NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260808_0600
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)
=== ===== === ==== ==== === === === ====
Sat 08/08 06Z 0.21 2208  85  83  16 0.00
Sat 08/08 07Z 0.22 2208  82  83  16 0.00
Sat 08/08 08Z 0.23 2407  85  82  16 0.00
Sat 08/08 09Z 0.19 2606  90  81  15 0.01
Sat 08/08 10Z 0.12 2704  91  84  15 0.01
Sat 08/08 11Z 0.08 2802  94  92  15 0.00
Sat 08/08 12Z 0.09 2502  97  92  15 0.00
Sat 08/08 13Z 0.12 2403  98  89  15 0.00
Sat 08/08 14Z 0.20 2306  98  90  15 0.00
Sat 08/08 15Z 0.17 2106  96  86  15 0.01
Sat 08/08 16Z 0.18 2007  94  80  15 0.00
Sat 08/08 17Z 0.31 2110  94  76  15 0.00
Sat 08/08 18Z 0.42 2212  93  67  15 0.00
Sat 08/08 19Z 0.47 2312  91  64  16 0.00
Sat 08/08 20Z 0.54 2412  88  53  16 0.00
Sat 08/08 21Z 0.69 2415  93  49  16 0.00
Sat 08/08 22Z 0.61 2515  93  52  16 0.01
Sat 08/08 23Z 0.54 2515  92  62  16 0.01
Sun 08/09 00Z 0.48 2513  89  71  16 0.01
Sun 08/09 01Z 0.49 2513  89  75  16 0.01
Sun 08/09 02Z 0.53 2515  91  73  16 0.01
Sun 08/09 03Z 0.58 2618  90  60  16 0.02
Sun 08/09 04Z 0.64 2720  91  48  16 0.01
Sun 08/09 05Z 0.57 2719  90  44  16 0.00
Sun 08/09 06Z 0.58 2719  91  40  16 0.00
Sun 08/09 07Z 0.54 2819  89  42  15 0.00
Sun 08/09 08Z 0.52 2818  89  47  15 0.00
Sun 08/09 09Z 0.49 2817  90  43  15 0.00
Sun 08/09 10Z 0.43 2815  88  22  15 0.00
Sun 08/09 11Z 0.36 2814  82  16  15 0.00
Sun 08/09 12Z 0.37 2813  82  25  15 0.00
Sun 08/09 13Z 0.39 2714  83  29  15 0.00
Sun 08/09 14Z 0.44 2814  85  35  15 0.00
Sun 08/09 15Z 0.45 2813  83  20  14 0.00
Sun 08/09 16Z 0.55 2813  83  10  14 0.00
Sun 08/09 17Z 0.73 2812  84  14  14 0.00
Sun 08/09 18Z 1.19 2813  84  20  14 0.03
Sun 08/09 19Z 1.06 2914  79  18  14 0.01
Sun 08/09 20Z 0.82 3013  72  21  14 0.01
Sun 08/09 21Z 0.42 2910  65  30  15 0.00
Sun 08/09 22Z 0.44 2911  66  33  15 0.00
Sun 08/09 23Z 0.34 2909  67  31  15 0.00
Mon 08/10 00Z 0.33 2909  66  31  15 0.00
Mon 08/10 01Z 0.39 2810  68  27  15 0.00
Mon 08/10 02Z 0.33 2809  68  29  15 0.00
Mon 08/10 03Z 0.36 2811  69  35  15 0.00
Mon 08/10 04Z 0.29 2910  70  29  15 0.00
Mon 08/10 05Z 0.23 2909  65  22  16 0.00
Mon 08/10 06Z 0.20 2908  66  17  15 0.00
Mon 08/10 07Z 0.16 2706  62  24  15 0.00
Mon 08/10 08Z 0.16 2506  57  28  16 0.00
Mon 08/10 09Z 0.16 2306  51  27  16 0.00
Mon 08/10 10Z 0.17 2208  45  31  17 0.00
Mon 08/10 11Z 0.22 2210  43  31  16 0.00
Mon 08/10 12Z 0.25 2211  39  35  16 0.00
Mon 08/10 13Z 0.27 2211  37  34  16 0.00
Mon 08/10 14Z 0.32 2312  40  40  16 0.00
Mon 08/10 15Z 0.34 2312  49  57  15 0.00
Mon 08/10 16Z 0.41 2312  59  65  15 0.00
Mon 08/10 17Z 0.52 2213  71  61  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.16 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