Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Omaha/valley NE
330 PM CST Friday Feb 5 2016
Short term...(tonight through monday)
issued at 330 PM CST Friday Feb 5 2016
There are several short term forecast concerns...light snow ending
this evening...potential for fog overnight and then strong winds
with light snow/blowing snow Sunday/Monday.
Amplified middle tropospheric pattern remains in place over the Continental U.S..
trough moving through now will push east/southeast of the area this
evening and snow will end. Ridge over The Rockies will build east
into the area but weaken through Saturday. By late Saturday...a
shortwave trough should extend from southern Manitoba back into
Wyoming. The pattern will amplify again Sunday as a ridge
strengthens over western North America and that shortwave
intensifies and forms a closed low over Minnesota and Wisconsin.
Tonight...warm front and surface trough will move eastward through
the area but winds will drop off. Depending on cloud cover...there
may be some fog. Experimental hrrr model has been hinting at dense
fog formation for the past several model runs...starting north of
the Platte River prior to 06z. That model then expands the fog and
keeps it into middle morning Saturday. This all depends on cloud cover.
Thinking is that there will be enough subsidence behind the
system moving through this afternoon to bring clear to partly
cloudy skies. That should allow for some at least some radiational
cooling and decoupling of winds over deeper snow cover. Surface
winds from the west/northwest are not all that favorable for fog
locally...but airmass behind this trough/wind shift is fairly
moist. Low temperatures tonight will be very tricky...with snow
and fog potential. Most locations should drop into the teens.
Saturday...clouds and fog may linger in the morning especially over
western Iowa and east central Nebraska. Winds back to the southwest
late tonight and should generally be out of the southwest through
Saturday afternoon. If clouds decrease as expected and we can get
some sunshine...highs in the middle 30s to lower 40s should be realized.
Areas with little or no snow in southeast Nebraska should reach into
the middle 40s.
Look for dry weather Saturday night and most of Sunday. A cold front
will sweep quickly southeast across the area Saturday night. Winds
are expected to increase (possibly into Wind Advisory category) as
pressure gradient tightens Sunday...but clouds and light snow
showers will lag a bit. Will keep some areas of blowing snow for
Sunday afternoon and small chances for snow. Best chances for
measurable snow will stay east of the forecast area but included
some low probability of precipitation in our area...with some moisture wrapping into the
area. Lapse rates steepen below 750 in GFS and NAM forecast soundings
so the idea of snow showers still seems prudent. Snow chances will
linger into Monday. Areas of blowing snow could become problematic
Sunday and Monday. Will monitor this for later forecasts and may
need to hit harder with some type of advisory later.
Long term...(monday night through friday)
issued at 330 PM CST Friday Feb 5 2016
Little or no precipitation is expected in this period...and temperatures will
moderate a bit from Tuesday into Thursday.
Strong 500 mb ridge is expected to be over western North America
Tuesday and our area will be in strong northwest flow. That ridge
should deamplify through Friday with the overall pattern becoming
Aviation...(18z tafs for kofk...klnk and koma.)
Issued at 1120 am CST Friday Feb 5 2016
Variable conditions exist across the taf sites this afternoon as a
band of snow continues to move across area. A secondary wave will
bring another brief shot...mainly late this afternoon across
northeast Nebraska. Ceilings should continue to improve through
the evening with some chance of patchy fog setting up overnight.