Storm Prediction Center Update: 8/2/17

The Storm Prediction Center (SPC) Outlook shows some severe threats this week.

Day 1:  Slight Risk

There are two threat regions (1 Slight, 1 Marginal) in place for this evening and the early morning hours.  The Slight Risk is over the central high plains, and the Marginal Risk is over western Arizona.


Associated with the Slight Risk is a 2% Tornado Threat Ring.

The Slight Risk is due to an ongoing system of thunderstorms that is moving south to southeast from northeastern Colorado and southwestern Nebraska into northwestern Kansas. These storms are moving ahead of a shortwave trough into an area of limited instability, but large hail is still possible.

The Marginal Risk over western Arizona is due to the high-based storms that have already formed in this area.  Gusty downdraft winds are the largest threat associated with these storms.


Day 2:  Slight Risk

Day 2 shows a Slight Risk over northern Illinois and southern Wisconsin, as well as a Marginal Risk over the Panhandles Region and northeastern New Mexico

The Slight Risk is due to the threat associated with the same shortwave trough that contributed to storms today.  This trough is expected to deepen, an weak cyclogenesis is expected.  A trailing cold front will provide some lift, in an area with adequate deep-layer shear.  Marginal supercellular structures are possible with this threat.

In the Panhandles Region, a cold front will begin moving southwest from Kansas into the Panhandles and New Mexico.  Ahead of the front, there are moderate lapse rates and moisture.  Soundings are expected to take on an inverted-v shape, leading to gusty downburst winds.


Day 3:  Slight Risk

There is a Slight Risk area through much of New England, and a Marginal Risk is in place for northeastern Colorado.


The shortwave trough that has been the focus of much of the discussion today will progress east, and the trailing cold front will push into a region of 1000-1500 J/kg of Convective Available Potential Energy (CAPE) over the moist east coast.  A few supercells are possible, given the forecasted wind profiles and limited Convective Inhibition (CINH).

To the west, a smaller shortwave trough will drop south into the high plains.  Southerly surface winds will bring low-level moisture into the pre-frontal region, increasing the likelihood of storms.  Hail will be the primary threat.


Day 4-8:  Predictability Too Low to Potential Too Low

The first trough and associated cold front is expected to continue east into a region with limited instability, reducing the severe threat by Day 4, though some storms are possible.

The second shortwave trough is not expected to dig as deeply south, and its frontal boundary will be parallel to the wind direction.  This will limit the severe threat, and storms will favor a linear mode, though heavy rains will be possible.

After that trough weakens, we enter a more zonal flow pattern with limited severe threat.

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.
This entry was posted in Models, Practicing Concepts, Predictions, Severe Weather, SPC 1-7 day and tagged , , . Bookmark the permalink.

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