Severe Storm Risk - Decatur, AR

There is a Slight Severe Storm Risk for your location. Continue reading for today's outlook from the National Weather Service's Storm Prediction Center. -------------------- National Severe Storm Outlook THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE MID MISSISSIPPI VALLEY INTO THE SOUTHERN GREAT LAKES...AND FROM WEST TEXAS INTO SOUTHWEST OKLAHOMA SUMMARY Severe thunderstorms are forecast today from the southern Plains into the southern Great Lakes vicinity. All severe hazards are possible, including the risk for a few strong to intense tornadoes and very large hail. Synopsis A split-flow upper pattern persists across the CONUS this morning. Early-morning satellite imagery shows a well-defined upper low over the central Baja Peninsula within the southern stream and a subtle, low-amplitude shortwave trough moving through the Pacific Northwest within the northern stream. Surface analysis shows a large reservoir of low-level moisture from the southern Plains and Lower MS Valley northeastward into the southern Great Lakes. General expectation is for both the southern-stream upper low and northern-stream shortwave to progress eastward today, as some modest phasing occurs between these two features. This evolution will contribute to strengthening mid-level flow across much of the Plains and MS Valley, while also resulting in increased ascent across the broad warm sector. This will result in a large area of strong to severe thunderstorms from the southern Plains into the southern Great Lakes, beginning during the early afternoon and persisting through the evening and overnight. Two areas within this broader region, west TX into southwest OK and the Mid MS Valley into the southern Great Lakes, have environmental conditions that support the potential for significant severe weather, including very large hail greater than 2" in diameter and strong to intense tornadoes. Mid MS Valley into the Southern Great Lakes Northern-stream shortwave trough is forecast to move out of MT/WY this evening, accompanied by strong mid-level flow (over 100 kt at 500 mb). However, this will be well west of the moist and buoyant airmass across the Mid MS Valley. Even so, modest height falls are anticipated over the region beginning during the late afternoon. Of more consequence for the severe-weather potential, a surface low (currently over the central NE/KS border vicinity) will eject northeastward ahead of the shortwave, moving along the stationary boundary that currently extends into far southern WI. This boundary is also expected to sharpen throughout the day as low-level moisture advection persists to its south and cold, northeasterly surface winds persist to its north. Low-level convergence near the surface low and stationary front will be augmented by the previously mentioned subtle height falls to support thunderstorm development. These mesoscale details as well as which side of the stationary boundary storms develop will be key for determining the primary severe hazard. The airmass south of the stationary front is expected to be moderately to strongly unstable, as temperatures in the 80s, dewpoints in the low/mid 60s, and steep mid-level lapse rates combine to support 2000+ J/kg of MLCAPE. Steep mid-level lapse rates and associated moderate elevated buoyancy will persist north of the front as well. Given the subtle forcing and mesoscale character of this set up, CAM guidance varies notably on the timing and location of thunderstorm development. Kinematic profiles suggest that any surface-based warm sector development should quickly become supercellular, with all severe hazards possible, including very large hail and tornadoes. A strong to intense tornado is possible, particularly with any storms ongoing around 00Z when the low-level flow increases notably, resulting in considerable elongation of the low-level hodograph. Latest guidance suggests this tornado risk will exist into parts of far southwest Lower MI, so probabilities were expanded accordingly. Very large hail (i.e. 2"+ in diameter) will also be possible north of the front where strong deep-layer vertical shear exists. Southern Plains The southern-stream upper low is forecast to eject eastward across northern Mexico today, with ascent preceding this low overspreading a West TX dryline by the afternoon. Initial storm development is anticipated over the Permian Basin/Big Bend vicinity, with moderate buoyancy and very strong vertical shear supporting a quick evolution into supercells capable of very large hail greater than 3" in diameter. Increasing thunderstorm coverage is expected from southwest TX into southwest OK as the upper low continues eastward. Very large hail will remain the primary severe risk although a trend towards a more linear mode is expected throughout the evening. Strong gusts could accompany the resulting squall line. The tornado risk is expected to remain low, owing primarily to the modest low-level flow. This low-level flow is expected to increase across the TX Hill Country tonight, where a relatively greater tornado risk could materialize if cells remain discrete. Northern OK/KS into the Lower OH Valley Most guidance has trended towards greater thunderstorm coverage tonight near the front across northern OK and KS. Moderate buoyancy and shear will be in place, supporting strong to severe thunderstorms. Large to isolated very large hail is possible with the initial development before a trend towards a linear mode shifts the primary hazard to damaging gusts. The resulting convective line is then expected to continue eastward across AR and MO before reaching the Lower OH Valley early tomorrow morning. Damaging gusts will remain possible as the line moves east overnight. A low-probability tornado threat could also exist within this line as it moves into the greater low-level moisture and stronger low-level flow farther east across central/southern MO and far southern IL.