Friday, September 20, 2019  3:10 AM

Back to Hot! Hot! Hot! and Humid

Yesterday Was the "Reprieve"

The summer extension continued yesterday in Minnesota. It was another day with highs in the 80's (see 3-day loop of high temperatures from NWS/University at Albany) after an early morning low in the middle to upper 50's (see NWS: Last 72 hours of St. Cloud Observations). During the second half of September, highs are supposed to be in the upper 60's with lows in the 40's (see St. Cloud September average temperatures), so this weather is more typical of the first week of August. And with all of the wet ground from the frequent rainfall (more than 8 inches in the past 30 days on the NWS Minnesota rainfall map of the past 30 days), any slightly drier air mass will moisten up quite quickly.

Tropical Air Moving Back in Today With Small Chance for Morning Thunderstorms

However, the really steamy air that we had earlier in the week is poised to make a comeback. Dew points (number at the lower left on the NWS Aviation Weather Center METAR map) are already back in the middle 60's in southern Minnesota and South Dakota with upper 60's and Florida-like 70's in most of Iowa and Nebraska. As the next major storm system (counterclockwise circulation on the Mid-Tropospheric water vapor loop from Colorado State satellite slider menu) is moving across eastern Washington and Oregon, south-to-north wind flow has broken out again to the east. Overnight, the heat and humidity pump has triggered another round of showers and thunderstorms (see Shortwave Albedo from Colorado State satellite slider menu) from Colorado into Kansas and Nebraska. These storms have been weakening in the early morning hours, but there are most storms in eastern Montana and North Dakota. The strongest flow of the sticky air over the slightly cooler and drier air will be in the Dakotas and into Canada this morning, so central Minnesota will mainly see the leftover middle clouds from the earlier storms in Nebraska and points south. A few scattered showers or thunderstorms might pop up this morning, but I think we will see a smaller chance of morning storms than we did on Tuesday or Wednesday.

More Rain and Storms Likely Late Tonight and Tomorrow

As the day goes on, the warmer and more humid air will come in and we will see some sunshine. That will likely produce a high of over 80 degrees for the 6th straight day, the longest streak since the first week of August. There is still a small chance of a late day or evening shower or thunderstorm, but the strongest heat and humidity pump will remain to our west. We will likely see a steamy night with persistent south to southeast winds helping to keep the temperatures in the 70's for much of the night. The bulk of the afternoon and evening storms will develop in Nebraska, Montana, and the Dakotas. Severe weather, especially straight-line damaging winds, and heavy rainfall with potential for localized flooding will be the main severe weather threats. By late at night, those storms will have a good chance to advance into western and central Minnesota. So, the St. Cloud area is likely to see another round of early morning thunderstorms that could linger into the daylight morning hours. While there is some threat of large hail and damaging winds, the biggest problem will be the potential for heavy downpours on top of already saturated ground.

Cooler and drier air will work its way into Minnesota behind the cold front on Saturday evening. Temperatures will back down into the 50's with dew points becoming more comfortable. I'm backing off on the Sunday morning fog threat since it appears the winds will stay up all night.

Cooler Sunday, But Still With Occasional Showers

On Sunday, the cooler air will be over Minnesota, but the upper air low is expected to pass right over the state. That low will produce a pocket of cool air aloft. The temperature difference between the near average September high temperature expected (upper 60's to near 70) and the mid-level air will create a lot of puffy clouds from midday through the afternoon with widespread brief showers and thunderstorms.

Drier and Slightly Cooler Early Next Week

The best hope for a dry period will be from Sunday night into Tuesday. The winds will calm down Sunday night, allowing low temperatures to drop to near 50. This will again create the potential for dense fog. Monday's highs will return to the 70's. We might see another 80 degree high on Tuesday, despite having fewer than 12 hours of sunshine after the September equinox on Monday.

There may be another cold front due Tuesday night or Wednesday. That would create yet another unneeded chance for rain, followed by a more prolonged period of cooler air.

Major East Texas Flooding

Meanwhile, the leftovers from Tropical Storm Imelda have continued to produce thunderstorms in eastern Texas (see Shortwave Albedo from Colorado State satellite slider menu). Some rainfall totals in southeastern Texas, especially the Beaumont-Port Arthur area, have reached 20-40 inches, beginning to rival the insane amount of rain from Hurricane Harvey 2 years ago. Elsewhere in the tropics, Hurricane Jerry is moving through the western Atlantic with top winds of 105 MPH. At this point, the storm appears to be tracking far enough to the north to spare the Windward Islands from damaging winds. However, there is the possibility of heavy rainfall and flooding.

Humberto hit Bermuda earlier in the week with strong winds and some rain, but the island was spared major damage.

Saturated with Rainy Statistics

So far in September, the St. Cloud Airport has picked up 6.04 inches of rain. That's only 0.08 inch short of cracking the 10 rainiest Septembers on record. The total 2019 rainfall of 33.38 inches now ranks as the 5th highest January through September rainfall and is merely 0.06 inch from 4th place. The total rainfall is less than 2 inches away from breaking into one of the 10 wettest years of all time. The 4 September days with at least half an inch of rain pushes the 2019 total to 27 days, 5th highest on record. Over the past 30 days, Stearns and Benton Counties and central Minnesota are among the highest totals with 8-10 inches of rainfall. Eastern South Dakota and southwestern Minnesota continue to have after effects from the heaviest rainfall a week ago.

This is why any significant rainfall through Sunday could cause major flooding problems.

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

Friday 9/20/2019: Perhaps a morning shower or thunderstorm. Partly sunny, breezy, very warm, and becoming uncomfortably humid midday and afternoon. High: between 82 and 86. Winds: SE 10-25 MPH. Chance of measurable rainfall: 30%.

Friday Night: A better chance for showers and thunderstorms, especially late at night. Breezy, warm, and sticky. Low: between 65 and 70. Winds: SE 10-25 MPH. Chance of measurable rainfall: 60%

Saturday 9/21/2019: A good chance of morning showers and thunderstorms. Then, mixed clouds and sun, windy and still humid in the afternoon. A chance of a late afternoon shower or thunderstorm. High: between 80 and 85. Winds: SW 20-30 MPH with higher gusts. Chance of measurable rainfall: 60% in the morning, 40% in the afternoon.

Saturday Night: Clearing, breezy, and turning cooler and drier. Low: between 52 and 58. Winds: W 10-25 MPH evening, 5-15 MPH late. Chance of measurable rainfall: 10%.

Sunday 9/22/2019: Morning sunshine, then lots of midday and afternoon clouds with occasional showers or thunderstorms. Not as warm or as humid. High: between 68 and 73. Winds: WNW 10-25 MPH. Chance of measurable rainfall: 40%.

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

Sunday Night: Clearing, light winds, and cool with areas of dense fog by morning. Low: between 48 and 53. Winds: SW 5 MPH. Chance of measurable rainfall: 0%.

Monday 9/23/2019: Early fog, then sunny and seasonable for late September. High: between 72 and 78. Winds: SW 8-15 MPH. Chance of measurable rainfall: 10%.

Monday Night: Partly clear and not quite as cool. Low: between 53 and 58. Winds: S 5-15 MPH. Chance of measurable rainfall: 0%.

Tuesday 9/24/2019: Partly sunny, breezy, warmer, and becoming noticeably humid again. High: between 76 and 82. Winds: SW 8-15 MPH. Chance of measurable rainfall: 10%.

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

.Extended: Chance for Tuesday night or Wednesday rain??? Turning cooler the second half of next week???

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"): 7 Friday, 6 Friday night through Sunday, 5 Sunday night and Monday, 4 Monday night and Tuesday, 2 Tuesday night and Wednesday.

Yesterday's High: 83°F; Overnight Low (through 3 AM Friday): 63°F
St. Cloud Airport 24-Hour Precipitation (through 3 AM Friday): None; SCSU Precipitation (through 3 AM Friday): None

Next Update: Monday, September 23 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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