Raw model output on the native 0.25° grid — no MOS, no bias correction, no post-processing. Scores understate operational forecast quality. Read the fairness statement →

CastCheck methodology v0.2 · data through 2026-08-30

Washington Reagan · NCEP GFS · lead day 4

KDCA · gfs · lead 4

Target day = initialization date + 4 days. This page is a permanent link: the numbers change as history accumulates, the address and the methodology version do not.

Scores use the latest model version segment, gfs-0p25, starting 2026-08-01 — days before that ran a different version of the model and are excluded rather than silently pooled. Of the scored days, 1 carry a QC flag on the observation.

JSON for this page CSV of the daily errors Cite this page

Every number for this combination

All four windows × both initializations × both interpolations × both variables. Errors are computed in °C and shown in °F; CI is a 95 % moving-block bootstrap interval. MAE debiased and skill, debiased remove the constant offset of the window first, so a station that the model always reads a degree too warm is not scored as if it had no skill — compare the two skill columns to see how much of the error is a fixed offset. n QC next to n counts days whose observation carries a QC flag.

VariableInitMethod Windown MAE °F MAE debiased Bias °F RMSE °F ±1 °F±2 °F±3 °F Skill Skill, debiased Period
tmax00Zbilinear30d26 1 QC3.69 [2.37, 5.31]3.57-1.49 [-3.05, 0.08]5.08 [2.93, 6.96]19% [11%, 28%]38%46%+0.19+0.212026-08-05 → 2026-08-30
tmax00Zbilinear90d26 1 QC3.69 [2.19, 5.34]3.57-1.49 [-3.15, 0.21]5.08 [2.53, 7.04]19% [11%, 30%]38%46%+0.19+0.212026-08-05 → 2026-08-30
tmax00Zbilinear365d26 1 QC3.69 [2.07, 5.59]3.57-1.49 [-3.49, 0.17]5.08 [2.36, 7.35]19% [10%, 31%]38%46%+0.19+0.212026-08-05 → 2026-08-30
tmax00Zbilinearall26 1 QC3.69 [2.07, 5.43]3.57-1.49 [-3.19, 0.30]5.08 [2.38, 7.16]19% [10%, 31%]38%46%+0.19+0.212026-08-05 → 2026-08-30
tmax00Znearest30d26 1 QC3.74 [2.34, 5.37]3.68-1.28 [-3.05, 0.38]5.13 [2.89, 7.00]15% [7%, 26%]31%46%+0.18+0.192026-08-05 → 2026-08-30
tmax00Znearest90d26 1 QC3.74 [2.02, 5.40]3.68-1.28 [-3.21, 0.69]5.13 [2.38, 7.09]15% [5%, 29%]31%46%+0.18+0.192026-08-05 → 2026-08-30
tmax00Znearest365d26 1 QC3.74 [1.89, 5.56]3.68-1.28 [-3.50, 0.52]5.13 [2.22, 7.26]15% [0%, 30%]31%46%+0.18+0.192026-08-05 → 2026-08-30
tmax00Znearestall26 1 QC3.74 [1.87, 5.44]3.68-1.28 [-3.17, 0.65]5.13 [2.23, 7.19]15% [3%, 31%]31%46%+0.18+0.192026-08-05 → 2026-08-30
tmax12Zbilinear30d26 1 QC3.03 [2.14, 4.24]3.05-1.23 [-3.26, 0.79]4.40 [2.63, 6.18]19% [9%, 29%]50%62%+0.33+0.332026-08-05 → 2026-08-30
tmax12Zbilinear90d26 1 QC3.03 [2.07, 4.41]3.05-1.23 [-3.50, 1.09]4.40 [2.55, 6.36]19% [8%, 29%]50%62%+0.33+0.332026-08-05 → 2026-08-30
tmax12Zbilinear365d26 1 QC3.03 [2.05, 4.43]3.05-1.23 [-3.64, 1.05]4.40 [2.53, 6.47]19% [9%, 29%]50%62%+0.33+0.332026-08-05 → 2026-08-30
tmax12Zbilinearall26 1 QC3.03 [2.03, 4.52]3.05-1.23 [-3.78, 1.10]4.40 [2.52, 6.58]19% [7%, 29%]50%62%+0.33+0.332026-08-05 → 2026-08-30
tmax12Znearest30d26 1 QC3.17 [2.20, 4.21]3.30-0.72 [-2.90, 1.53]4.47 [2.87, 6.10]27% [15%, 40%]38%62%+0.30+0.272026-08-05 → 2026-08-30
tmax12Znearest90d26 1 QC3.17 [2.12, 4.39]3.30-0.72 [-3.12, 1.92]4.47 [2.82, 6.27]27% [14%, 43%]38%62%+0.30+0.272026-08-05 → 2026-08-30
tmax12Znearest365d26 1 QC3.17 [2.12, 4.35]3.30-0.72 [-3.28, 1.91]4.47 [2.78, 6.30]27% [12%, 43%]38%62%+0.30+0.272026-08-05 → 2026-08-30
tmax12Znearestall26 1 QC3.17 [2.15, 4.41]3.30-0.72 [-3.40, 1.93]4.47 [2.81, 6.46]27% [14%, 43%]38%62%+0.30+0.272026-08-05 → 2026-08-30
tmin00Zbilinear30d26 1 QC2.98 [2.37, 3.58]2.85-1.23 [-2.64, 0.13]3.44 [2.79, 4.02]15% [0%, 30%]27%46%+0.15+0.182026-08-05 → 2026-08-30
tmin00Zbilinear90d26 1 QC2.98 [2.31, 3.64]2.85-1.23 [-2.71, 0.17]3.44 [2.71, 4.02]15% [0%, 31%]27%46%+0.15+0.182026-08-05 → 2026-08-30
tmin00Zbilinear365d26 1 QC2.98 [2.26, 3.75]2.85-1.23 [-2.82, 0.24]3.44 [2.64, 4.05]15% [0%, 32%]27%46%+0.15+0.182026-08-05 → 2026-08-30
tmin00Zbilinearall26 1 QC2.98 [2.20, 3.66]2.85-1.23 [-3.01, 0.40]3.44 [2.66, 4.05]15% [0%, 29%]27%46%+0.15+0.182026-08-05 → 2026-08-30
tmin00Znearest30d26 1 QC3.09 [2.39, 3.78]2.79-1.74 [-3.10, -0.39]3.64 [3.00, 4.21]15% [0%, 31%]35%46%+0.12+0.202026-08-05 → 2026-08-30
tmin00Znearest90d26 1 QC3.09 [2.33, 3.85]2.79-1.74 [-3.20, -0.35]3.64 [2.91, 4.22]15% [0%, 33%]35%46%+0.12+0.202026-08-05 → 2026-08-30
tmin00Znearest365d26 1 QC3.09 [2.23, 3.96]2.79-1.74 [-3.29, -0.29]3.64 [2.81, 4.33]15% [0%, 33%]35%46%+0.12+0.202026-08-05 → 2026-08-30
tmin00Znearestall26 1 QC3.09 [2.20, 3.95]2.79-1.74 [-3.50, -0.08]3.64 [2.80, 4.28]15% [0%, 33%]35%46%+0.12+0.202026-08-05 → 2026-08-30
tmin12Zbilinear30d26 1 QC2.87 [2.14, 3.53]2.68-0.61 [-1.84, 0.66]3.46 [2.56, 4.11]23% [14%, 31%]38%54%+0.18+0.232026-08-05 → 2026-08-30
tmin12Zbilinear90d26 1 QC2.87 [2.07, 3.55]2.68-0.61 [-1.94, 0.65]3.46 [2.40, 4.11]23% [13%, 30%]38%54%+0.18+0.232026-08-05 → 2026-08-30
tmin12Zbilinear365d26 1 QC2.87 [1.91, 3.58]2.68-0.61 [-2.07, 0.81]3.46 [2.24, 4.14]23% [12%, 30%]38%54%+0.18+0.232026-08-05 → 2026-08-30
tmin12Zbilinearall26 1 QC2.87 [2.05, 3.54]2.68-0.61 [-2.07, 0.87]3.46 [2.36, 4.13]23% [13%, 31%]38%54%+0.18+0.232026-08-05 → 2026-08-30
tmin12Znearest30d26 1 QC2.98 [2.35, 3.59]2.58-1.05 [-2.29, 0.25]3.48 [2.73, 4.06]12% [0%, 23%]35%54%+0.15+0.262026-08-05 → 2026-08-30
tmin12Znearest90d26 1 QC2.98 [2.28, 3.64]2.58-1.05 [-2.41, 0.25]3.48 [2.63, 4.08]12% [0%, 24%]35%54%+0.15+0.262026-08-05 → 2026-08-30
tmin12Znearest365d26 1 QC2.98 [2.21, 3.66]2.58-1.05 [-2.47, 0.40]3.48 [2.53, 4.10]12% [0%, 25%]35%54%+0.15+0.262026-08-05 → 2026-08-30
tmin12Znearestall26 1 QC2.98 [2.27, 3.66]2.58-1.05 [-2.58, 0.51]3.48 [2.63, 4.07]12% [0%, 26%]35%54%+0.15+0.262026-08-05 → 2026-08-30

+ model too warm · − model too cold · bias interval includes zero · ★ lowest MAE · = not distinguishable from the leader · ▼ significantly worse · n < 30 greyed and unranked · CI is a 95 % moving-block bootstrap interval.

Daily error, last 90 days

Daily forecast minus observed error in °F for NCEP GFS at KDCA, lead day 4, 00Z bilinear tmax+20+100-10-202026-08-05: -0.94 °F2026-08-06: +3.19 °F2026-08-07: +5.09 °F2026-08-08: -6.28 °F2026-08-09: -1.3 °F2026-08-10: +1.24 °F2026-08-11: +0.1 °F2026-08-12: -5.37 °F2026-08-13: -3.31 °F2026-08-14: +3.63 °F2026-08-15: -6.01 °F2026-08-16: +8.42 °F2026-08-17: -15.43 °F2026-08-18: -3.66 °F2026-08-19: -0.07 °F2026-08-20: -2.94 °F2026-08-21: -11.08 °F2026-08-22: -1.3 °F2026-08-23: -0.58 °F2026-08-24: -4.11 °F2026-08-25: +1.16 °F2026-08-26: +2.61 °F2026-08-27: +3.14 °F2026-08-28: -0.29 °F2026-08-29: -3.03 °F2026-08-30: -1.57 °F2026-08-052026-08-30°F, forecast − observed
Forecast − observed, °F, 00Z bilinear daily maximum. The dashed line is zero; the thick line is a centred 7-day mean, drawn only where the whole window is present. Gaps are days with no score, never interpolation. Hover a point for its date and value.
The same series as a table (26 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-1.57
2026-08-29-3.03
2026-08-28-0.29
2026-08-27+3.14
2026-08-26+2.61
2026-08-25+1.16
2026-08-24-4.11
2026-08-23-0.58
2026-08-22-1.30
2026-08-21-11.08
2026-08-20-2.94
2026-08-19-0.07
2026-08-18-3.66
2026-08-17-15.43
2026-08-16+8.42
2026-08-15-6.01
2026-08-14+3.63
2026-08-13-3.31
2026-08-12-5.37
2026-08-11+0.10
2026-08-10+1.24
2026-08-09-1.30
2026-08-08-6.28
2026-08-07+5.09
2026-08-06+3.19
2026-08-05-0.94

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KDCA, lead day 4-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 1 day-14 to -12 °F: 0 days-12 to -10 °F: 1 day-10 to -8 °F: 0 days-8 to -6 °F: 2 days-6 to -4 °F: 2 days-4 to -2 °F: 4 days-2 to 0 °F: 7 days0 to 2 °F: 3 days2 to 4 °F: 4 days4 to 6 °F: 1 day6 to 8 °F: 0 days8 to 10 °F: 1 day10 to 12 °F: 0 days12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.08 · P90 |e| 7.35 °F-200+20 °Fn = 26 days
All scored days for 00Z bilinear daily maximum, 20 equal bins. The dashed marks are the 50th and 90th percentiles of the absolute error, mirrored on both sides. Hover a bar for its bin and count.
Bin counts as a table
From °FTo °FDays
-20.00-18.000
-18.00-16.000
-16.00-14.001
-14.00-12.000
-12.00-10.001
-10.00-8.000
-8.00-6.002
-6.00-4.002
-4.00-2.004
-2.00+0.007
+0.00+2.003
+2.00+4.004
+4.00+6.001
+6.00+8.000
+8.00+10.001
+10.00+12.000
+12.00+14.000
+14.00+16.000
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08263.69 -1.49

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26
NCEP GFS2026-08-05 → 2026-08-30 26

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means NCEP GFS has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 26 +0.86 [-1.22, 2.53] no
GraphCast (IFS init) 25 -1.04 [-3.35, 0.76] no
ECMWF IFS HRES 20 +0.17 [-2.16, 2.10] no
Persistence (baseline) 26 -0.85 [-2.22, 0.78] no

Cite this page

ShortCastCheck, KDCA gfs lead 4, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDCA/model/gfs/lead/4/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDCA (Washington Reagan), model gfs, lead day 4. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KDCA/model/gfs/lead/4/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

JSON CSV all scores methodology v0.2 licence