Monday, June 21, 2010

6/21/10: Monday's Weather Report

Issued at 3:44 PM CDT, Monday, June 21st, 2010

...Updated information on last Thursday's tornado outbreak in Minnesota... Source, NWS Duluth MN, Grand Forks ND, and Chanhassen MN...

*17 confirmed tornadoes in Minnesota on 6/17/10...This number could rise in coming days.

*3 of the tornadoes were rated EF4
*4 of the tornadoes were rated EF3
*2 of the tornadoes were rated EF2
*5 of the tornadoes were rated EF1
*3 of the tornadoes were rated EF0

*The last EF4 tornado prior to last Thursday occurred in Ohio on June 5th, 2010.

*Otter Tail County tornado information: EF4 with estimated winds to 175 mph. Track length: 36 miles!

*Wadena County tornado information: EF4 with estimated winds to 170 mph. Track length: 10 miles!

*EF2 tornado confirmed in far Southeast Pine County in Eastern Minnesota last Thursday. The NWS in Duluth has upped the previous EF0-EF1 tornado rating to an EF2 for a portion of far Southeast Pine County in Eastern Minnesota with estimated winds of 110-135 mph!

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

Low pressure of 1008 mb was centered over Eastern North Dakota (W/SW of Grand Forks) This Afternoon. A trough extended southeast of this low through the Northern half of Minnesota and Northern Wisconsin. Some instability and increasing amounts of moisture led to the development of showers and thunderstorms Today in parts of Northern, Northeast, and Eastern Minnesota as well as most of Northwest Wisconsin. Heavy rain and dangerous lightning strikes have been occurring with these storms with isolated severe thunderstorms developing late Today in parts of Northern/Eastern Minnesota. Some of the strongest thunderstorm activity This Afternoon has been affecting portions of Northwestern Wisconsin with hourly rainfall rates per doppler radar of 1.00"-1.50"! Partly sunny-mostly cloudy skies were found across our local area Today with high temperatures generally in the 70s which dropped into the 60s in areas that have seen rain...A few locales are into the lower 80s late Today around the Brainerd/Aitkin areas. Dewpoints Today have climbed into the 60s away from far Northeast Minnesota while Afternoon PWS ranged from 1.00"-1.60"!

Today's 500 mb analysis:

W/SW flow aloft continued across the Upper Midwest Today. Upper level low (570 meters) covered portions of the Northern Rockies, Pacific Northwest, and Southwestern Canada. Two upper level disturbances were heading E/NE through the Northern Plains and Upper Midwest Today per water vapor satellite imagery, out ahead of that 500 mb low to our west.


Scattered showers and thunderstorms will continue This Evening in Northwest Wisconsin and in portions of Northern/Eastern Minnesota. Locally heavy rainfall and dangerous lightning strikes will be the main hazards out of these storms This Evening, but there is also an isolated risk for severe thunderstorms with large hail and damaging winds in Western areas, mainly in Koochiching and Itasca Counties Minnesota. Partly-mostly cloudy skies will be found across our area Tonight with areas of fog late. Isolated showers or thunderstorms could continue Overnight, mainly across Northcentral Minnesota as a low level jet increases to around 25 knots later in the night in Central-Northern Minnesota. Lows Tonight will be in the 50s to lower 60s with winds out of the south or east under 15 mph.

Tuesday and Tuesday Night:

The surface trough which was over the Northern half of Minnesota and Northern Wisconsin This Afternoon will head north Tonight while the main stationary front which has been over the Northern parts of the Central Plains the past few days starts to lift north as a warm front, likely reaching Southcentral areas of Minnesota during this period.

The atmosphere across our area will become rather unstable Tomorrow Afternoon and Evening with models showing CAPES of 1000-2000 j/kg with Lifted Indices ranging from -2/-5 degrees C. Low level jet looks very weak however, but the mid/upper level winds look rather strong. There will also be a change of wind direction with height with S/SW winds at 850 mb veering more westerly at 500 mb.

There is a risk for a few showers and thunderstorms Tomorrow and Tomorrow Night in our area, but the overall severe threat looks limited at this time due mainly to the very weak or non-existent low level jet, but this could be off-set a bit by the strong instability and the 30-40 knots of SHEAR that is being forecast by the models. Damaging winds and possibly some large hail appear to the main threat if severe weather does develop Tomorrow Afternoon and Evening. Heavy rainfall and dangerous lightning strikes will also occur. Partly-mostly cloudy skies are expected during this period with highs Tomorrow in the 70s and 80s with lows Tomorrow Night in the 50s and 60s.

Note: All but far Northeast Minnesota is in a Slight Risk for Severe Thunderstorms Tomorrow and Tomorrow Night per SPC 12:30 PM update.

Extended Forecast:

An upper level trough and cold front will push south/east through the Upper Midwest on Wednesday...Some showers or thunderstorms could occur across Northern Minnesota and Northwest Wisconsin on Wednesday as this system moves through. It looks like things will dry out from Wednesday Night through Thursday Night, then a southwest flow aloft will kick back in late this week and possibly into the weekend and this combined with low pressure, a warm front and cold front, along with increasing amounts of moisture and instability could go on to trigger more scattered showers and thunderstorms and possibly some severe weather across the Upper Midwest for Friday and Saturday, possibly even into Sunday.

High temperatures for Wednesday and Thursday will be mainly in the 70s with lows Wednesday Night and Thursday Night in the 50s.

5 Day Forecast for Duluth/Superior

.Tonight... A few showers or thunderstorms possible This Evening. Areas of fog. Mostly cloudy with some clearing late. Low 51 to 56. Wind east at 5 to 15 mph.

.Tuesday... Humid. Warmer. Partly to mostly sunny. Afternoon showers or thunderstorms possible. Areas of fog early. High 76 to 81 but it could be cooler at times closer to Lake Superior. Wind south to southwest at 5 to 15 mph. Chance of rain 30%.

.Tuesday Night... Showers or thunderstorms possible. Variable cloudiness. Low 55 to 60. Wind variable at 5 to 15 mph. Chance of rain 30%.

.Wednesday... Showers or thunderstorms possible, partly sunny. High 73 to 78. Chance of rain 30%.

.Wednesday Night... Becoming partly cloudy. Low 52 to 57.

.Thursday... Partly cloudy. High 72 to 77.

.Thursday Night... Partly cloudy. Low 50 to 55.

.Friday... Partly sunny. Showers or thunderstorms possible. High 70 to 75 but cooler near Lake Superior. Chance of rain 20%.

Normal High Temperature Today 72 degrees

Normal Low Temperature Today 50 degrees