Issued at 6:47 PM CDT, Saturday, July 10th, 2010
Forecast Discussion for Northeast Minnesota and Northwest Wisconsin
A cold front as of 6 PM CDT was moving into extreme Northwestern Minnesota. A southerly flow of warm, moist, and unstable air was found along and out ahead of this boundary Today. High temperatures were generally in the lower to middle 80s across our local area Today with late Afternoon dewpoints running in the upper 50s to middle 60s. PWS as of late Afternoon ranged from 1.00"-1.30" with 850 mb td's of +9/+14 degrees C. Winds Today were out of the south or southwest at 10-20 mph with a few higher gusts. As stated above, the atmosphere has been quite unstable across our local area Today with Afternoon CAPES anywhere from 1500-3000 j/kg! Lifted Indices ranged from -5/-8 degrees C along with Lapse Rates of 6.5-8.5 c/km per meso-analysis as of 6 PM CDT. A persistent warm advection pattern has been occurring in Minnesota since early This Morning and this has resulted in the development of a few showers and thunderstorms early This Morning over parts of Northern-Northeast Minnesota as well as over parts of Eastcentral Minnesota and Northwest Wisconsin. Locally heavy downpours and occasional lightning strikes were the main threats out of this activity from earlier Today with some locales receiving upwards of one quarter to one half inch of rainfall... Another small area of severe thunderstorms erupted late This Afternoon over Northwestern Wisconsin...Affecting the Counties of Bayfield and Ashland where a ping pong to golf ball size hail threat was possible, but there have been no reports of severe weather from those storms from late This Afternoon. Tornadic supercells exploded late This Afternoon and continued early This Evening over portions of Westcentral Minnesota, generally between the Fergus Falls/Alexandria/Morris areas, so far just 1 confirmed tornado Today (3 miles North of Hoffman, MN in Grant County) There have been numerous tornado warnings though across Westcentral Minnesota over the past 3 hours due to doppler radar picking up on strong rotation within these supercellular thunderstorms.
Note: Severe thunderstorms with a threat of golf ball size hail has recently spread into parts of Cass/Crow Wing Counties MN with cloud tops as high as 56, 000 feet per Duluth Doppler Radar!
This Evening's Upper Level Analysis:
West-northwest flow aloft was evident across the Upper Midwest late Today per water vapor satellite imagery. Several disturbances have been tracking E/SE through the Northern Plains and Upper Midwest Today while a larger upper level trough pushes south/east from Northern Alberta/Saskatchewan/Manitoba Provinces. Note: A very powerful upper level low currently spinning E/NE in the Gulf of Alaska and Southern Alaska per water late Afternoon water vapor satellite imagery could result in a rather significant severe weather event for some parts of the Upper Midwest around the middle of next week.
A cold front entering far Northwest Minnesota early This Evening will sag south-east and should reach Northcentral Minnesota by dawn. A southwest low level jet from 25-35 knots will be in place ahead of this boundary across Central Minnesota into Northwest Wisconsin Tonight. The atmosphere will remain unstable through the night with CAPES of 1000-2500 j/kg and Lifted Indices from -2/-6 degrees C.
Scattered showers and thunderstorms will be possible over all of Northern Minnesota and Northwest Wisconsin Tonight with an isolated risk for severe thunderstorms with large hail to 1.00" in diameter and damaging wind gusts to 60 mph being the main threats. Marginal winds aloft and limited shear should limit the overall severe threat in our local area Tonight, but winds are veering with height...S-SW near the surface, SW at 850 mb, and W-NW at 500 mb so some supercell type storms are possible through mid-Evening, generally in Southwest parts of our area...Including the Brainerd Lakes/Walker locales, hail up to the size of golf balls and an isolated tornado risk may occur in these areas until around 10 PM This Evening. 0-6 KM Bulk Shear and Effective Bulk Shear is generally around 30 knots in the Southwest part of our area early This Evening with 1 KM and 3 KM SRH around 150-250 m2/s2, this is favorable for more discrete thunderstorms into mid-Evening for Cass/Crow Wing Counties Minnesota.
The showers and thunderstorms Tonight could also contain heavy downpours along with dangerous lightning strikes!
Lows Tonight under partly-mostly cloudy skies will be in the 50s and 60s with winds out of the south, southwest, or north under 20 mph.
Sunday and Sunday Night:
A cold front will head south/east through Northeast-Eastcentral Minnesota Sunday Morning and will pass through Northwest Wisconsin Sunday Afternoon. Scattered showers or thunderstorms can be expected on Sunday in Northwest Wisconsin, Northeast Minnesota and Eastcentral Minnesota, but the severe threat looks low at this time due to the timing of the cold front coming through our area along with limited amounts of sunshine out ahead of this boundary. Heavy downpours and dangerous lightning strikes will be the bigger hazards from any thunderstorm on Sunday. Partly sunny-mostly cloudy skies are forecast on Sunday with highs mainly in the 70s, lows Sunday Night will be in the 40s and 50s as skies become partly cloudy with any threat for showers confined to the early Evening hours in Northwest Wisconsin. Winds Tomorrow will be out of the southwest or north at 10-20 mph. North winds at 10-20 mph will occur Tomorrow Night.
High pressure will result in pleasantly cool temperatures and low humidity across Northern Minnesota and Northwest Wisconsin for Monday and Monday Night, highs will be in the 60s and 70s with lows in the 40s and 50s. The area of high pressure will shift off to our east by Tuesday which will cause winds to become southerly, this will result in a warm/moist advection scenario setting back up across the Upper Midwest for Tuesday and Wednesday. Highs on Tuesday will be mainly in the 70s with lows Tuesday Night in the 50s and 60s.
The threat for showers and thunderstorms will return to Northern Minnesota and Northwest Wisconsin from Tuesday Night through Wednesday Night as a strong upper level low centers itself well to our northwest while low pressure heads E/NE out of the Western High Plains-Northern Plains. Winds aloft look very favorable at this time for a severe weather event on Wednesday with westerly winds at 500 mb of 50-65 knots while southerly or southeast winds will be found near the surface and at 850 mb. A low level jet could also increase to around 35 knots ahead of the low and cold front on Wednesday while a potent upper level jet >90 knots noses into the Upper Midwest by way of the Northern Plains.
The period from Tuesday Night into Wednesday Night certainly has potential of being an active one over portions of Minnesota with Wednesday and Wednesday Evening of particular interest, that's when we could see some tornadic supercells evolve if current model projections hold-up in coming days. It should be noted that there are differences between the models for the middle of next week so nothing is set in stone quite yet.
5 Day Forecast for Duluth/Superior
.Tonight... Humid. Partly to mostly cloudy. Scattered showers or thunderstorms possible. Low 60 to 65. Wind south to southwest at 10 to 20 mph. Chance of rain 40%.
.Sunday... Humid. Scattered showers or thunderstorms into early Afternoon. Mostly cloudy. High 70 to 75. Wind west to southwest at 10 to 15 mph becoming north by Afternoon. Chance of rain 40%.
.Sunday Night... Less humid. Decreasing cloudiness. Cooler. Low 51 to 56. Wind north at 10 to 20 mph.
.Monday... Cooler and less humid. Partly cloudy. High 70 to 75.
.Monday Night... Mostly clear. Low 50 to 55.
.Tuesday... Partly cloudy. High 70 to 75.
.Tuesday Night... Showers or thunderstorms possible. Partly to mostly cloudy. Low 55 to 60. Chance of rain 20%.
.Wednesday... Showers or thunderstorms possible. Partly sunny. High 70 to 75. Chance of rain 30%.
Normal High Temperature Tomorrow 76 degrees
Normal Low Temperature Tomorrow 54 degrees