NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260804_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)
=== ===== === ==== ==== === === === ====
Tue 08/04 00Z 0.68 3126  94  49  10 0.00
Tue 08/04 01Z 0.77 3128  88  16  10 0.00
Tue 08/04 02Z 0.73 3129  84   7  10 0.00
Tue 08/04 03Z 0.59 3128  80   4  10 0.00
Tue 08/04 04Z 0.58 3125  72   2  11 0.00
Tue 08/04 05Z 0.78 3024  69   2  11 0.00
Tue 08/04 06Z 0.86 2925  74   1  11 0.00
Tue 08/04 07Z 0.85 2926  70   2  11 0.00
Tue 08/04 08Z 0.80 2925  68   3  11 0.00
Tue 08/04 09Z 0.76 2923  67   2  11 0.00
Tue 08/04 10Z 0.79 2924  66   2  11 0.00
Tue 08/04 11Z 0.74 2923  62   2  12 0.00
Tue 08/04 12Z 0.69 2922  59   2  12 0.00
Tue 08/04 13Z 0.70 2922  58   2  12 0.00
Tue 08/04 14Z 0.68 2920  56   2  12 0.00
Tue 08/04 15Z 0.64 2918  54   2  12 0.00
Tue 08/04 16Z 0.51 2914  53   2  13 0.00
Tue 08/04 17Z 0.42 2910  55   2  13 0.00
Tue 08/04 18Z 0.43 2808  58   3  14 0.00
Tue 08/04 19Z 0.52 2607  61   5  14 0.00
Tue 08/04 20Z 0.54 2507  65   8  14 0.00
Tue 08/04 21Z 0.39 2407  66  14  15 0.00
Tue 08/04 22Z 0.27 2308  64  21  15 0.00
Tue 08/04 23Z 0.26 2308  59  26  16 0.00
Wed 08/05 00Z 0.28 2310  56  30  16 0.00
Wed 08/05 01Z 0.28 2310  51  31  17 0.00
Wed 08/05 02Z 0.26 2310  46  32  17 0.00
Wed 08/05 03Z 0.25 2310  41  35  18 0.00
Wed 08/05 04Z 0.25 2311  38  35  18 0.00
Wed 08/05 05Z 0.27 2312  37  34  19 0.00
Wed 08/05 06Z 0.28 2412  39  27  19 0.00
Wed 08/05 07Z 0.28 2512  41  17  18 0.00
Wed 08/05 08Z 0.31 2513  47   9  18 0.00
Wed 08/05 09Z 0.28 2611  50   5  17 0.00
Wed 08/05 10Z 0.24 2710  52   6  17 0.00
Wed 08/05 11Z 0.24 2709  57   5  16 0.00
Wed 08/05 12Z 0.17 2807  58   5  16 0.00
Wed 08/05 13Z 0.14 2705  59   3  16 0.00
Wed 08/05 14Z 0.10 2403  58   6  16 0.00
Wed 08/05 15Z 0.17 2404  64   9  15 0.00
Wed 08/05 16Z 0.17 2304  63   9  15 0.00
Wed 08/05 17Z 0.21 2204  60   6  15 0.00
Wed 08/05 18Z 0.37 2205  54   3  16 0.00
Wed 08/05 19Z 0.37 2306  48   2  16 0.00
Wed 08/05 20Z 0.39 2306  46   0  16 0.00
Wed 08/05 21Z 0.30 2408  46   0  17 0.00
Wed 08/05 22Z 0.28 2408  47   0  17 0.00
Wed 08/05 23Z 0.27 2508  55   0  17 0.00
Thu 08/06 00Z 0.28 2609  63   0  17 0.00
Thu 08/06 01Z 0.29 2609  67   0  17 0.00
Thu 08/06 02Z 0.25 2608  66   1  17 0.00
Thu 08/06 03Z 0.22 2607  65   4  17 0.00
Thu 08/06 04Z 0.24 2608  67  14  17 0.00
Thu 08/06 05Z 0.28 2509  70  25  17 0.00
Thu 08/06 06Z 0.34 2511  73  34  17 0.00
Thu 08/06 07Z 0.36 2612  77  53  17 0.00
Thu 08/06 08Z 0.32 2611  77  64  17 0.00
Thu 08/06 09Z 0.31 2711  78  61  17 0.00
Thu 08/06 10Z 0.27 2710  78  61  17 0.00
Thu 08/06 11Z 0.24 2709  79  62  17 0.00

Run total areal avg QPF for the Central_Greens is: 0.00 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