Updraft: July 13, 2010 Archive

Weather Lab Forecast Discussion

Posted at 4:55 PM on July 13, 2010 by Paul Huttner
Filed under: Severe weather

There is mixed news as the picture becomes a little clearer looking at severe weather potential through Wednesday. The frontal timing may preclude severe storms in some areas. But the potential for damaging storms still exists in some areas of the Upper Midwest.

Here's the deal, these situations are always complex and this one is no exception. They say timing is everything, and the timing of the approaching cold front will be everything when it comes to where severe weather may occur.

Here's what we think we know, and what we don't know at the Huttner Weather Lab.

What we think we know:

-It looks like we will be storm free in the metro and most of southern and eastern Minnesota this evening. If nothing pops, it should be a great but breezy and increasingly humid summer evening and overnight. Dew points will rise through the 60s in most areas and into the 70s in southwest Minnesota.

Dew points on the rise with sticky 70s nosing into southwest Minnesota.

-The first real wave of severe storms developed pretty much as expected in eastern North Dakota today. An MCS is evolving and will roll east into northwest Minnesota tonight. If the system persists tonight as they sometimes do... and if it turns right down I-94 following the highest moisture values and instability...it could roll through Alexandria and Brainerd and St. Cloud overnight and possibly survive the trip into the Twin Cities area toward morning.

GOES IR image shows storm complex developing over eastern North Dakota late Tuesday.

-The biggest risk for severe weather overnight will run from the Grand Forks and Fargo areas down into northern and central Minnesota. Think Fergus Falls, Wadena, Bemidji, Brainerd and St. Cloud.

-If the complex persists and strengtens overnight it has the potential to become a derecheo event with widspread hail and damaging winds in the northern half of Minnesota into Wisconsin.

What we don't know yet:

-How long will the overnight convective complex persist? The latest thinking is that is may go strong to possibly severe until after midnight into western and central Minnesota, then weaken a bit as it approaches eastern MN (and the metro?) toward morning.

-How much debris could cover will linger and limit heating tomorrow? The latest thinking is that we'll have some debris clouds around in the morning, and that may limit surface heating in eastern Minnesota.

-Where will the front be early tomorrow PM, and where will the next batch of storms fire? Current thinking is that the front will be right over the Twin Cities area around lunchtime tomorrow. This may mean the when storms do develop tomorrow early PM, they fire right over the Twin Cities...or develop just east of the metro and clobber western Wisconsin.

If there's enough debris around through the morning, the metro COULD escape widespread severe weather. If the sun is out early..look out. Storms (potentially tornadic?) could blow right over the Twin Cities around lunchtime.

Wherever storms do deveop Wednesday, there is sufficent low level wind shear to spawn tornadoes. SPC is monitoring the risk, and may upgrade parts of eastern Minnesota and western Wisconsin to a moderate risk for severe weather.

Keep an eye on the sky overnight in northwest and central Minnesota, and in eastern Minnesota and western Wisconsin as we head through the day Wednesday!

PH