Spring 2013 Highlights

The spring months of March - May across eastern Oklahoma and northwest Arkansas were on average cooler than normal, with Tulsa, OK and Fort Smith, AR drier than normal, and Fayetteville, AR wetter than normal.  Heavy rains in April and May helped to alleviate the persistent drought conditions across the region, and even led to flooding on several area rivers.  Several daily high and low temperature records were broken, along with the latest ever snowfall for both Tulsa, OK and Fayetteville, AR.  An active severe weather season set up during April and May, with several rounds of thunderstorms bringing large hail and damaging winds, along with 44 total tornadoes.

Temperatures . . .

The following line graphs depict the mean temperature for the months of March - May (in blue) along with the expected mean temperature (in red) for Tulsa, OK, Fort Smith, AR and Fayetteville, AR.  The mean temperatures were taken from 1980 - 2010.

The spring months of 2013 started out cool, with the beginning of March slightly below normal.  Temperatures warmed some by the middle of the month, followed by a more pronounced cold snap during the latter third of the month.  This led to average temperatures ranging between 3 and 4 degrees below normal for the month at all three sites.  While conditions remained cooler than normal during April in Tulsa (4.3 degrees below normal), Fort Smith and Fayetteville temperatures were near normal for the month (0.7 and 1.5 degrees below normal, respectively).  May started out very cold, with temperatures at all three sites between 15 and 20 degrees below normal for several days.  By the second week of May, conditions warmed near normal, with slight variations for the rest of the month.  This let to slightly below normal temperatures in Tulsa (2.5 degrees below normal), while Fort Smith and Fayetteville were closer to normal (0.9 and 1.5 degrees below normal, respectively).

Precipitation . . .

The following bar graphs depict the mean precipitation and snowfall for the months of March - May (in blue) along with the expected mean precipitation and snowfall (in red) for Tulsa, OK, Fort Smith, AR and Fayetteville, AR.  The mean precipitation and snowfall amounts were taken from 1980 - 2010.

First, looking at the precipitation (top row), rainfall amounts were near normal in March for both Fort Smith and Fayetteville, while Tulsa was over 2 inches below normal.  April and May brought more much needed rainfall to the region, with slightly below normal precipitation at Tulsa and Fort Smith, and above normal rainfall for Fayetteville, with over 3.5 inches of excess precipitation for the spring season.

Spring snowfall (bottom row) was lacking this year, with only trace amounts during the months of March at Tulsa and Fayetteville.  April brought no snow at all, which is normal for eastern Oklahoma and northwest Arkansas.  Record snows occurred in May, with daily record snows at Tulsa and Fayetteville, and record latest snowfall ever recorded at both Tulsa and Fayetteville (May 2 and May 3, respectively).  Fort Smith received no snowfall for the entire spring season.

Drought Progression . . .

The following chart depicts the amount of precipitation that fell leading up to, and during the spring months of 2013, and how that impacted the current drought across the area.  The first image is the amount of rainfall that fell during the month (observed precipitation).  The second image is the percentage of expected rainfall that fell during the month (percent of normal).  The third image is the state of drought near the end of that month (drought progression).

	Observed Preciptation	Percent of Normal	Drought Progression
February 2013			February 26, 2013
March 2013			March 26, 2013
April 2013			April 30, 2013
May 2013			May 28, 2013

At the end of winter 2013, eastern Oklahoma and northwest Arkansas were still experiencing a persistent drought, with the entire forecast area under a D2 (severe) or greater drought.  During the month of March, much of east central Oklahoma received below normal amounts of precipitation, while some of far eastern Oklahoma and western Arkansas saw above normal amounts of rain.  This led to drought improvements along and east of Highway 69, and continued D2 - D3 drought across east central Oklahoma.  Above normal precipitation fell during the month of April, with much of eastern Oklahoma and western Arkansas receiving between 5 - 8 inches of rain.  This served to greatly reduce the drought conditions across the forecast area, dropping the D1 - D3 levels to D0 or no drought for most of the region.  Locations along and north of Highway 44 remained in D2 - D3 drought, as precipitation in this area was slightly below normal for the month.  Additional heavy rainfall occurred over the area again in May, with much of eastern Oklahoma and western Arkansas receiving above normal precipitation.  Many locations saw between 8 - 10 inches during the month.  This extra rainfall further lessened the drought across the area, eliminating all drought in northwest Arkansas and far southeast Oklahoma, and reducing the drought over northeast Oklahoma.  D2 drought or less still remained along and northwest of Highway 44.

Averages and Records . . .

Below are tables for Tulsa, OK, Fort Smith, AR and Fayetteville, AR with their monthly averages and records for temperatures, precipitation, and snowfall for the spring months of March - May, along with the spring seasonal average.  Below the tables are the daily temperature and precipitation records set this spring season.

Tulsa:

* March 15, tied the highest maximum temperature record of 84 degrees (other records from 1914 and 1921).

* April 19, tied the lowest minimum temperature record of 34 degrees (other record from 1953).

* April 24, set a new lowest minimum temperature record of 32 degrees (old record was 37 degrees from 1909 and 2005).

* April 25, set a new lowest minimum temperature record of 34 degrees (old record was 36 degrees from 1910).

* May 12, tied the lowest minimum temperature record of 40 degrees (other record from 1960).

* No daily precipitation records set during the spring in Tulsa.

* March 22, tied the highest daily snowfall record with a trace of snow (other records from 1915, 1932, 1953, 1968, 1992, 1999, 2006).

* May 2, set a new highest daily snowfall record with a trace of snow.   This also set a new latest snowfall date of May 2 (old record was April 18, 1953 with a trace of snowfall).

Fort Smith:

* March 15, tied the highest maximum temperature record of 83 degrees (other record from 1961).

* May 3, tied the lowest minimum temperature record of 37 degrees (other records from 2005 and 2011).

* May 5, set a new lowest minimum temperature record of 39 degrees (old record was 40 degrees from 1954).

* May 21, set a new highest daily rainfall record with 2.46 inches of rain (old record was 1.88 inches from 1979).

* No daily snowfall records set during the spring season in Fort Smith.

Fayetteville:

* March 15, set a new highest maximum temperature record of 79 degrees (old record was 77 degrees from 1961).

* April 25, set a new lowest minimum temperature record of 27 degrees (old record was 33 degrees from 1977 and 1983).  This also set a new latest hard freeze (temperature at or below 28 degrees) date of April 25th.

* May 5, set a new lowest minimum temperature record of 31 degrees (old record was 35 degrees from 1954).

* April 18, set a new highest daily rainfall record with 1.61 inches of rain (old record was 1.17 inches from 1970).

* May 30, set a new highest daily rainfall record with 2.28 inches of rain (old record was 1.00 inches from 1990).

* May 3, set a new highest daily snowfall record with 0.5" of snow.  This also set a new latest snowfall date of May 3 (old record was April 18, 1953 with a trace of snowfall).

Weather Highlights . . .

Here are a few of the more significant events of the spring season 2013, including winter weather, severe weather, heavy rain, and flooding.

March:

March 9 - 10, 2013 Heavy Rainfall Event Photo Credit: AHPS	March 23 - 24, 2013 Snowfall Event Photo Credit: NWS Tulsa, OK	March 30, 2013 Severe Weather Event Photo Credit: Von Castor (Fox 23 News), photo taken near Muskogee, OK

March brought a mix of severe and winter weather, along with several days of elevated fire dangers to eastern Oklahoma and northwest Arkansas.  From March 9th into March 10th the combination of a strong upper level low pressure system and a surface cold front triggered strong showers and thunderstorms over the southeast portion of the forecast area.  As these showers and storms tracked northeast, they traveled over the same locations, dropping several inches of rain over a narrow path extending from near Durant, OK toward Stilwell, OK.  Freezing temperatures on the back side of an exiting low pressure system caused several inches of snow to accumulate over northern portions of the forecast area overnight on March 23rd, and into the morning hours of March 24th.  Up to 3 inches of snowfall was reported within Ottawa and Nowata Counties.  A significant severe weather event occurred at the end of the month, during the evening hours of March 30th, as a cold front pushed through the area.  Showers and storms developed along the front, some becoming severe, with numerous reports of quarter size hail (1 inch).  Tennis ball size hail (2.75 inch) was reported in Muskogee, OK, and 3 inch hail was reported west of Fort Gibson, OK.  Two brief tornadoes were also confirmed, an EF-0 near Fort Gibson, OK, and an EF-1 near Sallisaw, OK.  More information about the severe weather of March 30, 2013 can be found here.

April:

April 1 - 3, 2013 Heavy Rainfall Event Photo Credit: OK Mesonet	April 17 - 18, 2013 Severe Weather Event Photo Credit: NWS Tulsa, OK	April 23 - 25, 2013 Cold Snap Event Photo Credit: OK Mesonet

April brought several rounds of heavy rain, along with severe weather, and a late month cool down with light snow.  Several days of heavy rain occurred during the first few days of April, dropping between 3 - 5 inches of precipitation across much of southeast Oklahoma.  The rain caused flooding across portions of Pittsburg County, where two state highways had to be closed, and forced the Poteau River at Panama to rise above flood stage.  Thunderstorms developed along a cold front during the evening hours on April 17th.  These storms brought very heavy rain, with many locations receiving between 3 - 5 inches, and even isolated reports of 7 inches of rain.  This caused flash flooding along the corridor of heaviest rainfall, extending from near Welty, OK, northeast toward Bentonville, AR.  Late on April 17th, and into the early hours of April 18th, some of the storms formed into a bow echo, producing very strong winds, and several brief tornadoes, including the EF-2 tornado near Butler, OK pictured above.  More information about the severe weather of April 17 - 18, 2013 can be found here.  A strong cold front pushed into eastern Oklahoma and northwest Arkansas late in the month, bringing unseasonably cold temperatures to the area.  Between April 23 - 25, temperatures ran on average 10 - 15 degrees below normal.  Light snow was also reported across for northeast Oklahoma, near the Kansas border.

May:

May 2 - 4, 2013 Snowfall Event Photo Credit: NWS Tulsa, OK	May 19 - 20, 2013 Severe Weather Event Photo Credit: NWS Tulsa, OK	May 29 - 31, 2013 Severe Weather Event Photo Credit: NWS Tulsa, OK

May brought the areas latest snowfall on record, along with several rounds of severe weather, and heavy rain causing flooding on many area rivers.  A strong cold front brought cold arctic air into the region in early May, dropping temperatures well below normal, with average temperatures around 20 degrees below normal for several days.  On the back side of the front, precipitation turned from a cold rain over to sleet and snow during the afternoon and evening hours of May 2nd.  Snowflakes were observed at the National Weather Service Office in Tulsa, OK, making this the latest snowfall since records began in 1900 (the previous record was April 18, 1953), and the only time since records began that snow has fallen in Tulsa, OK in May.  Snow was also reported across far northeast Oklahoma, and in the higher elevation areas of southeast Oklahoma, where accumulations up to 2 inches were seen during the morning hours of May 3rd.  A second round of snow fell during the late hours of May 3rd and during the morning of May 4th.  Snow accumulations between 1 - 2 inches were reported across far northwest Arkansas, making this the latest snowfall on record for Fayetteville, AR, as well as the entire state of Arkansas.  More information about the historic snowfall event of May 2 - 4, 2013 can be found here.  Thunderstorms developed along a dryline, and outflow boundaries during the afternoon hours of May 19th and May 20th, as the atmosphere became very unstable across the region.  Several of these thunderstorms quickly became severe, producing strong damaging winds, large hail, along with 12 tornadoes across northeast Oklahoma and northwest Arkansas.  As the storms approached the Arkansas border in northeast Oklahoma, they merged into a bow echo (pictured above), and produced several weak tornadoes.  More information about the severe weather of May 19 - 20, 2013 can be found here.  A second round of severe weather occurred at the end of the month, from May 29 - 31, when 3 waves of heavy rainfall, along with severe weather, tracked across eastern Oklahoma and northwest Arkansas.  On May 29th, a strong low pressure system was located over the Northern Plains, with a cold front and dryline draped across western Oklahoma, and a very moist and unstable airmass over the area.  Thunderstorms developed along the cold front and dryline, and tracked northeast into eastern Oklahoma and northwest Arkansas, producing strong damaging winds, large hail, and very heavy rainfall.  The cold front stalled across the area, triggering additional storms during the afternoon hours of May 30th.  These storms again produced damaging winds, large hail, and several tornadoes, along with the EF-2 tornado that affected portions of Broken Arrow, OK pictured above.  The storms tracked over the same locations, producing very heavy rainfall, which lead to flash flooding in portions of Le Flore County where bridges were washed out and homes were inundated with water.  A third round of severe weather developed during the afternoon hours on May 31st, as thunderstorms developed along the stalled dryline and cold front in central Oklahoma.  The storms tracked northeast into eastern Oklahoma and northwest Arkansas bringing more severe weather, including several tornadoes, along with heavy, flooding rains to the area.  Once the three day event was over, countless reports of severe hail and wind damage occurred, along with 12 tornadoes, and widespread areal and flash flooding.  Rainfall totals ranged between 5 - 8 inches across much of the area, with a weather observer outside of Okemah reporting 7.54 inches in 24 hours between 7am May 31st - 7am June 1st.  Several of the area's rivers rose to flood levels, including the Illinois River, the Neosho River, the Kiamichi River, the Caney River, the Verdigris River, the Spring River, the Poteau River, and the Bird Creek.  More information about the severe weather and flooding of May 29 - 31, 2013 can be found here.

Summer 2013 Forecast . . .

Below is a chart with the Climate Prediction Center's forecast for both temperatures and precipitation for the next three months (July - September), along with the Seasonal Drought Outlook for the summer months of June - August.  For temperatures, there is an increased chance of above normal temperatures for all of eastern Oklahoma and northwest Arkansas.  For precipitation, while western Oklahoma has a slight chance for below normal precipitation, eastern Oklahoma and northwest Arkansas shows an "equal chance" rating.  This means that there are no indications that the precipitation amounts will be either above or below normal, thus, normal precipitation, below normal, and above normal are all equally likely.  The third image depicts the drought outlook for the nation.  The only part of our forecast area which is currently under drought conditions is along and north of highway 44.  This area is expected to have improving drought conditions through the summer months.  Drought conditions are not expected to re-develop across the rest of our forecast area of eastern Oklahoma and northwest Arkansas.

Summer 2013 Temperature Outlook	Summer 2013 Precipitation Outlook	Summer 2013 Drought Outlook

Updated: June 27, 2013