St. Paul received 3.24" of rain this week. The Twin Cities, as a whole, is now running 1.47" above average with monthly rainfall. The singletrack gets a well-earned break. Low humidity and seasonal conditions make for good mountain biking weather through the weekend.
Radar could light up again next week with heavy rain-producing thunderstorms. Humidity levels begin to increase across the area but the core of highest heat remains just south of Minnesota. While this heat bubble remains over the Central Plains it puts Minnesota in a perfect position for large clusters of thunderstorms that could routinely migrate over the Upper Midwest.
On a recent mountain biking trip to the CAMBA trails overnight thunderstorms erupted producing a tremendous amount of lightning. The afternoon prior to these t-storms was hot (90s) and very humid. As it turns out the frequency of lightning from nighttime t-storms depends on the heat from the previous afternoon. As the Capital Weather Gang severe weather expert Jeff Halverson explains:
“When the atmosphere heats up so much during day, instability persists through the late night hours,” Halverson said. “The atmosphere is like a capacitor. When you charge it up with buoyant energy to such a great degree, that energy is still available after sunset to power these thunderstorms. It fuels strong updrafts that can create very concentrated and intense bursts of lightning in these storms.”
During the summer months Minnesota (and the Midwest in general) tends to receive the majority of the season's rainfall from these overnight thunderstorms.
Rainfall Forecast Tuesday-Thursday
While a passing thundershower is likely at any given trailhead this week the majority of the time will be spent under a somewhat cloudier sky with cooler conditions compared to last week. We get a break for now, long range models hint at another streak of 90s come early August.
July Rainfall DEPARTURE from Average
July 2016 has been undoubtedly wet for Minnesota, the Midwest, and Plains. This map above shows the departure from average rainfall, which clearly shows the preferred track of storm complexes.
As it would break down this week, the rainfall won't be overly impressive. The majority of central Minnesota, including the Twin Cities, will receive a total of 0.75" by the end of the week.
Rain chances remain through Friday with a drying trend into the weekend. Looking ahead the 8-14 Day Outlook indicates a warm and wet pattern developing across the Upper Midwest through the first full week of August.
Minneapolis/St Paul has had 4 days at or above 90 degrees so far this month. The greatest number of days spent in the 90s through the 22nd of July was 15 back in 1936.
On Thursday the average temperature across the country was 90 degrees. Almost 90% of the nation was over 80 degrees. Closer to home Alexandria reported a heat index of 121°F. Incredible!
The intense summer heat and humidity is over by the end of the weekend. The potential for severe thunderstorms on Saturday marks the arrival of a much needed cool front.
Severe Storm Threat Saturday
A dramatic drop of temperature and dewpoint will occur by next week...much more comfortable weather for cycling. Dry for much of Sunday and Monday with only an isolated threat for t-storms midweek.
The hottest days of summer are upon us. Daytime highs will approach 90 degrees as an upper-level ridge of high pressure reduces mixing and results in mostly sunny skies. Thursday will be the hottest day with some nearby areas close to 100 degrees. The last 100-degree day in the Twin Cities was July 6, 2012 when the mercury reached 102 degrees.
Warm conditions under mostly sunny skies will enhance ozone production and encourage poor air quality. In addition, winds will remain light under the bubble of high pressure inhibiting pollution dispersion. This means that air quality will be rather poor, especially Thursday. Those that suffer from asthma or a respiratory illness may need to limit the time on the bike and/or complete outdoor activities early in the day.
Best chance of wet trails will be Wednesday and this weekend. Heavy rain on Saturday could leave trails too wet to ride into early next week. Stay tuned.
The hottest days of summer are still yet to come. Next week looks to fit the bill. From about Wednesday onward a stretch of 90-degree heat will take over the Twin Cities.
In case anyone is wondering the hottest day ever in Twin Cities history was 108 degrees. The longest stretch of 90-degree heat was 14 consecutive days also set during the same heat wave in 1936.
The anticipated heat wave next week could rival the heat wave of 1936 as the mid and upper level patterns are very similar. From a recent Twin Cities National Weather Service forecast discussion:
Reanalysis data for 850 mb temperatures and 500 mb heights indicate a good fit to the July heat wave in 1936. We could see some 100 degree temperatures by the time it is over. Confidence for the 100 degrees is highest across west central MN. Dew points will also be rising well into the 70s. Their rise will be aided by the evapotranspiration from the corns and bean fields. Heat indices on Thursday are already shown to be near 100 degrees. In addition, it's possible as we head into the weekend that MSP could have an overnight low or two near 80 degrees.
Over the past 7 days Minnesota has received the most rain out of any state in the Midwest. TheCuyuna Lakes Mountain Bike Trails received a whopping 7 to 8 inches in one evening. This led to considerable trail erosion and a whole lot of tree clean up as well.
The rain hasn't been all bad, however. Drought has significantly decreased across the state. Good for the lawns, gardens, and farms.
A southerly flow returns this weekend that will transport higher moisture-laden air back into Minnesota. Showers and thunderstorms will occasionally develop in response to little ripples of low pressure moving through the upper level flow over the state. Saturday night could be the wettest period in the short term with the heaviest rain falling just southwest of the Twin Cities.
Weekend Rainfall Forecast
Minneapolis and St. Paul missed the big rain on Monday. Over 5" of rain fell across the Cuyuna Lakes Mountain Bike Trails...basically a month's worth of rain in just a matter of hours.
Can't rule out an afternoon thundershower the rest of this week. Otherwise, the flow becomes more northwesterly allowing much cooler and drier air to arrive Wednesday-Friday. Forecast dewpoints Friday will be in the 40s & 50s. Very dry air for July!...especially during the hottest week of the year, historically.
Higher humidity values creep back into the area this weekend followed by a good ol' fashion heat wave next week. A few models are hinting at 100 degrees close to the area. For reference the hottest day so far this summer was 96 degrees back in late June.
But the hottest days of summer might be yet to come. The long range outlook indicates above normal temperatures over the majority of the country the next 8-14 days out.
The Minnesota monsoon season is over...for now. A dry breeze and lukewarm sunshine will make for good riding conditions this weekend. An unusually strong cyclone will then develop over Saskatchewan on Monday. This upper level low will slow the progression of a cold front over Minnesota resulting in widespread heavy rain and thunderstorms next week. Get the dry dirt while you can.
Upper level weather map (above) shows the unseasonably strong low tracking across the Upper Midwest all next week. This should keep rather unsettled weather conditions across Minnesota in the extended forecast.
Rainfall the past 7 days topped 1 to 2 inches in many areas. This was much needed rain as drought conditions have been expanding across the state. More rain next week will further slow the drought expansion.
After a cool-ish weekend heat and humidity return next week. High temperatures Wednesday of next week could be close to the mid-90s with the heat index value pushing 100 degrees!
The singletrack is now fully saturated. Reports of 1 to 2 inches of rain in an hour were common across the metro Tuesday evening. Some locations in central Minnesota reported widespread wind damage after severe thunderstorms packed (hurricane-force) winds of 70 mph. Thunderstorms will again develop through the end of the week with the risk for heavy rain. Rain totals by Friday could top 2 inches.
Wouldn't be surprised to find fallen tree branches across the trails. Minor tree and roof damage along with ping pong size hail was reported in Burnsville on Tuesday, close to Murphy-Hanrehan. Also numerous trees were reported down in Maple Grove, just west of Elm Creek singletrack.
Rain Totals Tuesday Night
The heavy rain on Tuesday made up for the lack of rain the past 2 weeks. Before Tuesday, the last soaking rain in the Twin Cities occurred in mid-June. Drought conditions began to creep back into parts of Minnesota. The trails were becoming very dusty.
Heavy rain Wednesday night through Thursday should add another inch or two to the topsoil. Expecting isolated t-storms Sunday through early next week so plan on occasional, temporary trail closures as a result.
Summer brings warm afternoons perfect for biking, but the summer heat and humidity can also spark thunderstorms and severe weather. Be prepared for any type of adverse weather headed your way with Aeris Pulse.
NWS Twin Cities Weather Story