Tuesday, September 21, 2010

9/21/10: Tuesday's Weather Report

Issued at 3:18 PM CDT, Tuesday, September 21st, 2010

Local Storm Report for Monday Night/Tuesday Morning, September 20th-21st, 2010. Source: NWS Duluth, Minnesota.

*10:55 PM CDT 9/20/10: Thunderstorm Wind Damage. 1 mile west of Kimball WI (Iron County) Trees down over Lake Head Road, south of U.S. Highway 2.

*4:20 AM CDT 9/21/10: 0.75" diameter hail. Hurley WI (Iron County)

*4:25 AM CDT 9/21/10: Thunderstorm Wind Damage. 3 miles northwest of Hurley WI (Iron County) Several trees over Defer Road.

Note: Temperatures aloft were just too warm for thunderstorms to develop in Northeast Minnesota Monday Night, and by the time the air aloft cooled enough, the threat for strong to severe thunderstorms had shifted into Northwest Wisconsin through the southern half of Minnesota early Tuesday Morning as the low pressure system and it's warm front and cold front exited the north-east parts of Minnesota around Midnight-1 AM This Morning. The Storm Prediction Center did issue a *Severe Thunderstorm Watch* around 2 AM This Morning for much of northwest Wisconsin through Southcentral Minnesota, and a few severe thunderstorms did develop between 1-4 AM Today around Minneapolis and also in far western-northern Wisconsin into western Upper Michigan.

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

Strong low pressure averaging 994 mb has moved into southern Hudson Bay as of 3 PM with high pressure of 1016 mb building southeast out of western Saskatchewan Province. Quite a bit of cloudiness has been spreading south-southeast through the area Today on the backside of the deep low to our northeast. High temperatures Today due to the clouds and cold advection (850 mb temps of +2/+6 C in far Northwest Wisconsin and Northern Minnesota) were in the 50s to lower 60s, but milder mid 60s and low 70s were common over portions of Northwest Wisconsin. Winds Today were out of the northwest or west at 5-15 mph with higher gusts to 25 mph.

Today's Upper Level Analysis:

The flow aloft has transitioned to zonal, (west to east) Today over the Upper Midwest. The next system of interest for the Upper Midwest is currently moving onshore into Oregon-northern California This Afternoon with another system dropping southeast out of western Canada per water vapor satellite imagery.


High pressure will continue to build southeast out of western Saskatchewan Province with partly to mostly cloudy skies covering northern Minnesota and Northwest Wisconsin Tonight. Lows will be in the 30s and 40s with winds out of the northwest or west around 20 mph or less.

Wednesday and Wednesday Night:

High pressure will remain in control of our weather for Wednesday with partly to mostly cloudy skies and highs in the 50s and 60s. By Wednesday Night, the high moves off to our north/east with low pressure taking shape across the Central Rockies. The cold front which moved through our area earlier Today will stall out and turn into a warm front during this period with this boundary heading into Southern Minnesota by Wednesday Night. Warm and moist advection will get underway by Wednesday Night with PWS of one half to three quarters of an inch on Wednesday increasing to 1.00-1.50" by Wednesday Night. Rain and a few thunderstorms should develop by Wednesday Night, especially south of a line from Walker to Duluth to Ashland. Some of the rain could be heavy at times Tomorrow Night, especially in far southern areas...including the Pine City, Grantsburg, Shell Lake and Minong areas where rainfall amounts of one half to one inch are possible. North of here, rain totals should remain under one quarter inch. Mostly cloudy skies are expected for Wednesday Night with lows in the 40s to lower 50s. Winds will shift to the east during this period at 10-20 mph with some higher gusts.

Extended Forecast:

Deep low pressure averaging 991-995 mb is forecast to reach eastern Nebraska/southeast South Dakota Thursday Morning before moving across the southern half of Minnesota Thursday Afternoon, then into northcentral Wisconsin by late Thursday Night. This low combined with a warm front which will remain south of our local area will result in a continued threat for rain in northern Minnesota and northwest Wisconsin from Thursday into early Friday. Some of the rain will be heavy at times, especially in northwest Wisconsin back into eastcentral Minnesota...rain totals in these areas could reach 1-2" by late Thursday Night. Rainfall totals in northern Minnesota should be less, generally under one half inch the way it looks now. Isolated thunderstorms could also occur for Thursday and Thursday Evening from eastern Minnesota through northern Wisconsin. High temperatures on Thursday will be in the 40s and 50s with gusty easterly winds which could reach 25-35 mph near Lake Superior. Note: *Gale Watch* is in effect for portions of Lake Superior, including the Duluth-Superior Harbor area for Thursday Afternoon and Thursday Evening. Wave heights could approach 10 feet at the peak of this event as northeast winds increase to 40 knot gales!

Rain should continue in our area Thursday Night, but should begin to decrease from west to east during the night. Lows Thursday Night will be in the 40s to around 50 degrees.

Strong low pressure moves into the eastern Great Lakes on Friday with a threat for some lingering showers across our area. Highs on Friday will be in the 50s with lows Friday Night in the 30s and 40s...Mainly dry conditions should return to northern Minnesota and northwest Wisconsin for Friday Night.

5 Day Forecast for Duluth/Superior

*Gale Watch* in effect for the Twin Ports Harbor from Thursday Afternoon through Thursday Evening

.Tonight... Mostly cloudy with some clearing developing late. Low 40 to 45. Wind west to northwest at 10 to 15 mph.

.Wednesday... Partly sunny. High 55 to 60. Wind east at 10 to 20 mph.

.Wednesday Night... Mostly cloudy. Occasional rain possible. Low 43 to 48. Wind east ato 10 to 20 mph. Chance of rain 40%.

.Thursday... Breezy with occasional rain. High 48 to 53. East winds could occasionally gust to 30 mph. Chance of rain 80%.

.Thursday Night... Occasional rain. Mostly cloudy. Low 40 to 45. Chance of rain 70%.

.Friday... A few showers possible. Mostly cloudy. High 55 to 60. Chance of rain 20%.

.Friday Night... Partly to mostly cloudy. Low 40 to 45.

.Saturday... Mostly cloudy. Showers possible. High 55 to 60. Chance of rain 20%.

Normal High Temperature Today 63 degrees

Normal Low Temperature Today 43 degrees