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000
FXUS63 KOAX 152051
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
351 PM CDT Mon Apr 15 2024

.KEY MESSAGES...

- Very high to extreme fire danger is expected this evening for
  portions of northeast Nebraska and west-central Iowa.

- Several rounds of strong to severe thunderstorms are possible
  beginning this evening through Tuesday afternoon. All modes
  of severe weather are possible at this time.

- Much cooler temperatures work their way into the region
  beginning Wednesday and are expected to last through the
  weekend.

&&

.DISCUSSION...
Issued at 350 PM CDT Mon Apr 15 2024

Surface analysis shows a stationary front pushing north now as
a warm front. It`s currently south of the Omaha metro and
visible on satellite imagery. It will continue northeast
through the night and act as a focus for severe weather,
especially as the LLJ ramps up. Water vapor imagery shows a
closed low pushing east into Colorado.

Warm air has built into the entire area with a wide range of
dewpoints accompanying them. Dewpoints range from the 30s up
north to the 60s along the Kansas state line which produces RH
values from the teens to near 50%. A RED FLAG WARNING continues
for Pottawattamie County, IA and points north until 7pm this
evening.

For severe weather, model consensus is growing as to the timing
and location of best threats. Believe the cap (stronger than -200
J/Kg) holds through the afternoon hours. Expect first
convection to likely fire along the warm front as it treks
north. First radar returns will generally be found near a line
from Council Bluffs, IA to Fremont to Norfolk to near Wagner,
SD. Already CAPE values along the KS state line have pushed over
2000 J/kg.

Strongest convection overnight tonight looks to be primarily
limited to the warm front (north) and the dry line developing in
central Nebraska (west). HREF/SREF probabilities show severe
threat (hail/wind/tornado) peak around the 10pm time frame with
best chances in northeast Nebraska. Hodographs reveal a threat
of supercells capable of very large hail (2-3 inches) and
tornado development, especially along the warm front, but also
in the warm sector should any storms develop there. The LLJ
cranks up at 800 hPa overnight... keeping the tornado threat
going after dark (a rarity around here) and indicates
prospective downbursts could produce wind gusts of 70mph.

Flash flood concerns are highest along the SD/NE border and
unfortunately peak overnight. Rainfall rates of 1.5" per hour
are possible with strongest storms with localized rain totals
over 3" possible with training storms. With dry soils in place,
believe flash flood concern will be mostly limited to urban
areas and their hydrophobic surfaces.

With reduced CAPE overnight, storm coverage should diminish,
though severe storms remain possible through the night,
especially on the nose of the LLJ. An early morning push of CAPE
up the Missouri River Valley coincides with the jet streak`s
location. This will maximize 0-6km wind shear and reinvigorate
the thunderstorm activity in far southeast Nebraska / southwest
Iowa / Omaha metro. These storms will move quickly to the east
and take the strongest storms with them although thunderstorms
may remain well into Tuesday afternoon as mid-levels quickly
cool closer to the low center. Funnel clouds may be a result on
Tuesday afternoon just behind the departing system.

High temperatures will be notably cooler on Wednesday with
strong northwesterly flow developing before sunrise. Expect
seasonal highs though it will feel cooler with gusts up to
40mph.

Highs on Thursday through Saturday will peak below normal with
highs in the 50s expected. Will have to speak with growers in
the area and neighboring offices as to whether a frost/freeze
headlines are necessary as morning lows will slip into the low
30s at times.

Thursday brings high chances (60-85%) of rain and thunderstorms
along with a potent shortwave and cold front caught up in
quasi-zonal flow.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 157 PM CDT Mon Apr 15 2024

Expect strong southeasterly winds to continue through the TAF
period with gusts of 20-30 knots at times.

Timing of forecast thunderstorms has tightened and has been
narrowed down in the updated TAFs. Expect occasional cigs at
FL015 to FL025 with thunderstorms. Heavy rain is possible with
some of the storms with visibility slipping below 5 miles.

Scattered showers and storms will become less numerous after
midnight before redeveloping again before sunrise.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Red Flag Warning until 7 PM CDT this evening for NEZ011-012-
     015-018-032>034-045.
IA...Red Flag Warning until 7 PM CDT this evening for IAZ043-055-
     056-069.

&&

$$

DISCUSSION...Nicolaisen
AVIATION...Nicolaisen