NWS Omaha, NE wrote its last area forecast discussion before the first event at Mar 25, 2:57 AM CST, 3 minutes earlier. Its key messages:
Area forecast discussion, Mar 25, 2:57 AM CST, 3 minutes before
Area Forecast Discussion
National Weather Service Omaha/Valley NE
357 AM CDT Mon Mar 25 2024
.KEY MESSAGES...
- Mixed precipitation, heavy snow, and 35-45 mph wind gusts will
lead to dangerous travel in portions of Knox and Antelope
counties today into Tuesday morning. Whiteout conditions will
be possible at times (40-60% chance). A Winter Storm Warning
is in effect.
- Light icing and 1-3 inches of snow will lead to slick roads
from Cedar county toward Platte county today into Tuesday
morning. A Winter Weather Advisory is in effect.
- A few slick spots will be possible (10-30% chance) for the
remainder of the area, including Omaha and Lincoln into
Tuesday morning.
- There is a 5 to 10 percent chance for strong to isolated
severe thunderstorms in far eastern Nebraska into southwest
Iowa, primarily from 2 PM to 10 PM. Hail and damaging winds
will be the primary threats, but a tornado cannot be ruled out
(2% chance).
- Dry weather returns for Wednesday and Thursday with
temperatures trending back up into the 60s by Thursday into
the weekend.
&&
.DISCUSSION...
Issued at 357 AM CDT Mon Mar 25 2024
Early morning analysis showed the well-advertised strong
surface low spinning over southwest KS, with widespread
associated precip stretching north across much of NE and into
SD/IA/MN. There was also quite the temperature gradient across
the area, with mid to upper 20s across north-central and
northeast NE under northerly flow on the cold side of a
stationary boundary and mid 40s to near 50 in southeast
NE/southwest IA under southerly flow on the warm side. As the
cold air continues to work in any rain will switch to a wintry
mix of rain, sleet, freezing rain, and/or snow, with a warm nose
aloft also contributing to the mix of precip types. When all is
said and done, we'll have a fairly significant snowfall (4 to
locally 10 inches) stretching from southwest NE into SD,
clipping Knox and Antelope counties in northeast NE in our
forecast area.
Regarding the details, the general trend has been for colder
air to move in faster with guidance in turn bringing the primary
snow band slightly farther east. With these heavier snowfall
rates, the northwest winds that are expected to gust 30 to 45
mph will lead to increased probability of whiteout conditions.
In fact, per 25.00Z HREF guidance, there is about a 40-60%
chance of blizzard conditions in Knox/Antelope counties, with
the primary threat being this morning into early afternoon (1-2
PM or so). That said, snow will continue to fall after those
hours and travel will remain dangerous, but confidence in
whiteouts/blizzard conditions decreases heading into this
evening. In addition, the heavy, wet nature of the snow should
at least somewhat limit blowing of snow that has already fallen.
Really this is probably the biggest deterrent to issuing a
blizzard warning at this time. Regardless of blizzard vs. winter
storm warning, travel in those areas will be treacherous, so
we'd recommend just staying home.
To the east of the primary snow band, expect a very sharp
cutoff in snow amounts. Current forecast is for around 1-3" from
Cedar down to Platte county, and just a few tenths of an inch
for most areas to the southeast of that. There are also some
signs for some light icing (a few hundredths up to 0.1") prior
to the changeover to snow which will gradually work from west to
east today into this evening (most likely after commute time in
Omaha and Lincoln), though confidence in this occurring is
rather low. So for now, kept the Winter Weather Advisory as it
was, as that area continues to have the greatest overlap in
icing amounts and snowfall amounts. However, if the icing threat
ends up panning out to the southeast, the advisory may need to
be expanded. In addition, there remains some signs that we see
an additional lighter band of snow/snow showers (another 1-3
inches) to the east of the primary band. It's very possible it
ends up falling in the current advisory, but a few pieces of
guidance suggest it could slide a few counties to the east.
The final thing to mention with this system will be the small
chance for some stronger to isolated severe storms in far
eastern NE into southwest IA this afternoon and evening (roughly
2 PM to 10 PM). Guidance continues to suggest we see a narrow
area of breaks in the clouds in vicinity of the surface low as
it pushes into the forecast area today. In addition, a plume of
near 50 degree dewpoints looks to push in just northeast of the
surface low. As a result, we could see SBCAPE values around 750
J/kg. With steep lapse rates in an already cold environment, it
wouldn't take much for some hail development. Add in strong deep
layer shear, we should see some degree of storm organization
with any stronger cores potentially bringing the much stronger
winds aloft toward the surface, resulting in a damaging wind
threat. Finally, while hodographs are fairly straight, enhanced
vorticity and convergence in vicinity of the surface low could
yield a small (2% chance) tornado threat. If any were to
develop, they would likely be weak and short-lived, but the
threat is definitely worth mentioning.
Some light snow showers/flurries could linger into Tuesday with
cyclonic flow aloft remaining in place, but accumulations
should largely come to an end by early Tuesday morning.
Otherwise, gusty northwest winds will persist and keep us cool,
with temperatures topping out in the mid 20s to mid 30s. Surface
high pressure will then build in and help keep us dry through
at least Thursday. We'll also see a return to southerly surface
flow which will help us to start warming up on Wednesday (highs
in the 30s and 40s). Warm air advection will continue through
the end of the week with mid level ridging settling in over the
center of the CONUS, with 50s and 60s looking to return by
Thursday, followed by 60s and potentially lower 70s by Friday. A
weak cold front will work into the area for the weekend, but
still expect highs in the 50s to lower 60s. A few pieces of
guidance suggest there could be some precip along this front at
times during the weekend, but currently looks pretty spotty with
the best moisture remaining to our south. As of now, have 20-30
percent chances going Saturday night and Sunday.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1138 PM CDT Sun Mar 24 2024
Thunderstorm chances tonight have decreased from the last
forecast issuance, so have removed TS from TAFs. There is still
ongoing convection in northeast Kansas that will work its way
into southeast Nebraska over the next couple hours, reaching
KLNK between 06Z and 07Z, and KOMA around 08Z. A few lightning
strikes may be possible with this round of precip before 12Z at
KLNK and KOMA. A second round of spotty showers and
thunderstorms (40%-50% chance) may impact portions of east-
central Nebraska and southwest Iowa (KOMA) tomorrow after 21Z.
Have opted to exclude from TAFs at this time due to timing and
coverage concerns.
Widespread precip has brought LIFR ceilings and reduced
visibilities across northeast Nebraska (KOFK) and western Iowa.
Current guidance suggests that snow will remain west of KOFK
until 14Z, but more recent short range model runs have trended a
little cooler and quicker. As such, there is a chance (30-40%)
that the rain to snow transition will happen sooner than
previously thought (as early as 10Z - 12Z).
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Warning until 7 AM CDT Tuesday for NEZ011-016.
Winter Weather Advisory until 7 AM CDT Tuesday for NEZ012-017-
030-031-042.
IA...None.
&&
DISCUSSION...CA
AVIATION...Darrah