Tornado Threat Forecast: May 13-19, 2013

I gotta tell ya, Ian and I are among the most excited people on the planet right now. Fairly solid looking setup for our first chase day (Saturday). We’re leaving Friday afternoon, so I may or may not be able to do an update on Thursday, depending on what prep is left to do on that day.

1-3 DAY

Monday

No tornadic activity expected.

Tuesday

Northwestern Midwest — POTENTIAL: Very Low — CONFIDENCE: Normal
Very conditional threat as good instability and low-level veering provide the chance for storms to build and rotate, but dry air in the low-levels and high CIN will greatly limit storm coverage and tornadic potential.

Wednesday

Southern Plains — POTENTIAL: Low — CONFIDENCE: Normal
Speed shear will be on the low side, but moderate to high instability and ample directional shear will allow for rotating storms. A lee low will aid in triggering storms under an upper-level trough, though the weak speed shear could prevent storms from organizing enough to produce tornadoes.

4-7 DAY

Thursday

No tornadic activity expected.

Friday

North Dakota, Nebraska — POTENTIAL: Low — CONFIDENCE: Low
The day before the day… a lack of storm coverage and capping will keep the overall potential low, but if storms fire they will have moderate to high instability and enough directional shear to maybe produce a tornado or two.

Saturday

Central Plains — POTENTIAL: High — CONFIDENCE: Normal
A broad upper-level trough will work into the Plains on Saturday, with a deepening surface low helping to trigger a fairly active storm day. This is perhaps the best looking setup for the Plains so far this year at this range, with moderate to high CAPE and very favorable shear for tornado development. Fairly disjointed area of upper-level energy will probably keep things from becoming massively organized with this disturbance, and there is some model disagreement with the evolution of this system, which could impact where the storms form. Regardless of uncertainties, this setup looks fairly good as a whole and will probably yield at least several tornadoes. A tornado outbreak is possible during this period, though confidence in such an event is not that high at this time.

Sunday

Western Midwest — POTENTIAL: Medium — CONFIDENCE: Low
Uncertainty in the progression of the disturbance will keep the confidence low and the potential at medium, though there is an upside risk to the forecast. Most of the uncertainty lies with how the upper-level trough evolves, which if it ends up going more negative tilt will put a hamper on the directional shear needed for storm rotation. Despite uncertainties, there is plenty of storm coverage within an area of moderate to high instability that there could/should be at least a handful of storms that are capable of producing a tornado.