2/9/09: Storm Update Number 4

Issued at 10:38 PM CST, Monday, February 9th, 2009

At 04z…Low pressure of 981 mb was centered between Huron and Mitchell South Dakota which is located in the Southeast portion of that state. Strong 3 mb per 2 hour pressure falls are occurring over Southwest and Westcentral Minnesota late This Evening, so we should see this very deep and mature area of low pressure head toward Western Minnesota by Morning. 12 hour H5 height falls have reached 240 meters in Southwest Minnesota and Southeast South Dakota This Evening with 150 meter H5 12 hour height falls extending up to Duluth. One thing this storm has done is pull a tremendous amount of warm air north into Minnesota…This in part has been due to a powerful low level jet which at 10 PM Tonight ranged from 50-70 knots across Southern, Central, and Eastern Minnesota.

Surface temperatures have risen into the 40s as far north as Brainerd to near Aitkin Minnesota late This Evening with some cities in Southern Minnesota closing in on the low 50s at this late hour! Amazing!

The threat for further icing has ended in Northern Minnesota This Evening thanks to all the warm air pumping north ahead of this powerful low. All the winter weather headlines have been cancelled with just the far Northwest part of Minnesota still under an *Ice Storm Warning* until Midnight CST Tonight.

Here are some of the lower pressure readings as of 10 PM CST Tonight…

Pipestone MN: 28.96″

Canby MN: 29.00″

Slayton MN: 29.01″

Watertown SD: 28.97″

Brookings SD: 28.98″

Sioux Falls SD: 28.96″

Mitchell SD: 28.95″

Huron SD: 28.94″

Water vapor satellite imagery shows a powerful negatively tilted storm covering the Northern Plains and Upper Midwest with a well defined dry slot continuing to surge north across Western, Central, and Eastern Minnesota as of 9 PM Tonight.

The atmosphere has become weakly unstable across much of Southern, Central, and Eastern Minnesota as of mid-evening with mid level lapse rates of 6.0-7.0 c/km and elevated capes around 100 j/kg…This area of instability will continue to lift N/NE the rest of Tonight.

Radar imagery shows a growing area of rain lifting north-northeast through Southern, Central, and Eastern Minnesota attm…Some strong winds have been mixing down to the surface in some of the heavier showers across Southern Minnesota This Evening with wind gusts nearing 40-50 mph in some locales.

Rain will likely move into Duluth around Midnight Tonight with rain likely lingering at least off an on through the Overnight period. The forecast models are showing that the upper level temperatures will start to fall toward Morning with H85 temps hovering around zero degrees C by mid-morning Wednesday, surface temps should remain warm enough though to keep this batch of precip in liquid form the way it looks now. Areas of fog, some of which will be dense will also linger around the city the rest of Tonight. Temperatures will be in the 34-39 degree range with east/southeast winds at 10 to around 25 mph.

Tim