Issued at 4:13 PM CDT, Monday, June 6th, 2011
-Warm and muggy away from Lake Superior into Tuesday Evening
-Excessive heat warnings/advisories in effect thru Tuesday Night for portions of Southern Minnesota
-Shower and thunderstorm threat lingers into early Wednesday
-Severe weather potential into Tuesday Evening
-Much cooler weather arrives after Wednesday
Forecast Discussion for Northeast Minnesota and Northwest Wisconsin
A weak frontal boundary was draped from Northcentral Minnesota to Northcentral Wisconsin late This Afternoon while a warm front remained over Southern Minnesota. Very warm temperatures covered almost all of our area Today with highs in the 80s with a few locales nearing 90 degrees from the Brainerd Lakes to Hayward Lakes areas. Cooler 50s and lower 60s were found in Downtown Duluth and Superior due to a stubborn lake breeze Today. Dewpoints are somewhat uncomfortable away from Lake Superior with widespread 50s and 60s. Winds Today were variable or east in direction under 15 mph. Skies were mostly sunny Today but isolated showers and thunderstorms have erupted along the lake breeze front in Northwest Wisconsin, one storm blew up about a half hour ago in Southern Ashland county WI. There is plenty of instability in the air Today per latest meso-analysis with CAPE of 1000-3500 j/kg, highest in southern areas. Lifted Indices ranged from -3 to -8 degrees C with Lapse Rates >6.0 c/km.
Today's Upper Level Analysis:
Westerly 500mb flow was in place across the Upper Midwest while a massive upper level ridge covered the Central-Southern Plains, Ohio Valley, Central-Southern Great Lakes, and portions of the Upper Midwest Today per RUC model analysis. 850mb temperatures underneath this ridge were in the +20 to +34 degree C range late Today with surface temperatures of 90-100 degrees from South Dakota through the Southern halves of Minnesota and Wisconsin, down through the Central-Southern U.S. The strong storm which was west of California the past two days has moved onshore Today and was pushing east across Nevada.
Weak boundary in Southern parts of our area late This Afternoon will continue to dissipate Tonight while the warm front in Southern Minnesota becomes the main front during the night. Scattered showers and thunderstorms are possible in Northern Minnesota and Northwest Wisconsin Tonight due to the fronts nearby and plenty of instability with CAPE values of 1000-2500 j/kg with Lifted Indicies of -2 to -6 degrees C. A layer of warm air aloft or cap with 700mb temperatures around +10 degrees C could hinder thunderstorm development, however, but if a storm can get going it has the potential of turning severe with favorable wind shear in place north of the warm front. Large hail and damaging winds would be the main threats along with dangerous lightning and heavy downpours. Partly to mostly cloudy skies are expected Tonight with lows in the 50s and 60s with a few 40s near the head of Lake Superior. Winds will be out of the south or east under 15 mph.
Tuesday and Tuesday Night:
Low pressure of 992-998mb will move from the Northern Plains toward Northern Minnesota during this period. A warm front attached to this low will head north and is forecast to move into Northern-Northeast Minnesota by late Tuesday Afternoon before a cold front moves east and through most of our area Tuesday Night. Instability and shear will be very high along and north of the warm front through Tuesday Evening, but a very strong cap will be present with 850mb temperatures of +22 to +26 degrees C along with 700mb temperatures around +12 degrees C. It's uncertain whether or not surface based thunderstorms will be able to develop due to the incredible amounts of warm air aloft, but if a thunderstorm can bust through this cap then there will be a threat for isolated tornadoes from 4-10 PM Tuesday, especially along and north of Highway 2 in Minnesota. 1KM Helicity will range from 150m2/s2 to 350m2/s2 in Northcentral and Northeast Minnesota Tuesday Afternoon-Evening with 0-6 KM Shear and Effective Bulk Shear of 35-50 knots. Mid level winds from the southwest will approach 45 knots while upper level winds increase to around 60 knots by early Evening. The potential also exists for large hail and damaging winds if severe thunderstorms can develop Tomorrow and Tomorrow Evening.
Partly to mostly cloudy skies are forecast during this period with highs Tomorrow in the 70s and 80s with a few 90s possible from Brainerd east to Hayward. Cooler 50s will be found near the head of Lake Superior. Lows Tomorrow Night will be in the 50s and 60s. Winds on Tuesday will be out of the south or east at 10-25 mph with winds Tuesday Night from the north, east, or southwest under 20 mph.
Low pressure and cold front will exit to our east on Wednesday with less humid and cooler weather to follow. Looks dry from Wednesday into Friday, June 8th-10th. High temperatures on Wednesday will be in the 60s and 70s with a few 80s possible in Northwest Wisconsin. Lows Wednesday Night will be in the 40s to around 50 degrees. Highs Thursday will only be in the 50s to lower 60s with lows Thursday Night in the 30s and 40s.
5 DAY FORECAST FOR DULUTH/SUPERIOR
.Tonight... Partly cloudy. Showers or thunderstorms possible late. Low 50 to 55 with 40s closer to Lake Superior. Wind east to southeast at 5 to 15 mph. Chance of rain 30%.
.Tuesday... Breezy. Considerable cloudiness. Showers or thunderstorms possible. High 68 to 73 with 50s near Lake Superior. Wind east to southeast at 15 to 25 mph. Chance of rain 30%.
.Tuesday Night... Showers or thunderstorms possible mainly during the Evening. Partly to mostly cloudy. Low 50 to 55. Wind southeast, becoming southwest at 10 to 20 mph. Chance of rain 30%.
.Wednesday... Partly sunny. High 70 to 75.
.Wednesday Night... Partly cloudy. Low 40 to 45.
.Thursday... Partly cloudy. High 57 to 62.
.Thursday Night... Partly cloudy. Low 40 to 45.
.Friday... Partly cloudy. High 57 to 62.
Normal temperatures for Today
High: 69 degrees
Low: 46 degrees
Tuesday's Pollen Forecast:
Sunrise Tomorrow: 5:15 AM CDT
Sunset Tomorrow: 9:00 PM CDT