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329
FXUS63 KOAX 111112
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
612 AM CDT Tue Jun 11 2024

.KEY MESSAGES...

- Warmest days of the year so far Wednesday and Thursday with heat
  index values of 95 to 100 across much of the area today and 100 to
  105 across portions of southeast Nebraska and southwest  Iowa
  Thursday.

- Our next chances for stronger to severe storms arrive
  Wednesday (northeast Nebraska) and Thursday (southeast
  Nebraska and southwest Iowa).

- Details remain unclear, but we`ll have daily storm chances
  Friday into next week with potential for strong to severe
  storms at times.

- Warm weather expected to stick around for the weekend and much
  of next week (highs in the upper 80s and 90s).

&&

.DISCUSSION...
Issued at 404 AM CDT Tue Jun 11 2024

Today:

Water vapor imagery this morning features largely zonal flow across
the central CONUS, with a departing trough over New England, a
compact shortwave swirling over the Texas panhandle, and a
stationary cutoff low off the Baja coast. Embedded in that zonal
flow locally, is a shortwave trough dragging a surface cold
front that was analyzed from northeast Colorado extending
northeast into southeast South Dakota. Light returns on radar
are all that is left of convection that moved along the front
last night, with the expectation that this activity continues to
weaken as the cold front washes out over the forecast area with
little effect on the area today aside from a sprinkle to light
rain shower through this morning. Despite cloud cover lingering
from the slow moving and dissolving front, we`re still expected
to reach highs in the upper 80s this afternoon with light winds
and thankfully lower relative humidity values that will limit
the "soupiness" that can come with summertime days with little
wind.

Wednesday and Thursday:

With the departing shortwave trough exiting to the east,
stronger warm air advection is expected to take hold and usher
in an eastward expansion of the low-level thermal ridge centered
over the High Plains. The increased low-level temperatures will
help increase temperatures a tick or two, with highs reaching
the mid 90s for most of the forecast area while a few spots in
northeast Nebraska could reach near 100 degrees in Knox County.
Along with the warmer temperatures will come increasing surface
moisture ahead of an incoming front, which will work along with
the warm air advection to provide broad lift to the area during
the afternoon and evening hours. Steep mid-level lapse rates
send signals for large hail, while DCAPE values over 1500 J/kg
according to extended HRRR runs in northeast Nebraska.
Sufficient curvature in the low-levels exist for an isolated
tornado threat, but the abundance of the aforementioned DCAPE
also means that there is a deep and dry lower layer of the
atmosphere and LCLs will be rather high. As far as coverage
goes, extended hours in the CAMs depict little beyond a few
isolated storms in northeast Nebraska Wednesday evening, most
likely due to the lack of focused lift and the abundance of dry
air that will make updrafts struggle to get going. If any
activity does get going, the most likely time for any strong to
severe storms to occur will be from 4 PM to midnight.

Thursday will see the extension of storm chances and hot
temperatures, as the front in the day prior stalls out. The axis of
highest instability generally stretches from northeast Kansas east-
northeastward, clipping southeast Nebraska and southwest Iowa with
mixed-layer CAPE values of 2500+ J/kg and sufficient shear for
supercells. With most of the instability and forcing for ascent
being south and east of the area, we`ll likely see storms initiate
in far southeast Nebraska and southern Iowa, then move out of the
area and limiting overall severe risk. Aside from the rain chances,
highs across southeast Nebraska will top out in the upper 90s, with
heat indices approaching 100 degrees.

Friday and Beyond:

For Friday into the weekend, we`ll see an intruding and narrow ridge
moving in taking zonal flow to northwesterly flow Friday and
ushering slightly cooler temperatures in the low-to-upper 80s. A
deepening shortwave trough entering the High Plains Friday night
could help serve as the initiation for a larger MCS that would push
eastward during the evening and overnight hours across the forecast
area. Chances for showers and storms continue Saturday as the main
axis of the shortwave trough pushes through the area, bringing a
broad swath of rain and storm chances for Saturday afternoon
and evening after highs hit the upper 80s to low 90s. This
shortwave trough will take just a little bit longer to mosey on
out of the area, lingering shower and storm chances into Sunday
morning with similar highs to Saturday. Similar conditions
linger early next week in anticipation of a deeper trough
exiting the Pacific Northwest Monday, keeping our active pattern
going.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
-- Changed Discussion --
Issued at 608 AM CDT Tue Jun 11 2024

VFR conditions are expected through this TAF cycle with passing
mid/high clouds clearing from west to east this morning leaving
mostly sunny skies for the late morning/early afternoon. Surface
winds will remain under 15 kts from the west/southwest and
become light and variable this evening.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Petersen
AVIATION...Kern