Issued at 4:37 PM CDT, Saturday, April 30th, 2011
-Strong spring storm passing west-north of us thru Sunday
-Isolated thunderstorm risk This Evening
-Scattered snow showers possible late Tonight thru Sunday for Northern Minnesota?
-Next system set to arrive the mid to late part of next week
Forecast Discussion for Northeast Minnesota and Northwest Wisconsin
Powerful low pressure of 990mb was centered near Jamestown, North Dakota as of 4 PM. An occluded front attached to this low was pushing northeast out of Central Minnesota This Afternoon. A 45-65 knot low level jet, PWS nearing 1.00" combined with strong lift associated with the low and also because of a strong mid/upper level jet stream caused widespread rain in our area Today with some heavy downpours in some locations. Hasn't been much in the way of thunderstorm activity with this system due to the lack of instability and warm air, but a few lightning strikes were being detected in Eastern Minnesota and Northwest Wisconsin earlier This Afternoon. Highs Today were in the 40s with some 50s showing up in the Pine River and Brainerd, MN areas as a dry slot (partial clearing) lifts E-NE into Central Minnesota This Afternoon. Winds Today were out of the south, east, or west at 10-20 mph with a few higher gusts.
The same storm giving us rain Today is hammering parts of North Dakota with a spring blizzard. Winds of 50-70 mph combined with falling snow has resulted in blizzard conditions Today with I-94 closed west of Dickinson, ND to the Montana border. So far, 4.0" of snow had fallen at Bowman, North Dakota with 5.1" of snow at Williston, North Dakota per Bismarck NWS report.
Today's Upper Level Analysis:
Strong surface and upper level low in the Dakotas with 120-150 meter 12 hour H5 height falls was spreading northeast into the Upper Midwest late Today per water vapor satellite imagery and RUC model analysis. An 80 knot mid level jet streak and a 120 knot upper level jet streak were moving northeast from Eastern Nebraska and Western Iowa Today. Plenty of cold air was found on the back side of this storm in Northern and the Western half of North Dakota with temperatures only in the 20s This Afternoon while it was in the 70s from Southeast Iowa to near Chicago, Illinois. Late Afternoon 850mb temperatures ranged from -8 degrees C in Northwest North Dakota to +4 degrees C at Duluth, Minnesota to +10 degrees C at Chicago, Illinois.
Low pressure of around 991mb will reach Southwest Ontario Province Overnight. Steady rain in Northeast Minnesota and Northwest Wisconsin from southwest to northeast between 6-8PM This Evening. A dry slot surging north/east out ahead of the upper level low will cause the atmosphere to become slightly unstable through mid-Evening as some partial clearing takes place. CAPE values of 100-200 j/kg combined with lapse rates around 7.0 c/km and Lifted Indices nearing zero degrees C might be enough to trigger a few fast moving showers or thunderstorms This Evening in Northcentral through Eastcentral Minnesota and in parts of Northwest Wisconsin. None of these storms are expected to be severe, but brief gusty winds and possibly some small hail may accompany one or two of the more robust storms through mid-Evening. A strong push of cold air advection will sweep in from the west-southwest late Tonight as 850mb temperatures drop to between -4 and -8 degrees C Overnight. Lingering showers will occur after Midnight, and as colder air moves in and thickness values lower, the potential does exist for the rain showers to mix with and turn to snow showers and flurries mainly in the North half of Minnesota. Lows Tonight will be in the 30s with winds becoming southwest at 10-20 mph with gusts over 30 mph.
Sunday and Sunday Night:
Deep low pressure of 992-995mb will track into Central-Northern Ontario Province during this period. Unseasonably cold air will be found on the back side of this low with 850mb temperatures around -5 degrees C on Sunday, dropping to -8 to -12 degrees C Sunday Night. Highs Tomorrow will only be in the 30s and 40s which will be 15 to 20+ degrees below average for the 1st day of May. Lows Sunday Night will be in the 20s and 30s. Mostly cloudy skies are forecast Tomorrow with partly to mostly cloudy skies Sunday Night. A few showers of snow or rain are possible on Sunday with mainly dry weather for Sunday Night.
Note: Snowfall accumulations of up to 1" are possible late Tonight and Sunday in Northern Minnesota.
Monday and Tuesday, May 2nd and 3rd look dry at this time with highs on Monday in the 40s to around 50 degrees with highs for Tuesday in the 50s to lower 60s. Lows will be in the 20s and 30s Monday Night with 30s on tap for Tuesday Night. Wednesday through Friday, May 4th-6th could turn unsettled once again as a W-NW flow develops which will send some disturbances in our direction, there will also be a surface low and cold front moving across the Upper Midwest from mid to late week. Rounds of showers could develop from Wednesday through Friday with isolated Afternoon thunderstorms possible as well.
5 Day Forecast for Duluth/Superior
.Tonight... Turning windy. Partial clearing early. Becoming mostly cloudy by mid-Evening. A few showers and possibly a thunderstorm before 10 PM. A few showers possible Overnight. Low 30 to 35. Wind south at 10 to 15 mph, becoming southwest at 15 to 30 mph.
.Sunday... Windy and cool. Considerable cloudiness. A few rain showers possible which could mix with snow especially during the Morning. High 38 to 43. Wind west to southwest at 15 to 30 mph.
.Sunday Night... Variable cloudiness. Low 27 to 32. Wind west to northwest at 10 to 20 mph.
.Monday... Partly sunny. High 45 to 50.
.Monday Night... Partly cloudy. Low 29 to 32.
.Tuesday... Partly cloudy. High 55 to 60.
.Tuesday Night... Partly cloudy. Low 35 to 40.
.Wednesday... Mostly cloudy. Showers possible. High 52 to 57.
Normal temperatures for Today
Sunrise Tomorrow: 5:54 AM CDT
Sunset Tomorrow: 8:19 PM CDT