553
FXUS63 KOAX 171745
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1245 PM CDT Mon Jun 17 2024

.KEY MESSAGES...

- Storm chances remain in the forecast for northeast Nebraska
  this this evening. A slight risk of severe storms exists.

- Highs today in the lower 80s to lower 90s, with afternoon heat
  index values of 92 to 98 southeast Nebraska and southwest Iowa.
  Southerly winds 20 to 35 mph.

- Strong and possibly severe thunderstorms are expected Tuesday
  into Wednesday, along with locally heavy and possible flooding
  rains.

- Rain chances continue every day Thursday through Sunday.

&&

.DISCUSSION...
Issued at 335 AM CDT Mon Jun 17 2024

A stalled frontal boundary remains across northeast NE, between
Columbus and Albion, and between Tekamah and Sioux City.
Widespread thunderstorms have continued north of the this
boundary this morning, and that trend will continue as a weak
upper wave continues to move off the front range of the Rockies.
The area of strong thunderstorms developed farther north than
where the heavy rains set up on Saturday evening, thus canceled
the flood watch that was in effect for a handful of counties a
couple of hours ago. Will maintain these Pops north of I80 this
morning, but precipitation will also continue to lift to the
north and out of the area by this afternoon. Southerly winds
increasing to 20 to 35 mph today will help boost afternoon
temperatures into the upper 80s to lower 90s, and when combined
with dewpoints in the upper 60s to lower 70s, afternoon heat
index values will range from 92 to 98.

Convection chances tonight again remain in question with most of
the CAMs indicating another potential round of storms developing
in central NE, moving into northeast NE. The HRRR is the lone
model that doesn`t produce any convection, so there`s at least a
small chance that nothing additional happens, although the HRRR
hasn`t exactly been handling this morning`s convection very well
either. If storms develop this evening, there is a slight risk
that they could be severe with damaging winds and large hail in
northeast Nebraska. Otherwise, breezy southerly winds continue
overnight at 20 to 35 mph, which keeps temperatures fairly warm
in the middle 70s.

Tuesday brings another impactful weather day as a cold front
moves into the region. This front will be the focus for showers
and thunderstorms becoming likely Tuesday afternoon, with
widespread thunderstorms expected Tuesday night. SPC has placed
the entire area in a Slight risk for severe storms with damaging
winds and large hail the primary hazards. Heavy rainfall will
also be possible with a widespread 1 to 2.5 inches possible by
daybreak Wednesday. WPC has the entire forecast area in a slight
risk for excessive heavy rainfall. Those counties that received
3 to 6 inches of rain in northeast NE could be susceptible to
flooding. And we`ll have to see how this plays out, but PW
values will be quite high from 1.75 to 2", which places the
moisture in the 99th climatological percentile. A few of the
various models also have closer to 2.5 to 3.5 inches of rain,
so it`s something we`ll be monitoring closely. WPC will also be
monitoring for a possible later upgrade to a moderate risk of
excessive heavy rainfall as well.

The frontal boundary stalls perhaps in southeast NE and
southwest IA on Wednesday. We`ll be north of the boundary, so
the severe weather threat may be lower, but widespread
precipitation will still be possible through the day Wednesday.
Highs will only range 65 to 70 for portions of central through
northeast NE, but still in the lower 80s in southeast NE and
southwest IA. Depending on where the heavy rains set up Tuesday
night, there will still be a slight chance of excessive heavy
rainfall on Wednesday.

The frontal boundary begins to lift back north Wednesday night,
and then north of the area by Thursday. Thus, Pops will remain
quite high during this time in the 60-80% range, with
temperatures warming back up into the 80s to lower 90s by the
end of the week.

Friday morning may be dry, but rain chances return again by
Friday afternoon and night, and then another frontal boundary
moves into the region Saturday into Saturday night. The rain
could very well be east of the area by Sunday, but the blend
maintains a 20% chance, although is confidence is pretty low
that far out.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1218 PM CDT Mon Jun 17 2024

Moist isentropic ascent and diabatic mixing is aiding in the
development MVFR ceiliings FL030-040 early this afternoon at all
three TAF sites. As low level winds veer through the afternoon,
mixing will help to dissipate these ceilings, leaving sct-broken
ceilings at or above FL150. Surface southerly winds 170-190
degrees will be sustained 15-25 kts with gusts to 30 kts. Not
anticipating much decoupling during the evening and overnight
hours, allowing gusty southerly winds to continue; however, a
stout 50kt low level jet FL020-030 will create low level wind
shear conditions at OFK and LNK. LLWS may need to be added to
OMA.

There are 15 to 25% chances of thunderstorms at OFK 18/01-05
UTC,but given low probability left out of TAF for now. The
chances for thunderstorms during the same time period at LNK and
OMA are 5 to 10%.

Late in the TAF period, low level flow will transport increased
moisture at FL010 to FL030, allowing for MVFR ceiling
development at all three TAF sites between 18/12-15 UTC.


&&

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

&&

$$

DISCUSSION...DeWald
AVIATION...Fortin