NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260810_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)
=== ===== === ==== ==== === === === ====
Mon 08/10 00Z 0.52 3014  82  26  14 0.00
Mon 08/10 01Z 0.63 3016  81  29  14 0.00
Mon 08/10 02Z 0.51 3016  83  28  14 0.00
Mon 08/10 03Z 0.33 3114  82  27  14 0.00
Mon 08/10 04Z 0.26 3113  79  29  14 0.00
Mon 08/10 05Z 0.24 3112  74  33  14 0.00
Mon 08/10 06Z 0.19 3212  69  38  14 0.00
Mon 08/10 07Z 0.08 3311  64  39  14 0.00
Mon 08/10 08Z 0.03 3508  61  38  14 0.00
Mon 08/10 09Z 0.07 0006  62  38  14 0.00
Mon 08/10 10Z 0.07 0203  65  41  13 0.00
Mon 08/10 11Z 0.07 1002  65  35  13 0.00
Mon 08/10 12Z 0.07 1505  64  33  13 0.00
Mon 08/10 13Z 0.03 1607  63  29  13 0.00
Mon 08/10 14Z 0.05 1710  65  35  13 0.00
Mon 08/10 15Z 0.36 1911  71  58  13 0.00
Mon 08/10 16Z 0.93 2011  74  55  13 0.00
Mon 08/10 17Z 2.71 2112  73  40  14 0.00
Mon 08/10 18Z 3.27 2212  72  42  14 0.00
Mon 08/10 19Z 2.19 2211  76  35  14 0.00
Mon 08/10 20Z 0.99 2112  76  43  15 0.00
Mon 08/10 21Z 0.50 2113  75  84  16 0.00
Mon 08/10 22Z 0.73 2118  83  68  15 0.00
Mon 08/10 23Z 0.76 2220  88  71  15 0.00
Tue 08/11 00Z 0.72 2419  89  82  15 0.00
Tue 08/11 01Z 0.77 2522  95  86  15 0.01
Tue 08/11 02Z 0.73 2722  90  81  15 0.01
Tue 08/11 03Z 0.69 2822  90  75  15 0.01
Tue 08/11 04Z 0.68 2722  90  75  15 0.02
Tue 08/11 05Z 0.68 2721  90  68  15 0.01
Tue 08/11 06Z 0.75 2722  92  46  14 0.01
Tue 08/11 07Z 0.76 2722  93  39  14 0.01
Tue 08/11 08Z 0.75 2822  94  38  13 0.01
Tue 08/11 09Z 0.63 2919  94  39  13 0.01
Tue 08/11 10Z 0.61 2919  95  35  12 0.01
Tue 08/11 11Z 0.53 2918  92  36  12 0.01
Tue 08/11 12Z 0.47 2917  87  36  12 0.01
Tue 08/11 13Z 0.48 2918  83  33  12 0.00
Tue 08/11 14Z 0.45 2917  75  27  12 0.00
Tue 08/11 15Z 0.51 3018  77  23  12 0.00
Tue 08/11 16Z 0.66 2919  81  20  12 0.00
Tue 08/11 17Z 1.07 3017  80  20  12 0.00
Tue 08/11 18Z 3.44 3016  79  25  11 0.00
Tue 08/11 19Z 4.11 3015  79  31  12 0.00
Tue 08/11 20Z 2.52 3014  79  32  12 0.00
Tue 08/11 21Z 1.28 3013  77  29  12 0.00
Tue 08/11 22Z 0.77 3012  77  19  12 0.00
Tue 08/11 23Z 0.56 3012  78  22  12 0.00
Wed 08/12 00Z 0.44 3113  78  25  12 0.00
Wed 08/12 01Z 0.45 3013  82  26  12 0.00
Wed 08/12 02Z 0.43 3013  82  25  11 0.00
Wed 08/12 03Z 0.35 3012  81  23  11 0.00
Wed 08/12 04Z 0.35 3012  82  25  11 0.00
Wed 08/12 05Z 0.29 3112  82  24  11 0.00
Wed 08/12 06Z 0.26 3110  83  21  11 0.00
Wed 08/12 07Z 0.27 3111  82  20  11 0.00
Wed 08/12 08Z 0.29 3111  83  23  11 0.00
Wed 08/12 09Z 0.29 3010  82  24  11 0.00
Wed 08/12 10Z 0.28 3010  80  31  11 0.00
Wed 08/12 11Z 0.30 3112  81  43  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.13 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