Scientific Forecaster Discussion
fxus63 koax 162030
Area forecast discussion
National Weather Service Omaha/valley NE
230 PM CST Sat Nov 16 2019
issued at 230 PM CST Sat Nov 16 2019
The main forecast concerns are precipitation chances tonight into
Sunday morning, chances Sunday night into Monday, and then again
from Wednesday afternoon into Wednesday night and Thursday. The
last event in that list could have some thunder Wednesday evening,
then rain changing to snow. Some snow accumulations possible, but
way too early to start looking at specific amounts.
Short term...tonight through Tuesday.
A fairly strong shortwave trough and an associated cold front will
continue to push eastward across the region tonight into Sunday.
This trough had 12 hour height falls of 50 to 100 meters from Wyoming
up into Saskatchewan and Manitoba at 12z. There was also decent
upper level jet support.
Cold front will continue to push through the area overnight, with
precipitation chances developing with mid level lift associated
with large scale forcing. Trough axis will not be through the
forecast area by 12z and so had added some pops for Sunday morning
with an update earlier today. Most model guidance is picking up on
the precipitation development in IA, but favored the rap and some
of the other short range cams for precipitation later tonight into
mid morning Sunday across southeast NE (and southwest ia). This
looks to be mostly a rain event, with a light wintry mix at least
Another fast moving, but weaker, shortwave trough will bring a
chance for light precipitation late Sunday night into Monday
morning. This also looks to be mainly rain, with some brief
freezing rain or sleet possible.
Look for highs Sunday in the mid 40s to lower 50s, mainly 50s
Monday and Tuesday.
Long term...Tuesday night through Saturday.
At the start of this period we should be under the influence of
weak mid level ridging with a couple of troughs to our west. One
will be over baja, with another stretching from the Pacific northwest
into northern California. This will transition to more of a split flow by
Wednesday, as a 500 mb low tries to close off near the California coast.
Will start increasing chances for rain Wednesday afternoon, with
some thunder possible by Wednesday evening. The 12z GFS model
showed some cape by that time across parts of southeast NE and it
does fit a common pattern. Several things will be coming together
for a moderate precipitation event for our area, with the heaviest
amounts likely farther south of our area, with better/deeper
moisture. Cold air moving in should bring a transition of rain to
snow, with details yet to be worked out. Just how fast the cold
air works in will help determine snow amounts. Best chances for
precipitation being in the form of snow are in northeast NE, but
at this time that is also where precipitation amounts (water
equivalent) are expected to be the lowest.
There are some fairly large model differences (gfs versus ecmwf)
for Thursday. The 12z European model (ecmwf) has a much stronger shortwave trough
in the northern stream (and is colder) compared to the 12z GFS.
The period from Thursday afternoon into Friday looks mainly dry,
with chances for rain and snow increasing again toward Friday
night and Saturday.
Temperatures should be fairly mild Wednesday, ranging from near 50
at the South Dakota border to lower 60s at the Kansas border. Thursday will be
noticeably cooler with highs in the upper 30s to mid 40s. Highs
Friday and Saturday should be mostly in the 40s.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1111 am CST Sat Nov 16 2019
Cloudiness will increase and thicken the next 6 to 9 hours, with
some light rain possible later. Rain chances are highest at koma
and klnk, where MVFR ceilings and visibilities seem possible later
tonight into Sunday morning.