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000
FXUS63 KOAX 132312
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
612 PM CDT Sat Apr 13 2024

.KEY MESSAGES...

- Very high fire danger is expected to linger into early this evening,
  especially over southeast Nebraska and southwest Iowa.

- Thunderstorms late Monday afternoon into Monday night may
  become severe. Currently there is about a 20 percent chance
  for severe weather within 25 miles of any location in eastern
  Nebraska or southwest Iowa late Monday.

- Another round of strong to severe storms is possible late
  Tuesday morning into the afternoon, with the best chance
  currently over southeast Nebraska and southwest Iowa.

- Cooling down to end next week, with highs in the 40s and 50s
  and lows in the upper 20s and 30s by Friday.

&&

.DISCUSSION...
Issued at 311 PM CDT Sat Apr 13 2024

Some patchy fire weather concerns linger this afternoon with
breaks in some otherwise thicker clouds leading to deeper mixing
and some gusts around 30 mph and RH values in the mid 20s,
primarily in southeast NE and southwest IA. So far, haven`t
reached true Red Flag Warning criteria, but we could be close at
times in those breaks in the clouds. If we do, it should remain
somewhat spotty and brief, with the strongest winds aloft
remaining somewhat collocated with the most cloud cover the
remainder of the afternoon. Otherwise, temperatures as of 3 PM
were in the upper 70s to mid 80s, closer to June averages than
April.

Heading into tonight, a weak surface cold front/wind shift
currently across northwest SD will push southeast through the
area, with winds becoming northerly and eventually northeasterly
for the day on Sunday. Temperatures behind the front are only a
few degrees cooler than those ahead, so not expecting much
change for highs tomorrow, with widespread 80s still on tap. The
air will remain quite dry with minimum RH values in the teens
and 20s, but fire weather concerns will be on the lower side
with lighter winds than those seen today.

Attention then turns to shower and storm chances Monday into
Wednesday as a strong trough/low currently off the coast of CA
will approach and eventually push through the area. There has
been fairly decent agreement on timing over the last few runs of
the various ensembles, but still plenty of smaller scale
details to work out. As of now, the general idea is that by
early Monday afternoon, the surface low will be over northeast
CO with the 500 mb low lagging behind near the UT/CO border and
the exit region of the mid-level jet just starting to edge into
southwest KS. Ahead of the system and over our forecast area,
southeasterly surface flow will be strengthening behind a
northward-advancing warm front with guidance in good agreement
of moisture transport pointing into the area and 60s dewpoints
nearing the I-80 corridor. While depth of the moisture looks to
be somewhat limited at this time, around 30-40 percent of
various ensemble members, as well as the 13.12Z GFS and ECMWF,
suggest shower and storm development on the nose of the
aforementioned moisture transport and in vicinity of the warm
front Monday afternoon. With deep layer shear remaining weak in
this timeframe, anything that does develop would likely be
rather unorganized at first, but could pose a bit of a severe
weather risk with decent instability in place and strengthening
low level shear by late afternoon/early evening. However, model
soundings do show a bit of a cap, so confidence is rather low in
how widespread this development would be, if it happens at all,
and what its impacts would be on later convection as moisture
transport continues to strengthen and the low continues to edge
eastward with some stronger forcing, steeper lapse rates, and a
touch more deep layer shear. Overall, there is a threat for
severe weather as early as Monday afternoon, with chances
increasing as we go through the evening and overnight hours.
Large hail and damaging winds would be the main threats, but
tornadoes cannot be ruled out.

Tuesday seems to be trending toward an increasing severe
weather threat, particularly in the morning/early afternoon as
the cutoff low finally ejects and moves through/near the
forecast area. Guidance suggests there could be a break in
precip sometime Tuesday morning, from around 4-7 AM before the
stronger forcing works in. Despite the time of day and earlier
convection, ensemble mean SBCAPE values approach 1000 J/kg once
again with very little CIN, along with a dry punch/dry line
pushing into southeast NE, resulting in storm development
Tuesday morning/early afternoon. As mentioned in the previous
discussion, wind profiles do look rather messy, but should be
enough shear for some degree of storm organization and a severe
weather threat, including tornado potential with enhanced
vertical vorticity in vicinity of the surface low. Finally,
guidance does suggest we could get some decent rain out of this
system, with ensembles showing a 50+ percent chance of at least
1" generally near and north of Interstate 80, with some
suggestions of 2" by Wednesday morning in the primary "band" of
precipitation. Should any areas see repeated rounds of storms,
some localized flooding cannot be ruled out. So overall, Monday
afternoon into Tuesday afternoon is a period you`ll want to pay
attention to for severe weather threats, though plenty of
smaller scale details still need to be worked out, with
potential for rounds of storms impacting evolution of later
rounds of storms.

Precip should exit by Wednesday morning with northwesterly flow
persisting behind the departing low and bringing in some cooler
air. Expect widespread 60s on Wednesday before a reinforcing
cold front and shortwave energy slide through sometime Wednesday
night into Thursday bringing us our next chance of rain along
with highs in the 40s and 50s and lows in the upper 20s to lower
30s to end the work week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 612 PM CDT Sat Apr 13 2024

VFR conditions will prevail through the forecast period with
SCT-BKN clouds at FL250 this evening into tonight. Gusty south
winds will diminish within the next hour with LLWS developing
between 03-04z at KOMA and KLNK. A weak front will move through
the area tonight with winds switching to northwest and
eventually northeast behind the front late tonight into Sunday
morning. Northeast winds are expected to increase to 12-13 kt by
mid-morning Sunday.

&&

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

&&

$$

DISCUSSION...CA
AVIATION...Mead