Definition
A short-range weather forecast describing current conditions and their expected evolution over the next two hours, based on real-time observations such as radar, satellite, surface reports, and pilot reports. In the context of Center Weather Advisories (CWAs), a nowcast addresses hazardous weather affecting an Air Route Traffic Control Center's airspace within that two-hour window.
Plain English
A very short forecast — covering the next two hours — that tells you what the weather is doing right now and what it is likely to do in the immediate future.
Context Anchor
Seen in Center Weather Advisories, where fast-changing weather may affect aircraft in the near future.
Derivation
A blend of 'now' and 'forecast.' The name signals what makes it different from a regular forecast: it is anchored to what is happening this moment, not hours ahead.
Why Pilots Care
Allows pilots to anticipate rapid changes in weather that could affect safety during the current phase of flight.
Intuition Check
Do not read “nowcast” as only a report of current weather. It includes what is happening now and what is expected to happen very soon.
Example Sentence 1
The CWSU issued a nowcast warning of rapidly developing thunderstorms across the western half of the Center's airspace over the next hour.
Example Sentence 2
Reviewing the nowcast helped the pilot decide to delay takeoff until conditions stabilized.