Tornado Threat Forecast: May 21-27, 2012

1-3 DAY

Monday

Southern High Plains — POTENTIAL: Low — CONFIDENCE: High
An isolated tornado or two are possible within a low CAPE, low speed shear environment thanks to good low-level directional shear and upslope enhancement. Primary concern will be during the late afternoon and early evening, with little to no tornado risk outside of this time frame.

Tuesday

Northern Plains — POTENTIAL: Low — CONFIDENCE: Normal
Enhanced upper-level dynamics will allow for a low tornado potential in a low/moderate CAPE and moderate shear environment. Dry air in the low-levels will inhibit storm formation and will keep LCLs high during the peak hours. The best chance for tornadoes will be in the northern areas near the triple-point.

Wednesday

Central Plains, western Midwest — POTENTIAL: Medium — CONFIDENCE: Normal
A fairly large cap will be in place across the warm sector, but low to moderate CAPE and shear near a frontal boundary should be enough to trigger at least one tornado-producing storm, with the greatest tornado risk over Nebraska where the highest instability is expected.

4-7 DAY

Thursday

Western Midwest — POTENTIAL: Medium — CONFIDENCE: Normal
Upper-level forcing will strengthen some compared to Wednesday, but lingering issues with the cap and more unidirectional wind profile will inhibit the tornado potential. The latest 12z GFS and NAM do not have much precipitation within the area of the greatest tornado potential, but the more aggressive ECMWF shows greater storm coverage, bringing the potential up to medium.

Friday

Kansas — POTENTIAL: Low — CONFIDENCE: Low
Model agreement starts to wane significantly at this range, with some support for tornado potential south of a lingering frontal boundary in an environment with low to moderate CAPE, low speed shear and good directional shear. The cap remains one of the biggest storm inhibitors within the risk area.

Saturday

Central and southern High Plains — POTENTIAL: Medium — CONFIDENCE: Low
A strong upper-level trough is forecast to develop over the western U.S. on Saturday as a surface low deepens in the central High Plains. This new disturbance will bring moderate to strong shear to the High Plains, but moisture may be lacking, which will inhibit the instability. Discrepancies in the storm coverage and uncertainty in the amount of moisture available will limit the tornado potential and will keep the confidence low.

Sunday

Plains, western Midwest — POTENTIAL: High — CONFIDENCE: Low
The upper-level trough will try to progress eastward into the Plains on Sunday, and although the trough will weaken as it tries to work into a strong ridge settled over the eastern U.S., it will bring enough shear and dynamics to provide a medium to high tornado threat even with modest instability. Due to the potential complications and disagreement between the models with respect to the actual risk area, confidence will remain low.