Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 170446

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1146 PM CDT Sat Sep 16 2017

Issued at 1145 PM CDT Sat Sep 16 2017

Thunderstorms should continue to decrease in coverage from
northwest to southeast the next several hours, but could linger
near the MO border until around 09z or 10z. Clouds will also
decrease from north to south.


.SHORT TERM...(Tonight through Tuesday)
Issued at 242 PM CDT Sat Sep 16 2017

A potent shortwave trough will eject east-northeast across the
Dakotas and the ND-MN Red River Valley this afternoon into tonight
with the southern fringe of mid-level height falls glancing the
forecast area. At the same time, a cold front will steadily
advance south through the remainder of southeast NE and southwest
IA, ushering a cooler and drier air mass into the region.

Pre-frontal showers and thunderstorms have limited the degree
of destabilization within warm sector so far today. However,
pockets of stronger heating will yield a moderately unstable and
weakly capped environment by mid to late afternoon when surface-
based storms will become increasingly likely. Latest convection-
allowing model guidance suggests that this scenario is most likely
to unfold across far southeast NE into southwest IA after 4 PM
with additional storms forming nearer to the 850-mb front along
and south of I-80 this evening. The most intense storms are
expected to be those forming along the surface front where
instability will be greater. Large hail and damaging wind gusts
will be the primary hazards. A strong storm or two is also
possible later this evening with the elevated activity mentioned
above, and some hail cannot be ruled out.

Precipitation will end from north to south tonight and the
majority of Sunday looks to remain dry as high pressure builds
through the area.

On Sunday night into Monday, low-level warm advection will
strengthen ahead of a low-amplitude shortwave trough tracking from
the Rockies into northern and central Plains. This process in
conjunction with deeper-layer forcing attendant to the approaching
mid-level wave will support a good chance of showers and
thunderstorms across much of the area. Locally heavy rainfall is
possible, especially nearer to the NE-KS border. Both
precipitation and clouds should diminish during the afternoon on
Monday as the mid-level impulse shifts east of the region.

Monday night into Tuesday, another powerful jet streak and
associated shortwave trough will migrate from the Interior West
into the northern High Plains. This will drive the deepening of a
lee cyclone and the eastward advance of a cold front through the
High Plains. This large-scale pattern evolution will support
afternoon temperatures warming well into the 80s and perhaps lower
90s with breezy to windy conditions.

.LONG TERM...(Tuesday night through Saturday)
Issued at 242 PM CDT Sat Sep 16 2017

The above-mentioned shortwave trough will traverse the northern
Plains and upper-MS Valley Tuesday night into Wednesday with the
associated surface cold front weakening as it moves into the mid-
MO Valley. Thereafter, medium-range guidance is suggestive that a
longer-wavelength trough will become established over western
North America by late week before edging east toward the Great
Plains next weekend. Ahead of this trough, we will likely see near
to above-normal temperatures with increasing precipitation chances
by the weekend.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1145 PM CDT Sat Sep 16 2017

TSRA will be mainly south of KLNK and KOMA but could linger
through 06z to 07z in the vicinity. Then look for decreasing
cloudiness overnight. VFR conditions should prevail much of
Sunday, with TSRA chances increasing in the late afternoon or




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