1. 500 1000 1500 2000 2500 3000 3500 Figure 1. 30-sec mean topography (m, shaded following scale at upper left) of the Intermountain West and adjoining regions, with the height of Sierra Nevada crest between points N and S at lower left (position of Lake Tahoe indicated by vertical line). Abbreviations used for Lake Tahoe (LT) and the lower Colorado River Basin (LCRB). 500 1000 1500 2000 2500 3000 3500 Sierra Nevada Cascade Mountains N S 1000 2000 3000 4000 Elevation (m) N LT S LT High Sierra Intermountain West Nevada Utah Idaho Oregon California Arizona Pacific Ocean LCRB High Sierra

2. L SFC: 0000 UTC 26 Mar 20 16 12 08 04 00 96 10 12 70 80 90 0000 UTC 26 Mar L L SFC: 1200 UTC 25 Mar 10 12 08 06 04 02 12 14 16 18 70 80 90 700 hPa: 1200 UTC 25 Mar Figure 2. Synoptic structure of the 25 Mar 2006 cold front at 1200 UTC 25 Mar (left panels) and 0000 UTC 26 Mar 2006 (right panels). Manual surface analyses (top) include conventional frontal symbols, sea level contours (every 2 hPa), and surface wind observations (full and half barb denote 5 and 2.5 m s -1, respectively). NAM 700- hPa analyses (bottom) include temperature contours (every 2°C), wind (full and half barb denote 5 and 2.5 m s -1, respectively), and 800–500-mb mean relative humidity (shaded following scale at lower left). Adapted from Steenburgh et al. (2009).

3. a) FULLTER b) NOSIERRA 500 1000 1500 2000 2500 3000 3500 Figure 3. WRF topography [m, shaded following scale in (a)] for a subset of the (a) FULLTER and (b) NOSIERRA 12-km nested domain.

4. Figure 4. WRF-model analyses for 1500 UTC 25 Mar 2006. (a) FULLTER radar reflectivity [dBZ, color shaded according to scale in (a)], cloud-top temperature (°C, grey shaded according to scale in (b)], and 850-hPa geopotential height (solid contours every 10 m). (b) Same as (a) but for NOSIERRA. (c) FULLTER lowest half-η level potential temperature (every 2 K), wind (vector scale at left), and kinematic frontogenesis [K (100 km h) −1, shaded following scale at left]. (d) Same as (c), but for NOSIERRA. (e) Same as (c), but with diabatic frontogenesis. (f) As in (e) but for NOSIERRA. c) FULLTER Kinematic (F w ) 1500 UTC e) FULLTER Diabatic (F D ) 1500 UTC d) NOSIERRA Kinematic (F w ) 1500 UTC f) NOSIERRA Diabatic (F D ) 1500 UTC 288 296 288 296 288 10 -10 30 50 -30 -50 20 ms -1 288 296 288 296 288 a) FULLTER Cloud/Radar 1500 UTC b) NOSIERRA Cloud/Radar 1500 UTC 5 10 15 20 25 30 35 40 45 50 -70 -60 -50 -40 -30 -20 -10 0 10 X Y X Y

5. 288 296 288 296 288 296 304 288 296 304 a) FULLTER-NOSIERRA 1500 UTC c) FULLTER-NOSIERRA 2100 UTC b) FULLTER-NOSIERRA 1800 UTC d) FULLTER-NOSIERRA 0000 UTC 0 -2 2 8 -4 -6 20 ms -1 4 6 Figure 5. FULLTER lowest half-η level potential temperature (every 2 K), FULLTER- NOSIERRA lowest half-η level potential temperature difference [K, shaded according to scale in (a)], and FULLTER-NOSIERRA lowest half-η level vector wind difference [scale in (a)] at (a) 1500 UTC 25 Mar, (b) 1800 UTC 25 Mar, (c) 2100 UTC 25 Mar, and (d) 0000 UTC 26 Mar 2006. X Y X Y X Y X Y A

6. a) FULLTER 0000-1500 UTC Group X Group Y Group Z b) NOSIERRA 0000-1500 UTC Figure 6. Three-dimensional 15-h (0000−1500 UTC 25 Mar 2006) trajectories from (a) FULLTER and (b) NOSIERRA. Group X forward trajectories (brown) begin at 850 hPa upstream of the Sierra Nevada. Group Y and Z backwards trajectories (green and light green, respectively) terminate at 850 hPa or the half-η level, whichever is higher. FULLTER-NOSIERRA lowest half-η level potential temperature difference (color filled as in Fig. 5) and terrain difference (0–1000m gray, >1000m black). Trajectory layering based on plotting order and does not indicate relative altitude. Trajectories discussed in text and presented in Fig. 7 labeled to left of start position and right of ending arrow. 1 1 3 3 2 2 4 4 1 2 3 4 1 2 3 4 Group X Group Y Group Z 5 5 5 5

7. Figure 7. Pressure and potential temperature along (a) trajectories 1 and 2 and (b) trajectories 3 and 4 of Fig. 6. a) Trajectories 1 & 2b) Trajectories 3 & 4

8. Pressure (hPa) 500 600 700 800 1000 900 400 300 200 a) FULLTER 1500 UTC Figure 8. Cross sections along line XY (see Fig. 4 and other figures for locations) at 1500 UTC 25 Mar 2006. (a) FULLTER potential temperature (contours every 2K), total cloud water and ice mixing ratio (gray shaded at.0001,.1, and.2 g kg -1 intervals), total diabatic heating rate produced by the explicit moisture scheme and cumulus parameterization (K hr -1, shaded following inset scale), and vectors of along-section wind and pressure vertical velocity (following inset scale). (b) Same as (a) except for NOSIERRA. (c) FULLTER potential temperature [as in (a)] and FULLTER- NOSIERRA potential temperature difference (K, shaded following inset scale). Shading over Sierra Nevada indicates region where differences in the height of the half-η surfaces contribute to the anomaly and introduce a false positive bias. X Y Pressure (hPa) 500 600 700 800 1000 900 400 300 200 b) NOSIERRA 1500 UTC X Y 35 m s -1.03 hPa s -1 Pressure (hPa) 500 600 700 800 1000 900 400 300 200 c) FULLTER w/ Anomaly 1500 UTC X Y -8 -6 -4 -2 0 2 4 6 8 02468-2-4-6-8

9. Figure 9. Same as Fig. 4 except for 1800 UTC 25 Mar 2006. c) FULLTER Kinematic (F w ) 1800 UTC d) NOSIERRA Kinematic (F w ) 1800 UTC 10 -10 30 50 -30 -50 20 ms -1 e) FULLTER Diabatic (F D ) 1800 UTC f) NOSIERRA Diabatic (F D ) 1800 UTC 288 296 288 296 288 296 288 296 a) FULLTER Cloud/Radar 1800 UTC b) NOSIERRA Cloud/Radar 1800 UTC 5 10 15 20 25 30 35 40 45 50 -70 -60 -50 -40 -30 -20 -10 0 10 X Y X Y

10. Pressure (hPa) 500 600 700 800 1000 900 400 300 200 a) FULLTER 1800 UTC X Y Pressure (hPa) 500 600 700 800 1000 900 400 300 200 b) NOSIERRA 1800 UTC X Y 35 m s -1.03 hPa s -1 Figure 10. Same as Fig. 8 except for 1800 UTC 25 Mar 2006. 02468-2-4-6-8 Pressure (hPa) 500 600 700 800 1000 900 400 300 200 c) FULLTER w/ Anomaly 1800 UTC X Y -8 -6 -4 -2 0 2 4 6 8

11. 288 296 304 b) FULLTER-NOSIERRA 2100 UTC X Y 288 296 X Y a) FULLTER-NOSIERRA 1800 UTC 200 -200 100 -100 0 Figure 11. FULLTER lowest half-η level potential temperature (every 2 K) and FULLTER- NOSIERRA surface heat flux difference [W m -2, shaded according to scale in (a)] at (a) 1800 UTC 25 Mar and (b) 2100 UTC 25 Mar 2006.

12. Figure 12. Same as Fig. 4 except for 2100 UTC 25 Mar 2006. c) FULLTER Kinematic (F w ) 2100 UTC d) NOSIERRA Kinematic (F w ) 2100 UTC 10 -10 3030 50 -30 -50 20 ms -1 e) FULLTER Diabatic (F D ) 2100 UTC f) NOSIERRA Diabatic (F D ) 2100 UTC 288 296 304 288 296 304 a) FULLTER Cloud/Radar 2100 UTC b) NOSIERRA Cloud/Radar 2100 UTC 5 10 15 20 25 30 35 40 45 50 -70 -60 -50 -40 -30 -20 -10 0 10 288 296 304 288 296 304 X Y X Y A A

13. Pressure (hPa) 500 600 700 800 1000 900 400 300 200 a) FULLTER 2100 UTC X Y Pressure (hPa) 500 600 700 800 1000 900 400 300 200 b) NOSIERRA 2100 UTC X Y 35 m s -1.03 hPa s -1 Pressure (hPa) 500 600 700 800 1000 900 400 300 200 c) FULLTER w/ Anomaly 2100 UTC X Y -8 -6 -4 -2 0 2 4 6 8 Figure 13. Same as Fig. 8 except for 2100 UTC 25 Mar 2006. 02468-2-4-6-8

14. Pressure (hPa) 500 600 700 800 1000 900 400 300 200-10 0 10 20 30 -20-30-40-50-60-70 Figure 14. FULLTER (red) and NOSIERRA (blue) skew T–log p diagram (temperature and dewpoint) for point A (see Figs. 5c and 12c,d for location) at 2100 UTC 25 Mar 2006.

15. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Group A Group B Group C Group D Group E Group A Group B Group C Group D Group E a) FULLTER b) NOSIERRA 8 6 4 2 -2 8 6 4 2 Figure 15. Three-dimensional nine-hour trajectories ending at 2100 UTC. (a) FULLTER and (b) NOSIERRA. Trajectory number indicated to right of trajectory ending arrow. FULLTER-NOSIERRA lowest half-η level potential temperature difference (color filled following inset scale) and terrain difference shaded (0–1000m gray, >1000m black). Update w/ Same color Scale as Fig. 5 Update Fig. Cap following Fig. 6

16. c) FULLTER Kinematic (F w ) 0000 UTC d) NOSIERRA Kinematic (F w ) 0000 UTC 10 -10 3030 50 -30 -50 20 ms -1 c) FULLTER Diabatic (F D ) 0000 UTC d) NOSIERRA Diabatic (F D ) 0000 UTC Figure 16. Same as Fig. 4 except for 0000 UTC 26 Mar 2006. a) FULLTER Cloud/Radar 0000 UTC b) NOSIERRA Cloud/Radar 0000 UTC 5 10 15 20 25 30 35 40 45 50 -70 -60 -50 -40 -30 -20 -10 0 10 288 296 304 288 296 304 288 296 304 288 296 304 e) FULLTER Diabatic (F D ) 0000 UTC f) NOSIERRA Diabatic (F D ) 0000 UTC X Y X Y

17. a) FULLTER b) NOSIERRA c) FULLTER-FKDRYd) NOSIERRA-FKDRY Figure 17. Lowest half-η level potential temperature (thin contours every 2 K), potential temperature gradient magnitude [thick contours every 5 K (100 km) -1 beginning with 10 K (100 km) -1 ], wind [vector scale at upper left of (a)], and kinematic frontogenesis [K (100 km h) −1, shaded following scale in Fig. 4c] from (a) FULLTER, (b) NOSIERRA, (c) FULLTER-FKDRY, and (d) NOSIERRA-FKDRY at 0000 UTC 26 Mar 2006. 294 10 294 20 ms -1

18. Pressure (hPa) 500 600 700 800 1000 900 400 300 200 a) FULLTER 0000 UTC X Y Pressure (hPa) 500 600 700 800 1000 900 400 300 200 b) NOSIERRA 0000 UTC X Y 35 m s -1.03 hPa s -1 Pressure (hPa) 500 600 700 800 1000 900 400 300 200 c) FULLTER w/ Anomaly 0000 UTC X Y -8 -6 -4 -2 0 2 4 6 8 Figure 18. Same as Fig. 8 except for 0000 UTC 26 Mar 2006. 02468-2-4-6-8