What is the SPC Outlook?

The Storm Prediction Center (SPC) issues daily severe weather outlooks indicating the risk of organized severe thunderstorms (tornadoes, damaging winds, and large hail) over the contiguous United States. Risks are categorized from 1 to 5: Marginal, Slight, Enhanced, Moderate, and High.

Numerical Weather Prediction (NWP)

• NBM (National Blend of Models): The gold-standard official NOAA ensemble, blending dozens of models for the most accurate consensus.
• MOS (Model Output Statistics): Statistical post-processing that corrects known numerical model biases for specific point locations based on historical data.
• HRRR (High-Resolution Rapid Refresh): Short-range (0-48h), high-detail model updated every hour. Excellent for imminent thunderstorms.
• NAM 3KM (North American Mesoscale): High-resolution short-range model (0-60h) updated every 6 hours.
• RRFS (Rapid Refresh Forecast System): The next-generation experimental short-range ensemble model.
• GFS (Global Forecast System): The flagship US medium-range model (0-384h+), useful for forecasting broad weather patterns days in advance.

Live ASOS Observations

The Automated Surface Observing System (ASOS) is a massive network of climate sensors heavily concentrated at US airports. They provide highly accurate, minute-by-minute updates of the current temperature, wind speed, and visibility (METARs). When viewing the Local Forecast tab, TJFWeather queries the nearest aviation sensor to give you absolute ground truth.