461
FXUS63 KOAX 061208
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
708 AM CDT Mon May 6 2024

.KEY MESSAGES...

- Wind Advisory issued for northeast Nebraska for 10 AM through
  7 PM Monday, for gusty winds of 40 to 50 mph.

- Potentially strong storms are expected this evening,
  primarily from 4 to 10 PM as a line of storms moves thought
  the area. Damaging wind, hail, and embedded tornadoes are
  possible.

- Light showers and a few rumbles of thunder linger through the
  end of the work week, with drier conditions and highs in the
  70s returning for the weekend.

&&

.DISCUSSION...
Issued at 417 AM CDT Mon May 6 2024

Today:

Water vapor imagery this morning features a deep, negatively-tilting
mid/upper trough swirling over the Intermountain West, with
increasing heights to the east and a small shortwave powering an MCS
travailing into the western TN/KY area. After a 07z surface
analysis, very impressive moisture advection was noted, with 50
degree dewpoints being pulled as far north and west as northeast
Montana. A surface low sits in at the Colorado/southeastern
Wyoming border area, with a long dry line extending southward
from northeast Colorado to the western tip of Texas. A war front
stretches eastward through much of Nebraska before dipping
southeast into northeastern Kansas to southwest Missouri. Along
that front, relatively weak surface winds and convergence have
allowed for some fog formation, primarily in far southeastern
Nebraska and northeastern Kansas. These areas are expected to
lift northward over the next few hours and a good chunk of
eastern Nebraska and southwest Iowa will see continued dreary
skies with visibilities of less than 3 miles (really dense fog
with visibilities of less than one mile will likely stay
south). Dreary conditions will stick around or most morning and
early afternoon, and could lull those unaware of the afternoon
forecast into complacency. Strong winds also develop this
morning with gusts of 35 to 50 mph expected (the strongest of
which will be in northeast NE where a wind advisory is in
effect.

Severe weather continues to be on track for this afternoon with the
arrival of strong forcing for ascent this afternoon, with CAPE
values in the 1500-2000 J/kg range with bulk shear values of 40-50
kts supportive severe storms. Low-level shear vectors continue to be
largely parallel with the incoming boundary, quickly growing upscale
most convection that moves in. Ahead of the line of storms, CAMs are
continuing to pick up on the eastern edge of the warm sector and
area of favorable lapse rates in the form of semi-discrete
supercells. Both those storms and the main line pose a risk, and the
strong curvature in the low-level hodograph would indicate embedded
QLCS tornadoes being a possibility in addition to ones
associated in the warm sector cells (though the latter may have
to fight poor low- level lapse rates initially)

Turning our focus general timeline of events, the aforementioned
dryline is expected to have pushed eastward to central Nebraska
by noon today. Along or shortly ahead of this dryline, a line of
storms is expected to begin developing and pushing gradually
eastward. By 4 PM, this line of storms will have reached the
northwestern portion of the forecast area. The rest of the line
will push eastward during the early evening hours, arriving near
the Lincoln Metro near 6-7 PM, and Omaha around 7 PM. Smaller
storms to the east of the line should start developing around 6
PM, and could push chances for the Omaha Metro an hour ahead.
This line will then exit to the east of the area, leaving
southwest Iowa by 9 to 10 PM. The main hazards continue to be
damaging wind, hail, localized flooding (especially in areas
where storms ignite ahead of the main line), and a few
tornadoes. All storms that develop out ahead will be just as
worth a close eye as the main line will be. After the storms
exit to the east, westerly to southwesterly winds and lows in
the mid-to-upper 40s will carry us quietly into Tuesday for what
will be a much needed breather from hazardous weather.

Tuesday and Beyond:

With Monday`s storm system in the rear view mirror, the main
mid/upper trough is expected to cut off and drift northward, with a
center near the MT/ND border region. A strong zonal to slightly
southwesterly mid/upper jet will be settled over the area and will
provide no shortage of shortwaves and embedded impulses that will
keep light showers and a few rumbles of thunder in to the forecast
for the remainder of the week. Highs will take a slight hit and fall
into the 60s for much of the remaining work week before highs return
to the 70s for Saturday and Sunday. By that point the influence from
the Monday system will have finally left the area in favor of
increasing heights and northwesterly flow as a couple of days settle
in for the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 707 AM CDT Mon May 6 2024

IFR or LIFR conditions prevail at all three TAF sites this
morning in the form of ceilings FL003-FL006 and visibilities 3-5
BR. These conditions are expected to persist through at least
mid-morning, with ceilings improving into MVFR category at KOMA
and KLNK by 17z-18z, and perhaps at KOFK.

More significant aviation impact will be from thunderstorms
this afternoon through evening. Isolated thunderstorms may begin
to affect all TAF sites as early as 19Z, but the greatest impact
will be from a line of storms that moves into KLNK and KOFK
between 21Z and 23Z, and KOMA between 22Z and 00Z. Expect
ceilings and visibilities to facilate between IFR and MVFR
during most intense thunderstorm activity.Included the potential
for G50KT, though gusts in the 55-60kt range are possible.
Additionally, there is the potential for hail, but left that out
for now, and will let later forecasters fine tune.

Thunderstorms should come to an end at KOFK and KLNK by 02z and
KOMA 03z to 04z. VFR conditions are expected at all three TAF
sites by 05z-07z.



&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Wind Advisory from 10 AM this morning to 7 PM CDT this evening
     for NEZ011-012-015>018-031>034.
IA...None.

&&

$$

DISCUSSION...Petersen
AVIATION...Fortin