…UNSEASONABLY COLD AIR HEADED TOWARD OKLAHOMA…
A strong cold front will move into Northwest Oklahoma during the morning hours on Wednesday. This front will approach Central Oklahoma during the late afternoon and be passing through Southeast Oklahoma during the early morning hours of Thursday.
For Wednesday, the primary concern will be with thunderstorms that are expected to form near the front in the afternoon. Some of these storms are likely to become severe with scattered reports of large hail and damaging winds expected.
Wind will be an issue behind the front with much of the state seeing strong north winds gusting to between 35 and 45 mph Wednesday and Thursday. Over far Western Oklahoma and the Panhandle, winds are likely to gust to between 45 and 55 mph.
As the cold air settles into the state, gardeners will want to be aware that near or below freezing temperatures are likely. Northwest Oklahoma will see these cold temperatures on Thursday morning. By Friday morning, damaging cold will be possible across the northwest 2/3′s of the state. A solid freeze with temperatures falling into the 20′s will be possible across the northern part of the state Friday morning.
Precipitation is expected to linger through Friday across the state. As the cold air deepens, some snow is expected to mix with rain across the northern half of the state. Across Northwest Oklahoma, some of this may begin to accumulate. These areas have seen temperatures in the 90′s for the past couple of days, so ground temperatures are not likely going to allow significant accumulations.
This was a pretty straight forward chase day with a tight target, high confidence in supercell storms, and an outside chance at a tornado. We didn’t come away with the tornado, but everything else went to plan. Doug and I headed west on I-40 as storms were getting organized along a front in Northwest Oklahoma and near a triple point along the Texas/Oklahoma border near I-40. We got off at the Burns Flat exit and worked our way back to a nice viewing area just a couple miles south of I-40. We sat at that spot for a good 45 minutes watching a couple of supercell storms to our west and northwest. This allowed for some decent time lapse video. There was one area of interest in the updraft region of one of the storms which had us seriously wondering if a tornado was occurring. We were just too far away to tell for sure, and have written this off because it was in an area where there were likely a large number of spotters, and no reports of a tornado came in. We jogged east southeastward ahead of the storms as they tracked through Washita County. At times, there was some nice structure to be seen and we got some very nice sunset colors just north of Gotebo. On our way back, we found hail that still measured 1.94 inches in Caddo County, after about 30 minutes of melt time. There was also a large amount of hail north of Calumet which was still on the ground a couple of hours after falling from storms which moved through Canadian County.
April 26, 2013 Chase Route
Storm west of Elk City, Oklahoma.
Supercell moving east southeast through Washita County.
Sunset north of Gotebo, Oklahoma
Upper: Model data this evening is in fairly good agreement through 72 hours, which gets us to the end of this outlook period. There are some significant differences after Wednesday that hopefully get sorted by mid-week. The strongest mid-level flow through Monday will be found over the northern part of the U.S. Over the Southern Plains, a weak trough of low pressure will be located over Central and Southern Texas. A very strong jet segment will be moving southeastward over the Pacific Northwest. By late afternoon on Tuesday, a sharpening trough of low pressure will be found over the Snake River Valley and Great Basin. Weak low pressure will be moving eastward along the Gulf Coast. By Wednesday morning, the strong trough over the Rockies will be overspreading the High Plains with moderately strong southwest flow aloft beginning to spread over Oklahoma.
Surface: Pressures will fall steadily across the High Plains during the day Monday, with southwest winds over Oklahoma. By Noon Tuesday, a cold front will begin to move southward over the Central Plains while organized low pressure develops over Southeast Colorado. The cold front will be pushing into Northwest Oklahoma just before daybreak on Wednesday. This strong front will make it through almost all of the state by sunset.
Impacts: Southwest winds, warm temperatures and fairly low humidity will result in elevated fire danger across portions of Western Oklahoma on Monday. Near the Texas border, winds may gust during the day to near 40 mph. Similar conditions on Tuesday will again result in elevated fire danger. Winds will once again be gusting to around 40 mph. Temperatures will be above / well above in some areas / normal on Monday and Tuesday. As the cold front pushes through the state on Wednesday, strong north winds gusting to 40 mph and much cooler air will spread into Oklahoma. By afternoon, showers and thunderstorms are expected along and behind the front, with the greatest precipitation chances across the southeast 2/3′s of the state. Precipitation chances will remain quite high statewide into Thursday.
Monday morning: 58
Tuesday morning: 61
Wednesday morning: 62
Wednesday: 76 / Showers and thunderstorms
Model data over the last 24 hours has trended toward increased chances of severe storms in Oklahoma on Friday. An upper system will be moving from the Southern Rockies to the Southern Plains during the day, and surface low pressure is expected to organize over the Eastern Texas Panhandle. A warm front will lift northward through portions of Southern and Western Oklahoma. In the warm sector, the atmosphere should become increasingly moist and fairly unstable during the afternoon with MLCAPE reaching to near 1500 j/kg. The highest instability will be associated within the 50 to 100 mile wide plume of higher moisture which will extend along an axis from near Walters to near Woodward. Forecast wind profiles are supportive of supercell storms with strong veering in the lower levels under west southwesterly 50 to 60 knot mid-level winds. Early afternoon thunderstorms associated with warm air advection may generate some hail over Central and Southeast Oklahoma. By afternoon, stronger storms are expected to form over Western Oklahoma. Should supercell storms be able to develop, large hail to tennis ball size and damaging winds will be possible. While the tornado threat is low, it cannot be considered zero. Strong to severe storms will advance eastward into Central and Southern Oklahoma during the evening hours.
An unseasonably cold air mass moved south through the Plains resulting in numerous low temperature records being tied or broken. Most of the records were concentrated from Southern Nebraska to Central Texas.
Upper: A broad trough of low pressure will be located over the Eastern U.S. Thursday morning. A small, but fairly strong closed low will be found near San Diego, California. Precipitation chances over the next several days will be largely tied to the Southern California upper low. The system will be tracking across the Southern High Plains by sunrise Friday, and will have passed Oklahoma by early Saturday, as it moves toward Middle Mississippi Valley. Through the end of the weekend, stronger flow aloft will be confined to the northern half of the country, with weak and somewhat disorganized flow over the Southern Plains.
Surface: Thursday will start cold in Oklahoma. High pressure over the state will remain in control during the first part of the day with generally light and variable winds. Quite a few mid and high level clouds tonight will help keep temperatures just a bit warmer than they would be with clear skies. South winds will return across all of Oklahoma by Thursday afternoon, becoming quite strong over the Panhandle. By Friday morning, the approach of the upper system will result in surface low pressure becoming organized over the Texas Panhandle. Scattered showers thunderstorms are expected to increase during the morning hours as lifting associated with the upper system, and low-level moisture increases. This low will track eastward along the Red River from Friday evening into Saturday morning. The greatest chance for showers and thunderstorms will be over the southern half of the state late Friday and early Saturday. A few of the storms could become severe, with some large hail expected. As the low slides by, winds will become light northeasterly across the state and slightly cooler air will filter into Northeast and Central Oklahoma. The cool down will be brief with warm south winds returning statewide on Sunday.
Thursday morning: 32
Friday morning: 49 / Showers and thunderstorms
Friday: 64 / Showers and thunderstorms
Saturday morning: 49 / Showers
Sunday morning: 47
There were strong model signals that isolated or scattered thunderstorms would form across Northwest Oklahoma this afternoon. Meager moisture was resulting in only moderate, but sufficient instability, to support severe storms, and shear profiles favored rotating storms (supercells). I drove northwest and fueled in Seiling as storms formed near Woodward and along the Kansas border northwest of Alva. As I was leaving Seiling, the Woodward storms started weakening, both visually and on radar. The storms near the Kansas border were looking more impressive and they became my targets. A lead storm that moved just east of Cherokee was rather high-based, and had a lot of cold outflow undercutting it. A trailing storm was going to be passing close to Alva. This storm looked better on radar, and I figured that it might be able to perform a little better if it could play on a boundary put down by the Cherokee storm. While it is doubtful that the Alva storm produced a tornado, it did produce just about everything else. There were plenty of nice supercell features to observe with this storm as it rolled southeast through Woods and Alfalfa Counties. I even managed to get a few lightning images in Southern Alfalfa County before returning home.
April 22, 2013 Chase Route
Storms near Kansas border over canola field.
Supercell near Alva.