Early December is trending cold to very cold, snowy (and icy) for the Great Plains and possibly Texas eastward to the Ohio Valley to northern New England. Today's midday 12Z GFS is very aggressive with this potential scenario. The widespread and southern expanse of potential snow enhances the cold and limits moderation reaching Texas. The cold is less likely to impact the East.

Excessive rainfall with flood risk is forecast for today southwest of San Antonio and in Arkansas. Excessive rainfall with flood risk returns to Texas and the southeast Great Plains SUN/MON. The NBM 10-day rainfall forecast indicates 5-7 in. of rain just north of Dallas.

Stratospheric warming is developing on the North America side of the North Pole now, strengthening in the 6-10-day period, and peaking across northwest continent during the 11-15-day period. The attendant colder temperature trend at ground level causes a surge in U.S. gas population weight HDD for the week ending December 4th.

At day-16, the 12Z GFS shifts stratospheric warming from northwest continent indicated by all models during previous model runs, to Northern Canada. In this position, the model creates cold air quickly thrusted into the U.S. in the 11-15-day period), a dramatic cooler change.