The upper-level flow across the U.S. this afternoon is generally zonal with numerous embedded short wave troughs. One trough is currently moving through southeast Oklahoma and eastern Texas. This combined with an increase in low level moisture over the past 24 hours has resulted in shower and thunderstorm activity. In Oklahoma, the activity has been fairly scattered with only a few areas receiving brief heavy showers.
A second trough is moving southeast through Montana, with a third moving eastward through Utah and Arizona. These will advance eastward over the next 24 hours eventually phasing over the Plains and Mississippi Valley during the day Thursday. This will help push a cold front into Oklahoma during the early morning hours. Showers and thunderstorms will occur along and ahead of the front, with the strongest lifting / and higher coverage of precipitation / occurring across north central and northeast Oklahoma. It now appears that the onset of precipitation will be delayed beyond previous thinking and that showers and storms will be ongoing in eastern Oklahoma well into the afternoon hours. Temperatures will only peak in the mid 50′s on Thursday and winds will become gusty out of the north behind the front. The temperature will drop to near or just below freezing Thursday night.
Behind the Thursday system, a high pressure ridge aloft will work eastward over the Plains while a strong storm system moves onshore over the west coast. With mostly sunny skies, temperatures Friday will push to near 60 degrees as winds gradually become southeasterly. By late afternoon, winds will be gusting out of the south across the panhandle and extreme northwest. The low Friday night will be well above normal, in the upper 30′s.
24-48 hours ago, models were having a hard time coming up with similar solutions for the western U.S. system. The various models have come more in agreement over the past 24 hours and it now appears that a significant lead wave will eject out of the west on Saturday, reaching the central Plains by Sunday morning. As this occurs, a deep area of surface low pressure will take shape in eastern Colorado. With south winds, temperatures on Saturday will reach near 60 degrees (possibly warmer depending on the amount of cloud cover). The surface low will advance toward south central Nebraska during the overnight hours from Saturday into Sunday, while a cold front will start pushing eastward through Oklahoma. Low temperatures in central Oklahoma Saturday night are tricky to forecast. If the front passes between 3 am and 6 am, there may be a brief period where temperatures drop into the 30′s. Should frontal passage hold off until after sunrise, temperatures will only drop into the 40′s.
Strong lifting across Nebraska and adjacent areas of South Dakota will result in a significant snow event with near blizzard conditions on the northwest side of the surface low. A second area of large scale lift will be overspreading the warm sector in Oklahoma and Texas. Showers and thunderstorms will form along the front with the greatest chance of precipitation in central Oklahoma coming between Midnight and 6 am on Sunday. A few severe thunderstorms appear possible in Texas and southern Oklahoma during the early morning hours of Sunday. This threat will shift eastward into Arkansas and Louisiana by Sunday afternoon.
The pressure gradient in the wake of the cold front will not be that strong and winds Sunday will steadily weaken throughout the day. Temperatures should once again push to near 60 degrees.
Beyond the Thursday to Sunday period, things have taken a turn toward the interesting with a possible winter storm shaping up toward the start of next week. Once again, model agreement has boosted confidence and while attention is focused on the ejecting lead wave on Sunday, a strong speed max will be dropping south through the western U.S. into the base of the trough. This will help carve out a strong system that will approach the southern Plains by Tuesday. There should be a good supply of moisture to generate widespread precipitation with this system. Meanwhile, the column of air looks sufficiently cold for snow production / especially north of I-40. While there is plenty of time for things to change, current indications are that significant amounts of snowfall could occur in the state from Tuesday into Wednesday morning.