Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260702_1800
Using the MB925 to MB850 layer.
Assumes Central_Greens are orthogonal to 260 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Central_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Thu 07/02 18Z 2.94 2709  87  61  19 0.00
Thu 07/02 19Z 1.70 2511  88  57  19 0.00
Thu 07/02 20Z 0.89 2412  87  57  19 0.03
Thu 07/02 21Z 1.02 2515  86  53  20 0.04
Thu 07/02 22Z 1.17 2516  83  46  20 0.01
Thu 07/02 23Z 1.66 2520  80  39  20 0.00
Fri 07/03 00Z 1.54 2622  81  41  19 0.00
Fri 07/03 01Z 1.24 2724  79  59  19 0.00
Fri 07/03 02Z 1.19 2726  84  52  19 0.01
Fri 07/03 03Z 1.07 2827  89  50  18 0.00
Fri 07/03 04Z 0.73 2925  90  41  18 0.01
Fri 07/03 05Z 0.57 2923  88  26  18 0.00
Fri 07/03 06Z 0.54 2923  84  19  18 0.00
Fri 07/03 07Z 0.56 2923  83  31  18 0.00
Fri 07/03 08Z 0.51 2922  79  33  18 0.00
Fri 07/03 09Z 0.43 3022  75  31  18 0.00
Fri 07/03 10Z 0.37 3021  70  18  18 0.00
Fri 07/03 11Z 0.33 3020  64  19  19 0.00
Fri 07/03 12Z 0.30 3019  61  21  18 0.00
Fri 07/03 13Z 0.29 3017  54  13  19 0.00
Fri 07/03 14Z 0.36 2918  54   5  19 0.00
Fri 07/03 15Z 0.45 2919  58  15  18 0.00
Fri 07/03 16Z 0.59 2919  70  16  18 0.00
Fri 07/03 17Z 0.79 2819  78  24  18 0.00
Fri 07/03 18Z 1.49 2819  81  28  17 0.00
Fri 07/03 19Z 2.88 2820  77  41  17 0.00
Fri 07/03 20Z 5.13 2819  71  50  17 0.00
Fri 07/03 21Z 5.97 2720  66  66  18 0.00
Fri 07/03 22Z 3.49 2821  64  74  18 0.00
Fri 07/03 23Z 1.96 2721  62  61  18 0.00
Sat 07/04 00Z 1.45 2822  59  60  18 0.00
Sat 07/04 01Z 0.88 2920  56  58  18 0.00
Sat 07/04 02Z 0.71 2920  57  61  18 0.00
Sat 07/04 03Z 0.74 2921  62  63  18 0.00
Sat 07/04 04Z 0.74 2921  67  62  17 0.00
Sat 07/04 05Z 0.67 3021  73  65  17 0.00
Sat 07/04 06Z 0.64 3022  78  73  16 0.00
Sat 07/04 07Z 0.55 3020  82  74  16 0.00
Sat 07/04 08Z 0.48 3020  86  77  16 0.00
Sat 07/04 09Z 0.41 3019  90  68  16 0.01
Sat 07/04 10Z 0.35 3117  93  66  16 0.01
Sat 07/04 11Z 0.24 3115  95  59  15 0.01
Sat 07/04 12Z 0.19 3111  91  61  16 0.00
Sat 07/04 13Z 0.22 3111  93  67  15 0.00
Sat 07/04 14Z 0.24 3010  95  57  15 0.00
Sat 07/04 15Z 0.22 3009  96  45  15 0.00
Sat 07/04 16Z 0.25 3109  95  56  14 0.01
Sat 07/04 17Z 0.27 3112  89  72  14 0.05
Sat 07/04 18Z 0.27 3215  85  67  14 0.04
Sat 07/04 19Z 0.32 3216  81  58  14 0.00
Sat 07/04 20Z 0.44 3316  79  40  14 0.00
Sat 07/04 21Z 0.62 3316  74  24  14 0.00
Sat 07/04 22Z 0.36 3318  70  18  14 0.00
Sat 07/04 23Z 0.14 3419  65  13  14 0.00
Sun 07/05 00Z 0.05 3418  66  13  13 0.00
Sun 07/05 01Z 0.08 3518  71  16  13 0.00
Sun 07/05 02Z 0.11 3519  75  16  12 0.00
Sun 07/05 03Z 0.08 3418  76  17  12 0.00
Sun 07/05 04Z 0.06 3417  73  12  12 0.00
Sun 07/05 05Z 0.06 3516  70   7  12 0.00

Run total areal avg QPF for the Central_Greens is: 0.23 inches.

Froude Number (Frd#): 
Frd# < 0.5 Flow is subcritical and blocked.
         Upslope clouds/precip backed farther upwind of and up to mtn crest.
         W Upslope snow favors eastern Champlain Valley, BTV, and Western slopes.
         Gap winds possible.
Frd# 0.5-1 Flow is subcritical/slow moving/blocked.
         Upslope clouds/precip falls immediately upwind of mtn crest.
         W Upslope snow favors western slopes to the Green Mt. spine including:
         Montgomery,Underhill,Jericho,Bolton,Richmond,Huntington,Lincoln.
         Gap winds possible.
Frd# 1-2 Flow is critical.
         With strong winds, Mountain waves/downslope winds possible.
         Precip falls close to mountain ridge crests and on lee side.
         W Upslope snow favors Green Mt Spine,Jay,Stowe,Waterbury,NE Kingdom.
Froude > 2 Flow is supercritical/unblocked(rapid flow).
         Air flows freely over terrain.
         Persistent upslope snow not favored. Scattered snow showers and flurries.

Relative Humidity (RH): 
         925-850 mb RH > 90% needed for upslope precipitation.
         with 700mb RH > 70% favors upslope snow.
         with 700mb RH > 90% greater amounts of W upslope snow possible.

850mb Temperature (T degC) Westerly Upslope Snow Ratios: (Avg=28:1)
        T > -11       10-15:1
        T -11 to -15  25-35:1
        T < -15       15-20:1