83 F. average high for July 26.
84 F. high on July 26, 2011.
No significant rain through Sunday for the Twin Cities.
90-degree heat returns to KMSP by Sunday afternoon.
13.05% of the state is in a severe drought, up from 7.32% of Minnesota a week ago.
Dual Polarization. The local Twin Cities NWS is upgrading to "dual pol" on August 20; the radar may be down for as long as 2 weeks during the upgrade. Details below.
One More Wave Of Heat. The last spell of 90s? At the rate we're going I wouldn't be on that, but I suspect 3-4 more days at or above 90 F. next week. Highs should top 90 as early as Sunday; 90s likely the middle of next week. Model data: ECMWF.
Anatomy Of A Heatwave. 1,513 hot weather records (daytime highs and warm nighttime lows) in just the last week. Interactive map courtesy of Ham Weather.
Drought Deepens Over Plains. Showers and T-storms will drop welcome rain; some 1-2" amounts from Boston and New York southward to Mobile. But little rain is forecast for the next 5 days over the Central Plains, where the drought will worsen. Map: NOAA HPC.
Photo credit above: "Grain bins are silhouetted against approaching storm clouds that unfortunately contain very little water Thursday, July 26, 2012 in Pleasant Plains, Ill. The widest drought to grip the United States in decades is getting worse with no signs of abating. This week's U.S. Drought Monitor report highlights that the drought's severity is rapidly expanding across the nation." (AP Photo/Seth Perlman)
Photo credit above: "In this July 13, 2012 photo, the Memphis Queen riverboat moves down the Mississippi River in Memphis, Tenn. A year after nearly record floods, the Mississippi River level has dropped so low that it's beginning to affect commercial operations. Port managers worry that their passages to the river could fill up with silt, and barge operators may have to lighten their loads." AP Photo: Nikki Boertman.
Wild Thursday. The squall line that roared across the Ohio Valley into Pennsylvania, New Jersey and New York State. There was at least one tornado touchdown (near Elmira, New York) with considerable tree damage; 366 separate reports of severe wind damage along the leading edge of Canadian relief. Details from SPC.
* for the first time in 16 years, SPC issued a Day 2 "Moderate Severe Threat" east of the Rockies. A few photos of the resulting squall line:
Photo credit above: Travis Long/The News & Observer, via Associated Press. "Emergency repairs on a highway that buckled in triple-digit temperatures last month near Cary, N.C."
"The Twin Cities went from having an average of 13 cool summer days to 9, from 7 dangerously hot days to more than 11, and from 2 heat waves to 3 each summer."
- Heat waves lasting three days or more have become more common over the last six decades. St. Louis has approximately four more three-day heat waves each year than it did in the 1940s.
- On average, hot humid days have increased more rapidly in frequency, while hot dry days have increased in temperature more rapidly across the Midwest since the 1940s and 1950s.
- The meteorological characteristics of these weather types are also changing. In general, hot air masses have become hotter and more humid during nighttime hours.
- In some cities, average nighttime temperatures within some air mass types have increased as much as 4 to 5 degrees Fahrenheit (˚F) over the six decades.
- Relief from heat is harder to find—all of the cities studied now have fewer cool, dry days in the summer.
- The results aren’t due solely to an urban heat island effect on major cities. Less urban neighboring locations showed similar increases in hot summer air masses.
KMPX Upgrading To "Dual Polarization". As of August 20 the Twin Cities Doppler radar (based in Chanhassen) will be out of commission for 2 weeks while the NWS upgrades to the latest generation of Doppler: "dual pol". Details: "Beginning August 20, 2012, the Doppler radar at your National Weather Service Forecast Office will undergo an upgrade to incorporate new technology. While the work is being done, radar data will be unavailable from NWS Minneapolis! The radar is scheduled to be unavailable for two weeks during this upgrade. Recently, though, technicians have been completing the upgrade in 5 to 6 days, and radar data will become available as soon as the upgrade is complete.
The advantages of "dual pol"?
* Better estimation of total precipitation amounts.
* Better estimation of the size distribution of hydrometeors (raindrops, snowflakes, hailstones, drizzle).
* Much improved ability to identify areas of extremely heavy rainfall that are closely linked with flash floods.
* Improved detection and mitigation of non-weather related radar echoes (chaff, smoke plumes, ground clutter).
* Easier identification of the melting layer (helpful for identifying snow levels in higher terrain).
* Improved ability to classify precipitation type.
Photo above courtesy of Reid Wolcott.
A few fine photos....
Getting Better Out There. Dew point temperatures dropped into the 50s (down from low 70s Wednesday), a welcome dip in humidity levels. A few late-day instability showers and T-showers popped up. Highs ranged from a comfortable 68 at Grand Marais to 77 Alexandria, 83 St. Cloud and 84 in the Twin Cities.
Paul's Conservation Minnesota Outlook for the Twin Cities and all of Minnesota:
SATURDAY: Partly sunny (isolated T-shower over southwestern MN). Dew point: 62. High: 85
Photo credit above: "A thunderstorm rumbles through Kansas (file picture)." Photograph by Joel Sartore, National Geographic
Map credit above: "In this chart you can see that a very strong area of high pressure (in red shading surrounding Greenland) set up shop over Greenland during July, providing warmer than average air temperatures and clear skies to enhance surface melting." Credit: NOAA via Joe Witte.