602
FXUS63 KOAX 081928
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
228 PM CDT Wed May 8 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected to develop
  across northeast Nebraska and western Iowa this afternoon. A
  few strong storms with gusty winds, small hail, and a brief
  tornado will be possible.

- Scattered showers are expected to develop tomorrow across the
  region bringing a 20 to 40 percent chance of rain at any given
  location.

- Precipitation chances return by the beginning of next week
  with several rounds of showers and thunderstorms possible
  Sunday evening through the end of the forecast period.

&&

.DISCUSSION...
Issued at 228 PM CDT Wed May 8 2024

...Today Through Tomorrow...

Scattered showers and thunderstorms are expected to develop
across portions of western Iowa this afternoon by 3 PM (30 to 50
percent chance of rain). Additional development is possible
further west into portions of northeast and east-central
Nebraska, however coverage will be more limited if storms can
develop (20 to 30 percent chance of rain). Nonetheless, the
synoptic environment will be favorable for thunderstorm
development. Model soundings show what current observations
suggest, which is a deep boundary layer has developed across the
region. At the top of this boundary layer, relative humidities
are high, as evident in the developing cumulus field across
eastern Nebraska and additional cloud cover into Iowa. Strong
forcing for ascent associated with the left exit-region of a jet
max will be present this afternoon. However, the primary
limiting factor to storm development will be poor boundary layer
moisture, with surface dew points in the 40s and low 50s. This
precludes any higher precipitation chances this afternoon and
evening.

Inverted-V model soundings this afternoon and evening are
supportive of strong wind gusts in any storms that develop. Wind
gusts up to 60 mph will be possible in the strongest downdrafts.
Small hail will also be possible, especially in any storm that
can develop in west-central Iowa where boundary layer moisture
is slightly higher than adjacent areas to the west and south.
Furthermore, the potential for a funnel cloud or landspout
exists across northeast Nebraska and western Iowa. This low-end
risk is supported by enhanced surface vorticity as the surface
low-pressure lingers in northeast Nebraska and should slowly
track east. Any storms that develop this afternoon should
quickly weaken with the end of diurnal heating after sundown.

Tomorrow, steep lapse rates aloft associated with cold-air
advection in the mid-levels will bring a day of cumulus clouds
and scattered garden variety showers in the afternoon. No
thunderstorms are expected at this time. Similar to today, any
convection that is able to develop tomorrow will be tied to the
diurnal heating and destabilization of the boundary layer, and
should quickly weaken with sunset tomorrow evening.

...Friday through Tuesday...

The upper-level trough out west is expected to cut-off by this
weekend and linger in the southwest CONUS. Over the central
Plains, northwesterly flow aloft and synoptic scale subsidence
should keep any precipitation chances out of the region Friday
through Sunday morning. Temperatures will also be near or
slightly above average with highs in the 70s and low 80s.

By Sunday evening, the cut-off low southwest of the area should
slowly shift out into the southern Plains. Ahead of this
disturbance, southerly flow at the surface will aid in moisture
transport from the south, bringing dew points up into the 50s.
Positive vorticity advection downstream of this cut-off will
provide forcing for ascent across our area Sunday evening,
bringing the potential (20 to 40 percent chance) of showers and
thunderstorms.

Heading into next week, an amplifying trough and down stream
shortwaves embedded in northwesterly flow aloft will bring
additional forcing for showers and thunderstorms across the
region. Medium range guidance suggests that surface dew points
may return into the 60s, especially across far eastern Nebraska
and western Iowa. This pattern may favor stronger thunderstorms
in the afternoon if timed right with upper-level disturbances.
However, details are too uncertain at this time to definitively
point out periods of time where strong to possible severe
thunderstorms will be likely.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1154 AM CDT Wed May 8 2024

The surface wind field across eastern Nebraska and western Iowa
remains complex given two surface low-pressures in close
proximity to one another. At this time, the northeast Nebraska
low appears to dominate the surface flow at all TAF sites, so
have written TAFs given these current observations. As such,
winds will veer with time, ultimately becoming north-
northwesterly by the end of the forecast period. Scattered
showers and thunderstorms are expected to develop across
portions of northeast Nebraska and western Iowa by 20Z. Some of
these storms may be on the stronger side with winds gusting to
60 mph and hail up to an inch. These storms are largely expected
to remain northeast of TAF sites.

Tomorrow, scattered showers are expected to develop across the
region at the end or shortly after the end of this TAF period.
Will provide more detail regarding these in a subsequent TAF
issuance.

&&

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

&&

$$

DISCUSSION...Darrah
AVIATION...Darrah