Tuesday, May 5, 2009

Severe risk shifts east of metro area

(Update: 7:12 pm) Line of light to moderate showers moving through the metro area. Stronger cells near Hastings - potential for a few isolated severe storms still exists east of St. Paul, in the relatively warm, humid, unstable air. Best chance for warnings: western Wisconsin through the evening hours).

(Update: 6:45 pm) Line of storms entering the metro area is weakening rapidly. A few isolated strong/severe storms may still develop south/east of St. Paul, but most Twin Cities suburbs will experience 30-40 minutes of rain, wind gusts to 35-40 mph. The risk of large hail and violent winds has diminished substantially in the last hour or so.

(Update: 3:30 pm) Storms are turning severe in the St. Cloud area (severe storm warning for Benton Co. until 6 pm this evening....potential for 1-1.5" hail and isolated wind damage, but it's worth remembering that any damaging weather will affect a tiny percentage of the area...most of us will only see heavy rain, lightning and thunder). Most of the storms come through between 6 and 7 pm, and a few may still be marginally severe as they come through the metro area. Time to batten down the hatches and get the kids inside the house (no later than 5:45 pm or so).

(3-D view of developing line of severe thunderstorms west of the Twin Cities, around 3 pm)

According to SPC, the Storm Prediction Center, much of southeastern and southcentral MN, including the Twin Cities. A few isolated storms may produce 1-1.5" hail and violent winds. An isolated tornado can't be ruled out either. Check in often with mnweathercenter.org/weather and MinnPost.com for updates throughout the afternoon hours. We'll keep you up to date on the risk.

(Thanks to the Minnesota State Climatology Office for providing a wealth of information about weather on Minnesota's most important - unofficial - holiday. If nothing else it will give you something to talk about after you run out of Ole and Lena jokes).

Minnesota's Fishing Opener weather is typified by partly cloudy to cloudy skies, morning temperatures in the low 40's, and afternoon temperatures climbing to near 70. Three out of four years are free of measurable precipitation. A trace of snow has been reported in northern Minnesota on at least four of the last 56 fishing openers. On at least three occasions, some lakes were still frozen for the opener. Generally there is enough wind to be felt on the face, maybe enough to 'fly' a flag. Weather on Minnesota fishing opener dates is highly variable. 56 years of fishing opener weather data are summarized here to offer a glimpse of what is 'typical' and what is 'extreme'.

Opening day temperatures have started as low as 24 degrees at International Falls (1996,2004), with freezing temperatures possible even in Minneapolis (31 degrees in 1979). On the warm side, St. Cloud saw 92 degrees in 1987, Minneapolis reported 91 in 1987, and International Falls reached 88 in 1977. The average early morning temperature varies from the high 30's in the northeast to the high 40's along the southern border. The average afternoon temperature generally ranges from the mid 60's along the northern border, to the low 70's in the extreme south. Along the shore of Lake Superior, highs are held in the mid 50's.

Three quarters of past opening days have been free of measurable precipitation. Two thirds of the fishing openers have been free of any precipitation, measurable or not. On those days with measurable rain, the amounts averaged close to a half-inch in the south and a quarter inch in the north. No amounts over one inch were recorded at either St. Cloud or International Falls, while Minneapolis experienced 1.15 in 1962 and 1.64 in 1965. Snowfall has generally has been limited to traces. Traces of snow were officially recorded in 1963 and 1993 at International Falls, and in 1968 at St. Cloud. A tenth (.1) of an inch fell at International Falls in 2000.

Statewide, less than one year in five offers totally clear skies. The average amount of cloudiness lies near that fuzzy boundary between 'partly cloudy' and 'cloudy', but over half of the dates were classified as cloudy.

Average daily wind speeds generally range between 8 and 15 miles per hour. This range can is described as 'wind felt on face ...' to '... wind extends light flag'. The predominant wind direction is split fairly evenly between blowing from the northwest, south, and east.

Fog has been reported on the fishing opener, occurring about one year in ten in the south, about one year in six in the north. By early to mid May, Minnesota is entering its thunderstorm season. The possibility of thunderstorms is greatest in the south (about one in seven), less in the north (about one in eleven). The weather should be monitored carefully if the skies appear threatening.

Weather Headlines

* Slight severe storm risk for the Twin Cities and much of east central and south central MN. Potential for 1-1.5" hail and damaging winds, even an isolated tornado. Severe weather will affect a very tiny percentage of the region later today. Stay alert and check in often for possible watches and warnings.

* A few T-storms turn severe east of the Twin Cities metro Tuesday with hail up to 1" in diameter (nickel size) reported in Washington County. Severe storm warnings were posted for western Wisconsin for hail and damaging winds.

* 72 degree high in the Twin Cities Tuesday, .20" of rain falls. Nearly .50" soaks the Duluth area from today's frontal passage.

* Wednesday: last lukewarm day this week, low 70s likely.

* 1 in 3 chance of bumping into a late-day shower or T-storm Wednesday afternoon.

* Cooling into the upper 50s to near 60 later this week.

* Sunday now appears to be the drier, brighter day of the weekend.

* We seem to be entering a wetter pattern in general: more frequent showers, many farms/lawns pick up .50 to 1" of rain in the next 7-10 days.

* 70s may return by the middle of next week.

Fishing Opener Update

I know the weather flip-flop is annoying. It makes us crazy too, believe me. Not to blame "the pattern" but the jet stream is howling overhead (one reason why the winds at the surface have been so persistent in recent days). This also means rapid weather changes, which makes the concept of a 7-Day Outlook even more problematic than usual. The latest computer run hints at just enough instability for a few hours of showers on Saturday. I still don't think it will be an all-day washout, but you would be well advised to a). take a jacket, and b). make it waterproof, while you're at it. Sunrise temperatures start in the low 40s with "high" ranging from near 50 at Leech Lake to 54 at the Whitefish Chain, Gull, Pelican and North Long Lake, closer to 56 at Mille Lacs, and if the sun stays out for a few hours (likely) the mercury may brush 60 on Lake Minnetonka and White Bear Lake, where Gov. Pawlenty will be trying his hand at a trophy walleye. We've seen worse, true, but don't count on a picture-postcard-perfect Fishing Opener. Hey, why should this year be any different?

Paul's Outlook

Wednesday: Morning sun, clouds build in the afternoon with a pop-up shower or T-storm. Winds: W 10-15. High: 74

Wednesday night: Gradual clearing. Low: 49

Thursday: A mix of clouds and sun, an isolated PM shower mainly north/east of the Twin Cities. High: 67

Friday: Intervals of sunshine, a bit cooler - probably dry. High: near 60

Saturday (Fishing Opener): Mostly cloudy, a few showers and sprinkles. High: 57

Sunday: Brighter, better, drier. Partly cloudy and a bit milder. High: 64

Monday: Increasing clouds, rain late (possible thunder). High: 70

Tuesday: Showers taper, drying out during the day. High: 68

Wednesday: Milder with showers and T-storms. High: 73

Thursday: Rain likely, tapering later in the day. High: 64

Friday: Partly sunny and cooler. High: 60

Saturday (May 16): Mix of clouds and sun, turning milder. High: 71

Sunday: Increasing clouds, warmer. A T-storm possible late. High: 74

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