Scientific Forecaster Discussion
fxus63 koax 101709
Area forecast discussion
National Weather Service Omaha/valley NE
1109 am CST Tue Dec 10 2019
..updated aviation forecast discussion...
issued at 252 am CST Tue Dec 10 2019
expect below-normal temperatures today with moderating conditions
through the remainder of the workweek. Another surge of cold air
is forecast for the weekend. While no significant precipitation
systems are expected, some light snow is possible tonight over
far northeast NE with off-and-on chances areawide this weekend
into early next week.
Today and tonight:
a vorticity lobe over the ND-Minnesota Red River valley early this
morning will pivot into the upper Midwest, driving a reinforcing
surge of Arctic air into the mid MO valley today. Low-level cold
advection and patches of clouds will yield below-normal
temperatures with highs in the upper teens north to mid to upper
20s south. A few flurries are possible owing to low-cloud
temperatures in the dendritic-growth zone.
In response to another strong shortwave trough moving into the
upper Great Lakes, a low-level warm advection regime will develop
across the area tonight. That forcing mechanism will Foster a
band of light snow that could glance our far northern counties.
Amounts currently appear minimal.
Wednesday and Wednesday night:
increasing zonal flow aloft will promote the deepening of a Lee
trough over the High Plains, which in turn will support the
erosion of the Arctic air mass deposited over the mid MO valley.
Highs will be in lower 20s north to mid 30s south. A mid-level
disturbance will traverse the northern plains Wednesday night with
another band of snow passing to our north.
Thursday and Thursday night:
the development of a strong upper-level jet from the northeast
Pacific through the interior west will contribute to mid-level
height falls over the Great Plains, and the equatorward advance of
another Arctic airmass along the Lee of the Canadian rockies.
Over the Central Plains, a westerly downslope wind component in
the low levels will favor continued warming temperatures with
highs in mid 30s north to mid to upper 40s south.
Friday and Friday night:
the aforementioned upper-level jet over the interior west will dig
into the lower MS valley, gradually phasing with a strong polar-
branch vorticity lobe over the Canadian prairie provinces to
promote mid-level trough amplification along the MS valley. In
response to those developments, the Arctic air mass funneling
through the Canadian High Plains will spill south toward the
region. While we will indicate further warming of temperatures on
Friday (highs in the lower 40s north to lower 50s south), there
is a fair amount of uncertainty to those values as the cold air
could arrive sooner than what is currently anticipated.
Light snow chances will increase with the arrival of the Arctic
front; most likely on Friday night.
Saturday and sunday:
mid-level troughing initially along the MS valley will give way to
an amplifying mid-level trough over the western U.S. With the mid
MO valley remaining largely under the influence of a broad surface
high building south out of central Canada. Expect below-normal
temperatures with the best chance of light snow being Sunday into
latest model data suggest that mid-level troughing will persist
over the Great Plains at least through early next week, arguing
for a continuation of below-normal temperatures.
Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1111 am CST Tue Dec 10 2019
Cigs remain low across the area today with decks generally around
3000 ft above ground level. Temporarily lower cigs are possible in the Omaha area
where some snow showers have developed. Brief bursts of snow are
possible through 20z Tuesday at koma.
Cigs will generally lift allowing borderline MVFR conditions to
turn VFR by at least 01z Wednesday.