Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 112113
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
313 PM CST Mon Dec 11 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 309 PM CST Mon Dec 11 2017

Dry northwesterly flow continues across the central US. Subjective
12Z upper-air analysis indicates continued troughing over the
eastern half of the US, with a ridge west of the Rockies. A
shortwave trough over the Dakotas/MN was dropping through the
northwesterlies, with 500mb height falls up to 190m associated with
it. Moisture was scant, though, with 850mb temperature-dewpoint
depressions on the lower side in ND, MN, and northeastern SD.
Temperatures at 850mb were above 0C from SD to southwestern MN and
southward, with cold air advection bringing sub-0C temperatures
southward on northwest winds up to 60kt. The cold air advection and
tight pressure gradient was leading to surface winds of 25-35mph,
with gusts up to 40-55mph, across central to eastern NE and into
western IA. The surface low at 20Z was centered in central IL, with
a surface high in eastern MT.

Main forecast concerns are temperature fluctuations and potential
for measurable precipitation on Thursday. Cool-down associated with
shortwave pasasge today won`t last long, with warm air advection
beginning this evening and with 850mb temperatures reaching the
upper single digits to around 10C by Tuesday afternoon/evening.
Another transient shortwave will bring a cool-down on Wednesday.
Have some concerns that it could bring sprinkles/flurries, as well,
given the lift moving through during the afternoon. With such
pervasive dry air, have left mention out until I see the "whites of
its eyes" and/or some model consistency in picking up a
precipitation trend, with significant intermodel and intramodel
variability.

Another wave is forecast to drop through the Dakotas into NE on
Thursday. It`s a little more westward than its predecessor, and
moisture looks better. As a result, models are a bit more
consistent in developing more robust precipitation. Have kept a
slight chance/small chance in the forecast for Thursday into
Thursday evening, with precipitation type ranging from rain to
snow. Little/no snow accumulation is forecast, with high
temperatures during the day reaching the upper 30s to low 40s, but
range of possibilities does include more accumulations than
current forecast indicates.

.LONG TERM...(Thursday night through Monday)
Issued at 309 PM CST Mon Dec 11 2017

Cracks in the armor of the trough-east-ridge-west armor begin to
arrive by the weekend as a broader trough dips into the Rockies,
though weakened ridging still will linger around the Pacific
coast. Temperatures will remain above normal, with highs in the
40s to 50s. Models indicate a deeper trough moving across the
central US around Saturday night or Sunday, though they disagree
(with each other and run to run) about if and where there is
precipitation potential. Left the small area of slight chance
mention in on Saturday evening, but have low confidence on the
eventual outcome, which could range from dry to a rain/snow mix to
a light snow. Behind that system, dry weather reigns again
through the rest of the forecast period (and likely beyond).

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1133 AM CST Mon Dec 11 2017

Strong northwest winds averaging 25 to 35kt will continue through
00Z, then settle back to near 12kt by 06Z. An area of MVFR cigs
spreading south may affect KOFK and KOMA TAF sites for a few hours
between 20Z and 03Z, with spotty rain showers possible as well.
Clouds are forecast to scatter by 03Z, leaving mainly VFR
conditions through Tuesday late morning.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Wind Advisory until 6 PM CST this evening for NEZ011-012-015>018-
     030>034-042>045-050>053-065>068-078-088>093.

IA...Wind Advisory until 6 PM CST this evening for IAZ043-055-056-069-
     079-080-090-091.

&&

$$

SHORT TERM...Mayes
LONG TERM...Mayes
AVIATION...Dergan


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