Issued at 3:06 PM CDT, Monday, June 14th, 2010
Forecast Discussion for Northeast Minnesota and Northwest Wisconsin
Some partial sunshine was found at times across Northern Minnesota Today which led to the build-up of some marginal Afternoon instability leading to the development of a small area of showers and possibly an isolated thunderstorm with locally heavy downpours over parts of Southern Itasca County MN, mainly near the Grand Rapids, Deer River, Marble, and Coleraine areas...This batch of showers was heading west-northwest. A larger area of light to moderate rain was moving northeast through most of Northwest Wisconsin and Eastern Minnesota This Afternoon with rainfall estimates per doppler radar anywhere from 0.10"-0.40". Areas outside of Northern Minnesota saw mostly cloudy skies Today with areas of fog near Lake Superior as winds shifted back to an easterly direction Today. High temperatures Today were generally in the lower to middle 60s with a few lower 70s in Western-Northwest areas while 50s were found near Lake Superior. 850 mb temperatures as of 2 PM were in the +9/+10 degree C range. Winds Today were out of the northeast or east at 5-15 mph with higher gusts near Lake Superior. Surface map as of mid-Afternoon featured high pressure of 1021 mb centered just northwest of Lake Superior. A stationary front extended from Southern Iowa to Central Illinois with low pressure of 1012 mb centered in Southwestern Iowa.
Today's 500 mb analysis:
An upper level low (570 meters) was dropping south/east across the Dakotas Today per water vapor satellite imagery and RUC model analysis. A southwest flow aloft was in place across the Upper Midwest Today out ahead of this upper low. An upper level ridge (588 meters) continued to cover the Southern-Eastern U.S. Today per RUC model analysis while a potent upper level low/trough dig S/SE across Western Canada, toward the Pacific Northwest This Afternoon per water vapor satellite imagery. 90-130 knot jet stretched from Eastern Ontario/Southern Quebec Province through the Northeast U.S. Today with two other areas of strong upper level winds (80-90 knots) covering portions of the Northern Plains/Upper Midwest and over Western Canada per RUC model analysis.
The area of light-moderate rain across Northwest Wisconsin and far Eastern Minnesota late This Afternoon will move out of those areas from west to east before 7 PM. The small area of heavy showers and possibly an isolated thunderstorm tracking W/NW through Southern-Central Itasca County MN late Today will continue on it's W/NW track through 6 PM. Other isolated showers may form in Northern Minnesota This Evening while some additional areas of rain develop during the night across our local area. Mostly cloudy skies with areas of fog can be expected Tonight with lows in the 40s and 50s. Winds will be out of the north or east at 5-15 mph with higher gusts near Lake Superior.
Tuesday and Tuesday Night:
Upper level low analyzed over the Central-Western Dakotas This Afternoon will head east-southeast, passing through the Upper Midwest on Tuesday before exiting off to our east by Tuesday Night. Occasional rain will occur across all of Northern Minnesota and Northwest Wisconsin Tomorrow into Tomorrow Evening as this system moves through. Locally heavy downpours are possible thanks to PWS up to 1.00"-1.25" and 850 mb td's around +8 degrees C. Isolated thunderstorms could also develop from time to time, but severe weather is not expected. Mostly cloudy skies are forecast Tomorrow and Tomorrow Night with areas of fog, mainly near Lake Superior. Highs Tomorrow will be in the 50s and 60s with lows Tomorrow Night in the 40s and 50s. Winds on Tuesday will be out of the south, north, or east at 5-15 mph with stronger gusts near Lake Superior. Winds Tomorrow Night will be out of the north, west, or east under 15 mph.
Rainfall totals from Tonight through Tuesday Evening:
Anywhere from 0.10"-0.25" of rain is expected to fall across our area, but there will be pockets of heavier amounts ranging from 0.50" to 1.00".
Wednesday and Wednesday Night look dry across all of Northern Minnesota and Northwest Wisconsin as the upper low from Tuesday departs to our east making way for a brief ridge of high pressure which will pass through the Upper Midwest on Wednesday. This high pressure ridge exits to our east on Thursday which will set-up a return flow from the south. Moisture will be on the increase across our area from Thursday into Friday Morning with dewpoints expected to reach the 60s, possibly the lower 70s away from Lake Superior with 850 mb td's climbing toward +14/+18 degrees C with PWS of 1.25"-1.75" by Thursday Afternoon-Overnight.
A strong area of low pressure averaging 994 mb is forecast to track NE through the Northern Rockies/Northern Plains into Southern Manitoba Province, then across Central Ontario Province from Thursday into Friday. A warm front attached to this low is expected to lift N/NE into our local area late Thursday Afternoon through Thursday Night while a cold front surges east through our local area late Thursday Night into Friday Morning. Note: There continues to be some timing differences between the forecast models Today with the GFS the quicker solution compared to most of the other models.
...CONCERNING THE SEVERE RISK...
Strong instability is forecast to develop over the majority of our local area from Thursday Afternoon into Thursday Night with the NAM and GFS models from Today indicating CAPES anywhere from 1000-3500 j/kg while Lifted Indices drop to between -3/-7 degrees C. A layer of warm air aloft is also expected to advect NE into our area Thursday Afternoon as 700 mb temperatures warm to around +10 degrees C. Scattered showers or thunderstorms...possibly as a complex could develop on the nose of the cap Thursday Morning while tracking E/SE through the Southwest-Southern portions of our local area. Thunderstorms if they develop Thursday Morning should stay below severe levels the way it looks now.
The main show could then develop late Thursday Afternoon into Thursday Night, but this will be dependent on how soon the cap can erode (if one develops) and also on the timing of the key features, being the warm front, cold front, and the strong VORT (disturbance) which will push E/NE through the Dakotas.
It does appear that there will be at least a narrow window of opportunity where a few supercells and possible tornadoes could develop (6PM-10PM Thursday), mainly affecting the Southwest portion of our area, near Brainerd/Fort Ripley/Pine Center MN...And then on to the south toward the Interstate 94 corridor in Central Minnesota. The 12z NAM from Today as well as the 09z SREF model from earlier Today indicate favorable parameters in place for possible severe weather and tornadoes in those areas with 30-40 knots of 6KM and Effective Bulk Shear...Helicities around 200 m2/s2. A low level jet from the S/SE upwards of 35 knots while 500 mb winds veer more southwesterly between 25-45 knots depending on the model. An upper level jet of 70-80 knots is also expected to be in place across the Western High Plains/Northern Plains region by late Thursday. Note: The 09z SREF model has a tornado parameter of 2-4 late Thursday Afternoon in parts of Central-Eastern Minnesota which is very high considering it's still a few days away.
A risk for scattered showers and thunderstorms with at least an isolated severe weather potential will continue late Thursday Night into Friday Morning across the entire area as this system moves through. Large hail and damaging winds would be the main risks from any severe weather late Thursday Night.
High temperatures on Thursday will be in the 60s and 70s, but 80s are possible in Western-Southern areas. Lows Thursday Night will be in the 50s and 60s.
Stay tuned in coming days for any possible changes concerning the Thursday/Thursday Night risk for severe weather.
5 Day Forecast for Duluth/Superior
.Tonight... Breezy with areas of fog and drizzle. Occasional showers. Overcast. Low 48 to 53. Wind east at 10 to 20 mph. Chance of rain 60%.
.Tuesday... Areas of fog and drizzle. Mostly cloudy with occasional rain. High 56 to 61. Wind east at 10 to 20 mph. Chance of rain 70%.
.Tuesday Night... Showers during the Evening...Otherwise mostly cloudy with areas of fog. Low 48 to 53. Wind northeast at 5 to 15 mph. Chance of rain 50%.
.Wednesday... Partly sunny. High 68 to 73.
.Wednesday Night... Partly cloudy. Low 50 to 55.
.Thursday... Showers or thunderstorms possible. Partly sunny. High 67 to 72 but cooler near Lake Superior. Chance of rain 30%.
.Thursday Night... Showers or thunderstorms possible. Variable cloudiness. Low 50 to 55. Chance of rain 30%.
.Friday... Warmer. Showers or thunderstorms possible early. Partly to mostly sunny. High 75 to 80. Chance of rain 20%.
Normal High Temperature Today 71 degrees
Normal Low Temperature Today 48 degrees