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_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)
=== ===== === ==== ==== === === === ====
Thu 07/09 06Z 0.58 2715  83  14  16 0.00
Thu 07/09 07Z 0.58 2716  84   8  16 0.00
Thu 07/09 08Z 0.50 2815  80  12  16 0.00
Thu 07/09 09Z 0.43 2814  77  23  16 0.00
Thu 07/09 10Z 0.44 2913  78  25  15 0.00
Thu 07/09 11Z 0.36 2910  82  34  15 0.00
Thu 07/09 12Z 0.31 2908  88  53  14 0.00
Thu 07/09 13Z 0.27 2707  91  52  14 0.01
Thu 07/09 14Z 0.27 2506  92  51  15 0.00
Thu 07/09 15Z 0.29 2406  90  34  15 0.00
Thu 07/09 16Z 0.43 2407  87  22  15 0.00
Thu 07/09 17Z 0.66 2407  83  37  16 0.00
Thu 07/09 18Z 1.41 2308  83  45  16 0.00
Thu 07/09 19Z 1.57 2308  81  56  16 0.00
Thu 07/09 20Z 1.95 2311  82  68  16 0.01
Thu 07/09 21Z 1.81 2312  81  68  16 0.00
Thu 07/09 22Z 0.91 2314  86  73  16 0.01
Thu 07/09 23Z 0.80 2417  90  72  16 0.05
Fri 07/10 00Z 0.68 2616  93  72  16 0.05
Fri 07/10 01Z 0.52 2614  92  68  16 0.07
Fri 07/10 02Z 0.44 2512  94  61  16 0.01
Fri 07/10 03Z 0.43 2512  96  67  16 0.01
Fri 07/10 04Z 0.44 2513  96  75  15 0.01
Fri 07/10 05Z 0.48 2514  97  70  15 0.01
Fri 07/10 06Z 0.48 2715  97  67  15 0.04
Fri 07/10 07Z 0.39 2916  98  64  14 0.03
Fri 07/10 08Z 0.25 3116  97  65  14 0.02
Fri 07/10 09Z 0.18 3216  96  63  14 0.01
Fri 07/10 10Z 0.17 3216  91  69  14 0.01
Fri 07/10 11Z 0.10 3316  86  69  13 0.00
Fri 07/10 12Z 0.06 3415  84  73  13 0.00
Fri 07/10 13Z 0.05 3415  84  70  13 0.00
Fri 07/10 14Z 0.04 3413  85  67  12 0.00
Fri 07/10 15Z 0.05 3511  87  69  12 0.00
Fri 07/10 16Z 0.09 3410  88  64  12 0.00
Fri 07/10 17Z 0.13 3411  86  52  12 0.00
Fri 07/10 18Z 0.16 3411  83  49  12 0.00
Fri 07/10 19Z 0.38 3410  79  33  13 0.00
Fri 07/10 20Z 0.53 3309  74  26  13 0.00
Fri 07/10 21Z 0.74 3309  72  21  13 0.00
Fri 07/10 22Z 0.28 3309  73  33  13 0.00
Fri 07/10 23Z 0.13 3310  74  30  13 0.00
Sat 07/11 00Z 0.17 3311  77  44  12 0.00
Sat 07/11 01Z 0.14 3312  81  33  12 0.00
Sat 07/11 02Z 0.11 3413  83  30  11 0.00
Sat 07/11 03Z 0.11 3415  82  37  11 0.00
Sat 07/11 04Z 0.04 3414  80  35  11 0.00
Sat 07/11 05Z 0.03 3413  77  34  10 0.00
Sat 07/11 06Z 0.08 3511  78  39  10 0.00
Sat 07/11 07Z 0.14 0009  79  25  10 0.00
Sat 07/11 08Z 0.20 0108  81  25  10 0.00
Sat 07/11 09Z 0.21 0208  82  27   9 0.00
Sat 07/11 10Z 0.22 0208  82  16   9 0.00
Sat 07/11 11Z 0.19 0207  82   8   9 0.00
Sat 07/11 12Z 0.16 0106  81  11   9 0.00
Sat 07/11 13Z 0.23 0006  82  14   9 0.00
Sat 07/11 14Z 0.25 3506  83  17   9 0.00
Sat 07/11 15Z 0.17 3507  83  19   9 0.00
Sat 07/11 16Z 0.19 3508  82  20   9 0.00
Sat 07/11 17Z 0.34 3509  79  25   9 0.00

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