Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 172152
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
352 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
Montana...Nevada...to 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
50s

.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
Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1136 AM CST Fri Nov 17 2017

Lingering MVFR ceilings may lift for a few hours this afternoon
but will deteriorate again this evening if they do. Winds will
shift to northwesterly and increase to around 10-15kt through the
afternoon/evening. Behind that cold front, rain could affect all
sites tonight. Later tonight, there is some potential for rain to
mix with snow. For now, have included this mention as tempo only
at KOFK, but the potential at KOMA/KLNK bears watching.


&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Mayes


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