Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260702_0000
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 00Z 0.57 2618  66  58  22 0.00
Thu 07/02 01Z 0.75 2620  74  72  21 0.00
Thu 07/02 02Z 0.83 2623  90  60  20 0.03
Thu 07/02 03Z 0.65 2719  89  59  20 0.07
Thu 07/02 04Z 0.75 2722  92  62  19 0.02
Thu 07/02 05Z 0.67 2822  85  65  19 0.14
Thu 07/02 06Z 0.42 2717  65  54  20 0.01
Thu 07/02 07Z 0.45 2519  70  57  20 0.00
Thu 07/02 08Z 0.58 2725  68  52  20 0.00
Thu 07/02 09Z 0.56 2926  79  54  19 0.00
Thu 07/02 10Z 0.47 3025  75  53  20 0.00
Thu 07/02 11Z 0.46 3026  70  50  20 0.00
Thu 07/02 12Z 0.43 3025  63  47  20 0.00
Thu 07/02 13Z 0.42 3025  64  38  20 0.00
Thu 07/02 14Z 0.38 3022  68  49  20 0.00
Thu 07/02 15Z 0.41 3021  71  42  20 0.00
Thu 07/02 16Z 0.55 2920  80  49  19 0.00
Thu 07/02 17Z 0.59 2817  83  52  19 0.00
Thu 07/02 18Z 0.62 2814  85  58  19 0.00
Thu 07/02 19Z 1.09 2713  90  52  19 0.00
Thu 07/02 20Z 1.74 2614  89  53  19 0.00
Thu 07/02 21Z 2.85 2616  85  60  19 0.01
Thu 07/02 22Z 2.12 2617  83  52  19 0.01
Thu 07/02 23Z 1.75 2619  85  53  19 0.00
Fri 07/03 00Z 1.17 2722  84  54  19 0.00
Fri 07/03 01Z 0.95 2723  88  49  19 0.00
Fri 07/03 02Z 0.94 2725  87  45  19 0.00
Fri 07/03 03Z 0.83 2727  82  46  20 0.00
Fri 07/03 04Z 0.76 2828  81  45  20 0.00
Fri 07/03 05Z 0.75 2829  76  38  20 0.00
Fri 07/03 06Z 0.78 2930  78  45  19 0.00
Fri 07/03 07Z 0.77 2930  77  46  18 0.00
Fri 07/03 08Z 0.77 2930  83  49  18 0.00
Fri 07/03 09Z 0.74 2929  87  49  18 0.00
Fri 07/03 10Z 0.62 2926  85  52  18 0.00
Fri 07/03 11Z 0.58 2925  83  62  18 0.00
Fri 07/03 12Z 0.56 2923  89  53  18 0.00
Fri 07/03 13Z 0.53 2920  88  52  18 0.00
Fri 07/03 14Z 0.57 2819  88  61  18 0.00
Fri 07/03 15Z 0.66 2719  91  63  18 0.00
Fri 07/03 16Z 0.74 2718  93  73  18 0.00
Fri 07/03 17Z 0.88 2719  95  75  17 0.01
Fri 07/03 18Z 0.83 2718  95  74  18 0.01
Fri 07/03 19Z 0.97 2820  93  68  18 0.12
Fri 07/03 20Z 1.04 2820  89  60  18 0.04
Fri 07/03 21Z 1.11 2821  85  34  18 0.01
Fri 07/03 22Z 1.13 2820  76  19  18 0.00
Fri 07/03 23Z 1.60 2823  75  16  17 0.00
Sat 07/04 00Z 1.67 2824  76  15  16 0.00
Sat 07/04 01Z 1.23 2824  79  18  16 0.00
Sat 07/04 02Z 1.01 2925  84  27  16 0.00
Sat 07/04 03Z 0.95 2927  89  23  15 0.00
Sat 07/04 04Z 0.78 3027  88  27  15 0.00
Sat 07/04 05Z 0.68 3127  84  33  15 0.00
Sat 07/04 06Z 0.67 3127  82  27  15 0.00
Sat 07/04 07Z 0.59 3126  83  31  15 0.00
Sat 07/04 08Z 0.53 3125  83  30  15 0.00
Sat 07/04 09Z 0.48 3123  85  36  14 0.00
Sat 07/04 10Z 0.48 3122  84  50  15 0.00
Sat 07/04 11Z 0.45 3022  81  38  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.48 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