Friday, July 19, 2019  3:30 PM Update for Central Minnesota Tornado Watch

Update: Central Minnesota Tornado Watch Until 10 PM

The NWS Storm Prediction Center has issued a tornado watch in central Minnesota until 10 PM. The watch area includes Brainerd, Wadena, Moose Lake, Lake Mille Lacs, Detroit Lakes, Fergus Falls, Alexandria, Long Prairie, Morris, Willmar, St. Cloud, Redwood Falls, Hutchinson and the Twin Cities Metro. There are already a few scattered storms (see Shortwave Albedo satellite loop from Colorado State satellite slider) that have developed from Breckenridge to Fergus Falls to Wadena to Brainerd to Moose Lake (see NWS Upper Mississippi Valley radar loop). Some of these early storms could produce hail up to 3 inches in diameter, and wind gusts to 80 MPH. As the storms get more organized in the late afternoon, there is a threat for tornadoes with a long track tornado possible. During the evening hours, the main threat will change to widespread wind damage from winds gusting to 80 MPH.

Sultry Conditions Continue to the South of the Storms

The excessive heat warning is still in effect across central and southern Minnesota until 10 PM. To the south of the area with the scattered thunderstorms, heat indices are current 100-115 (see NWS Minnesota hourly weather round-up for the latest heat indices). Conditions will remain sultry until the storms begin to ease southward later tonight or in the early morning hours. In central Minnesota to the south of the thunderstorms, the lingering clouds have kept temperatures down, but heat indices are still in the 90's (see NWS Aviation Weather Center METAR map)..

Previous Discussion: Late Day and Evening Scattered Storms Could Produce Severe Weather Close to Us

New storms will likely fire late this afternoon along and to the north of this wind shift line. They will be inhibited by the plume of warm air aloft, but this still could lead to pockets of showers and thunderstorms downwind of where the morning storms end up in eastern Minnesota and Wisconsin and along the southern edge of the rain-cooled air, somewhere in central Minnesota or the Minnesota River Valley. The storms this afternoon into the evening could produce any type of severe weather, so there will likely be severe weather or tornado watches and warnings in central Minnesota late this afternoon and during the evening. Straight line damaging winds or even tornadoes could be produced by these storms, especially in central and east central Minnesota into western and northern Wisconsin.

Heat Warnings and Advisories for Most of Southern Half of Minnesota

To the south of the area of midday storms will be the most oppressive air with high temperatures climbing to the upper 80's to middle 90's across the southern half of Minnesota. The nearby thunderstorms will push all the dew points well into the tropical 70's, so heat indices will be in the 100-110 in east central and southern Minnesota (see. This is the area covered by theissued by the National Weather Service, which includes southern, southwestern, and east central Minnesota, including most of the Minnesota River Valley, the Twin Cities, Litchfield, Hutchinson, Mankato, Pipestone, and southern Minnesota from the South Dakota border through Albert Lea. St. Cloud, Willmar, Princeton, and Pine City are covered by a heat advisory. The midday storms and morning clouds will likely keep high temperatures in the middle to perhaps upper 80's, but the sultry dew points could still push heat indices well into the 90's.

Make sure young people and seniors have a cool indoor play to be this afternoon. For healthy adults, move strenuous outdoor activities indoors and to the early morning. More people are killed by heat than any other weather cause.

Another Wave of Late Night and Saturday AM Storms

Besides the storms redeveloping near the southern edge of the midday cloud line, more showers and thunderstorms will develop overnight in the Dakotas and they will push into Minnesota later tonight. Any storms in Minnesota during the evening will have the potential to produce any type of severe weather, but the storms moving into Minnesota late tonight and tomorrow morning will still have the potential to produce some wind damage, but a larger potential to cause heavy rainfall and flash flooding, especially over areas that received heavy rain last night or this morning.

Much Drier and Cooler Air to Filter In Beginning Tomorrow, Grab Hold on Sunday

There is relief closer to us than you might think. Note that the dew points are in the more comfortable 50's across northern Minnesota early this morning (see NWS Aviation Weather Center METAR map). That warm and slightly drier air will begin to work its way into Minnesota tonight. We still have that shot of thunderstorms overnight, since this front will lift some of the sultry air over the drier air near the ground. As tomorrow goes on, however, the dew points will ease a bit from the sultry 70's to the merely uncomfortable 60's. And, when the sun pops out tomorrow midday and in the afternoon, highs will be suppressed to the upper 70's to near 80.

Finally, by tomorrow night, the major steering wind shift that will begin to steer weather systems from central Canada into the North Central and Eastern States will begin. That will allow us to tap some much drier air with dew points in the 40's and 50's beginning Sunday. Highs will be more seasonably warm, remaining mostly in the 70's or perhaps brushing 80 from Sunday well into next week.

PM Storm Chances? Sunday?? Beyond???

The main forecast issue is a series of low pressure systems caught up in the northwest-to-southeast flow. Each of these will have a pool of cool air aloft, so there may be enough temperature difference between the sun-heated ground and the pocket of cool air to trigger a lot of midday and afternoon clouds and perhaps even a few brief showers and thunderstorms. These likely won't produce much in the way of severe weather, but some small hail and wind gusts could occur. It appears that one batch of storms could develop Sunday late afternoon into the early evening. There is another system forecast to come through on Tuesday, but these systems are going through a part of the earth where there are few observing stations, so I'm going to take the forecast as being more than a little iffy 3-4 days down the road.

The other issue that could come up is smoke from the out-of-control fires that have been burning in northern Alberta, Saskatchewan, and Nunavut. Right now, there is some high-level haze from the smoke in southern Manitoba and Saskatchewan and some (see smoke plume chart from NASA) and some of this could be blown in when the winds shift to northwest. Thus far, there isn't much pollution reaching the ground (air quality index in the green across the Canadian Prairie Provinces on the EPA airnow site), but this will have to be watched.

The severe heat to our south will spread eastward to the Ohio Valley, Northeast, and Mid-Atlantic states this weekend (a New York City triathlon scheduled for Sunday has been cancelled due to the expected oppressive conditions)

Confidence Level: "The Bulb on That Hard-To-Reach Light in the Foyer Will Burn Out"

Tornado Watch Until 10 PM

Friday Late PM 7/19/2019: Heat Advisory through 8 PM. Scattered late day showers and thunderstorms. Some storms could produce any type of severe weather, including tornadoes, large hail, and damaging winds. High: between 88 and 90. Winds: SE 8-15 MPH, becoming NW 8-15 MPH late in the day. Chance of measurable rainfall: 40% after 5 PM.

Confidence Level: "Every Time I Try to Put in a New Bulb, the Light Fixture Will Try to Detach From the Ceiling"

Friday Night: Scattered showers and thunderstorms, possibly producing severe weather, in the evening. More widespread showers and thunderstorms moving in during the early morning hours. The late night storms could produce heavy rainfall, hail, and damaging winds. Low: between 57 and 63. Winds: NE 8-15 MPH. Chance of measurable rainfall: 50% evening, 70% late at night.

Saturday 7/20/2019: A good chance for morning showers or thunderstorms, then partly sunny, breezy, not quite as warm, and a shade less humid. High: between 75 and 80. Winds: NW 8-15 MPH. Chance of measurable rainfall: 50% in the morning, 10% in the afternoon.

Saturday Night: Natural air conditioning. Clearing, a bit of a breeze, cooler and drier. Low: between 53 and 58. Winds: NE 5-15 MPH. Chance of measurable rainfall: 10%.

Sunday 7/21/2019: Sunny in the morning, mixed sun and clouds in the afternoon with a better chance of an afternoon shower. Breezy, seasonably warm, and even less humid. High: between 73 and 78. Winds: NW 10-20 MPH. Chance of measurable rainfall: 40%.

Sunday Night: Perhaps an evening shower or thunderstorm, then partly clear, less windy, and a shade cooler. Some fog possible by morning. Low: between 49 and 54. Winds: NE 5-15 MPH evening, 5-10 MPH late. Chance of measurable rainfall: 40%.

Monday 7/22/2019: Morning sun, mixed clouds and sun in the afternoon with a slight chance of a shower. Breezy and seasonably mild again. High: between 73 and 80. Winds: NW 8-15 MPH. Chance of measurable rainfall: 20%.

Confidence Level: "The Only Way I'll Be Able to Change the Bulb and Hold the Fixture in Place Will Be to Yell At It

Monday Night: Clear and continued comfortable. Low: between 54 and 58. Winds: NW 5-10 MPH. Chance of measurable rainfall: 10%.

Tuesday 7/23/2019: A sunny start, some afternoon clouds and a slight chance for a shower. Continued seasonably warm. High: between 76 and 82. Winds: NW 8-15 MPH. Chance of measurable rainfall: 20%.

Extended: Continued seasonably warm with lower humidity. Highs mostly in the 70's. Lows in the 40's and 50's.

Forecast Confidence (10 - "The Rabbits Will Thump, Objecting to Me Yelling at the Light Bulb"; 0 - "I Will Be Hosting a DIY Show on Home Repairs"): 6 Thursday, 5 Thursday night and Friday, 4 Friday night through Monday.

Today's High (through 3 PM): 88°F; Overnight Low (through 7 AM Friday): 67°F
St. Cloud Airport Total Storm Precipitation (through 3 PM Friday): Trace; SCSU Precipitation (through 3 PM Friday): None

Next Update: Monday, July 22 8 AM (or as needed)

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Let me know what you think about this forecast and discussion by emailing SCSU meteorology professor Bob Weisman. Please note that I make the forecast, not the weather!

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