:: Just in time for travel (and Winter)
Just in time for the holiday travel season, and the official start of the winter season, a winter storm has taken strong shape to affect the majority of the CONUS from now through Sunday. Currently, the southwest-born storm has tapped a boatload of Pacific moisture, with the upper/mid level cyclone now pushing into southern CO and the surface low approaching the TX panhandle. Ahead of the the surface low, frontogenesis is occuring with a warm front extending across the Red River and the cold front now crossing the Rio Grande. Already the system shows some signs of tapping Gulf moisture, as the Pacific moisture laden upper/mid low is set to drop heavy snow on the front range overnight.
Models are now agreeing on system movement, but disagreeing on moisture content and precip potential...particularly at the end of the short term model (now on the 22nd) which is decidedly "white" now, due to the fact that a new push of cold cP air from Canada is being tagged by the models now to invade coincedentally with the arrival of the low. So as fasr as snow is concerned, the only question is how much accumulation we will have. Currently, winter storm watches are posted as close as SoDak for the intrusion of freezing precip starting late Wednesday. As the models prog the upper low to couple with the surface low, the main difference in the last runs is in the jet. Now the split-off southern branch is looking more like it will run with the system, with both GFS and NAM painting a 120kt max nosing over central MO Thursday evening. This will punch the warm air from the southern jet over IA and southerm MN while the cold cP slides underneath from the north and hugs the barren ground of the Gopher state. The result will mean mixed precip for sure, and a great possibility for freezing precip as temps plunge Thursday.
As the system tracks from CO to NE to IA to IL over the next 12, 24, 48, and 72 hours respectively, all eyes will be on travel conditions as they deteriorate. First hunches for the Lakeville area per the model output stats are in agreement between the GFS and NAM for freezing rain or sleet changing to snow overnight Wednesday, then a mix of sleet and rain Thursday, changing all over to snow sometime late Thursday, and then snow for at least the first half of Friday. The models break from each other on the snow potential and amounts on the Thursday - Friday period...with the NAM progging 1-3" and GFS 4-6".
No confidence has been given in either of these projections, as the amount of drier air that could stymie the system is still a question. Tonight the s/w trough that will usher in the cP is also showing strong subsidence and drying tendancies. Future model runs, as well as upper air data soundings, will give us much more certainty tomorrow. Your Lakeville forecast...slightly extended:
Wednesday...clear skies in AM turning mostly cloudy by sundown. High 43. Mixed precipitation moves in after 10pm, mainly sleet, temps drop to 26. 50% chance of precip. WNW winds 5-7.
Thursday...wake up to freezing rain or sleet. 70% chance of precip through the day. Highs right around 32. Precip changes to all snow after dark. Low 22. NW winds 5-10
Friday...Snow showers. 70% chance of precip, with 2" of accumulation possible. High 30. Low 23. NE wind 5-7.