Friday, June 16, 2017

Changing jet stream pattern brings severe threat for the weekend

Upper level winds, or our jet stream winds will change from an amplified ridge ( which brought our 6 straight days of 90's) to flattened zonal flow. Zonal flow essentially means winds flows from west to east. Oftentimes showers and storms develop in this type of pattern when you get multiple disturbances that ride along that same flow. A zonal pattern is taking shape today, and a few different impulses or disturbances that move along it will bring scattered chances for showers and storms through the weekend. The first of those will arrive this evening, and will prompt a few showers and storms in the evening. The severe threat stays west of the area, though we could get a couple gustier storms in the evening. The best chance for showers or storms will be after 7pm this evening.

The threat for severe weather goes up Saturday for a few reasons. First we will have more CAPE or energy available for the storms to feed off of. Also the impulse or vorticity will be stronger then the one arriving this evening. We also have more of something called, directional shear. Shear basically equates to winds that change direction with respect to height. So winds aloft are coming in from the west, while our surface winds will arrive from the south. This will give storms the the potential to form and become severe.

Threats for Saturday include mainly large hail, strong damaging winds, and heavy rain. The tornado threat is low, but not zero.

One big question for severe weather on Saturday will be what happens with storms Saturday morning. If the atmosphere is able to recharge essentially then storms will be likely into the afternoon. Storms could arrive as early as 3/4pm.

Severe weather is not set in stone for Saturday, but the threat is definitely there, so make sure you stay weather aware this weekend!

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