NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260710_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 07/10 00Z 0.61 2713  68  56  17 0.00
Fri 07/10 01Z 0.38 2912  73  52  17 0.00
Fri 07/10 02Z 0.28 3010  77  51  16 0.00
Fri 07/10 03Z 0.28 2809  84  57  15 0.00
Fri 07/10 04Z 0.35 2610  88  65  15 0.00
Fri 07/10 05Z 0.47 2613  92  79  15 0.04
Fri 07/10 06Z 0.53 2715  94  84  14 0.05
Fri 07/10 07Z 0.54 2816  94  84  14 0.02
Fri 07/10 08Z 0.51 2917  93  80  14 0.00
Fri 07/10 09Z 0.47 2917  95  81  14 0.01
Fri 07/10 10Z 0.35 3117  95  79  14 0.02
Fri 07/10 11Z 0.26 3218  94  69  13 0.01
Fri 07/10 12Z 0.18 3316  92  62  13 0.01
Fri 07/10 13Z 0.16 3315  89  56  13 0.01
Fri 07/10 14Z 0.09 3414  87  46  13 0.00
Fri 07/10 15Z 0.09 3413  88  40  12 0.00
Fri 07/10 16Z 0.10 3512  85  31  12 0.00
Fri 07/10 17Z 0.16 3510  84  28  12 0.00
Fri 07/10 18Z 0.21 3509  81  25  12 0.00
Fri 07/10 19Z 0.21 3409  76  29  13 0.00
Fri 07/10 20Z 0.39 3410  74  34  13 0.00
Fri 07/10 21Z 0.52 3311  72  39  13 0.00
Fri 07/10 22Z 0.19 3411  68  39  13 0.00
Fri 07/10 23Z 0.07 3412  69  39  13 0.00
Sat 07/11 00Z 0.04 3512  73  32  12 0.00
Sat 07/11 01Z 0.05 3514  72  20  12 0.00
Sat 07/11 02Z 0.12 3514  72  22  12 0.00
Sat 07/11 03Z 0.14 3415  69  19  11 0.00
Sat 07/11 04Z 0.12 3416  67  16  11 0.00
Sat 07/11 05Z 0.07 3416  65  10  11 0.00
Sat 07/11 06Z 0.07 3514  63   9  11 0.00
Sat 07/11 07Z 0.16 0013  64  12  10 0.00
Sat 07/11 08Z 0.19 0011  65  11  10 0.00
Sat 07/11 09Z 0.26 0110  65  12  10 0.00
Sat 07/11 10Z 0.27 0209  65  17  10 0.00
Sat 07/11 11Z 0.20 0107  64  17  10 0.00
Sat 07/11 12Z 0.14 0007  63  19   9 0.00
Sat 07/11 13Z 0.11 3506  63  15   9 0.00
Sat 07/11 14Z 0.22 3406  64  15   9 0.00
Sat 07/11 15Z 0.48 3306  64  18  10 0.00
Sat 07/11 16Z 0.84 3307  63  20  10 0.00
Sat 07/11 17Z 0.94 3308  61  19  10 0.00
Sat 07/11 18Z 0.37 3409  60  15  10 0.00
Sat 07/11 19Z 0.36 3509  62  15  11 0.00
Sat 07/11 20Z 0.33 3509  64  14  11 0.00
Sat 07/11 21Z 0.34 3510  67  15  11 0.00
Sat 07/11 22Z 0.42 3511  72  17  11 0.00
Sat 07/11 23Z 0.36 0012  75  21  10 0.00
Sun 07/12 00Z 0.27 0014  76  25  10 0.00
Sun 07/12 01Z 0.38 0115  74  29  10 0.00
Sun 07/12 02Z 0.47 0117  73  30  10 0.00
Sun 07/12 03Z 0.52 0216  74  31   9 0.00
Sun 07/12 04Z 0.57 0216  76  30   9 0.00
Sun 07/12 05Z 0.58 0316  75  30   9 0.00
Sun 07/12 06Z 0.57 0315  74  29   9 0.00
Sun 07/12 07Z 0.53 0314  74  26   9 0.00
Sun 07/12 08Z 0.46 0212  76  23   9 0.00
Sun 07/12 09Z 0.37 0212  76  19   9 0.00
Sun 07/12 10Z 0.27 0112  76  16   9 0.00
Sun 07/12 11Z 0.23 0112  75  15   9 0.00

Run total areal avg QPF for the Central_Greens is: 0.17 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