Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 151134

Area Forecast Discussion
National Weather Service Omaha/Valley NE
634 AM CDT Thu Mar 15 2018

.SHORT TERM...(Today through Saturday)
Issued at 345 AM CDT Thu Mar 15 2018

The main forecast issues are in regards to ice accumulation in the
northern parts of the forecast area, starting tonight and
continuing into Friday night.

500 mb chart from last evening showed a ridge extending from
Saskatchewan down into western NE then into NM. To the west, a
trough was moving through the Rockies with 12 hour height falls of
up to about 100 meters. The models are in general agreement that
both features will progress east today. At the surface, a weak
cold front was pushing south through the local area. That will
move down into the northern parts of KS and MO, then become nearly
stationary. We should have a decent range of high temperatures
across the area today, from near 50 at the SD border to near 70 at
the KS border. Have some concerns for fire danger today in our
southern counties, but not as much as yesterday since we expect RH
values to be higher today.

Things change fairly quickly tonight, as the system to the west
approaches. Lift will be strengthening tonight with increasing
moisture in diffluent flow aloft ahead of negatively tilted
trough/closed low. Models are in fairly good agreement that a
closed low at 500 mb will move into northwest KS by 12z Friday.
Precipitation should develop from southwest to northeast across
the area overnight. Surface temperatures in the northern parts of
northeast NE look cold enough for mixed precipitation, mainly
freezing rain and sleet. Farther south, there will be rain or
showers. Also look for isolated thunder across southeast NE as
some elevated instability develops with steep lapse rates.

Closed low should track toward southeast NE by 00z Saturday with
high precipitation chances. Surface low will be farther to the
south across KS. Dry slot should move into southeast NE Friday
afternoon, but this may end up destabilizing the atmosphere with
isolated to scattered thunderstorms. Meanwhile to the north, with
clouds and precipitation, temperatures will be held down. Slight
warming from late morning through mid afternoon could limit ice
accumulations, but there is still a threat of icing in a second
period from late afternoon through the evening. At this time, snow
amounts look to be less than an inch, but will monitor this. If
thermal profiles end up changing, that could mean more snow and
less ice. Precipitation chances should decrease by late Friday
night as a ridge of high pressure at the surface builds in from
the west. Then we have a dry forecast for Saturday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 345 AM CDT Thu Mar 15 2018

Dry weather should continue Saturday night into Sunday morning
but the next mid level trough will bring increasing moisture in
diffluent flow aloft by Sunday afternoon. Thermal profiles from
Sunday afternoon into Sunday evening favor liquid precipitation
but this will turn to a rain/snow mix Sunday night into Monday as
colder air moves in from the north/northwest.

The 500 mb pattern Monday into Tuesday is expected to be quite
messy with a closed low tracking to our south and a northern
stream shortwave digging southeast into the region from the
north. From Wednesday into Thursday, the pattern looks less active
and should turn slightly warmer.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 632 AM CDT Thu Mar 15 2018

VFR conditions are expected through the evening before lowering
cigs and rain moves in from the southwest after 06Z. Some MVFR
cigs/vsbys could result at all TAF sites between 06Z and 12Z.
Also, light winds early will become east and increase into the 15
to 25kt range during the afternoon, and will likely gust to 30kt
between 00Z and 12Z.


NE...Winter Storm Watch from late tonight through late Friday night
     for NEZ011-012.



LONG TERM...Miller
AVIATION...Dergan is the U.S. government's official web portal to all federal, state and local government web resources and services.