NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260708_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)
=== ===== === ==== ==== === === === ====
Wed 07/08 06Z 0.02 0100  63  44  14 0.00
Wed 07/08 07Z 0.03 3304  60  39  15 0.00
Wed 07/08 08Z 0.06 3206  64  34  14 0.00
Wed 07/08 09Z 0.09 3208  69  22  14 0.00
Wed 07/08 10Z 0.09 3309  72  11  14 0.00
Wed 07/08 11Z 0.05 3409  75   8  14 0.00
Wed 07/08 12Z 0.02 3408  78  16  14 0.00
Wed 07/08 13Z 0.02 3506  78  19  14 0.00
Wed 07/08 14Z 0.03 3405  81  16  14 0.00
Wed 07/08 15Z 0.08 3205  84  12  14 0.00
Wed 07/08 16Z 0.15 3004  86  21  14 0.00
Wed 07/08 17Z 0.30 2906  86  56  13 0.00
Wed 07/08 18Z 0.30 3007  80  70  14 0.00
Wed 07/08 19Z 0.41 3108  75  53  14 0.00
Wed 07/08 20Z 0.62 3109  76  31  15 0.00
Wed 07/08 21Z 0.57 3008  78  32  15 0.00
Wed 07/08 22Z 0.54 2708  83  32  15 0.00
Wed 07/08 23Z 0.42 2608  84  31  15 0.00
Thu 07/09 00Z 0.48 2511  79  33  15 0.00
Thu 07/09 01Z 0.52 2513  81  25  15 0.00
Thu 07/09 02Z 0.55 2613  80  16  15 0.00
Thu 07/09 03Z 0.61 2613  81  11  15 0.00
Thu 07/09 04Z 0.61 2614  82  12  15 0.00
Thu 07/09 05Z 0.66 2516  83  13  15 0.00
Thu 07/09 06Z 0.69 2518  81   9  15 0.00
Thu 07/09 07Z 0.70 2520  81   6  15 0.00
Thu 07/09 08Z 0.64 2521  81  12  15 0.00
Thu 07/09 09Z 0.60 2621  80  18  16 0.00
Thu 07/09 10Z 0.64 2521  88  12  15 0.00
Thu 07/09 11Z 0.60 2619  90  39  15 0.01
Thu 07/09 12Z 0.55 2617  96  53  15 0.02
Thu 07/09 13Z 0.49 2615  93  42  15 0.03
Thu 07/09 14Z 0.46 2614  91  25  15 0.00
Thu 07/09 15Z 0.49 2614  85  24  15 0.00
Thu 07/09 16Z 0.51 2512  83  23  15 0.00
Thu 07/09 17Z 0.72 2413  88  20  15 0.00
Thu 07/09 18Z 1.33 2514  90  22  15 0.01
Thu 07/09 19Z 0.89 2415  91  26  16 0.01
Thu 07/09 20Z 0.81 2417  92  25  16 0.01
Thu 07/09 21Z 0.70 2418  89  41  16 0.01
Thu 07/09 22Z 0.81 2520  90  56  16 0.01
Thu 07/09 23Z 0.92 2622  92  53  16 0.01
Fri 07/10 00Z 0.89 2721  93  64  16 0.01
Fri 07/10 01Z 0.66 2717  92  54  16 0.01
Fri 07/10 02Z 0.64 2718  94  65  16 0.02
Fri 07/10 03Z 0.55 2816  93  66  15 0.01
Fri 07/10 04Z 0.58 2716  95  70  15 0.00
Fri 07/10 05Z 0.58 2716  95  68  15 0.00
Fri 07/10 06Z 0.54 2715  96  55  15 0.00
Fri 07/10 07Z 0.54 2715  96  69  15 0.01
Fri 07/10 08Z 0.55 2716  97  74  14 0.02
Fri 07/10 09Z 0.48 2714  95  76  14 0.02
Fri 07/10 10Z 0.49 2715  97  82  14 0.07
Fri 07/10 11Z 0.38 2813  96  82  14 0.04
Fri 07/10 12Z 0.28 2910  97  90  14 0.01
Fri 07/10 13Z 0.27 2909  97  84  14 0.00
Fri 07/10 14Z 0.22 3008  97  83  14 0.00
Fri 07/10 15Z 0.20 3007  98  89  14 0.00
Fri 07/10 16Z 0.15 3106  97  89  14 0.00
Fri 07/10 17Z 0.11 3205  95  84  14 0.01

Run total areal avg QPF for the Central_Greens is: 0.35 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