Monday, September 20, 2010

9/20/10: Monday's Weather Report

Issued at 4:54 PM CDT, Monday, September 20th, 2010

Low temperature report for Monday, September 20th, 2010. Source: NWS Duluth, Minnesota.

International Falls MN: 34 degrees

Ashland WI: 34 degrees

Silver Bay MN: 30 degrees

Grand Marais MN: 30 degrees

Ely MN: 30 degrees

Superior WI: 37 degrees

Embarrass MN: 28 degrees

3 miles east of Orr MN: 31 degrees

2 miles south of Tower MN: 33 degrees

Butternut WI: 35 degrees

Upson WI: 33 degrees

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

Quick changes are taking place across the Upper Midwest Today as a strong area of low pressure (1000 mb) which was centered in southern South Dakota at 4 PM heads northeast. A very strong warm front extends east of that low through the south half of Minnesota late Today and seperates 80 and 90 degree heat and 60+ degree dewpoints from southern Minnesota through parts of Iowa, Nebraska and South Dakota to temperatures in the 50s and dewpoints in the 40s and 50s across our local area Today. Widespread stratus clouds along with areas of haze/fog/drizzle have been occurring across our area Today as we sit north of that warm front. There is alot of warm air moving in aloft Today with 4 PM 850 mb temperatures of +10/+20 degrees C for areas south of the Iron Range while 700 mb temperatures late Today ranged from +10/+14 degrees C which is resulting in a very formidable cap which has prevented thunderstorms from breaking out Today, this despite increasing amounts of elevated CAPE This Afternoon. Winds Today were out of the southeast or east at 10-25 mph.

Today's Upper Level Analysis:

Southwest flow aloft has developed across the Upper Midwest Today per RUC model analysis with a potent low pressure system heading east out of the Northern Rockies and into the Northern Plains late This Afternoon.


Low pressure will continue on it's northeast track, reaching Western Ontario Province Overnight. A warm front currently over Southern Minnesota will surge N/NE This Evening on the nose of an impressive 40-65 knot southerly low level jet! A cold front will also head east and will move through northern Minnesota and northwest Wisconsin Tonight. Very strong warm and moist advection will continue This Evening ahead of this system with dewpoints in the 50s with some 60s moving into southern areas. PWS will remain in the 1.00-1.25" range with 850 mb td's of +8/+14 degrees C.

Lift associated with the low/fronts along with the low level jet combined with some forcing associated with a 90-110 knot upper level jet streak which will spread E/NE out of the Dakotas should be enough to overcome the strong cap that is in place. Scattered showers and thunderstorms will develop between 6-8 PM and will continue until around 1-3 AM. Plenty of CAPE (around 1000 j/kg) to support vigorous thunderstorm development will be in place through early Tuesday Morning with Lifted Indicies of -1/-5 degrees C. Around 40 knots of SHEAR will also be in place This Evening along with off the chart HELICITY values >500 m2/2! A few of the thunderstorms that develop could become severe during the mid to late Evening hours across our local area with the main threat coming in the form of large hail. Although a wind damage and isolated tornado threat may also develop especially in southern parts of our area, between 7 PM-11 PM Tonight.

Mostly cloudy skies will clear out somewhat Overnight. Areas of drizzle and fog will continue mainly through Midnight. Lows Tonight will be in the 40s and 50s with winds out of the southeast or east, shifting to the southwest at 10-25 mph.

Note: Rainfall totals for Tonight should generally be under one quarter inch, although any thunderstorm that develops will have the potential of producing locally heavier amounts.

Tuesday and Tuesday Night:

Low pressure will be tracking through central-eastern Ontario Province on Tuesday with high pressure building into the Upper Midwest. A few showers could linger Tomorrow Morning in Northwest Wisconsin, otherwise expect mainly dry conditions during this period. Highs Tomorrow will be in the 50s and 60s with lows Tomorrow Night in the 30s and 40s. Winds will be out of the west at 10-25 mph Tomorrow and under 20 mph Tomorrow Night.

Extended Forecast:

Dry weather should continue on Wednesday in Northern Minnesota and Northwest Wisconsin with high pressure still in control, highs will be in the 50s and 60s. High pressure moves off to our north/east by Wednesday Night as low pressure develops across the Rockies and Western High Plains. This system will head E/NE, likely passing just south of our local area during the Thursday-Thursday Night time period. Rain is forecast to develop and spread N/NE across the area Wednesday Night-early Thursday and will linger into Thursday Night before coming to an end. Some of the rain could be locally heavy, but where the heaviest axis of rain sets up is handled differently with the forecast models due to differing tracks this late week low may take. Lows Wednesday Night will be in the 40s to around 50 degrees with highs on Thursday nearly steady in the 40s and 50s. Lows Thursday Night will be mainly in the 40s.

5 Day Forecast for Duluth/Superior

.Tonight... Areas of haze, fog and light drizzle through Midnight. Scattered showers or thunderstorms developing after 8 PM, then ending Overnight. Mostly cloudy. Low 50 to 55. Wind east to southeast at 10 to 20 mph with a few higher gusts. Wind becoming southwest at 10 to 20 mph Overnight.

.Tuesday... Breezy. Variable cloudiness. High 62 to 67. Wind west at 15 to 25 mph.

.Tuesday Night... Partly cloudy. Low 38 to 43. Wind west at 10 to 15 mph.

.Wednesday... Partly cloudy. High 55 to 60.

.Wednesday Night... Increasing cloudiness. Rain possible toward dawn. Low 43 to 48. Chance of rain 30%.

.Thursday... Occasional rain. Isolated thunderstorms also possible. Mostly cloudy. High 50 to 55. Chance of rain 70%.

.Thursday Night... Occasional rain, tapering off late. Mostly cloudy. Low 40 to 45. Chance of rain 70%.

.Friday... Partly sunny. High 55 to 60.

Normal High Temperature Tomorrow 63 degrees

Normal Low Temperature Tomorrow 43 degrees