Subject: NAM3 EXPERIMENTAL Froude Number for the Northern_Greens

Model run: BTV_GRID_D2D_NAM3_20260612_1200
Using the MB925 to MB850 layer.
Assumes Northern_Greens are orthogonal to 290 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Northern_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 06/12 12Z 0.13 2405  93  67  17 0.00
Fri 06/12 13Z 0.10 2305  92  67  16 0.00
Fri 06/12 14Z 0.06 2105  88  59  17 0.00
Fri 06/12 15Z 0.03 2005  87  51  17 0.00
Fri 06/12 16Z 0.18 2205  87  50  17 0.00
Fri 06/12 17Z 0.75 2407  86  40  17 0.00
Fri 06/12 18Z 1.10 2508  84  39  17 0.00
Fri 06/12 19Z 1.06 2607  79  24  18 0.00
Fri 06/12 20Z 1.08 2607  81  45  18 0.00
Fri 06/12 21Z 0.74 2611  89  82  18 0.03
Fri 06/12 22Z 0.35 2512  72  63  18 0.32
Fri 06/12 23Z 0.52 2513  65  11  18 0.05
Sat 06/13 00Z 0.82 2518  74   9  17 0.00
Sat 06/13 01Z 1.03 2523  89  20  16 0.00
Sat 06/13 02Z 1.04 2727  79  20  15 0.03
Sat 06/13 03Z 1.17 2829  78  11  13 0.01
Sat 06/13 04Z 1.13 2929  73  10  13 0.00
Sat 06/13 05Z 0.93 2928  81  14  12 0.00
Sat 06/13 06Z 0.82 3027  82  17  12 0.00
Sat 06/13 07Z 0.67 3025  80  12  12 0.00
Sat 06/13 08Z 0.58 3022  77  14  12 0.00
Sat 06/13 09Z 0.55 3022  78  13  12 0.00
Sat 06/13 10Z 0.53 3022  80  12  11 0.00
Sat 06/13 11Z 0.49 3021  74  13  11 0.00
Sat 06/13 12Z 0.48 3020  70  15  11 0.00
Sat 06/13 13Z 0.52 3019  72  15  11 0.00
Sat 06/13 14Z 0.53 3017  72  14  11 0.00
Sat 06/13 15Z 0.62 2916  74  15  11 0.00
Sat 06/13 16Z 0.69 2914  79  15  11 0.00
Sat 06/13 17Z 1.09 2713  85  14  11 0.00
Sat 06/13 18Z 1.57 2612  90  12  11 0.00
Sat 06/13 19Z 1.86 2613  90  14  11 0.00
Sat 06/13 20Z 4.01 2614  83  17  12 0.00
Sat 06/13 21Z 3.08 2714  76  15  12 0.00
Sat 06/13 22Z 1.91 2715  71  18  12 0.00
Sat 06/13 23Z 1.25 2715  69  26  13 0.00
Sun 06/14 00Z 1.77 2718  69  43  12 0.00
Sun 06/14 01Z 2.19 2820  73  77  12 0.00
Sun 06/14 02Z 0.88 2716  65  77  13 0.00
Sun 06/14 03Z 0.62 2616  59  66  13 0.00
Sun 06/14 04Z 0.65 2518  62  55  13 0.00
Sun 06/14 05Z 0.66 2520  63  57  13 0.00
Sun 06/14 06Z 0.62 2422  61  46  13 0.00
Sun 06/14 07Z 0.70 2427  50  69  14 0.00
Sun 06/14 08Z 1.27 2431  69  67  13 0.00
Sun 06/14 09Z 1.12 2435  77  55  12 0.01
Sun 06/14 10Z 1.27 2435  77  61  12 0.01
Sun 06/14 11Z 1.11 2532  77  69  13 0.00
Sun 06/14 12Z 0.85 2527  79  71  13 0.00
Sun 06/14 13Z 0.66 2424  75  53  14 0.00
Sun 06/14 14Z 0.59 2423  74  48  14 0.00
Sun 06/14 15Z 0.53 2321  72  39  14 0.00
Sun 06/14 16Z 0.44 2119  74  34  14 0.00
Sun 06/14 17Z 0.87 2119  75  37  14 0.00
Sun 06/14 18Z 0.46 2120  75  44  14 0.00
Sun 06/14 19Z 0.36 2120  74  41  15 0.00
Sun 06/14 20Z 0.22 2021  65  35  15 0.00
Sun 06/14 21Z 0.13 2023  62  26  15 0.00
Sun 06/14 22Z 0.11 1922  66  63  15 0.01
Sun 06/14 23Z 0.11 1928  80  77  15 0.04

Run total areal avg QPF for the Northern_Greens is: 0.51 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