Friday, May 21, 2010

5/21/10: Friday's Weather Report

Issued at 3:27 PM CDT, Friday, May 21st, 2010

Note: Today, May 21st, 2010 marks the 7th day in a row with a high temperature of at least 70 degrees at Duluth, Minnesota. We are now tied with the year's 1988 and 1973 for 2nd place with 7 consecutive days with high temperatures of at least 70 degrees for the month of May. The record is 9 straight days which occurred in May 1977.

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

Moisture has increased somewhat Today compared to recent days as dewpoints have risen into the mid 40s to lower 50s except in far Northeast Minnesota where Afternoon dewpoints were in the middle to upper 30s. PWS have climbed to between 1.00"-1.10" across almost all of Northwest Wisconsin back through Eastcentral Minnesota. Partly sunny to mostly cloudy skies covered our local area Today with high temperatures in the lower to middle 70s from Brainerd to the Iron Range on north to International Falls, elsewhere highs were in the 60s Today with 50s closer to Lake Superior. 850 mb temperatures as of 3 PM ranged from +9/+14 degrees C, warmest northern areas and coolest in the south. Winds Today were very light, generally under 12 mph and variable in direction. Surface map late Today featured a few areas of low pressure 1000-1008 mb centered in the Central-Southern Rockies. A cold front was centered over the Central Dakotas. Low pressure of 998 mb was centered in Central Alberta Province Canada. Low pressure 1010 mb was centered in Westcentral Illinois.

Today's 500 mb analysis:

Southwest flow aloft was overspreading the Western U.S. and Northern Plains Today as the upper level pattern begins to change. A fairly vigorous disturbance continued to lift E/NE across Illinois and Indiana Today with troughing extending northwest/north of this system into the Upper Midwest and Great Lakes Today per water vapor satellite imagery. A cold upper level trough covered the Pacific Northwest for the 2nd day in a row with 500 mb temperatures as low as -30 degrees C in portions of Oregon and Washington This Afternoon per RUC model analysis. Winds aloft were increasing Today (90-120 knots) on the south/southeast side of the Pacific Northwest upper level low from Central California to Western Wyoming.

Tonight:

Partly to mostly cloudy skies will cover our area with the disturbance over Western Illinois continuing to track off toward the E/NE Tonight, some moisture lifting northwest/north of that feature will continue to cause a few light rain showers This Evening, mainly in parts of Northwest Wisconsin back through Eastcentral Minnesota, none of this rain is expected to be heavy with only trace amounts of precipitation expected. Lows Tonight will be in the 40s and 50s for most areas with variable winds under 12 mph.

Saturday and Saturday Night:

Low pressure will be centered well to our west during this period while a warm front begins to lift northeast out of the Northern Plains into the Upper Midwest. Southerly winds will develop ahead of this system on Saturday which will transport higher amounts of moisture north into our area. Dewpoints will climb into the 50s and lower 60s for areas away from Lake Superior during this period with PWS averaging 1.00"-1.25". Partly sunny to mostly cloudy skies are forecast on Saturday with partly-mostly cloudy skies for Saturday Night. A few showers or thunderstorms could develop, especially Tomorrow Night in Western-Northwest areas, but no severe weather is expected at this time. Highs Tomorrow will be in the 60s and 70s but it will be cooler near Lake Superior. Lows Tomorrow Night will be in the 50s to around 60 degrees but it will be cooler near Lake Superior. Winds during this period will be out of the south or east at 10-20 mph.

Extended Forecast:

The basic pattern from Sunday through at least the middle of next week will be for a southwest flow aloft to cover the Upper Midwest while an upper level trough remains in place in the Western U.S.

A cold front will head east into Minnesota on Sunday but will weaken as it does so. A fairly strong cap is forecast to be in place along and ahead of this boundary on Sunday with 700 mb temperatures of +8/+12 degrees C with 850 mb temperatures warming to between +14/+20 degrees C. The models do show some cooling taking place in the atmosphere by Sunday Afternoon and that combined with some convergence near the cold front may result in the development of a few showers and thunderstorms across our area Sunday Afternoon-Evening.

Plenty of instability is forecast to be in place around our area Sunday Afternoon with CAPES of 1500-3000 j/kg with Lifted Indices from -3/-6 degrees C. A muggy airmass will also be in place with widespread dewpoints in the 60s with PWS averaging 1.00"-1.50" with H85 td's from +12/+16 degrees C!

There will be some shear in place, although it could be better...Generally around 30 knots of 0-6 KM and Effective Bulk Shear is forecast over our area per SREF model, winds aloft will be out of the SW, generally less than 40 knots, while the low level jet isn't ideal either with speeds at or less than 30 knots, but these numbers when combined with the amount of instability that is forecast to be in place should be enough to cause a few severe thunderstorms Sunday Afternoon and Evening.

At this time it appears that Eastcentral Minnesota and portions of Northwest Wisconsin would have the best chance at seeing a few storms and possibly some severe weather late this weekend. Areas along and east of a Hibbing to Aitkin Minnesota line and west of a Bayfield to Shell Lake line in Wisconsin would be most at risk for isolated severe thunderstorms capable of producing damaging winds >58 mph and large hail up to 1" in diameter. Sunday Afternoon and Evening would be when any severe weather would occur the way it looks now.

High temperatures on Sunday will be in the 70s and 80s across Northern Minnesota and Northwest Wisconsin with lows Sunday Night in the 50s and lower 60s.

The weakening cold front that will pass through our area late this weekend will turn into a warm front on Monday. This boundary will head north and through our local area Monday Night, then will see a new cold front settle south/east out of the Northern Plains the early to mid part of next week.

The air will remain warm, moist, and unstable across the Upper Midwest from Monday-Wednesday of next week with additional chances for a few showers/thunderstorms at times. High temperatures on Monday will be in the 70s and 80s with lows Monday Night in the 50s and lower 60s.

5 Day Forecast for Duluth/Superior

.Tonight... Mostly cloudy. Sprinkles possible before 8 PM. Low 45 to 50. Wind variable under 12 mph.

.Saturday... Partly sunny. High 65 to 70 but cooler near Lake Superior. Wind east at 10 to 20 mph.

.Saturday Night... Partly to mostly cloudy. Low 50 to 55. Wind southeast at 10 to 15 mph.

.Sunday... Humid. Variable cloudiness. Showers or thunderstorms possible, mainly during the Afternoon. High 75 to 80. Chance of rain 20%.

.Sunday Night... Showers or thunderstorms possible. Variable cloudiness. Low 52 to 57. Chance of rain 20%.

.Monday... Partly sunny. Showers or thunderstorms possible. High 73 to 78 but cooler near Lake Superior. Chance of rain 20%.

.Monday Night... Partly cloudy. Showers or thunderstorms possible. Low 55 to 60. Chance of rain 20%.

.Tuesday... Partly sunny. Showers or thunderstorms possible. High 73 to 78. Chance of rain 20%.

Normal High Temperature Today 65 degrees

Normal Low Temperature Today 42 degrees

Tim