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_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)
=== ===== === ==== ==== === === === ====
Mon 08/10 06Z 0.17 3212  72  36  14 0.00
Mon 08/10 07Z 0.17 3213  72  38  14 0.00
Mon 08/10 08Z 0.16 3213  73  37  13 0.00
Mon 08/10 09Z 0.14 3312  74  40  13 0.00
Mon 08/10 10Z 0.05 3410  76  39  13 0.00
Mon 08/10 11Z 0.07 0006  75  37  13 0.00
Mon 08/10 12Z 0.12 0703  73  33  13 0.00
Mon 08/10 13Z 0.09 1304  72  33  13 0.00
Mon 08/10 14Z 0.03 1607  74  34  13 0.00
Mon 08/10 15Z 0.14 1809  75  35  13 0.00
Mon 08/10 16Z 0.43 1910  77  38  13 0.00
Mon 08/10 17Z 1.37 2011  77  42  13 0.00
Mon 08/10 18Z 1.40 2112  76  50  14 0.00
Mon 08/10 19Z 1.65 2212  74  57  14 0.00
Mon 08/10 20Z 1.78 2112  74  58  14 0.00
Mon 08/10 21Z 1.54 2114  80  82  14 0.00
Mon 08/10 22Z 0.82 2016  82  87  14 0.00
Mon 08/10 23Z 0.78 2118  89  94  14 0.01
Tue 08/11 00Z 0.58 2217  88  80  14 0.01
Tue 08/11 01Z 0.69 2220  92  66  15 0.00
Tue 08/11 02Z 0.65 2421  89  69  15 0.09
Tue 08/11 03Z 0.62 2521  86  68  15 0.03
Tue 08/11 04Z 0.65 2623  89  71  15 0.00
Tue 08/11 05Z 0.66 2723  91  63  15 0.00
Tue 08/11 06Z 0.69 2723  92  57  14 0.01
Tue 08/11 07Z 0.77 2724  95  34  14 0.01
Tue 08/11 08Z 0.76 2825  95  29  13 0.02
Tue 08/11 09Z 0.64 2925  93  22  12 0.01
Tue 08/11 10Z 0.57 3025  91  23  12 0.01
Tue 08/11 11Z 0.50 3025  88  32  12 0.01
Tue 08/11 12Z 0.47 3123  86  40  12 0.01
Tue 08/11 13Z 0.47 3124  81  28  12 0.01
Tue 08/11 14Z 0.51 3024  79  22  11 0.00
Tue 08/11 15Z 0.61 3022  84  21  11 0.00
Tue 08/11 16Z 1.10 3019  86  23  11 0.00
Tue 08/11 17Z 5.48 3018  83  22  11 0.00
Tue 08/11 18Z 8.70 2917  78  19  12 0.00
Tue 08/11 19Z 8.12 2917  80  24  12 0.00
Tue 08/11 20Z 2.87 2919  78  19  12 0.02
Tue 08/11 21Z 1.81 2917  75  23  12 0.00
Tue 08/11 22Z 1.09 2916  73  34  13 0.01
Tue 08/11 23Z 1.07 2917  68  42  13 0.00
Wed 08/12 00Z 1.03 3019  70  26  12 0.00
Wed 08/12 01Z 0.86 3020  78  30  12 0.00
Wed 08/12 02Z 0.57 3018  85  32  12 0.00
Wed 08/12 03Z 0.52 3119  86  24  11 0.00
Wed 08/12 04Z 0.39 3119  84  24  11 0.00
Wed 08/12 05Z 0.35 3117  83  22  11 0.00
Wed 08/12 06Z 0.30 3116  84  23  11 0.00
Wed 08/12 07Z 0.30 3115  81  23  11 0.00
Wed 08/12 08Z 0.28 3115  79  22  11 0.00
Wed 08/12 09Z 0.31 3115  78  26  11 0.00
Wed 08/12 10Z 0.28 3114  79  33  11 0.00
Wed 08/12 11Z 0.25 3113  76  43  11 0.00
Wed 08/12 12Z 0.22 3112  72  75  11 0.00
Wed 08/12 13Z 0.23 3111  72  76  11 0.00
Wed 08/12 14Z 0.23 3110  71  73  11 0.00
Wed 08/12 15Z 0.26 3109  70  62  11 0.00
Wed 08/12 16Z 0.71 3108  69  52  11 0.00
Wed 08/12 17Z 1.02 3105  66  45  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.26 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