Issued at 3:38 PM CDT, Friday, August 6th, 2010
Forecast Discussion for Northeast Minnesota and Northwest Wisconsin
Our area remains under the influence of high pressure (1016 mb) which was located in far Western Minnesota/Eastern Dakotas This Afternoon. Northwest winds up to 20 mph along with partly cloudy-sunny skies prevailed Today along with high temperatures in the lower to middle 70s. Moisture levels remain on the low side Today with Afternoon dewpoints only in the 40s and lower 50s with PWS of 0.50" across the North to 0.90" in far Southern areas.
Today's Upper Level Analysis:
A deep upper level trough (5460 meters) covered Central-Eastern Canada, the Upper Midwest and Great Lakes Today per water vapor satellite imagery with a northwest 500 mb flow occurring Today across the Upper Midwest on the southwest side of the cold upper low in Northeast Canada where 850 mb temperatures were as low as zero/+4 degrees C late Today per RUC model analysis. Upper level ridging (5880 meters) covered much of the Central-Southern U.S. as well as the Southern Rockies Today per RUC model analysis. An upper level trough was starting to develop over the Western U.S. Today with a plume of deep tropical moisture (monsoon moisture) streaming north through the Southwest U.S. and Rockies Today per water vapor satellite imagery. This moisture along with the upper trough out west will be players in our weather for the next several days.
High pressure will remain in control of our weather Tonight as it continues moving off toward the east out of Western Minnesota. Mostly clear skies with lows in the 40s and 50s can be expected Tonight with winds out of the north or west turning south and east Overnight, wind speeds will be under 15 mph. Note: A couple locations dipped into the lower 40s in Northern Minnesota Thursday Night with the cold spot being Grand Marais Minnesota where low temperatures bottomed out in the upper 30s earlier Today!
Saturday and Saturday Night:
Changes will take place during this period as our recent spell of pleasant temperatures and low humidity will be replaced by increasing amounts of mugginess and warm air.
High pressure pushes east of our area on Saturday allowing a southerly flow to develop. This will cause dewpoints to come up into the 50s and 60s during this period while PWS increase to between 1.00-1.50".
A warm front will develop over Southcentral Minnesota Saturday Morning before lifting north a bit Saturday Afternoon through Saturday Night. At this time it appears that this boundary will not make it much farther north then the Interstate 94 corridor in Central Minnesota.
A warm/moist advection regime could generate scattered showers and thunderstorms late Tonight over the Dakotas before spreading into Westcentral and possibly Southern Minnesota Saturday Morning before shifting into Central/Eastern Minnesota Saturday Afternoon. Thunderstorms associated with this activity should remain below severe levels.
Instability will begin to increase from southwest to northeast by Saturday Afternoon with CAPES expected to climb to between 1000-2000 j/kg...Highest in Southern parts of our area. Lifted Indices by Saturday Afternoon/Night will range from -1/-5 degrees C. Additional development of scattered showers and thunderstorms will likely take place across our local area late Saturday Afternoon into Saturday Night with a threat for locally heavy downpours thanks to the increasing amounts of moisture.
A risk for some severe weather also exists Saturday Afternoon and Saturday Evening...Especially south and southwest of a line from Walker Minnesota to Moose Lake Minnesota to Hayward Wisconsin...This would include the Counties of Cass, Crow Wing, Aitkin and Pine in Minnesota and Burnett, Washburn and Sawyer Counties in Wisconsin. Large hail and damaging winds will be the main threats along with dangerous lightning strikes.
Winds will be changing directions with height Tomorrow and Tomorrow Evening as we see S/SE surface winds go SW at 850 mb and NW at 500 mb, this could lead to a few rotating supercells especially near the warm front in Western/Central Minnesota, but the overall tornado threat appears low at this time as the low level jet will be rather weak, generally around 20 knots around our local area, with that said there could still be an isolated tornado risk late Saturday Afternoon/early Saturday Evening especially if thunderstorms remain discrete and not form into a line/s.
Partly-mostly cloudy skies will cover our local area Tomorrow and Tomorrow Night with highs in the 70s and 80s with lows in the 50s and 60s. Winds during this period will be out of the south or east around 20 mph or less.
The weather pattern from Sunday into the middle of next week will be characterized by a west or southwest flow aloft. A couple of disturbances embedded within this fast 500 mb flow will track north of a building dome of hot air to our south and those disturbances combined with a surface boundary across the Northern Plains and Upper Midwest will likely lead to periodic episodes of showers/thunderstorms around our local area from Sunday through Tuesday of next week. Plenty of moisture and instability should also be in place across our area at times during that aforementioned time frame which will also help in triggering those thunderstorms.
High temperatures for Sunday and Monday will be in the 70s and 80s, but it's not out of the question that a few locales could get into the 90s both days depending on the amount of sunshine that we see. Low temperatures Sunday Night and Monday Night will be in the 50s and 60s.
5 Day Forecast for Duluth/Superior
.Tonight... Mostly clear. Low 52 to 57. Wind northwest at 5 to 15 mph becoming east late.
.Saturday... Partly sunny. Afternoon showers or thunderstorms possible. High 75 to 80. Wind south to southeast at 10 to 20 mph. Chance of rain 20%.
.Saturday Night... Scattered showers or thunderstorms under mostly cloudy skies. Low 58 to 63. Wind southeast at 5 to 15 mph. Chance of rain 50%.
.Sunday... Humid. Partly sunny. Showers or thunderstorms possible. High 75 to 80. Chance of rain 20%.
.Sunday Night... Showers or thunderstorms possible. Partly cloudy. Low 58 to 63.
.Monday... Partly sunny. High 80 to 85.
.Monday Night... Partly to mostly cloudy. Low 60 to 65.
.Tuesday... Showers or thunderstorms possible. Partly sunny. High 78 to 83. Chance of rain 30%.
Normal High Temperature Today 76 degrees
Normal Low Temperature Today 55 degrees