Question 1

What does the SPP footprint cover?

Accepted Answer

Southwest Power Pool operates the bulk transmission system across the central United States, with a footprint that historically spanned Kansas, Nebraska, Oklahoma, the Dakotas, and parts of surrounding states. Effective April 1, 2026, SPP expanded westward to incorporate the Colorado Front Range (Denver, Colorado Springs), southeastern Wyoming (Cheyenne), and a portion of north-central Montana (Great Falls), bringing former Western Area Power Administration and other entities into the SPP footprint. The expansion stretches SPP from the Canadian border to the Texas Panhandle and from the Mississippi River nearly to the Rockies.

Question 2

What does the SPP generation mix look like?

Accepted Answer

SPP leads the United States in wind generation as a percentage of total system load, with annual wind energy share periodically exceeding 50%. Oklahoma, Kansas, and the Texas Panhandle host massive wind resources along the I-35 and Caprock corridors. Coal remains a significant share of the generation mix, particularly in Wyoming, Kansas, and Oklahoma, although retirement schedules are accelerating. Natural gas combined-cycle capacity is concentrated in the eastern footprint and in Oklahoma. Nuclear contributions come from Wolf Creek (Kansas) and Cooper (Nebraska). Hydro from the Missouri River dams contributes baseload and flexibility. Solar and battery storage are growing, especially in Oklahoma and the new Colorado footprint.

Question 3

What weather events most stress the SPP grid?

Accepted Answer

SPP sits in the heart of Tornado Alley, and the defining historical event is Winter Storm Uri in February 2021 — extended cold across the southern footprint forced controlled rotating outages, the first in SPP's history. Spring brings violent severe weather (tornadoes, large hail, damaging straight-line winds) that test grid hardening, and summer extreme heat across Oklahoma and Kansas regularly exceeds 100°F for extended stretches. The April 2026 western expansion adds high-altitude weather variability — Chinook downsloping winds along the Front Range, intense thunderstorms, and rapid snowmelt cycles. Hailstones large enough to damage solar panels are a regular spring and summer concern.

Question 4

How does the Storm Prediction Center warn for severe weather across SPP?

Accepted Answer

The Storm Prediction Center publishes daily convective outlooks (Marginal, Slight, Enhanced, Moderate, and High Risk) covering days 1 through 8, flagging areas where severe thunderstorms, tornadoes, and damaging winds are likely. Across the SPP footprint — the heart of Tornado Alley — Moderate and High Risk days drive the most aggressive grid-hardening posture. Tornado Watches typically precede Tornado Warnings, which are real-time alerts based on radar-detected rotation or trained spotter reports, and they routinely interrupt transmission and distribution operations across Kansas, Oklahoma, and the Texas Panhandle.

Question 5

What weather drives the SPP footprint's coldest emergency events?

Accepted Answer

Arctic air masses spilling south out of central Canada drive the most extreme cold across SPP. The Climate Prediction Center 6–10 and 8–14 day outlooks often signal these events a week or more in advance, followed by Wind Chill Watches and Warnings as the airmass approaches. Wind Chill Warning criteria across the northern footprint are typically -35°F or lower; across Oklahoma and Kansas the threshold is closer to -10°F. The February 2021 Winter Storm Uri event produced sustained sub-zero conditions across the entire SPP footprint and is the modern reference case.

Question 6

How are large-hail events tracked across the central plains?

Accepted Answer

Large hail (one inch or greater) is one of the most common severe-weather threats across SPP, and the SPC explicitly forecasts hail probability in its convective outlooks. Severe Thunderstorm Warnings are issued in real time when radar or spotter reports confirm hail of one inch or greater. Hailstones of 1.75 inches and up — often called 'significant severe' — are a particular concern for the rapidly growing utility-scale solar fleet across Oklahoma, Kansas, and the new Colorado footprint.

Question 7

What weather alerts dominate the new Colorado SPP footprint?

Accepted Answer

The Colorado Front Range adds high-altitude weather variability to SPP. The NWS issues High Wind Warnings for Chinook downsloping events along the Front Range that can produce gusts above 75 mph, Winter Storm Warnings and Blizzard Warnings for upslope snow, and Red Flag Warnings during the dry, windy transitions of spring and fall. Wildfire smoke from regional fires can also degrade solar output across the Colorado and southeastern Wyoming portions of the footprint for days at a time.

Question 8

How do Heat Advisories and Excessive Heat Warnings work across SPP?

Accepted Answer

The NWS issues Heat Advisories when forecast heat indices reach 100°F to 105°F for two or more hours and Excessive Heat Warnings at 105°F to 110°F or higher, with thresholds varying by climate zone. Across the central and southern SPP footprint — Oklahoma City, Tulsa, Wichita, Kansas City — these alerts are routine through July and August. Multi-day heat events with overnight lows in the 80s drive the highest summer cooling demand across the system.

Question 9

What sources are referenced for the historical events on this page?

Accepted Answer

Specific event references on this page (the February 2021 Winter Storm Uri rotating outages and the April 2026 western footprint expansion) are drawn from the FERC, NERC, and Regional Entity Joint Inquiry into the February 2021 Cold Weather Event, SPP's Winter Storm Uri Comprehensive Report and integration filings at spp.org, and the NWS Storm Prediction Center convective outlook documentation at spc.noaa.gov.

City	Wed May 27	Thu May 28	Fri May 29	Sat May 30	Sun May 31	Mon Jun 1	Tue Jun 2	Norm
Kansas City, MO	8665	8366	8064	8264	8162	8462	8461	76/57
Oklahoma City, OK	7864	8064	8468	8669	8667	8465	8163	80/59
Tulsa, OK	8166	7866	8268	8369	8568	8465	8263	80/59
Omaha, NE	9165	9065	8464	8463	8361	8560	8360	74/53
Wichita, KS	8364	7863	8165	8366	8465	8463	8361	79/57
Lincoln, NE	9063	8864	8362	8362	8460	8560	8459	75/53
Topeka, KS	8663	8264	8163	8364	8362	8561	8460	77/56
Sioux Falls, SD	9263	9061	8761	8660	8358	8358	8057	71/47
Des Moines, IA	8964	8763	8563	8562	8360	8560	8560	73/52
Little Rock, AR	8367	8066	8266	8467	8365	8263	8161	82/60
Fayetteville, AR	8265	7865	7865	8166	8264	8162	8060	78/55
Shreveport, LA	7970	8370	8672	8872	8872	8669	8466	84/62
Denver, CO	7354	8055	8454	8253	8354	8254	7954	71/47
Colorado Springs, CO	6550	7552	7951	8151	8052	8053	7552	68/44
Cheyenne, WY	7050	7350	7749	7347	7548	7549	7249	71/46
Great Falls, MT	8456	9257	9155	7247	6643	6944	7247	68/44

City	Wed May 27	Thu May 28	Fri May 29	Sat May 30	Sun May 31	Mon Jun 1	Tue Jun 2
Kansas City, MO	5	390.02"	480.08"	34	340.11"	18	6
Oklahoma City, OK	680.19"	450.15"T-STORM	440.10"	460.13"T-STORM	380.37"MOD	260.07"	150.13"
Tulsa, OK	640.17"T-STORM	620.29"T-STORM	580.10"	520.07"T-STORM	330.18"	20	150.02"
Omaha, NE	1	8	23	28	280.08"	14	10
Wichita, KS	450.04"	710.20"T-STORM	550.02"	510.05"	350.23"	23	21
Lincoln, NE	0	22	33	32	320.11"	180.05"	13
Topeka, KS	10	460.14"	470.07"	33	300.08"	21	11
Sioux Falls, SD	260.02"	21	7	18	21	18	17
Des Moines, IA	2	2	7	8	9	9	5
Little Rock, AR	640.32"MOD	690.51"MOD	690.46"MOD	510.17"	330.06"	250.02"	250.04"
Fayetteville, AR	600.06"T-STORM	840.27"T-STORM	800.28"MOD	660.11"T-STORM	470.09"T-STORM	300.05"	150.04"
Shreveport, LA	630.81"T-STORM	510.41"MOD	390.13"	310.02"	420.15"T-STORM	390.23"	300.06"
Denver, CO	560.02"T-STORM	37	340.11"	30	490.07"	530.18"	480.13"T-STORM
Colorado Springs, CO	800.16"T-STORM	390.02"	210.06"	10	37	450.08"	540.25"T-STORM
Cheyenne, WY	440.04"	37	460.04"T-STORM	610.32"T-STORM	410.18"	490.31"MOD	410.07"
Great Falls, MT	570.02"	33	53	890.36"MOD	860.67"MOD	340.09"	20

City	Wed, 5/27	Thu, 5/28	Fri, 5/29	Sat, 5/30	Sun, 5/31	Mon, 6/1	Tue, 6/2
Kansas City	3 mphLowENE	6 mphLowE	7 mphLowESE	6 mphLowESE	8 mphModerateESE	6 mphLowE	6 mphLowE
Oklahoma City	7 mphLowSE	4 mphLowSSE	5 mphLowS	8 mphModerateSSE	8 mphModerateSSE	7 mphLowESE	7 mphLowE
Tulsa	4 mphLowESE	3 mphLowESE	3 mphLowS	4 mphLowSE	5 mphLowSE	5 mphLowE	5 mphLowNE
Omaha	3 mphLowSSE	6 mphLowESE	6 mphLowESE	7 mphLowSE	8 mphModerateSE	5 mphLowESE	5 mphLowESE
Wichita	7 mphLowESE	6 mphLowE	6 mphLowESE	7 mphLowSE	8 mphModerateSE	7 mphLowESE	6 mphLowENE
Lincoln	5 mphLowSE	7 mphLowESE	7 mphLowSE	8 mphModerateSE	8 mphModerateSE	5 mphLowESE	5 mphLowESE
Topeka	4 mphLowE	5 mphLowE	5 mphLowESE	5 mphLowESE	6 mphLowESE	4 mphLowE	4 mphLowE
Sioux Falls	3 mphLowSW	8 mphModerateESE	8 mphModerateSE	10 mphModerateSE	12 mphModerateSE	7 mphLowSE	7 mphLowSE
Des Moines	4 mphLowWSW	5 mphLowE	7 mphLowESE	6 mphLowESE	8 mphModerateESE	5 mphLowESE	6 mphLowESE
Little Rock	4 mphLowSE	2 mphLowESE	2 mphLowNNE	2 mphLowNNE	3 mphLowENE	6 mphLowNNE	7 mphLowNE
Fayetteville	5 mphLowSE	3 mphLowESE	3 mphLowSSE	4 mphLowSSE	5 mphLowESE	5 mphLowENE	6 mphLowE
Shreveport	7 mphLowSSE	3 mphLowE	2 mphLowSSE	3 mphLowSSW	3 mphLowESE	4 mphLowNE	5 mphLowNE
Denver	9 mphModerateSSE	4 mphLowSE	4 mphLowSE	5 mphLowS	5 mphLowWNW	6 mphLowENE	6 mphLowESE
Colorado Springs	4 mphLowSE	5 mphLowSSE	6 mphLowSSW	7 mphLowWSW	7 mphLowWNW	7 mphLowESE	4 mphLowSW
Cheyenne	14 mphModerateSSE	15 mphHighSSE	12 mphModerateSSE	9 mphModerateSW	7 mphLowWSW	7 mphLowS	8 mphModerateS
Great Falls	5 mphLowWSW	4 mphLowSW	5 mphLowS	8 mphModerateWNW	15 mphHighWSW	7 mphLowW	4 mphLowWSW

Date	HDD Fcst	CDD Fcst	HDD Norm	CDD Norm	HDD Dep.	CDD Dep.
Wed May 27	0.9	7.8	2.6	1.9	-1.7	+5.9
Thu May 28	0.3	7.4	2.6	1.9	-2.3	+5.5
Fri May 29	0.1	7.4	2.6	1.9	-2.5	+5.5
Sat May 30	0.7	7.5	2.6	1.9	-1.9	+5.6
Sun May 31	0.9	6.8	2.6	1.9	-1.7	+4.9
Mon Jun 1	0.7	6.4	2.6	1.9	-1.9	+4.5
Tue Jun 2	0.7	5.2	2.6	1.9	-1.9	+3.3
7d Total	4.3	48.5	18.2	13.3	-13.9	+35.2

Metric	Actual	Normal	Departure
CDD	210.6	51.3	+159.3
HDD	2348.8	2825.8	-477.0

SPP

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