Agios Stefanos weather — 14-day forecast

Seasonal calibration and ECMWF verification

Six model feeds are shown. The default daily high combines GFS, ECMWF IFS 9 km, AIFS and GEM. The low keeps GFS, ECMWF IFS 0.25°, AIFS and GEM. AIGFS remains visible with zero default temperature weight. Calibrated precipitation uses GFS, IFS 0.25°, AIFS and GEM, matching the annual verification. AIGFS precipitation has zero default weight because its archive is limited. Wind, pressure and the unadjusted baseline keep the original five feeds.

The September 2025–August 2026 comparison includes 295 / 291 / 305 valid temperature days at 1 / 3 / 7-day lead times. IFS 9 km improved highs, while IFS 0.25° remained better for lows. High-temperature seasonal offsets were recalculated; low-temperature offsets were retained. Days 8–14 have no correction and were not verified.

Offsets subtract the mean signed error. Days 1–3 approximate the tested 1- and 3-day horizons, days 4–7 use the tested 7-day horizon. Day 1 is today in Greece. Final offsets are fitted values, not independently verified future accuracy. Saved personal settings are retained; choose the recommended preset and Save to adopt the new defaults.

Daily values require a complete local day for each model and variable. Missing values are not zero. Pressure is mean sea-level pressure in hPa; wind is at 10 m, not gusts. Precipitation includes snow water equivalent. Model disagreement is not probability.

Detailed model charts and correction table (Greek) · Calibration settings (Greek)

Precipitation verification uses 338 common days in September 2025–August 2026. Default winter multipliers are ×1.30 for days 1–3 and ×1.50 for days 4–7, applied to the equal four-model blend. Other seasons and days 8–14 use ×1.00. If a required model lacks a complete day, the default multiplier is skipped.

Expanding-history winter validation reduced MAE from 3.54 to 3.42 mm for 1/3-day offsets pooled (114 cases, 58 distinct dates), and from 5.64 to 5.52 mm at 7 days (52 dates), with more false wet-day signals. Final fitted multipliers are not independent future validation. Personal weights are outside this verification.

New snowfall in cm is the provider’s snowfall field, summed over the local day and averaged across the available original five feeds. No local snowfall calibration is applied. Some provider snowfall fields, including ECMWF products, are derived from precipitation and temperature. Falling snow is not guaranteed settled snow depth; melting and compaction matter. The precipitation multiplier does not alter snowfall cm.

Icons summarize daily snowfall, precipitation and mean cloud cover, not every hour. Missing snowfall is shown as —, not zero. Precipitation mm already includes snow water equivalent.

Provider snowfall definitions