NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260814_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)
=== ===== === ==== ==== === === === ====
Fri 08/14 00Z 0.59 3113  84  59  12 0.00
Fri 08/14 01Z 0.63 3116  84  61  11 0.00
Fri 08/14 02Z 0.54 3218  83  65  11 0.00
Fri 08/14 03Z 0.45 3218  77  59  11 0.00
Fri 08/14 04Z 0.50 3220  77  59  11 0.00
Fri 08/14 05Z 0.47 3220  77  64  11 0.00
Fri 08/14 06Z 0.41 3219  81  66  10 0.00
Fri 08/14 07Z 0.38 3218  81  59  10 0.00
Fri 08/14 08Z 0.41 3118  81  56  10 0.00
Fri 08/14 09Z 0.41 3117  80  57  10 0.00
Fri 08/14 10Z 0.41 3118  78  57  10 0.00
Fri 08/14 11Z 0.38 3119  77  55  10 0.00
Fri 08/14 12Z 0.37 3118  78  52  10 0.00
Fri 08/14 13Z 0.36 3118  78  51   9 0.00
Fri 08/14 14Z 0.39 3116  77  53   9 0.00
Fri 08/14 15Z 0.53 3215  75  58   9 0.00
Fri 08/14 16Z 1.45 3214  72  61   9 0.00
Fri 08/14 17Z 1.69 3214  69  62   9 0.00
Fri 08/14 18Z 1.71 3214  66  65  10 0.00
Fri 08/14 19Z 1.87 3212  70  67  10 0.00
Fri 08/14 20Z 2.36 3112  74  63  10 0.00
Fri 08/14 21Z 1.57 3211  74  57  10 0.00
Fri 08/14 22Z 0.77 3212  73  52  10 0.00
Fri 08/14 23Z 0.40 3213  73  49  10 0.00
Sat 08/15 00Z 0.28 3215  71  41  10 0.00
Sat 08/15 01Z 0.29 3317  71  34   9 0.00
Sat 08/15 02Z 0.17 3319  71  33   9 0.00
Sat 08/15 03Z 0.16 3419  73  26   9 0.00
Sat 08/15 04Z 0.03 3416  70  20   9 0.00
Sat 08/15 05Z 0.07 3414  73  19   8 0.00
Sat 08/15 06Z 0.05 3411  73  17   8 0.00
Sat 08/15 07Z 0.04 3409  72  16   8 0.00
Sat 08/15 08Z 0.12 3310  73  17   8 0.00
Sat 08/15 09Z 0.10 3312  73  16   8 0.00
Sat 08/15 10Z 0.15 3316  75  19   8 0.00
Sat 08/15 11Z 0.15 3318  73  21   8 0.00
Sat 08/15 12Z 0.11 3317  65  16   8 0.00
Sat 08/15 13Z 0.09 3315  68  13   8 0.00
Sat 08/15 14Z 0.08 3414  70  14   8 0.00
Sat 08/15 15Z 0.24 3312  72  14   7 0.00
Sat 08/15 16Z 0.16 3412  70  15   8 0.00
Sat 08/15 17Z 0.08 3509  66  15   8 0.00
Sat 08/15 18Z 0.20 3407  68  18   9 0.00
Sat 08/15 19Z 0.24 3306  68  19   9 0.00
Sat 08/15 20Z 0.29 3209  63  21   9 0.00
Sat 08/15 21Z 0.17 3311  53  21  10 0.00
Sat 08/15 22Z 0.04 3411  50  19  10 0.00
Sat 08/15 23Z 0.07 3410  53  19  10 0.00
Sun 08/16 00Z 0.05 3409  56  18  10 0.00
Sun 08/16 01Z 0.04 3409  59  17  10 0.00
Sun 08/16 02Z 0.02 3408  61  17  10 0.00
Sun 08/16 03Z 0.03 3405  62  18  10 0.00
Sun 08/16 04Z 0.03 3303  61  18  10 0.00
Sun 08/16 05Z 0.02 2800  60  16  11 0.00
Sun 08/16 06Z 0.07 2202  63  16  10 0.00
Sun 08/16 07Z 0.15 2305  67  13  10 0.00
Sun 08/16 08Z 0.23 2407  72  12  10 0.00
Sun 08/16 09Z 0.23 2308  73   7  10 0.00
Sun 08/16 10Z 0.23 2208  74   5  10 0.00
Sun 08/16 11Z 0.25 2110  78   4  10 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