It is time for another Storm Prediction Center (SPC) update. This will give us some indication of what severe weather is possible this week.
Day 1: Slight Risk
The SPC has issued a Slight Risk area today for parts of the Northern Great Plains:
Associated with the Slight Risk is a smaller 2% Tornado Threat Ring:
The severe weather threat today is based on the combination of outflow boundaries, deep moisture, a surface front, and some minor upper level disturbances moving through the polar jet. There are some ongoing storms that will continue to weaken throughout the morning. However, these weaker storms are generating outflow boundaries, and their anvils are providing areas of shade for differential heating. This, combined with a deep moisture axis that runs through the Northern Great Plains from the southwest will provide plenty of buoyancy. Storms will favor supercellular form at their onset, but as more and more outflow boundaries merge, storms will morph into a cluster.
Day 2: Marginal Risk
The SPC has issued a Marginal Risk area for parts of the Great Plains tomorrow.
The severe weather threat is based on a mid-level speed max that will drift through the area in the afternoon. Remaining outflow boundaries, adequate moisture and and some upslope flow into the high plains may produce a few severe storms. However, timing of these events is a limiting factor, as each of these effects is slight, and the timing must work out for storms to become severe.
Day 3: Marginal Risk
The SPC has issued two Marginal Risk areas for Day 3. One risk area is for the Great Plains, and the other is for the Mid-Atlantic.
The Great Plains risk is based on a series of upper-level impulses passing over an area of high surface dewpoints. Shear will be adequate for organized storms, based on the flow aloft. The SPC anticipates upgrading this area to a Slight Risk after a few ensemble forecasts.
The Mid-Atlantic risk is based on the extremely damp conditions (surface dewpoints over 70 F, over 2 inches of precipitable water) over this area as well as a speed max that will pass through this area. However, like Day 2, timing is questionable, as is the intensity of the speed max.
Day 4-8: Predictability Too Low
The SPC has issued a Predictability Too Low statement for the remainder of the time period. Currently, there is an anticyclone that sits over the Great Basin region, and it is what is pumping moisture into the Desert Southwest and the Great Plains. We also have a zonal flow pattern aloft, though a few shallow troughs and ridges may form in the northern half of the country by this time period. Depending on how these form, there may be a risk of severe weather during this time period, but the models are not in agreement on when and where these threats could occur.
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All data and images are from the Storm Prediction Center Website.