Watching Hurricane Erin; Heavy Rainfall Threat for Upper Midwest; Heatrisk for Mississippi Valley

Hurricane Erin continues to track westward with its outer bands bringing heavy rainfall and gusty winds for Puerto Rico and US Virgin Islands. Life-threatening surf and rip currents are occurring and will spread across the Atlantic coasts this week. Meanwhile, heavy rainfall and possible flooding are in the forecast for upper Midwest through Monday. Heatrisk continues for the Mississippi Valley. Read More >

Graphical HWO - Thunderstorm Threat

This graphic reflects both the severity of any thunderstorm activity that may develop, as well as the potential coverage of severe thunderstorms.

For example, an area under the "Strong to Severe" category, at worst, will see storms that have severe-criteria damaging winds or large hail. However, only a few of the storms that will develop are expected to meet these criteria.

Click the graphic to return to the graphical HWO page.

Categories

No Storms	Thunderstorms are NOT EXPECTED during the period.
General	Strong or severe thunderstorms are not anticipated. The main hazard with any storms would be cloud to ground lightning and brief gusty winds (30 mph or less).
Strong	Some strong thunderstorms are possible, with the main threats being frequent cloud-to-ground lightning, wind gusts to 50 mph, and hail to 1/2" in diameter.
Strong to Severe	The majority of storm activity is expected to remain below severe criteria. However, a few severe storms are possible, with the main threats being wind gusts to 60 mph and hail up to 1" in diameter.
Severe	There is an increasing probability of severe thunderstorms. The primary threats would be winds greater than 60 mph and hail up to 2" in diameter. Isolated, weak tornadoes are possible.
Widespread Severe	The occurrence of significant severe weather is likely. The main threats would be wind gusts in excess of 80 mph, very large hail (greater than 2" in diameter), along with an increasing threat for tornadoes. An isolated strong or violent tornado (F2 intensity or greater) is also possible.

Watching Hurricane Erin; Heavy Rainfall Threat for Upper Midwest; Heatrisk for Mississippi Valley

Thunderstorm Threats NWS Huntsville, AL