Summer-like temps to close out August

Hot conditions will be the rule as we close out August as temperatures are expected to climb into the 90s this week, with a shot of 100 degrees by Thursday. I don’t think we’ll see 100 in the Twin Cities, but high temperatures should be in the 95 to 99 degree range Thursday. Typically, Labor Day is the unofficial end to summer, but it will not feel like fall for at least a week.

 

The National Weather Service in the Twin Cities has issued an Excessive Heat Warning for Hennepin and Ramsey Counties for Thursday due to the urban heat island effect.

...EXCESSIVE HEAT WATCH IN EFFECT FOR THE TWIN CITIES THURSDAY...

.AN EXCESSIVE HEAT WATCH HAS BEEN ISSUED FOR HENNEPIN AND RAMSEY COUNTIES FOR THIS THURSDAY. WEDNESDAY NIGHT...THE ARRIVAL OF A WARM FRONT WILL BRING WITH IT SOUTHWEST WINDS AND VERY WARM TEMPERATURES INTO THE TWIN CITIES AREA FOR THURSDAY. RECORD HIGHS ARE EXPECTED THURSDAY...WITH ACTUAL AIR TEMPERATURES LIKELY APPROACHING OR EVEN EXCEEDING 100 DEGREES DURING THE AFTERNOON. THOSE PLANNING OUTDOOR ACTIVITIES THURSDAY OR IN STRUCTURES WITHOUT AIR CONDITIONING SHOULD PLAN FOR DANGEROUSLY HOT TEMPERATURES THURSDAY AFTERNOON.

Just when you thought summer was done with, think again.  This might be the last taste of hot weather we’ll see all year, but the way this year has been, we might see 90 degrees in November.  Crazy.

RS

Summary of recent heat wave and capping inversions explained

The heat wave concluded Friday night as a cold frontal boundary pushed from north to south across the southern half of Minnesota, and triggered a few rain showers and thunderstorms.  The hot weather went out with a bang as the high temperature in the Twin Cities reached 102 degrees.  It was also the first time since 1988 that one month has seen at least two days with temperatures at 100 degrees or above.

The stretch of eight days from June 29 to July 6 with high temperatures at 90 degrees or above has happened on five other occasions in the Twin Cities.  The average high temperature during this period was 96.4 degrees, and the average temperature was 84.5 degrees.  This would make it the 4th warmest heat wave ever based on mean temperature!

Date	High Temp	Record Temp	Year
6/29/12	90	102	1931
6/30/12	92	100	1931
7/1/12	94	100	1883
7/2/12	99*	96	1911
7/3/12	97	100	1949 1990
7/4/12	101*	100	1949
7/5/12	96	100	1982
7/6/12	102	104	1936

* = Indicates new record

The sagging frontal boundary was very visible on radar Friday night.  Thunderstorms developed along the leading edge on this boundary, but had a hard time surviving.

Why did the storms die off so quickly?  There was a capping inversion in the atmosphere.  What that means is there was a layer of warm (stable) air stacked on top of a colder layer.  Cloud formation from the lower layer is "capped" by the inversion layer.  Convection requires warm air rising into cold air.

Shown below is a temperature profile at the National Weather Service in Chanhassen at 7 pm Friday.  While temperatures (red line) initially decrease with height from the surface, temperatures increased with height from 925 millibars (~2500 feet above sea level) to 850 millibars (~4600 feet above sea level).  The limited how much storms could grow, even when there is plenty of energy for them to work with.

Dr. Greg Forbes from The Weather Channel briefly explains in the video clip below how the cap prevents thunderstorms from happening:

RS

Heat wave summary in the Twin Cities

Since June 29th, the high temperature in the Twin Cities has been at 90 degrees or above.  Combined with high dew point values, the heat index has reached in excess of 100 degrees for several periods during the heat wave.  New high temperature records were set on July 2 and July 4, as the mercury climbed to 99 and 101, respectively.  The daily high temperature reached 100 degrees or more for the 34th time since 1873 over the Fourth of July.

 

Date	High Temp	Record Temp	Year
6/29/12	90	102	1931
6/30/12	92	100	1931
7/1/12	94	100	1883
7/2/12	99*	96	1911
7/3/12	97	100	1949 1990
7/4/12	101*	100	1949
7/5/12	96	100	1982

* = Indicates new record

 

July 4th also marked the first time since 1995 an hourly observation at MSP Airport recorded a temperature of 100 degrees or more with a dew point of 70 or greater.  That statistic was impressive to me.  We do not often hit 100 degrees here, and to do with tropical humidity like this is quite an accomplishment.  A heat index of 109 was observed from my home in Shakopee at 7:15 pm Thursday.

 

 

RS

Just how rare is this heat in the Twin Cities?

The high temperature barely missed hitting the century mark in the Twin Cities on Monday as the mercury peaked at 99 degrees.  However, this did break the previous record of 96 degrees set over a century ago in 1911.

Just how often do we see these hot temperatures in the Twin Cities?  In the past 30 years, the temperature reached 100 degrees or more only 10 times.  That is once every three years on average.  The most recent 100 degree or higher reading was last year on June 7, when the temperature hit 103 degrees.  In most cases to top triple digits, a lower dew point, below the mid-60s, is needed for air to mix down to the surface efficiency.  Not often do you see temperatures greater than 100 when the dew point is at 70 degrees or more.  Here is a look at a few case studies:

On June 7, 2011, temperatures climbed as the dew point decreased.  Temperatures reached the 100 degree mark when the dew point dropped into the high 50s.  A humidity level in the “comfortable” range for most people.

The opposite was found to be true on July 31, 2006.  On this day, the maximum temperature of 101 was obtained as the dew point was rising steadily.  At 4 pm, the dew point was 68 degrees as the temperature peaked.  Would the temperature have hit 100 if the dew point was at 70?  Close call, but probably not.  98 or 99 degrees would have been more likely in that instance.

Jumping back over 10 years from 2006 to 1995 was the next occurrence of temperatures 100 degrees or greater.  July 13 was the date as temperatures soared to 101 degrees yet again.  This was one of the few times where the temperature hit 100 degrees as the dew point was over 70 degrees.  When this happened at the 4 pm hour, the dew point observation was 71.  The heat index was 109.

Monday’s 99 degrees was reached as the dew point was 67 degrees at the 6 pm hour.

RS

Hot, with severe thunderstorms possible over the Northland

A warm front, or is this instance, a “hot” front will move to the International border by this evening.  This front will be the focus for thunderstorms, some of which will be severe across the north.  To the south of the front, very warm air will dominate the state today.

The greatest area of concern for severe thunderstorms is north of a St. Cloud line, but the focus for storm development will be near the warm and cold front intersection.

The Storm Prediction Center has indicated hail as the greatest threat today, with the purple area below as the area at risk.

Unlike yesterday’s setup, a tornado threat does exist today as an area of low pressure moves into the northwest portion of the state.  Areas northwest from Bemidji may see an isolated risk of a tornado during the early stages of severe weather.

The high-resolution WRF model at 7 pm below depicts a bow echo moving through the Northland tonight, with a secondary bowing mesoscale convective system forming near Fargo and moving southeastward.  The Fargo bow misses the Twin Cities to the north.

Further south, it is just going to be hot.  Dew points in the 70s will keep temperatures from reaching 100, but highs around 95 degrees should be doable today in the Twin Cities.  The mid 90s will dominate most of southern Minnesota.

A heat advisory is in effect for the southern half of Minnesota today until 10 pm as heat indices will top 100 by the afternoon.

Stay cool today!

RS

First heat wave of the year

The first stretch of heat of 2012 will be upon us over the next several days as the jet stream lifts into Canada, allowing very mild air to travel northward across the area.

Our weather will be dominated by a ridge with Minnesota being on the northern periphery of a dome of high pressure sitting out in the Four Corners region.

The NAM model is hinting at our first chance of 100 degrees on Monday.  Lately, the NAM has been overdoing the high temperatures a bit, as it has some trouble with handling dew point temperatures.  It will depend on dew points.  If the air can remain relatively dry and dew points stay in the low 60s, then I think we have a legitimate shot of hitting 100 degrees Monday in the Twin Cities.

The record for July 2nd is 96 degrees, set in 1911.  Will a new record be set Monday?  Stay tuned!

RS

First real dose of heat this year

Perhaps the warmest day of the year for the Twin Cities is on tap Wednesday as high temperatures push into the mid-90s.  The mercury has topped out at 93 degrees on three occasions this year, including twice on June 10 and 19.  Combined with high humidities, the heat index, or “feels like temperature”, will exceed 100 degrees.  Air temperatures may approach 100 degrees across southwest Minnesota.

I think there will be a chance of seeing heat advisories issued for Wednesday as heat indices approach 105 degrees.  You will want to take it easy and drink plenty of water.  As the National Weather Service in Chanhassen states, “NEVER leave anyone unattended in an automobile. It takes less than a few minutes for the temperature to rise above safe levels. People (or pets) can die of hypothermia, even if the windows are cracked.”

RS

Will the Twin Cities see 80 degrees Sunday?

Clouds and southeast winds on Saturday locked temperatures across much of Minnesota into the upper 40s and 50s.  Where the sun did peak through in the southwestern part of the state, temperatures climbed into the low 60s.  If we do see peaks of sun, which is looking slimmer and slimmer by the hour, we could get temps between 55-60.  No sun means temps in the low 50s.

The possibility of 80 degree temperatures on Sunday has been in the conversation the last few days.  Since it appears winds will stay from the southeast as opposed to the south with some clouds present in the afternoon, MSP and southeast Minnesota wouldn’t see the full benefit of the warmth.  I tend to agree with the European solution on the temperature profiles for Sunday.  Much of southern Minnesota will see 70s, with 80s not making a grand appearance.

There could be a few stronger storms as we head towards the end of the day Sunday into overnight Monday with a frontal passage.  Storms with hail (“hailers”) will be possible, but the overall threat of severe storms is quite low.  We just don’t have the instability present (lack of moisture) for an outbreak.

Credit: Storm Prediction Center

RS

Week in review and a look ahead to next week

Monday saw the first severe thunderstorms of the year across Minnesota to end the winter season.  The National Weather Service in the Twin Cities determined that an EF-0 touched down across Waseca and Le Sueur Counties, impacting the town of Elysian the hardest.

This was the second earliest tornado recorded in the state’s history by one day.  The tornado was on the low-end (I avoid the term “weak tornadoes”.  ALL tornadoes are capable of causing damage and harming people) and embedded within straight-line winds, making it difficult for meteorologists to detect, thus may explain why no warning was issued when it occurred.

The record-breaking heat wave ended by Tuesday as a cold front moved through the area.  8 out of the 10 days between March 10 and 19th saw new records at MSP.  Included in this stretch was the earliest 80 degree reading ever recorded in the Twin Cities, and a record seven days of 70 degree or higher temperatures for March.

Through March 23rd, we are already on our way to the warmest March ever with the average temperature over three degrees warmer than the highest mark set in 1910.

From Bill Stein at The Minnesota Forecaster:

New dew point records were also established in March:

According to the Minnesota State Climatology Office, as noted by Dr. Mark Seeley before the recent warmth, "The highest March dewpoint in the Twin Cities climate record is 60 degrees F on March 24, 1945."

• On March 17th, 19th, and 22nd, a dew point of 60 degrees was reported on hourly observations at Minneapolis St. Paul International Airport, tying the March dew point record.
• March 17th is now the earliest date in the calendar year that a 60 degree dew point has been recorded in the Twin Cities.

Despite a cool down with a couple fronts moving in early next week, temperatures will remain above normal (45 to 49 degrees) for the week with highs at least into the 50s.

Thunderstorm threat will increase for the start of the week with the best chance of storms for Minnesota coming on Tuesday.  The parameters for severe weather do not look all that impressive for the state Tuesday.  The greatest threat for any severe weather will be Monday to our south and southwest across South Dakota and Nebraska.  With the best wind shear over northeast Nebraska, tornadoes will be possible with any supercells expected to develop that day.

We should dry out after Tuesday night and should remain that way until next Saturday when another disturbance moves through the area.

RS

March Madness

This unusual heat wave for this time of the year has broken records already this week east of the Rockies as temperatures have felt more like late April with the mercury reaching as high as 80 degrees across parts of southern Minnesota.  In the Twin Cities, our normal temperature for this time of the year is 41 degrees, and we are already 11 degrees above normal for March.  We are on pace for the warmest March on record According to the Minnesota Climatology Working Group, the greatest number of maximum temperatures at or above 70 in March is five such days, which occurred in 1910.  That year also happened to be the warmest March on record with an average temperature of 45 degrees.

Friday was the warmest day of the heat spell as highs nearly topped 80 degrees officially in the Twin Cities.  Officially, it was 79 degrees, but airports around the metro did record temperatures in the 80s as Flying Cloud Airport in Eden Prairie was the leader at 82 degrees.  80 degrees or more has occurred previously in the Twin Cities during the month with March 23rd being the earliest day of the year.  This record will likely be broken today.

With Friday’s 79 degrees smashing the old record of 71 set in 1930, five out of the last seven days have set new high temperature records in MSP.  The record for consecutive days is five, which occurred five different times: June 26-June 30, 1931, June 16-June 20, 1933, July 10-July 14, 1936, February 16-February 20, 1981, and the last stretch between March 4-March 8, 2000.  The trend in-between record dates certainly indicates the climate is much warmer now than a half century ago.

The Twin Cities should see it’s earliest 80 degree reading Saturday as I’m projecting temperatures to reach around 82 degrees.  Some clouds may hamper maximum sunlight late in the day during peak heating, keeping the air a bit cooler.  Temperatures will drop off next week as an unsettled wetter pattern arrives on our doorstep.

Heavier thunderstorms appear possible on Monday, but the dynamics for a severe weather outbreak do not appear all that favorable.  The Storm Prediction Center did go ahead and issue a slight risk of severe thunderstorms on Monday across south central and east central Minnesota.  With these storms, we are looking at hail less than an inch in diameter, and gusty winds as the main threats.

RS

Fire danger today with record breaking temperatures

The record high temperature in the Twin Cities will be flirted with today as temperatures are expected to climb close to 60 degrees behind a warm front moving through the area.  The record for March 10th at MSP is 59 degrees set back in 1878.

The mild air as eliminated the snow pack from the southern Twin Cities metro all the way to the Minnesota/Iowa border.  The snow pack is visible on satellite, as well as the larger lakes frozen over in northern Minnesota.  The exposed ground combined with unusually warm air and low relative humidity has triggered a fire danger across the southern third of Minnesota.

The result is a Red Flag Warning issued by the National Weather Service for the southern tier of counties in Minnesota effective until 6:00 PM today.  This includes Redwood Falls, Mankato, and Rochester.  It's quite rare to see a Red Flag Warning this early in the year.  Typically these are issued before the green-up in April.

If you are working with an open flame today (including cigarettes), be extra cautious of your surroundings.  It’s not going to take much to get a grass fire going.

RS

Record heat in October? Fire danger increases this week

The very nice stretch continues this week as warm, dry weather is the main weather story across the state.  We will be in the 80s through Friday before temperatures cool down a bit for the weekend and into next week.

We have a shot of breaking a 132-year-old record on Wednesday for high temperatures in the Twin Cities.  The record is 87 degrees, set in 1879.  Both the Twin Cities and southwest suburbs are projected to be around 88 degrees for the day.

Since the high was 85 degrees for Tuesday, and the models are projecting warmer air for Wednesday, I have no doubts that we should see temperatures approaching 90 degrees for a daytime high. It’s truly an amazing climatological feat considering the lower sun angles this time of the year.

The temperatures combined with the dry spell have set the state for fire conditions across much of southern and western Minnesota through Wednesday as a Red Flag Warning issued for approximately the western third of Minnesota.

So what is a Red Flag Warning?  It’s an alert for dangerous fire conditions and issued by the National Weather Service when these criteria exist:

1. Sustained one-minute winds at standard 20 foot level are at or above 20 mph. However, in the Red River Valley of northwest Minnesota and in the southwest corner of the state sustained winds must be at or above 25 mph.
   
2. Minimum relative humidity at or less than 25 percent.
   
3. Temperatures at or greater than 75 degrees F. A “soft temperature threshold” used, mainly in
   spring fire season.

According to Tom Romaine, fire supervisor south for the Minnesota Department of Natural Resources (DNR):

Unusually high temps and low humidity, combined with increasing winds are creating potentially dangerous fire conditions across much of our region.  In the past 24 hours, many counties have put burning restrictions in place and some have banned recreational fires. It is important to for people to check with their county to see what restrictions exist.

Even if restrictions have not been posted in your county, great care should be taken with any outdoor fire right now.

The potential for crop field fires is also high right now. The low moisture content in corn and soybean fields creates a heightened fire danger.  It is more important than ever for farmers to keep machinery clean, make sure guards are in place and carry a fire extinguisher.

Use extra caution with open flames through the end of the week.  Only the slightest chance of rain returns overnight Saturday, but overall the next week looks rain-free.

RS

Severe weather possible Friday

A cold front is projected to move across Minnesota during the day on Friday and exit the area by the overnight hours on Saturday.

Out and ahead of the cold front, another hot and humid day is on tap for Friday as temperatures will remain in the mid-90s for a second straight day with dew points well into the 70s.

The front will be the focus for thunderstorm development during the late afternoon and early evening hours.  A very unstable air mass is in place with a cap expected to weaken as the day moves along that will be the focal point for severe thunderstorms.  The greatest potential for severe weather appears to be along the Minnesota Highway 23 corridor from Marshall through St. Cloud to Hinckley.  It appears the time frame for thunderstorms rumbling through the state will be between 4 and 8 PM.  I’m expecting more of a line of embedded thunderstorms will large hail and strong winds as the main threats, although a tornado is possible early in the storm evolution.

With this being a travel weekend with the 4th of July weekend, you’ll want to keep an eye to the sky and radar before you head out on the roads.

Have a great holiday weekend!

RS

Summer is back!

It appears that our 103-degree temperature reading back in early June was not the only glimpse of summer we will see in June.  Temperatures on Thursday should soar into the 90s across Minnesota as the jet lifts into Canada with an upper-level ridge over the Rocky Mountains.  Much of South Dakota will likely hit the century mark for high temperatures, but the question is how far east will the heat spread with the ridge.

The NAM forecast model is more liberal with the heat and pushes upper 90s into southwest Minnesota:

The GFS forecast model is a bit more reserved with clouds and precipitation in the area, and keeps the hottest air over South Dakota in the five-state region:

Based on these two interpretations, I think 100-degree temperatures are out of the question locally.  Most of Minnesota will be in the 90s I believe.  Areas near the Minnesota/South Dakota border will see temperatures in the upper 90s, while from the Twin Cities and points south will be in the low to middle 90s.  In any case, it will feel more like summertime, which has been missing since summer officially began on June 21st.

RS