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Area forecast discussion 
National Weather Service Omaha/valley NE 
531 am CST Tue Jan 24 2017 


Short term...(today through thursday) 
issued at 301 am CST Tue Jan 24 2017 


..a significant winter storm will impact the area today into 
Wednesday... 


Manual 00z upper-air analysis and early-morning water vapor 
imagery indicate a substantial mid-level trough stretching from 
the far eastern Pacific to spine of the Rocky Mountains. 
Pronounced mid and upper-level wind maxima observed within the 
basal portion of the trough over the lower Colorado valley will eject 
northeast into the central and Southern Plains, driving the 
deepening of an associated mid-level trough and related surface 
cyclone over the Central Plains today. At the same time, a plume 
of steep mid-level lapse rates --best observed by the 00z 
soundings at Denver, Colorado and North Platte, NE-- will advect 
east/northeast in the mid MO valley, conditioning the environment 
for robust vertical motion within a frontogenetically forced 
precipitation band evolving to the north of the surface cyclone. 


Latest short-term model guidance indicates that strengthening 
lower to mid-tropospheric warm advection and isentropic upglide 
will Foster a broadening band of light snow (perhaps mixed with 
sleet) this morning from the vicinity of the western Kansas surface 
low northeast into east NE and perhaps west Iowa. This band will 
pivot north into northeast NE and west-central Iowa by afternoon and 
strengthen with time as the steepening mid-level lapse rates 
couple with intensifying frontogentical forcing. Embedded upright 
convection is not out of the question with periods of moderate to 
heavy snow occurring through the afternoon. Farther south across 
east-central NE, slightly warmer boundary-layer temperature 
profiles will yield a rain-snow mix. Some sleet or graupel is 
possible, as is a rumble of thunder. 


By tonight, precipitation will change over to all snow from 
northwest-to-southeast across the area as cold air deepens on the 
backside of the surface cyclone passing to the east. Strengthening 
gradient flow in the low levels will promote strong northwest 
winds, creating areas of blowing and drifting snow, especially 
across northeast NE and west-central Iowa. 


The 00z models continue to converge on a more southern track to 
the surface low along with higher quantitative precipitation forecast within the deformation axis. 
As a result, it is reasonable to expect storm-total snowfall 
accumulations in excess of a foot along the NE-South Dakota border with as 
much as six to eight inches possible along a line from Albion, NE 
to Onawa, Iowa. We, therefore, have included Boone, Madison, 
Stanton, Cuming and Burt counties in NE and Monona County in Iowa 
to the Winter Storm Warning, and added Saunders and Washington 
counties in NE and Harrison and Shelby counties in Iowa to the 
Winter Weather Advisory. 


Light snow along with gusty northwest winds will continue 
Wednesday before tapering off Wednesday night. 


Long term...(thursday night through monday) 
issued at 301 am CST Tue Jan 24 2017 


We will remain in a high-amplitude mid-level pattern through next 
weekend, featuring a western U.S. Ridge with a downstream trough 
over eastern North America. A number of disturbances will 
translate from central Canada into the central U.S. During that 
time frame. One such impulse is forecast to move into the mid MO 
valley Saturday into Saturday night when a chance for flurries or 
light snow will exist. Thereafter, medium-range guidance suggests 
that a significant short-wave trough will temporarily dampen the 
western U.S. Ridge prior to moving through the northern plains 
into upper Great Lakes next Monday/Monday night. These data 
indicate that the strongest forcing for ascent and associated 
precipitation potential would remain to the north of our area. 


The above-mentioned large-scale pattern will favor below normal 
temperatures into next weekend. This will especially be the case 
in areas that receive more significant snowfall over the next 
24-36 hours. 


&& 


Aviation...(for the 12z tafs through 12z Wednesday morning) 
issued at 527 am CST Tue Jan 24 2017 


Winter storm will affect the taf sites. LIFR conditions through 
the period at kofk. IFR initially at klnk/koma, but may transition 
to MVFR for a period at these two locations later this morning and 
afternoon, then eventually to LIFR. Some light snow near klnk/kofk 
this morning, and it could impact koma. Eventually a rain/snow/sleet 
mix could impact klnk/koma later this morning and afternoon, then 
eventually transition to all snow. Easterly winds eventually 
becoming northwest and gusty at times. Overall, a very busy 
weather period in the next 24 hours. 


&& 


Oax watches/warnings/advisories... 
NE...Winter Weather Advisory until 9 am CST Wednesday for nez042>045- 
050-051. 


Winter Storm Warning until 9 am CST Wednesday for nez011-012- 
015>018-030>034. 


Iowa...Winter Weather Advisory until 9 am CST Wednesday for iaz055-056. 


Winter Storm Warning until 9 am CST Wednesday for iaz043. 


&& 


$$ 



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