Monday, August 23, 2010

8/23/10: Monday's Weather Report

Issued at 3:13 PM CDT, Monday, August 23rd, 2010

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

A well defined cold front was marching east through the Dakotas and was entering the extreme Western part of Minnesota as of mid-Afternoon. Very warm, humid and windy conditions were found ahead of this boundary Today with much cooler, breezy and less humid conditions in wake of the frontal passage. High temperatures were in the middle 80s to lower 90s in our local area Today with cooler 60s and 70s from Superior and Downtown Duluth and along the North Shore of Lake Superior. Dewpoints Today were generally in the 60s to around 70 degrees. Winds Today were out of the south at 10-25 mph with occasional higher gusts. Very strong winds occurred for a time earlier This Afternoon in Northwestern Minnesota with wind gusts >40 mph! An area of showers were found near the cold front This Afternoon from Northwest Minnesota back through the Eastern Dakotas with movement toward the north/east, strong to severe thunderstorms have been erupting Today across parts of Southern-Eastern Manitoba Province Canada, near the better dynamics of this system.

Today's Upper Level Analysis:

An upper level trough covered the Northeast U.S. per water vapor satellite imagery with an upper level ridge in place from the Great Lakes through the Mid-Mississippi Valley/Southern Plains region. A vigorous upper level trough with 60-90 meter 12 hour 500 mb height falls was moving east across the Northern Plains This Afternoon with a southwest flow aloft in place over the Upper Midwest out ahead of this H5 trough.


A cold front will continue to move east and is forecast to pass through Northern/Eastern Minnesota between 8 PM-1 AM, and will move through Northwest Wisconsin Overnight. Weak instability consisting of CAPES around 100 j/kg and Lifted Indices around zero degrees C combined with a layer of warm air aloft (H7 temps around +12 degrees C) should result in only isolated thunderstorm development around our area Tonight as this cold front moves through. There is quite a bit of upper level support, however, with this system with a mid level jet >70 knots across the Northern Plains This Afternoon along with an upper level jet >100 knots which will spread toward the Red River Valley of Minnesota during the night. Lift associated with the cold front and also on the east side of these wind maxes should cause a rather large, but fairly quick moving area of rain showers across most of our area Tonight with precipitation lifting northeast as it spreads east with the front. Rainfall totals should generally remain under one quarter inch Tonight, but a few heavier showers could drop around one half inch of rain by dawn. Lows Tonight under partly-mostly cloudy skies will be in the 50s and 60s with winds out of the south, turning southwest to west at 10-20 mph.

Tuesday and Tuesday Night:

Drier and cooler air will advect south/east across our area during this period as deep low pressure around 993 mb centers itself well to our northwest while the cold front exits off to our east early Tuesday Morning. 850 mb temperatures which were around +20 degrees C in our area This Afternoon will drop to between +8/+12 degrees C on Tuesday. High temperatures Tomorrow will be in the 60s and 70s with much lower humidity levels as well. Lows Tomorrow Night will be in the 40s and 50s. Southwest or west winds will be quite breezy with wind speeds of 15-30 mph on Tuesday, decreasing to 10-20 mph Tuesday Night.

Extended Forecast:

A relatively quiet weather pattern (more typical for late August) is forecast from mid to late week as high pressure drops southeast through the Northern/Central Plains around mid-week, this high will shift off to our southeast late this week with increasing southerly winds overspreading Minnesota from Friday into the weekend. A warm-up and a gradual increase in moisture will occur over the Upper Midwest from Friday onward as the 500 mb pattern transitions from a northwest flow at mid-week to a southwest flow by this weekend and early next week.

The latest model guidance indicates that a cold front will become stationary, generally in a west-east-northeast fashion from the Northern Plains toward Northern Minnesota or Southern Canada from this weekend into early next week. This boundary combined with the increase in moisture and instability should cause scattered showers/thunderstorms at times, especially by Sunday or Monday the way it looks now. This boundary is expected to settle southeast as a cold front sometime the early to middle part of next week with shower/thunderstorm chances continuing until about Wednesday or until this boundary clears our area.

High temperatures will be in the 60s and 70s Wednesday and Thursday with lows in the 40s and 50s both nights, but some 30s are possible Wednesday Night in the typical cold spots.

5 Day Forecast for Duluth/Superior

.Tonight... Partly to mostly cloudy with occasional showers developing between 10 PM-Midnight. Isolated thunderstorms also possible. Low 60 to 65. Wind south to southeast at 10 to 20 mph, becoming west at 10 to 20 mph late. Chance of rain 70%.

.Tuesday... Breezy, cooler and less humid. Partly cloudy. High 70 to 75. Wind west at 15 to 30 mph.

.Tuesday Night... Mostly clear. Low 48 to 53. Wind west to northwest at 10 to 20 mph.

.Wednesday... Mostly sunny. High 68 to 73.

.Wednesday Night... Mostly clear. Low 45 to 50.

.Thursday... Mostly sunny. High 70 to 75.

.Thursday Night... Mostly clear. Low 50 to 55.

.Friday... Mostly sunny. High 73 to 78.

Normal High Temperature Today 73 degrees

Normal Low Temperature Today 52 degrees