By Al Dutcher
Warming or cooling trends? Here's what to watch for through the end of December, based on current Global Forecast System (GFS) model projections.
From Wednesday, Dec. 11, through Friday, Dec. 13, expect above-normal temperatures warming from the low 40s to the low 50s in the east to the mid/upper 40s to the mid 50s in the west. A cold front is projected to push through the state Friday afternoon through Saturday morning. The GFS model hints at the possibility of minor (less than 2 inches) of snow extending from northwest Nebraska through the western Sandhills, weakening as it reaches eastern Nebraska Saturday morning. Another system is projected to move out of the central Rockies on Sunday and move eastward across northern Kansas. The GFS model indicates that the eastern two-thirds of the state south of a line from Valentine to Norfolk has the best chance for accumulating snowfall. Areas south of I-80 may see the greatest accumulations (couple inches possible), but totals could increase if recent model strengthening continues.
Cold air will spill into the region on Monday and last at least through Wednesday (Dec. 16-18). By Dec. 19, a storm system entering the western U.S. will carve out a large trough across the western third of the country, which will translate into a ridging pattern over the central U.S. The GFS model indicates that above normal temperatures are likely Dec. 19-20. If we escape snowfall Sunday afternoon through Monday morning, highs will likely jump back into the 40s to low 50s. If we get more than a couple inches of snow, highs will still be above normal, but about 5-10 degrees (F) cooler. The first piece of energy out of the western U.S. trough will move into the southern Plains on Dec. 21, then head northeast. Currently, only extreme southeastern Nebraska is on the northwestern periphery of this storm system. Therefore, cloud cover will likely keep temperatures close to normal. The GFS model indicates a quick return to above normal temperatures Dec. 22-23 as the upper air trough across the western U.S. moves into the central Rockies.
If the GFS model depiction pans out, a vigorous system will impact the Central Plains Dec. 24 with accumulating snowfall. At present, most of the state would see a white Christmas. Unfortunately, what comes after Christmas will not be pleasant if the models are correct. The GFS surges Arctic air southward behind the departing low. GFS hints at sub-zero highs across North Dakota and Minnesota, with teens probable across Nebraska and sub-zero lows. If a decent snow pack develops across the central Plains, then highs will likely drop into the single digit territory Dec. 27-28 before slowly moderating.
Again, all of this is based upon the current GFS model run and the recent consistency of the model runs.
Source : unl.edu