NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260819_1800
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)
=== ===== === ==== ==== === === === ====
Wed 08/19 18Z 4.65 2509  83  62  12 0.00
Wed 08/19 19Z 2.95 2511  82  73  12 0.00
Wed 08/19 20Z 1.37 2413  84  85  13 0.00
Wed 08/19 21Z 1.35 2414  87  86  13 0.00
Wed 08/19 22Z 1.10 2514  83  83  13 0.00
Wed 08/19 23Z 1.20 2515  82  84  13 0.00
Thu 08/20 00Z 1.21 2517  84  77  13 0.00
Thu 08/20 01Z 1.13 2518  86  72  12 0.00
Thu 08/20 02Z 0.88 2617  88  62  12 0.00
Thu 08/20 03Z 0.62 2716  89  54  12 0.00
Thu 08/20 04Z 0.45 2814  84  44  13 0.00
Thu 08/20 05Z 0.40 2814  82  52  13 0.00
Thu 08/20 06Z 0.35 2914  79  53  13 0.00
Thu 08/20 07Z 0.25 3012  72  49  13 0.00
Thu 08/20 08Z 0.20 3010  70  51  13 0.00
Thu 08/20 09Z 0.18 3009  68  48  13 0.00
Thu 08/20 10Z 0.19 3010  68  50  13 0.00
Thu 08/20 11Z 0.17 3008  64  64  12 0.00
Thu 08/20 12Z 0.16 3108  65  68  12 0.00
Thu 08/20 13Z 0.15 3107  66  54  11 0.00
Thu 08/20 14Z 0.14 3106  67  24  11 0.00
Thu 08/20 15Z 0.20 3005  70  24  11 0.00
Thu 08/20 16Z 0.28 3002  73  18  10 0.00
Thu 08/20 17Z 0.50 3003  72  14  11 0.00
Thu 08/20 18Z 0.80 2904  69  14  11 0.00
Thu 08/20 19Z 0.27 2703  67  14  11 0.00
Thu 08/20 20Z 0.18 2803  66  18  11 0.00
Thu 08/20 21Z 0.16 2803  66  18  11 0.00
Thu 08/20 22Z 0.13 2903  67  15  11 0.00
Thu 08/20 23Z 0.13 3104  68  14  11 0.00
Fri 08/21 00Z 0.10 3204  68  13  10 0.00
Fri 08/21 01Z 0.09 3305  70  10  10 0.00
Fri 08/21 02Z 0.06 3506  73  12  10 0.00
Fri 08/21 03Z 0.05 0006  75  18  10 0.00
Fri 08/21 04Z 0.11 0007  77  19   9 0.00
Fri 08/21 05Z 0.18 0108  75  23   9 0.00
Fri 08/21 06Z 0.18 0208  73  22   9 0.00
Fri 08/21 07Z 0.21 0209  71  22   9 0.00
Fri 08/21 08Z 0.21 0208  71  23   9 0.00
Fri 08/21 09Z 0.26 0308  72  22   9 0.00
Fri 08/21 10Z 0.27 0408  72  19   9 0.00
Fri 08/21 11Z 0.27 0408  72  14   9 0.00
Fri 08/21 12Z 0.27 0408  72  12   9 0.00
Fri 08/21 13Z 0.28 0508  74  12   9 0.00
Fri 08/21 14Z 0.32 0607  78  12   8 0.00
Fri 08/21 15Z 0.49 0606  80   8   8 0.00
Fri 08/21 16Z 1.45 0704  81   7   8 0.00
Fri 08/21 17Z 1.09 0602  81   6   9 0.00
Fri 08/21 18Z 0.81 0601  81   6   9 0.00
Fri 08/21 19Z 0.40 0600  83   7  10 0.00
Fri 08/21 20Z 0.60 0702  84   7  10 0.00
Fri 08/21 21Z 0.64 0702  82   6  10 0.00
Fri 08/21 22Z 0.59 0703  82   6  10 0.00
Fri 08/21 23Z 0.47 0904  82   6  10 0.00
Sat 08/22 00Z 0.47 0905  83   6  10 0.00
Sat 08/22 01Z 0.49 1106  84   6   9 0.00
Sat 08/22 02Z 0.46 1207  86   6   9 0.00
Sat 08/22 03Z 0.36 1308  88   6   9 0.00
Sat 08/22 04Z 0.29 1408  86   6   9 0.00
Sat 08/22 05Z 0.26 1308  84   5   9 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