640
FXUS63 KOAX 150901
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
301 AM CST Fri Nov 15 2024

.KEY MESSAGES...

- Above-normal temperatures (highs in the upper 50 and 60s) are
  expected through Sunday.

- Widespread rainfall is forecast Monday into Monday night
  (PoPs increasing to 80-95+%) with the highest amounts of
  1-1.5" expected across southeast NE and southwest IA.

- The precipitation forecast becomes more uncertain by the
  middle of next week. However, there is high confidence in
  temperatures trending cooler at that time.

&&

.DISCUSSION...
Issued at 300 AM CST Fri Nov 15 2024

...Today through this Weekend...

Early morning water vapor imagery depicts a multi-stream short-
wave trough situated along the Pacific coast with downstream
ridging over the Great Plains. The southern portion of the
trough is comprised of a vigorous vorticity maximum and
attending mid-level jet streak, which are forecast to progress
into the northern Plains on Saturday. That system will continue
east through the upper MS Valley into the Great Lakes Saturday
night into Sunday with a trailing, weaker vorticity ribbon
moving through the mid MO Valley at that time.

In the low levels, a lee trough is forecast to deepen over the
High Plains today with that boundary progressing east/southeast
across the northern and central Plains as a cold front tonight
and Saturday, in tandem with a surface low developing across
the Dakotas. The front is projected to move through our area
Saturday afternoon into Saturday night with that boundary
stalling across northeast KS and northwest MO on Sunday.

The leading edge of mid-level height falls will overspread the
High Plains today, inducing a 30-40 kt low-level jet (LLJ)
across central and eastern NE this afternoon. That process will
coincide with the peak of diurnal mixing, yielding breezy
southeast winds as temperatures warm into the upper 50s to mid
60s. Low-level moisture is expected to correspondingly increase,
limiting any fire weather concerns.

The low-level mass response to the mid-level system advancing
into the northern Plains will sustain the LLJ tonight into
Saturday, which in turn will support continued moisture
advection into the region, and maintain gusty south winds. By
Saturday afternoon, the glancing influence of the mid-level
system passing to the north coupled with increasing convergence
in the vicinity of the cold front may be sufficient to support a
few showers across portions of southeast NE and southwest IA
(20% PoPs). Pre-frontal model soundings indicate a fairly strong
capping inversion, so any development would probably be
isolated, and potentially rooted above the cap. Highs on
Saturday are expected to be well-above normal with readings
generally in the low to mid 60s.

Surface high pressure will quickly build through the area on
Sunday with cooler, but still above-normal highs in the 50s.


...Sunday night through Monday night...

The 00z global models (both ensemble and deterministic) are in
good agreement in the track and intensity of a vigorous deep-
layer cyclone, which is forecast to move through the region
Monday and Monday night. The surface front that stalled to our
south on Sunday will lift back north through the area on Monday
ahead of a surface low developing almost due north along a cold
front moving into eastern NE from the west. Strong warm
advection and moisture flux occurring along a 40-50 kt LLJ will
combine with significant height falls preceding the mid-level
system to support a widespread rainfall event.

While some precipitation is possible near the KS border prior to
daybreak Monday, the bulk of the rainfall will occur Monday into
Monday night. Latest NBM 25-75th percentile storm-total QPF
ranges from 0.5-0.75" near the SD border to 1-1.5+" across
portions of southeast NE and southwest IA.

This synoptic system will be very dynamic with some model
indication that the local environment could become marginally
supportive of a strong storm over southeast NE Monday evening
(< 10% chance of occurrence).


...Tuesday through Thursday...

The Monday system is forecast to weaken over the upper MS Valley
on Tuesday ahead of another potentially significant mid-level
trough, which is forecast to evolve over the central part of the
nation around the middle of next week. There continues to be
notable model spread in the evolution of that system, which
leads to uncertainty in precipitation potential and type. What
we can say it that temperatures will trend cooler beginning
Tuesday.


&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 940 PM CST Thu Nov 14 2024

VFR conditions through the period. Winds at TAF issuance from
the southwest to southeast at 6 knots or less. Southeasterly
winds increase to 12 to 14 knots by 18z, with gusts up to 24
knots thereafter. LLWS likely develops at all sites toward the
end of the TAF period by 16/04-06z, but too far out to include
in this package.

&&

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

&&

$$

DISCUSSION...Mead
AVIATION...DeWald