A complex and possibly historic winter weather situation is upon us within the next 48 hours as two storms combine to potentially drop extreme snow amounts.
Blizzard Warning valid at Feb 01, 3:00 PM CST for Jo Daviess, Carroll, Whiteside and Stephenson [IL] till Feb 02, 12:00 PM CST
4:00 Update: Tonight we can expect 2-5 inches by Tuesday morning. The second round of snow arrives Tuesday night into Wednesday where we can expect another 7-13 inches (all forecasted total accumulation is for Rockford Metro). High amounts can be expected to the South with lesser amounts to the North.
Blizzard Watch valid at Feb 01, 3:00 PM CST for Green [WI] till Feb 02, 3:00 PM CST
Blizzard Warning valid at Feb 01, 3:00 PM CST for Jefferson, Rock and Walworth till Feb 02, 3:00 PM CST
Blizzard Warning valid at Feb 01, 3:00 PM CST for Boone, Cook, DeKalb, Lee, McHenry, Ogle and Winnebago till Feb 02, 3:00 PM CST
3:30pm Update – Here is a look at the raw output from the GFS model. It gives you an idea of the scope of this winter storm/blizzard. We expect all counties in our coverage area to be under Blizzard Warnings for the Tuesday night through Wednesday evening timeframe. Total snowfall accumulations will be in the 10-20 inch range from north to south across the WREX coverage area for Tuesday night into Wednesday morning. We will have a few inches between now and the time the main, system snow arrives Tuesday night. -ES
3:00pm Update: Just took a look at the newest model data and everything is still on track. The storm track runs from Southern Arkansas to Western Tennessee/Kentucky into Southern Indiana and Eastern Ohio by Wednesday morning. From Tuesday evening into Wednesday morning is the time-frame where we expect the strongest part of the storm. This is when we can expect snowfall rates between 1-3 inches per hour, winds gusting up to 40-50 mph as well as rumbles of thunder. This will create blizzard conditions with 4-8 ft snow drifts and visibility less than 1/4 mile. Traveling will likely become impossible during this time-frame of Tuesday night into Wednesday morning.
10:30am Update - as I continue to pour through model data and check out various forecasting methods (Cobb method and Magic Chart method for you snowheads), it appears as though our viewing area may have a substantial variation in accumulated snowfall if the system does in fact keep its current track. Locations in southwestern Wisconsin will likely see less snow than those that reside nearer to Chicago and points south of I-80.
Check out this forecast sounding from the NAM. If you are not familiar with the DGZ, you soon will be. The DGZ (Dendritic Growth Zone) is the column in our atmosphere, between -20 and -10 degrees, that is most efficient at producing snowflakes. When the air is saturated within this zone (the green moisture line near the red temperature line), snow is formed. The longer these saturated conditions exist as the snowflake falls, generally the bigger and more intense things will be at the ground. A saturated column from nearly 500mb to 925mb is certainly impressive and will yield very efficient snowfall if it verifies.
Today’s storm system, the weaker of the two, will slide off to our north and drop between 1-3″ of snow in the area. Look for slightly heavier amounts close to and just north of the Wisconsin state line. Tonight, there may be a slight lull in the snowfall as we transition to the second, and much stronger, system.
As an area of low pressure continues to deepen in the southern states today, it will ride along a strong temperature transition zone toward central Illinois. As the local area will be along the northern fringe of this low, we will be in prime position to see some of the heaviest snowfall. As it looks this morning, the potential exists for some people in our viewing area to see up to 15 inches of snow from Tuesday/Wednesday’ storm alone. Amounts will be greater to the southeast of Rockford toward the Chicago area where 20+ inch amounts are possible. Travel will become difficult if not impossible Tuesday afternoon through the entire day Wednesday as winds pick up and cause blowing and drifting to several feet above actual accumulated snowfall. Temperatures will become a concern with windchill values to -30 at times Wednesday.
One point I cannot stress enough is about the track of the storm. Although it is an almost 100% certainty that we will all see significant snowfall totals, a deviation in the track of the storm could mean the difference between 6″-12″ or a band of 12″-20″ for any given location. As this storm continues to evolve and phase with our weaker northern storm, slight tracking differences are inevitable. On the flip side of this point is the possibility for lighter snow amounts. Strong systems usually have a fairly narrow corridor of the heaviest snow which we will continue to refine as the storm draws nearer.
This morning, I ran our in-house computer model and changed the path of the storm to the north by 75 miles. Take a look at the absolutely impressive snowfall totals if this does in fact happen! As much as 18-22″ of snow would be on the ground if this scenario were to play out. Travel would be nearly impossible, even with 4 wheel drive. Now is the time to prepare and get any midweek plans completed.
Posted under snow, winter storm
This post was written by qni_it on January 31, 2011