SPC Outlooks: 9/7/15 to 9/14/15

I was not feeling well this morning, so I slept in rather than doing a full weather prediction.

This afternoon, however, I am feeling a little better and am ready to post about the Storm Prediction Center (SPC) outlooks for the next week.

Day 1: The SPC has issued a Slight Risk for northern Kansas. Through this evening, there is a west to east boundary that extends through northern Kansas. Near this boundary, dewpoints are in the low 70’s, there is moderate Convective Available Potential Energy (CAPE) and pockets of intense daytime heating. All of this is under an area of favorable shear profiles to support rotating storms. Notice that there is a 5% Tornado Threat Ring for this same area.

Day 2: The SPC has issued a Marginal Risk for part of the Great Plains and parts of the Mississippi River Valley. An upper level trough will move out of the Rocky Mountains and into the Central Great Plains tomorrow. As it does, it will bring an associated cold front through the area. Ahead of this cold front, the air will develop instability through diurnal heating, and then convection will trigger as the cold front approaches. The trough will also increase deep-layer shear such that rotating storms will be possible. Dewpoints are forecasted into the low 70’s, and the Mixed Layer CAPE (ML CAPE) is forecasted to be in the 2000-3000 J/kg range. The limiting factor is the moderate lapse rates, which may suppress some of the convection, hence the Marginal Risk instead of a Slight Risk.

Day 3: Showers and thunderstorms are possible across much of the United States. However, everywhere there will be adequate shear, there will be limited moisture and instability, and everywhere there will be ample moisture, shear will be limited. Therefore, there are no Severe Threats issued at this time.

Day 4-8: The pattern described in Day 3 will continue for several more days, where there is either limited shear or limited instability at any given place in the Continental United States. A few storms near the boundary of shear vs. instability may reach severe limits, but their areal coverage will be small, and well below the resolution of the global models. The smaller models likely diverge, and thus the SPC has issued a “Predictability Too Low” statement for Days 4-8.

Thank you for reading this post.

All data and images are from the Storm Prediction Center Website.


About highplainschasing

This blog is about my tales in storm chasing. My name is Seth Price and I am an instrumentation instructor at New Mexico Tech. My amateur radio call sign is N3MRA.
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