Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 172316

Area Forecast Discussion
National Weather Service Omaha/Valley NE
516 PM CST Fri Nov 17 2017

.SHORT TERM...(Tonight through Monday)
Issued at 330 PM CST Fri Nov 17 2017

Forecast concerns in the short term will be precipitation type
overnight(rain/drizzle/fog/thunder/mix/snow) and if there will be
snow accumulations...winds tonight and Saturday/if a wind
advisory is needed...then temperatures.

Water vapor satellite imagery and heights show a broad trough of
low pressure from Manitoba and Saskatchewan southwest toward California. Moisture was streaming eastward
ahead of the trough with an atmospheric river not from the Pacific
Ocean into southern California and the Four Corners area. Two
strong jet segments were noted on the 12Z UA maps with several
ripples of vorticity in the southwest flow aloft. H7 moisture was
noted on the UA maps with the -10 deg c line into the Pacific
Northwest. The H85 thermal ridge was over the area...with h85
moisture in place. The zero deg h85 isotherm extended from
northwest MT to northern CA.

The very warm air with 60s in southeast Nebraska is quickly being
replaced by cooler air with a cold front switching the winds
around to the northwest as far south as Millard and temperatures
are falling behind the front. The WSR-88D radar mosaic and
lightning show light rain and some thunder across parts of
Nebraska into Colorado. Snow was also being reported for parts of
WY and CO. Lightning was showing up in northern Colorado.

The main weather to discuss is in the first 12 to 18 hrs. A strong
upper level jet from California to Colorado pushes through the
Central Plains toward Indiana and Ohio...meanwhile...the jet
segment from North Dakota into Canada continues toward Hudson Bay
and the Great Lakes. Broad 60 to 80 meter height falls occur over
the Plains with the longwave trough passage.

Upward vertical motion combined with the upper level support...mid
level warm air advection...moisture and frontogenesis should
result in precipitation overnight...quickly moving to the east of
the area Saturday morning.

The short range models are in good agreement that light
precipitation will spread eastward this evening...light
rain...drizzle/fog and a few showers with thunder possible.
Forecast soundings and timesections point to a couple of hours of
intense lift with a frontogenetic band between 6 to 12Z where the
rain could change over to all snow. The straight model
accumulations are one half to 3 inches in spots.Our tools have a
half an inch or less in northeast Nebraska with little or no
accumulation farther south. This will need to be watched and did
include some light snow accumulation farther south toward I80.
There is some instability and steep lapse rates to work
with...thus have added some thunder in southeast Nebraska.

Strong winds develop on the back side of the storm system for
later tonight and Saturday. It will be windy, however the winds
were just below wind advisory criteria locally.

Dry weather is forecast through Monday with highs in the 40s and

.LONG TERM...(Monday night through Friday)
Issued at 330 PM CST Fri Nov 17 2017

Good travel weather is forecast for the week of Thanksgiving. A
cold front moves through Monday night with warmer weather for
Wednesday. The GFS/EC still have some differences has to how warm
it will be for Thanksgiving, however highs are currently forecast
to be in the 40s Tuesday and Wednesday with 50s for Thursday and


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 511 PM CST Fri Nov 17 2017

Complicated TAF set tonight with many parameters to consider.
Initially, there is some MVFR fog with patchy drizzle at KOMA,
but that may lift in the next hour or so. Otherwise, VFR at
KLNK/KOMA, but precip chances enter the picture through time
tonight, which could eventually mix with or change to snow 09-12z.
Could also see gusty winds for a time overnight from 17 to 25
knots. Strong winds continue into Saturday.




SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...DeWald is the U.S. government's official web portal to all federal, state and local government web resources and services.