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 6

KDCA · gfs · lead 6

Target day = initialization date + 6 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
tmax00Zbilinear30d24 1 QC3.59 [2.57, 4.79]3.60-0.47 [-1.77, 1.37]4.57 [3.32, 5.71]17% [6%, 26%]46%46%+0.26+0.262026-08-07 → 2026-08-30
tmax00Zbilinear90d24 1 QC3.59 [2.58, 4.73]3.60-0.47 [-1.71, 2.09]4.57 [3.20, 5.64]17% [0%, 26%]46%46%+0.26+0.262026-08-07 → 2026-08-30
tmax00Zbilinear365d24 1 QC3.59 [2.40, 4.85]3.60-0.47 [-1.77, 1.80]4.57 [3.10, 5.75]17% [0%, 29%]46%46%+0.26+0.262026-08-07 → 2026-08-30
tmax00Zbilinearall24 1 QC3.59 [2.40, 4.89]3.60-0.47 [-1.81, 1.92]4.57 [3.12, 5.79]17% [0%, 29%]46%46%+0.26+0.262026-08-07 → 2026-08-30
tmax00Znearest30d24 1 QC3.59 [2.39, 5.02]3.59-0.14 [-1.38, 1.68]4.62 [3.03, 6.03]25% [8%, 40%]46%50%+0.26+0.262026-08-07 → 2026-08-30
tmax00Znearest90d24 1 QC3.59 [2.38, 5.03]3.59-0.14 [-1.29, 2.37]4.62 [2.89, 5.94]25% [0%, 41%]46%50%+0.26+0.262026-08-07 → 2026-08-30
tmax00Znearest365d24 1 QC3.59 [2.23, 5.17]3.59-0.14 [-1.40, 2.21]4.62 [2.70, 6.09]25% [0%, 43%]46%50%+0.26+0.262026-08-07 → 2026-08-30
tmax00Znearestall24 1 QC3.59 [2.34, 5.18]3.59-0.14 [-1.51, 2.40]4.62 [2.80, 6.12]25% [0%, 43%]46%50%+0.26+0.262026-08-07 → 2026-08-30
tmax12Zbilinear30d24 1 QC4.33 [2.95, 5.44]4.23-1.98 [-4.17, 0.90]5.85 [3.63, 7.17]17% [8%, 28%]38%42%+0.11+0.132026-08-07 → 2026-08-30
tmax12Zbilinear90d24 1 QC4.33 [2.82, 5.52]4.23-1.98 [-4.50, 1.95]5.85 [3.54, 7.21]17% [7%, 29%]38%42%+0.11+0.132026-08-07 → 2026-08-30
tmax12Zbilinear365d24 1 QC4.33 [2.75, 5.55]4.23-1.98 [-4.60, 1.84]5.85 [3.48, 7.30]17% [7%, 31%]38%42%+0.11+0.132026-08-07 → 2026-08-30
tmax12Zbilinearall24 1 QC4.33 [2.77, 5.57]4.23-1.98 [-4.68, 1.98]5.85 [3.46, 7.41]17% [7%, 30%]38%42%+0.11+0.132026-08-07 → 2026-08-30
tmax12Znearest30d24 1 QC4.38 [3.14, 5.34]4.32-1.56 [-3.61, 1.29]5.70 [3.88, 6.84]17% [4%, 35%]33%46%+0.10+0.112026-08-07 → 2026-08-30
tmax12Znearest90d24 1 QC4.38 [2.93, 5.44]4.32-1.56 [-3.97, 2.12]5.70 [3.69, 6.84]17% [0%, 39%]33%46%+0.10+0.112026-08-07 → 2026-08-30
tmax12Znearest365d24 1 QC4.38 [2.81, 5.46]4.32-1.56 [-4.12, 2.11]5.70 [3.69, 6.90]17% [0%, 38%]33%46%+0.10+0.112026-08-07 → 2026-08-30
tmax12Znearestall24 1 QC4.38 [2.95, 5.49]4.32-1.56 [-4.14, 2.31]5.70 [3.63, 6.98]17% [0%, 40%]33%46%+0.10+0.112026-08-07 → 2026-08-30
tmin00Zbilinear30d24 1 QC3.16 [2.08, 4.15]3.16-0.18 [-1.91, 1.56]4.10 [2.65, 5.15]17% [3%, 37%]54%62%+0.27+0.262026-08-07 → 2026-08-30
tmin00Zbilinear90d24 1 QC3.16 [1.85, 4.13]3.16-0.18 [-1.98, 1.59]4.10 [2.44, 5.09]17% [0%, 45%]54%62%+0.27+0.262026-08-07 → 2026-08-30
tmin00Zbilinear365d24 1 QC3.16 [1.82, 4.25]3.16-0.18 [-1.94, 1.78]4.10 [2.41, 5.25]17% [0%, 46%]54%62%+0.27+0.262026-08-07 → 2026-08-30
tmin00Zbilinearall24 1 QC3.16 [1.69, 4.09]3.16-0.18 [-2.19, 1.92]4.10 [2.31, 5.07]17% [0%, 50%]54%62%+0.27+0.262026-08-07 → 2026-08-30
tmin00Znearest30d24 1 QC3.26 [2.33, 4.17]3.20-0.67 [-2.46, 1.11]4.06 [2.71, 5.07]8% [0%, 17%]42%62%+0.25+0.252026-08-07 → 2026-08-30
tmin00Znearest90d24 1 QC3.26 [2.24, 4.14]3.20-0.67 [-2.56, 1.15]4.06 [2.66, 5.04]8% [0%, 20%]42%62%+0.25+0.252026-08-07 → 2026-08-30
tmin00Znearest365d24 1 QC3.26 [2.15, 4.30]3.20-0.67 [-2.52, 1.38]4.06 [2.60, 5.21]8% [0%, 20%]42%62%+0.25+0.252026-08-07 → 2026-08-30
tmin00Znearestall24 1 QC3.26 [2.15, 4.20]3.20-0.67 [-2.75, 1.49]4.06 [2.56, 5.06]8% [0%, 20%]42%62%+0.25+0.252026-08-07 → 2026-08-30
tmin12Zbilinear30d24 1 QC3.96 [2.73, 5.23]3.99-1.18 [-3.63, 1.07]5.21 [3.22, 6.92]17% [7%, 26%]29%42%+0.09+0.062026-08-07 → 2026-08-30
tmin12Zbilinear90d24 1 QC3.96 [2.64, 5.25]3.99-1.18 [-3.69, 1.35]5.21 [3.08, 6.97]17% [6%, 27%]29%42%+0.09+0.062026-08-07 → 2026-08-30
tmin12Zbilinear365d24 1 QC3.96 [2.60, 5.27]3.99-1.18 [-3.71, 1.26]5.21 [3.12, 7.08]17% [3%, 29%]29%42%+0.09+0.062026-08-07 → 2026-08-30
tmin12Zbilinearall24 1 QC3.96 [2.58, 5.33]3.99-1.18 [-3.88, 1.54]5.21 [3.07, 7.13]17% [5%, 29%]29%42%+0.09+0.062026-08-07 → 2026-08-30
tmin12Znearest30d24 1 QC4.16 [2.78, 5.54]4.15-1.57 [-4.16, 0.71]5.37 [3.28, 7.21]12% [5%, 20%]25%33%+0.04+0.022026-08-07 → 2026-08-30
tmin12Znearest90d24 1 QC4.16 [2.65, 5.56]4.15-1.57 [-4.24, 0.90]5.37 [3.11, 7.19]12% [0%, 20%]25%33%+0.04+0.022026-08-07 → 2026-08-30
tmin12Znearest365d24 1 QC4.16 [2.69, 5.58]4.15-1.57 [-4.28, 0.93]5.37 [3.21, 7.29]12% [0%, 21%]25%33%+0.04+0.022026-08-07 → 2026-08-30
tmin12Znearestall24 1 QC4.16 [2.66, 5.66]4.15-1.57 [-4.40, 1.35]5.37 [3.15, 7.35]12% [0%, 20%]25%33%+0.04+0.022026-08-07 → 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 6, 00Z bilinear tmax+10+50-5-102026-08-07: +3.86 °F2026-08-08: +4.07 °F2026-08-09: +0.42 °F2026-08-10: +5.56 °F2026-08-11: +5.17 °F2026-08-12: -6.11 °F2026-08-13: -8.06 °F2026-08-14: -0.04 °F2026-08-15: -9.07 °F2026-08-16: +8.35 °F2026-08-17: -1.71 °F2026-08-18: -1.42 °F2026-08-19: +3.04 °F2026-08-20: -0.4 °F2026-08-21: +1.27 °F2026-08-22: -8.62 °F2026-08-23: +0.32 °F2026-08-24: -1.4 °F2026-08-25: +3.76 °F2026-08-26: -1.32 °F2026-08-27: -5.31 °F2026-08-28: -4.16 °F2026-08-29: -1.21 °F2026-08-30: +1.62 °F2026-08-072026-08-30°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 (24 days, newest first) · download CSV
Climatological dayError °F
2026-08-30+1.62
2026-08-29-1.21
2026-08-28-4.16
2026-08-27-5.31
2026-08-26-1.32
2026-08-25+3.76
2026-08-24-1.40
2026-08-23+0.32
2026-08-22-8.62
2026-08-21+1.27
2026-08-20-0.40
2026-08-19+3.04
2026-08-18-1.42
2026-08-17-1.71
2026-08-16+8.35
2026-08-15-9.07
2026-08-14-0.04
2026-08-13-8.06
2026-08-12-6.11
2026-08-11+5.17
2026-08-10+5.56
2026-08-09+0.42
2026-08-08+4.07
2026-08-07+3.86

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KDCA, lead day 6-10 to -9 °F: 1 day-9 to -8 °F: 2 days-8 to -7 °F: 0 days-7 to -6 °F: 1 day-6 to -5 °F: 1 day-5 to -4 °F: 1 day-4 to -3 °F: 0 days-3 to -2 °F: 0 days-2 to -1 °F: 5 days-1 to 0 °F: 2 days0 to 1 °F: 2 days1 to 2 °F: 2 days2 to 3 °F: 0 days3 to 4 °F: 3 days4 to 5 °F: 1 day5 to 6 °F: 2 days6 to 7 °F: 0 days7 to 8 °F: 0 days8 to 9 °F: 1 day9 to 10 °F: 0 daysdashed: P50 |e| 3.4 · P90 |e| 8.26 °F-100+10 °Fn = 24 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
-10.00-9.001
-9.00-8.002
-8.00-7.000
-7.00-6.001
-6.00-5.001
-5.00-4.001
-4.00-3.000
-3.00-2.000
-2.00-1.005
-1.00+0.002
+0.00+1.002
+1.00+2.002
+2.00+3.000
+3.00+4.003
+4.00+5.001
+5.00+6.002
+6.00+7.000
+7.00+8.000
+8.00+9.001
+9.00+10.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08243.59 -0.47

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24
NCEP GFS2026-08-07 → 2026-08-30 24

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 24 -0.20 [-2.41, 2.74] no
GraphCast (IFS init) 24 -1.41 [-3.51, 0.71] no
ECMWF IFS HRES 19 -1.29 [-2.05, 0.77] no
Persistence (baseline) 24 -1.28 [-2.69, 0.19] no

Cite this page

ShortCastCheck, KDCA gfs lead 6, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KDCA/model/gfs/lead/6/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KDCA (Washington Reagan), model gfs, lead day 6. 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/6/

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