather potential (peak PoPs of
40-90%) existing north of US 20.

Proximity soundings within the inflow region of the simulated
QLCS exhibit steep mid-level lapse rates and resultant moderate
instability, which will coincide with a vertically veering wind
profile with potentially large storm-relative helicity, and
modest deep-layer shear. The expected convective mode may
modulate the potential for significant hail (>=2"), though
occurrences of 1-1.5" hail appear possible. Damaging winds will
be the main concern, with some threat for a brief tornado or
two, given the strong low-level shear forecast. Locally heavy
rainfall is also possible, especially in any areas that
experience training storms.

Showers and a few thunderstorms could linger through at least
Thursday morning in northeast NE as strong forcing for ascent
preceding the mid-level vorticity maximum overspreads the area.
Otherwise, the main story of the day will be strong west winds
developing in the wake of the morning frontal passage. The
models indicate sustained speeds of 20-30 mph with gusts of
35-45 mph, which could require a wind advisory. Depending on how
much wetting rainfall occurs, there could be some fire weather
concerns as afternoon relative humidity values fall into the
20-30% range.

We`ll see cooler temperatures on Thursday with highs ranging
from around 70 along the SD border to lower 80s in southeast NE
and southwest IA.


Friday and Saturday:

A deep-layer low centered over MN Friday morning is forecast to
move into the Great Lakes Friday night and Saturday, with
upstream heights building across the Great Plains. Winds will
remain strong on Friday, especially in northeast NE and west-
central IA, in closer proximity to the departing cyclone. A few
showers are also possible near the SD border, with some fire
weather concerns as relative humidity falls into the 20-30%
range. Winds are expected to diminish on Saturday as surface
high pressure builds into the region. Highs will range from the
mid/upper 60s along the SD border to around 80 along the KS
border both days.


Sunday through Tuesday:

The 00z global models indicate the development of another
significant trough over the Interior West this weekend with that
feature advancing east into the Great Plains on Monday into
Tuesday. At the surface, there`s ensemble agreement in the
development of a lee cyclone over eastern CO on Sunday, with the
low advancing east through the central Plains Monday night into
Tuesday. Meanwhile, an associated front --initially stalled
over the southern Plains-- will lift north, with shower and
thunderstorm chances increasing to the north of that boundary
across our area late Saturday night into Sunday. Precipitation
chances continue Sunday night through Tuesday as the mid-level
trough moves into the Plains.

Latest machine-learning guidance suggests some severe weather
potential Sunday night with an elevated thunderstorm regime
forming along the nocturnal low-level jet. A potentially greater
severe storm threat may materialize late Monday into Tuesday
along and ahead of the main surface front and upper-air system
moving through the central Plains.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 114 PM CDT Wed May 14 2025

VFR conditions expected for the start of the TAF period at all
terminals. Main concerns continue to be southeasterly winds
this afternoon, with gusts somewhat subsiding as we head toward
the evening hours. Will see a squall line move through sometime
after 4 or 5z across our far north, potentially impacting KOFK,
so have kept TSRA mentions for this TAF site from 6z to 8z.
Could also see MVFR ceilings/lingering showers after 10z but
lasting to about 14 or 15z at KOFK. Otherwise the rest of the
terminals should see VFR conditions prevail with gusty winds
becoming west northwesterly after sunrise tomorrow.

&&

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

&&

$$

DISCUSSION...Mead
AVIATION...Castillo