More snow likely, models vary; long track tornadoes

Update 10:20am:

Morning 12Z NAM model run comes in with about 4" to 5" snowfall for metro Tuesday night.

Stay tuned....

Winter weather has overstayed its welcome this year, and it seems we're due for one more shot before spring finally takes hold.

The weather maps continue to look more like March this week. Another potent late winter storm (in springtime!) is heading for the upper Midwest Tuesday. There are still major model differences with this system, and another two "major" forecast model runs this morning and tonight may (hopefully) clarify the final outcome.

Winter storm watches have been posted for southern Minnesota, including the Twin Cities.

Twin Cities NWS Weather Story previews potential storm.

Based on what we know now, here's the rundown on snow possibilities Tuesday night into Wednesday morning.

The system:

Low pressure will track from Missouri to south of Chicago Tuesday night into early Wednesday.

There are still model differences in the track, with the European model taking the system furthest south.

Precip timing & type:

A mixed bag of rain & snow should develop Tuesday in Iowa & the I-90 corridor early, and then slide north toward the Twin Cities during the afternoon.

GFS model sets up heavy precip band in SE Minnesota late Tuesday.

Precip will likely be mixed rain & snow Tuesday, changing to all snow Tuesday evening. Snowfall rates could increase and be heavy at times Tuesday night. Snow should gradually end Wednesday morning.

Snowfal Totals:

It does appear the system has the potential to produce 6"+ in the heaviest snow band, which most likely will set up south of the metro from Mankato to Albert Lea northeast to Eau Claire. Right now, cities & towns with the best chance for 6"+ appear to be Waseca, Owatonna, Rochester, Northfield, Red Wing & Winona.

NAM model: Heavy snow band south of metro.

Metro totals?

At this time the metro appears to be north of the heaviest snow band.

With major model differences in the storm track, I'm not ready to sign off on big accumulations for the Twin Cities just yet. We still have more than 24 hours and two major model runs before the snow flies. But it does appear that we will see some accumulating snow Tuesday night into Wednesday morning...inches to be determined tonight or early Tuesday morning.

A "plowable" event for the metro? A big maybe.

Forecast could change:

File this forecast under "changeable."

There is still a lot that could go wrong with the models this time of year...and especially this year. Model performance (especially the GFS) has been downright poor with the last few "storm" systems. Early snowfall forecasts have been all over the place again with this system...from over a foot of snow down to an inch.

Because of this I am going to wait a little longer than usual to issue a specific snowfall forecast for the metro. Suffice to say you should plan for some snow from Tuesday evening through early Wednesday morning. Accumulations will most likely favor grassy areas again. With warm pavement and air temps near or above freezing, there will need to be heavy snowfall rates for a longer period of time to see significant accumulations on roads...but that could happen Tuesday night into early Wednesday.

There will be two major model updates in the next 24 hours beofre precip moves in.

Stay tuned...

Record southern tornado outbreak?

There's no doubt that the weekend tornado outbreak will go down as one of the biggest in U.S. history. The only question seems to be whether or not we will surpass the incredible number of 148 tornadoes in a 24 hour period form the April 3-4, 1974 "Super Outbreak."

248 tornadoes sweep the south in 3 days. (Map by Victor Gensini)

Here are some staggering numbers so far from last weekend's mega tornado outbreak.

248 - total number of preliminary tornado reports from Thursday-Saturday.

148 - Number of tornadoes in a 24 hour period in the 1974 "Super Outbreak."

45 - number of fatalities reported so far

63 miles - path length of Raleigh, NC tornado

65 miles - path length of the Fayetteville, NC tornado

3 miles - maximum path width of the Raleigh, NC tornado!

The numbers are staggering but don't even begin to tell the whole story. The size and intensity of these monster tornadoes over the weekend is frightening, even to trained meteroloigsts. The Raleigh tornado was 3 miles wide at the base! The storm chasers call these huge, violent tornadoes "wedges"...because they are so big they don't even look like tornadoes from a distance. You just see this big V-shaped cloud intersecting the ground.

Check out this remarkable time lapse video as the "rain wrapped" tornado moves into Raleigh, NC.

These big, violent EF3+ wedge tornadoes appear to have caused many of the tornado deaths this past weekend, especially in North Carolina.

Next severe outbreak Tuesday?

This overactive pattern looks like it will produce another severe weather outbreak Tuesday in the central plains on the southern end of our "winter storm."

SPC has already placed a moderate risk over the Ohio Valley.

Stay tuned...

PH