February 1-3 Potential Winter Storm

Image courtesy of Tropical Tidbits

The latest GFS forecast has an accumulating snowfall in the forecast from February 1 to February 3rd.

The above image shows the precipitation type, mean sea level pressure (black contour lines) and 1000-500mb thickness (dashed and colored contour lines) for the morning of February 2nd. This would then change the storm title to February 2-3, but the event is likely to put down precipitation beginning on the 1st. It appears a modest storm system will be pushing out of the Rockies, leading to precipitation across the North Plains and into the Midwest. I do not doubt this could be the result of two separate pieces of energy, and such a scenario would result in quite a storm further east. There is high pressure off the Mid-Atlantic, something that would result in the storm track being pushed further north and west, favoring a Great Lakes Cutter storm scenario.

Moving ahead 12 hours, the storm has intensified in the Great Lakes as I expected, and heavy snow is ongoing across the Midwest, Great Lakes and Upper Midwest while a rain event occurs in the Ohio Valley and Gulf Coast regions. Judging by the liquid equivalent snow legend on the right-hand side, it would not surprise me to see upwards of 4 inches of snow in many areas of the Midwest and Great Lakes if this forecast verifies, which isn't that likely at the moment. Strong Arctic high pressure filtering in through the Plains would provoke lake effect snow in the storm's wake.

Image courtesy of Tropical Tidbits

Another 12 hours into the future, we see the storm has further intensified, and is dropping large amounts of snow across much of the Ohio Valley and Great Lakes into southern Canada. A glance at the liquid equivalent legend for the hardest-hit areas would mean nearly 10 inches of snow could be falling within a 12 hour period if ratios remain the typical 10 inches of snow to 1 inch of rain. Any higher, and we would be talking about over a foot of solid snow on the ground in parts of the Ohio Valley. Rain is overspreading the Northeast area as a result of the warm sector impacting the region with...well, warm air.

So, this is just another fantasy model forecast that won't happen, right?

NOT SO FAST!

The Lezak Recurring Cycle (LRC) is involved here. The LRC includes a repeating pattern of weather disturbances and high pressure systems that repeat, or cycle, every 40 to 60 days. The cycle length varies year by year, and no winter's LRC pattern is the same. This winter, thanks to the dedicated folks at the AccuWeather Forums, it has been found that the cycle length is 53 days. If we rewind February 3rd back 53 days, we get December 11th. Now, look below and see the comparison between the forecasted 500mb height anomaly on February 3rd (top) and the observed 500mb height pattern from December 11, 2012 (bottom).

Image courtesy Tropical Tidbits

HPC

What a coincidence- they are almost a perfect match! You have the deep low pressure in the North Plains in both, slight high pressure in the Pacific Northwest in both, and even high pressure slightly displaced from the Southeast on Dec. 11, but still just offshore on Feb. 3. This proves that the LRC does indeed have a role to play here, and if we look at observed precipitation for that time period in mid December, we find that, should a similar precipitation pattern play out, over half a foot of snow for the Ohio Valley and parts of the Midwest.

Very exciting things happening here, so stay tuned!

Andrew