NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260709_1200
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)
=== ===== === ==== ==== === === === ====
Thu 07/09 12Z 0.38 2913  86  27  15 0.00
Thu 07/09 13Z 0.34 2911  80  18  15 0.00
Thu 07/09 14Z 0.36 2809  80  21  15 0.00
Thu 07/09 15Z 0.54 2806  79  21  15 0.00
Thu 07/09 16Z 0.82 2604  77  14  15 0.00
Thu 07/09 17Z 1.62 2305  75  12  16 0.00
Thu 07/09 18Z 2.38 2206  74  13  16 0.00
Thu 07/09 19Z 3.60 2109  76  32  16 0.00
Thu 07/09 20Z 3.77 2211  75  36  16 0.00
Thu 07/09 21Z 3.20 2313  77  28  16 0.00
Thu 07/09 22Z 1.02 2313  85  33  16 0.00
Thu 07/09 23Z 0.58 2413  86  51  16 0.01
Fri 07/10 00Z 0.65 2414  89  49  16 0.03
Fri 07/10 01Z 0.52 2413  91  53  16 0.01
Fri 07/10 02Z 0.50 2413  92  57  16 0.03
Fri 07/10 03Z 0.46 2514  94  57  16 0.04
Fri 07/10 04Z 0.41 2613  94  74  16 0.02
Fri 07/10 05Z 0.41 2713  92  70  16 0.01
Fri 07/10 06Z 0.42 2814  93  66  15 0.01
Fri 07/10 07Z 0.44 2816  92  70  15 0.01
Fri 07/10 08Z 0.43 2917  93  67  14 0.01
Fri 07/10 09Z 0.35 3017  96  68  14 0.01
Fri 07/10 10Z 0.26 3217  98  70  13 0.01
Fri 07/10 11Z 0.15 3316  97  70  13 0.01
Fri 07/10 12Z 0.11 3315  95  74  13 0.01
Fri 07/10 13Z 0.05 3414  90  71  13 0.00
Fri 07/10 14Z 0.06 3412  87  73  13 0.00
Fri 07/10 15Z 0.06 3411  86  79  13 0.00
Fri 07/10 16Z 0.05 3510  86  84  13 0.00
Fri 07/10 17Z 0.06 3509  87  79  13 0.00
Fri 07/10 18Z 0.11 3507  88  64  13 0.00
Fri 07/10 19Z 0.07 3407  88  65  13 0.00
Fri 07/10 20Z 0.15 3408  86  52  13 0.01
Fri 07/10 21Z 0.08 3409  81  58  13 0.01
Fri 07/10 22Z 0.14 3509  78  54  13 0.00
Fri 07/10 23Z 0.14 0009  74  51  13 0.00
Sat 07/11 00Z 0.16 0010  66  49  13 0.00
Sat 07/11 01Z 0.16 0011  61  47  13 0.00
Sat 07/11 02Z 0.19 0012  61  39  13 0.00
Sat 07/11 03Z 0.19 0111  66  37  12 0.00
Sat 07/11 04Z 0.16 0010  73  42  12 0.00
Sat 07/11 05Z 0.13 0010  76  45  12 0.00
Sat 07/11 06Z 0.11 0011  77  51  11 0.00
Sat 07/11 07Z 0.09 0010  77  53  11 0.00
Sat 07/11 08Z 0.14 0009  77  57  11 0.00
Sat 07/11 09Z 0.15 0107  76  54  11 0.00
Sat 07/11 10Z 0.14 0206  75  49  11 0.00
Sat 07/11 11Z 0.15 0206  75  46  11 0.00
Sat 07/11 12Z 0.13 0205  74  55  11 0.00
Sat 07/11 13Z 0.09 0104  75  56  11 0.00
Sat 07/11 14Z 0.12 0003  80  53  10 0.00
Sat 07/11 15Z 0.51 0004  81  35  10 0.00
Sat 07/11 16Z 0.43 0003  83  30  11 0.00
Sat 07/11 17Z 0.28 3505  84  35  11 0.01
Sat 07/11 18Z 0.26 3506  82  28  11 0.01
Sat 07/11 19Z 0.50 0006  80  15  11 0.00
Sat 07/11 20Z 0.66 0007  78  14  11 0.00
Sat 07/11 21Z 0.65 0007  77  13  11 0.00
Sat 07/11 22Z 0.56 0008  77  13  11 0.00
Sat 07/11 23Z 0.37 0008  76  11  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