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977
FXUS63 KOAX 170916
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
416 AM CDT Tue Sep 17 2024

.KEY MESSAGES...

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- Periodic shower and storm chances through the weekend,
  typically peaking at night. Highest chances are currently
  Friday night into Saturday night (peak probabilities of 50-70%).

- Temperatures are expected to remain above-normal through the
  work week with highs in the 80s. The weekend will be cooler.

- Significant rainfall of 1-3" is possible this weekend.
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&&

.DISCUSSION...
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Issued at 246 AM CDT Tue Sep 17 2024

Still holding mostly low 70s early this morning under partly
cloudy skies. A band of showers is working through northern
Kansas and eastern Nebraska, similar to the past couple of
mornings. So far, have not recorded a tipped bucket. Aided by a
nocturnal jet and a shortwave ejecting northeast out of Kansas,
20-40% PoPs are warranted through about 1pm as the wave
continues east. QPF should remain under half an inch. Will Omaha
get at least a trace? It`s been 18 days now... the first such
streak in almost 10 years.

Cloud cover will be slowest to clear over western Iowa. Temps
there will peak in the mid-80s with upper-80s and some low 90s
across eastern Nebraska. Breezy southerly flow will be stronger
in central Nebraska, but gusts of up to 35 mph are possible in
northeast Nebraska, especially after lunch. With dewpoints in
the mid-60s, RH values generally won`t fall below 40%. Fire
danger is much higher on the other side of the state of
Nebraska.

.TUESDAY NIGHT...

AM water vapor imagery shows an upper low spinning over Tahoe.
As that low streaks northeast and deepens, a shortwave rounds
its eastern edge and brings another opportunity for showers and
thunder on Tuesday night and Wednesday morning. It`ll have
another LLJ pumping moisture into the region and producing
isotropic lift. PoPs of 30-50% are a familiar result, mostly on
the western half of the CWA.

.WEDNESDAY NIGHT...

The week`s strongest convection may develop on Wednesday evening
ahead of the same system`s front / dry line. Moisture transport
helps develop CAPE values of 2,000 to 3,000 J/kg in the
afternoon and evening with steep low-level lapse rates. Warm
mid-levels produce paltry lapse rates there. Shear of nearly 30
knots may be enough to produce a couple of supercells and a
marginal threat of severe weather has been pointed out by SPC.

.THURSDAY...

Thursday may be the warmest day of the week with about half of
of the CWA expected to manage lower-90s. (Records are generally
about 5 degrees warmer than the forecast.) Severe weather is
possible again as the front slowly continues to push southeast
and out of the CWA. Dependent on how Wednesday night`s
convection plays out, some guidance produces enough instability
and shear ahead of the boundary to justify the SPC`s day three
marginal threat of severe weather.

.FRIDAY AND THE WET WEEKEND...

The front that pushes through the area on Thursday night will
lift north and back into the forecast area on Friday night in
response to the approaching west coast trof. Moisture is
forecast to be in the 90th percentile of climatology (NAEFS) and
some guidance produces heavy rainfall in the vicinity. FWIW,
NBM has widespread 1.5-3" over the course of the weekend. PoPs
peak at 55-70% on Saturday morning, but continue at about 50% on
Sunday, too as the system pushes northeast. High temperatures
under the clouds and occasional showers will provide sharp
contrast with the anomalously warm numbers of Thursday and
Friday. Expect mid- to upper 70s on Saturday and Sunday a couple
of degrees cooler still.
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&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
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Issued at 1139 PM CDT Mon Sep 16 2024

VFR conditions prevail at TAF sites late this evening, with
SCT-BKN skies at FL120-150. An broken area of showers with
isolated thunderstorms is moving from central Nebraska and north
central Kansas, forced by an upper disturbance moving into the
plains and increasing LLJ 35-45kt. Showers and storms are
expected to move into the western periphery of the forecast area
between 17/06-08z. CAM ensembles continue to show differences
in coverage and area of primary focus, thus not confident
include prevailing showers or storms, but did indicate VCSH
between 17/11z-16z. Any showers likely will reduce ceilings to
FL070-080. Precipitation coverage will diminish by late morning
as PIVA decreases and LLJ decouples. Clearing skies will occur
during the afternoon hours. VFR conditions will persist through
the remainder of the TAF cycle.

In addition to showers, models gradually increase sustained
wind speed into the 12-16kt range, with gusts 20-25kt,
mitigating LLWS.
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&&

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

&&

$$

DISCUSSION...Nicolaisen
AVIATION...Fortin