Tuesday, August 17, 2010

8/17/10: Tuesday's Weather Report

Issued at 3:10 PM CDT, Tuesday, August 17th, 2010

Weather Tibits:

*August 15th and 16th, 2010 featured back to back days with high temperatures in the 60s at Duluth, Minnesota. The last time this happened was back on June 15th-16th, 2010.

Low temperature report across Northern Minnesota and Northwest Wisconsin from Tuesday, August 17th, 2010. Source: NWS Duluth, Minnesota.

International Falls MN: 41 degrees

Hibbing MN: 38 degrees

Two Harbors MN: 43 degrees

Orr MN: 39 degrees

Bigfork MN: 39 degrees

Longville MN: 39 degrees

Hayward WI: 41 degrees

Cass Lake MN: 40 degrees

Northome MN: 40 degrees

Embarrass MN: 40 degrees

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

High pressure of 1020 mb has moved into Eastern Iowa as of mid-Afternoon with a southerly flow now occurring on the backside of this high in Minnesota which is beginning to transport 55-65 degree dewpoints which were located in Western-Southern Minnesota, Southeast South Dakota, Nebraska and Iowa slowly toward the north. Partly-mostly sunny skies were found across our area Today with high temperatures in the middle-upper 60s along and north of the Iron Range with lower to mid 70s for the remainder of our local area. Winds Today shifted to the southwest at 10-20 mph.

Today's Upper Level Analysis:

A fast flow from the west-northwest was in place across the Northern Rockies, Northern Plains, Upper Midwest and adjacent portions of Central/Western Canada per water vapor satellite imagery and RUC model analysis. One branch of strong winds aloft (100 knots or greater) was centered to our northwest Today with another corridor of strong winds aloft >100 knots covering the Eastern Great Lakes/Northeast U.S. Another highlight of this developing weather pattern is a tightning baroclinic zone (temperature gradient) with 850 mb temperatures Today per RUC model analysis ranging from +2/+4 degrees C across Central Canada to +14/+20 degrees C from Western Minnesota back through the Dakotas. Surface temperatures ranged from the 50s across parts of Ontario/Manitoba Province to the middle 80s across the Central-Western Dakotas.


A strong warm advection pattern will develop across Northern Minnesota and Northwest Wisconsin Tonight as a southwest low level jet increases to between 30-55 knots during the night. Meanwhile a cold front which was centered in Northwest North Dakota This Afternoon will be heading southeast and should reach Northern areas of Minnesota by dawn. The strong low level jet, warm advection and increasing amounts of moisture combined with the forcing associated with the approaching cold front should result in the development of scattered showers or thunderstorms Tonight, mainly west of a line from Grand Marais Minnesota to Siren Wisconsin. The showers and thunderstorms will move east or east-southeast Tonight so Northwest-Western parts of our area will see the precip first, with areas from the Arrowhead down through the Twin Ports and into far Northwest Wisconsin seeing possible rain during the Overnight hours.

Instability will be on the rise Tonight, especially in terms of elevated CAPE (1000 j/kg or less) with Lifted Indices from zero/-3 degrees C. Around 30-40 knots of SHEAR combined with the strong low level jet/strong warm advection pattern will promote an isolated risk for strong-severe thunderstorms Tonight generally west-northwest of a line from McGrath to Ely Minnesota. Hail and high winds will be the main threats from stronger storms Tonight along with locally heavy downpours and dangerous lightning strikes.

Partly-mostly cloudy skies will be found across our area Tonight with lows in the 50s to lower 60s. Winds will be out of the south, southwest or north around 20 mph or less.

Wednesday and Wednesday Night:

A cold front will sag toward the south during this period. The front should be over Northern Minnesota Tomorrow Morning, reaching the Twin Ports during the late Morning/early Afternoon, then continue sagging south, reaching the Lake Mille Lacs/Hayward Lakes area by mid or late Afternoon Tomorrow. Scattered showers and thunderstorms will occur near this boundary Tomorrow and Tomorrow Night along with partly-mostly cloudy skies.

The greatest potential for severe weather Wednesday and Wednesday Evening will be along and south of a line from Leader to Hinckley Minnesota to Danbury to Winter Wisconsin. In this corridor, CAPES are forecast to climb to around 1000 j/kg with Lifted Indices from -1/-3 degrees C. SHEAR of 30-45 knots along with fast mid level winds from the west around 40-50 knots will combine with southwest winds near the surface and at 850 mb to cause a severe weather threat with large hail and damaging winds being the main threats. Areas at risk include Southern Cass, Crow Wing, Southern Aitkin and Pine Counties in Minnesota, and Burnett, Washburn and Sawyer Counties in Northwest Wisconsin.

A threat for some thunderstorms also exist farther north toward Duluth, Hill City, Grand Rapids and in far Northwest Wisconsin Tomorrow but the storm threat in this area would be north of the southward moving boundary, thus any thunderstorm that were to develop in this environment would be in the cooler air and be elevated in nature, thus the threat for severe weather seems relatively low compared to areas farther south.

High temperatures Tomorrow will be in the 60s and 70s with a wide range in dewpoints from the 40s in far Northern Minnesota to the 60s farther south. Lows Tomorrow Night will range from the 40s across Northern Minnesota to the 50s and 60s elsewhere.

Winds will be out of the southwest, north or east around 20 mph or less Tomorrow and Tomorrow Night.

Extended Forecast:

A cold front will become stationary over Southern Minnesota on Thursday as an area of high pressure passes by to our north/east. The cold front in Southern Minnesota will turn into a warm front as it moves E/NE Thursday Night and Friday, the boundary will lift slightly to the north in response to a rather potent upper level disturbance/surface low pressure which will move from the Northern Plains to the Upper Midwest later this week. The forecast models differ a bit on where the axis of heavier rainfall will setup for Thursday Night and Friday, but right now it appears to be favoring portions of Northwest Wisconsin through Eastcentral/Southern Minnesota with some showers also possible Thursday Night and Friday across Northern-Northeast Minnesota. The chance for severe weather looks minimal around our area later this week, but scattered non-severe thunderstorms are a possibility in parts of our area for Thursday Night and Friday.

This weekend looks mainly dry at the moment as an upper level ridge builds north into the Upper Midwest.

High temperatures will be in the 60s and 70s Thursday and Friday with lows generally in the 50s both nights.

5 Day Forecast for Duluth/Superior

.Tonight... Partly cloudy with skies becoming mostly cloudy late. Scattered showers or thunderstorms possible Overnight. Low 55 to 60. Wind southwest at 10 to 20 mph. Chance of rain 50%.

.Wednesday... Scattered showers or thunderstorms. Considerable cloudiness. High 67 to 72. Wind variable at 5 to 15 mph. Chance of rain 40%.

.Wednesday Night... Partly to mostly cloudy. A few showers possible early. Low 50 to 55. Wind north at 5 to 15 mph. Chance of rain 30%.

.Thursday... Partly sunny. High 68 to 73.

.Thursday Night... Mostly cloudy. Showers possible. Low 50 to 55. Chance of rain 20%.

.Friday... Mostly cloudy. Showers possible. High 65 to 70. Chance of rain 20%.

.Friday Night... Mostly cloudy. Low 50 to 55.

.Saturday... Partly sunny. High 70 to 75.

Normal High Temperature Today 74 degrees

Normal Low Temperature Today 54 degrees