weatherreporter/internal/promptassets/assets/prompts/daily/daily_generated_text.user.md

TASK: You are writing structured prose slots for a daily weather report.

The calling application will render the final Markdown report. Your job is not to write the full report. Return only a JSON object matching the configured schema.

Use only the supplied data_package. Do not invent weather details, times, hazards, probabilities, or impacts that are not supported by the data. The report focuses on the upcoming civil day in report.valid_period for the configured location.

Return these fields:

• summary: required. One or two sentences summarizing the main weather story for the valid period.
• forecast_discussion: required. Three paragraphs explaining the broader setup, trend, or forecast reasoning most relevant to the valid period.
• precipitation_timing: required. When the deterministic precip_timing module contains precipitation windows, provide the supported timing prose described below. Otherwise, return an empty string ("").

Return JSON only.

Summary

The summary should typically consist of two sentences. If an active warning is relevant during the report period, lead with the hazard. Otherwise, state the most likely local weather outcome, including the overall character of the weather and expected temperature or temperature range. The second sentence should state the most important active hazard, caveat, uncertainty, or alternate outcome when one exists.

Distinguish the main weather outcome from its caveat. If showers and thunderstorms have different timing, state that difference rather than combining them as one risk throughout the period. If the main caveat is a regional severe-weather or precipitation risk displaced from the report location, state that limitation clearly.

Forecast discussion

The forecast discussion should explain the local forecast, not merely restate it or summarize every narrative product. Write for an informed reader who wants to understand what is driving the weather, what the important limitations are, and what the pattern may imply next.

Select the one to three source-supported details that most improve understanding of the forecast. When useful, connect them in this order:

1. the relevant weather feature, mechanism, or change;
2. the timing, parameter, or forecast evidence that matters;
3. the practical implication for precipitation, temperatures, hazards, confidence, or planning.

For example, explain not only that a front is approaching, but—when supported—whether its timing, instability, moisture, or movement changes the expected storm coverage, hazard ceiling, rainfall potential, or temperature trend. The reader should not need prior meteorological knowledge to understand why a technical detail matters.

Prefer explanatory synthesis over enumeration. Do not include a technical term or numerical parameter merely because it is available. Include it only when it materially helps explain the forecast, and translate its significance into plain language. Prefer the interpretation stated or clearly supported by the narrative products rather than independently diagnosing the atmosphere from isolated raw values.

Usually provide two or three paragraphs:

• Explain the main setup and its practical consequence for the valid period.
• Explain the most important uncertainty, conditional factor, or limiting factor when one exists.
• When supported, explain a meaningful consequence for the following day or broader pattern, including the causal connection. Do not add a broader-pattern paragraph merely to fill space.

If the narrative products do not provide a useful mechanism or broader explanation, keep the discussion concise and focus on supported timing, confidence, and alternate outcomes. Never invent a mechanism to explain the local forecast.

Precipitation timing

When precipitation windows are present, use one to four sentences to explain the supported timing, precipitation type, likely coverage or continuity, and the most important uncertainty. Mention intensity, duration, or the responsible weather feature only when those details are explicitly supported by the supplied data.

Distinguish a regional setup favorable for precipitation from the local probability of receiving it. When no precipitation windows are present, return an empty string ("") for precipitation_timing.

Source selection and grounding

Use the local derived summaries, narrative point forecast, and hourly forecast as the primary sources for what is expected at the configured location: timing, probability, temperatures, winds, and local conditions.

Use the AFD, Weather Story, applicable risk products, and alerts to explain why the weather is expected, the broader regional context, forecast confidence, conditional outcomes, and the ceiling for hazards. For a civil day several days away, the long-term AFD will often be more relevant than the short-term AFD.

Do not allow regional AFD language to override or strengthen the local point forecast. A regional expectation for thunderstorms does not make precipitation likely at the configured location when the local probability is lower. Clearly distinguish regional support for an event from the probability that the location itself will be affected.

Preserve relationships stated in the sources. Do not infer a front, trough, boundary, dry-air intrusion, clearing trend, instability level, severe threat, or rainfall hazard solely from changes in hourly probabilities or conditions. The absence of an alert or SPC outlook does not by itself prove that severe weather is impossible.

When a source describes a regional or conditional hazard, preserve its stated geographic scope, timing, and uncertainty. Do not infer that the hazard is either expected or excluded at the configured location unless the source or an applicable location-specific product supports that conclusion. When a risk product overlaps only part of the report period, state or respect that limited validity.

Before returning the JSON, verify silently that:

• every weather mechanism, parameter, hazard, and causal relationship is supported by the supplied data;
• every technical detail included has a clear practical significance for the reader;
• regional forecast language has not been converted into a stronger local forecast.