254
FXUS63 KOAX 080943
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
443 AM CDT Wed May 8 2024

.KEY MESSAGES...

- Marginal risk of severe thunderstorms today and thisevening
  in northeast Nebraska and western Iowa

- Some storms today and this evening could be strong to severe,
  capable of producing hail, damaging winds and funnel clouds

- Forecast for Friday through early Sunday is mostly dry. Chance
  of showers and thunderstorms returns Sunday afternoon and
  lingers into early next week.

- Warmer temperatures expected Sunday into Tuesday.

&&

.DISCUSSION...
Issued at 439 AM CDT Wed May 8 2024

.Today...

A band of showers continues to move northeast across the
forecast area this morning, associated with moist isentropic
lift along the 305-310K, prompted by increasing large scale
ascent in advance of H5 closed low digging southward into the
central plains. Drier air below 5K AGL is limiting measurable
precipitation. Better focus moves east of forecast area by mid-
morning, thus expect a lull in precipitation by then.

Upper level low begins to move east along the Nebraska-South
Dakota border by mid-day, sharpening the large scale wind field,
with bulk shear values of 40-70kt by midday. Lapse rates will
increase as cold core and vort lobe from upper low moves across
the area. In tandem, low level theta-e increases,which will
lead to SB/MUCAPE near 1000 J/Kg northeast Nebraska and western
Iowa, and about 1200 J/kg extreme southeast Nebraska. An
inverted trough will be oriented from southwest Iowa, across
extreme northeast Nebraska into southeast South Dakota,
providing adequate surface convergence to allow for scattered
thunderstorm development. Given proximity to upper low,
increased stretching and low-level shear, present an environment
conducive for funnels and/or possibly a tornado or two,
especially storms interacting with inverted trough across
extreme northeast Nebraska and northwest Iowa. Further south,
across southeast Nebraska, proximity to main surface low could
aid in low level convergence for storms, but tornado or funnel
threat in this area is not expected.

Threat of severe weather will diminish by early evening as vort
lobe moves east of the area, leading to subsidence across the
region. A few more showers could develop during the overnight
hours as another disturbances ripples through broad cyclonic
flow aloft.

Temperatures today will be similar to those seen yesterday.
Overnight lows will be in the 45 to 50 degree range.

.Thursday...

Area remains on the cyclonic shear side of broad, latidudnal
trough that stretches from North Atlantic to western U.S.
Mid-level isentropic convergence will help to sustain band of
showers and possibly isolated thunderstorms, especially during
the daytime when diabatic effects will aid in destabilization.
Precipitation coverage and chances will wane Thursday evening,
as upper trough axis moves south and east of the area, and
increases large scale subsidence.

Clouds, evaporative cooling and low level cold advection will
keep temperatures about 5 to 10 degrees cooler, with highs only
in the 60s. Lows will be in the 40s.

.Friday through Saturday...

Large scale subsidence will keep precipitation chances slim, and
will allow for temperatures to rebound into the 70s for highs.
Sharpening trough across the eastern U.S. pushes a backdoor cold
front into the area for Saturday. In cooling associated would
affect Iowa moreso than Nebraska, with downslope warming
mitigated low level cool air advection.

.Sunday through Tuesday...

Temperatures will increase as upper level ridging builds, with
high temperatures climbing into the 80s. An open H5 wave will
progress from the 4-corners area across the southern plains
Sunday and Monday, and bring another chance of showers and
thunderstorms. The surface pattern doesn`t suggest a threat of
severe weather, as better mass responsive will be south of the
area.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1134 PM CDT Tue May 7 2024

Primarily VFR conditions are expected through the period. A few
showers could sneak into southeast Nebraska tonight and drift
northward through Wednesday morning. Another round of showers
and thunderstorms will be possible over northeast Nebraska and
western Iowa Wednesday afternoon and evening. A few of these
storms could contain hail and gusty winds. Overall, confidence
remains low in whether or not precipitation will impact the TAF
sites at this time.

&&

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

&&

$$

DISCUSSION...Fortin
AVIATION...KG