Conditions will deteriorate rapidly this afternoon and evening as another major winter storm draws closer to the southern plains. This will result in snow developing across Kansas and Northwestern OK before spreading across the rest of Oklahoma later tonight, overnight, and into Wednesday. Snowfall accumulation forecasts remain clustered on 4 to near 10 inches of snow across the central and north central portions of the state. Localized higher amounts may be possible in a few spots. Afternoon highs will top out in the 20's or lower 30s near Tulsa, with upper 30s across southern OK. Winds will be shifting to the northeast as a surface area of low pressure forms to our west and dives across southeast Texas. The storm will be exiting the state by 2pm to 4pm Wednesday afternoon. Strong north winds will be likely tomorrow morning creating blizzard like conditions with blowing snow and very cold wind chills. Wind speeds are not expected to support blizzard warning criteria, but wind chill advisories will more than likely be required.
The upper air system will more than likely remain open and not closed. Most, but not all heavy snowfall events in the state are caused by closed lows. This system appears to remain an open positively tilted mid length wave as it traverses the region. The difference in the snowfall production will be the expected cold air aloft through the surface and moisture profiles in the snow growth region of the atmosphere. These parameters may allow for a greater snowfall ratio and therefore a production of moderate to heavy snow that would satisfy winter storm warning criteria.
Run to run model consistency has been very good over the past day, but there remain some noticeable outliers among the model suites. The GFS continues to dive the system southeast rapidly with very little snowfall across northeastern OK while producing the majority of the precipitation across western and central OK before moving into the Red River region early Wednesday morning.
The NAM runs bring the system across the body of the state, including the northeastern sections, with incredibly high snowfall output in the range approaching another 15 inch storm.
The EURO brings the system across the body of the state, including the northeastern sections, and would suggest the potential for snow from 6 inches up to near 14. Again, the exact snowfall ratio will be a mystery until the system unfolds. These profiles will also change hour by hour during the event.
Arctic air will also be moving southward soon and will set the stage for very cold air through Saturday morning. Sub freezing temps are likely Thursday morning over the snow pack with highs ranging near 20 or so.
The upper air pattern will change soon as I discussed over the past few days allowing for relatively warmer air to arrive into early next week, despite the presence of another cold front Monday, and the possibility of an upper level system by the middle of the week.
The bottom line take away: snow is likely, and some moderate to heavy snow is a possibility. This system, however, could still throw a last minute curve ball if the GFS somehow verifies and moves the bulk of the snow to the southeast. If the NAM verifies, we're going to be in a world of hurt. The EURO, which is the model of choice, would support heavy snow in the 4 to near 12 inch range with some higher localized totals in a few spots. I have used a blend of the EURO and GFS outputs to fashion the forecast, and I have used a lot of prayer to help me say and do the right things for this system.
I'll be working on the timing of the system during the next few hours, but a start time of 7pm northern OK seems reasonable with an exit time of Wednesday afternoon around 4pm is possible. We should be smack dab in the middle of the system Wednesday morning.