NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260811_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)
=== ===== === ==== ==== === === === ====
Tue 08/11 06Z 0.67 2823  86  74  14 0.00
Tue 08/11 07Z 0.71 2822  89  65  14 0.00
Tue 08/11 08Z 0.67 2821  93  61  13 0.01
Tue 08/11 09Z 0.65 2821  96  58  13 0.01
Tue 08/11 10Z 0.58 2921  92  59  13 0.01
Tue 08/11 11Z 0.53 3021  93  49  13 0.00
Tue 08/11 12Z 0.51 3020  93  37  12 0.00
Tue 08/11 13Z 0.56 3019  88  32  12 0.00
Tue 08/11 14Z 0.51 3018  80  27  12 0.00
Tue 08/11 15Z 0.52 3017  78  22  12 0.00
Tue 08/11 16Z 0.96 3015  83  20  12 0.00
Tue 08/11 17Z 3.69 3015  79  19  12 0.00
Tue 08/11 18Z 6.43 3016  70  22  12 0.00
Tue 08/11 19Z 6.73 3116  68  23  12 0.00
Tue 08/11 20Z 5.38 3114  70  25  12 0.00
Tue 08/11 21Z 3.36 3113  72  24  12 0.00
Tue 08/11 22Z 2.41 3012  73  35  12 0.00
Tue 08/11 23Z 1.01 2913  73  48  12 0.00
Wed 08/12 00Z 0.87 3014  77  63  12 0.00
Wed 08/12 01Z 0.66 3014  80  70  11 0.00
Wed 08/12 02Z 0.52 3015  80  57  11 0.00
Wed 08/12 03Z 0.41 3115  72  44  12 0.00
Wed 08/12 04Z 0.35 3115  68  40  12 0.00
Wed 08/12 05Z 0.37 3115  65  37  12 0.00
Wed 08/12 06Z 0.37 3114  65  32  11 0.00
Wed 08/12 07Z 0.34 3113  67  24  11 0.00
Wed 08/12 08Z 0.37 3113  72  30  11 0.00
Wed 08/12 09Z 0.34 3113  73  24  11 0.00
Wed 08/12 10Z 0.33 3113  72  22  11 0.00
Wed 08/12 11Z 0.33 3113  72  25  11 0.00
Wed 08/12 12Z 0.35 3112  72  28  11 0.00
Wed 08/12 13Z 0.38 3012  72  31  11 0.00
Wed 08/12 14Z 0.44 3010  73  36  11 0.00
Wed 08/12 15Z 1.60 3009  74  36  11 0.00
Wed 08/12 16Z 2.38 3007  73  54  11 0.00
Wed 08/12 17Z 2.65 2906  71  62  11 0.00
Wed 08/12 18Z 2.44 2905  70  72  12 0.00
Wed 08/12 19Z 2.19 2705  72  88  12 0.00
Wed 08/12 20Z 1.89 2605  72  80  12 0.00
Wed 08/12 21Z 1.83 2607  79  84  12 0.01
Wed 08/12 22Z 0.73 2509  80  70  12 0.01
Wed 08/12 23Z 0.53 2409  79  75  13 0.00
Thu 08/13 00Z 0.51 2409  80  69  13 0.00
Thu 08/13 01Z 0.52 2410  82  69  12 0.00
Thu 08/13 02Z 0.58 2411  85  76  12 0.04
Thu 08/13 03Z 0.65 2513  87  77  12 0.08
Thu 08/13 04Z 0.60 2614  86  80  12 0.07
Thu 08/13 05Z 0.50 2814  83  69  12 0.04
Thu 08/13 06Z 0.43 2914  82  65  12 0.00
Thu 08/13 07Z 0.45 2915  83  66  12 0.00
Thu 08/13 08Z 0.46 2915  82  72  11 0.00
Thu 08/13 09Z 0.45 2814  84  77  11 0.00
Thu 08/13 10Z 0.36 3014  94  67  11 0.00
Thu 08/13 11Z 0.24 3112  92  63  10 0.00
Thu 08/13 12Z 0.19 3212  92  59  10 0.00
Thu 08/13 13Z 0.16 3210  93  58  10 0.00
Thu 08/13 14Z 0.16 3209  94  57  10 0.00
Thu 08/13 15Z 0.33 3109  95  53  10 0.00
Thu 08/13 16Z 0.33 3108  91  48  10 0.00
Thu 08/13 17Z 0.73 3009  91  64  10 0.01

Run total areal avg QPF for the Central_Greens is: 0.29 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