Weather It Is (The Most Dangerous Storm)

Good Afternoon:

An extremely powerful and cold storm is poised to make it's way into our area within the next few hours.  It comes on the heels of other less cold, but equally potent storms since Friday night.  The storm will be arrive with a huge blast of heavy rain and strong winds -- it may seem like the world is about to end (at least for those who have ventured outside).  Temperatures will then drop through the night and wet snow should occur towards morning in the central, southern, and northern mountains.

There is still some uncertainty with this storm.  We know that the temperatures at 850 mb and 700 mb will be as cold as ever (-4 C, -14 C) -- well below the minimums required for snow.   However,  the 500 mb temperatures (-28 C to -31 C) and heights (near 5400 m -- the critical height for snow even at low elevations) continue to show a possible range indicating that the intensity of the storm is still somewhat in question.  In other words, if the temperatures do fall to -31 C, snow amounts in this extremely unstable air would be even larger, and extend to lower elevations.

The storm should continue to strengthen throughout the day on Wednesday and current indications from the ensemble are that the coldest temperatures aloft should arrive late Wednesday night or morning.  As the coldest air enters, it will create pockets of instability that should help to continue the snow into Thursday morning.

There is still a bit of a question of when the air will turn cold enough for snow -- either late Tuesday night or sometime in the early morning Wednesday.  In either case, schools and unnecessary travel will have to be postponed, quite possible until Sunday, as the lower level temperatures will remain cold through Friday.  Lightning is also expected in Thunder Snow.

The weather should moderate for several days, but already the GFS ensemble is showing a possible return to more winter weather about a week out.

Accumulation amounts are expected to be between 10-25 cm, but these amounts may have to be updated as we move into the forecast window of our highest resolution (1.3 km) forecast model.

Barry Lynn