NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260922_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)
=== ===== === ==== ==== === === === ====
Tue 09/22 00Z 0.32 0313  89   1   3 0.00
Tue 09/22 01Z 0.29 0414  81   2   4 0.00
Tue 09/22 02Z 0.30 0514  74   2   4 0.00
Tue 09/22 03Z 0.31 0713  78   2   4 0.00
Tue 09/22 04Z 0.30 0812  85   2   4 0.00
Tue 09/22 05Z 0.31 1011  84   2   3 0.00
Tue 09/22 06Z 0.28 1010  87   2   3 0.00
Tue 09/22 07Z 0.29 1111  87   1   2 0.00
Tue 09/22 08Z 0.28 1110  84   2   2 0.00
Tue 09/22 09Z 0.26 1109  82   2   2 0.00
Tue 09/22 10Z 0.27 1109  82   3   2 0.00
Tue 09/22 11Z 0.28 1008  81   2   2 0.00
Tue 09/22 12Z 0.28 0908  80   3   1 0.00
Tue 09/22 13Z 0.28 0908  80   3   1 0.00
Tue 09/22 14Z 0.29 0807  81   3   1 0.00
Tue 09/22 15Z 0.34 0707  83   3   1 0.00
Tue 09/22 16Z 0.53 0507  84   3   1 0.00
Tue 09/22 17Z 1.02 0406  84   4   1 0.00
Tue 09/22 18Z 1.38 0406  82   4   2 0.00
Tue 09/22 19Z 1.47 0507  79   4   2 0.00
Tue 09/22 20Z 1.26 0507  78   4   2 0.00
Tue 09/22 21Z 0.96 0507  80   4   2 0.00
Tue 09/22 22Z 0.73 0509  81   5   3 0.00
Tue 09/22 23Z 0.67 0511  81   7   2 0.00
Wed 09/23 00Z 0.71 0612  80   7   2 0.00
Wed 09/23 01Z 0.76 0713  80   9   2 0.00
Wed 09/23 02Z 0.74 0813  75  11   2 0.00
Wed 09/23 03Z 0.65 0814  69  12   3 0.00
Wed 09/23 04Z 0.60 0915  69  12   3 0.00
Wed 09/23 05Z 0.56 0816  67  14   3 0.00
Wed 09/23 06Z 0.60 0917  63  15   3 0.00
Wed 09/23 07Z 0.60 0918  57  17   3 0.00
Wed 09/23 08Z 0.54 0818  56  17   3 0.00
Wed 09/23 09Z 0.51 0818  54  16   4 0.00
Wed 09/23 10Z 0.49 0818  51  12   4 0.00
Wed 09/23 11Z 0.50 0819  50  10   4 0.00
Wed 09/23 12Z 0.51 0819  51   8   4 0.00
Wed 09/23 13Z 0.52 0820  52  10   4 0.00
Wed 09/23 14Z 0.50 0819  51  10   4 0.00
Wed 09/23 15Z 0.48 0817  51  11   4 0.00
Wed 09/23 16Z 0.50 0815  54  11   4 0.00
Wed 09/23 17Z 0.52 0814  55  10   4 0.00
Wed 09/23 18Z 0.63 0812  55   6   4 0.00
Wed 09/23 19Z 0.78 0812  56   4   4 0.00
Wed 09/23 20Z 0.72 0810  56   3   4 0.00
Wed 09/23 21Z 0.58 0810  56   3   4 0.00
Wed 09/23 22Z 0.48 0811  55   3   4 0.00
Wed 09/23 23Z 0.47 0712  54   3   4 0.00
Thu 09/24 00Z 0.46 0713  55   2   5 0.00
Thu 09/24 01Z 0.43 0713  54   2   5 0.00
Thu 09/24 02Z 0.40 0814  53   1   5 0.00
Thu 09/24 03Z 0.39 0714  47   1   6 0.00
Thu 09/24 04Z 0.38 0815  41   1   6 0.00
Thu 09/24 05Z 0.35 0814  36   1   6 0.00
Thu 09/24 06Z 0.33 0814  32   1   7 0.00
Thu 09/24 07Z 0.31 0813  29   1   7 0.00
Thu 09/24 08Z 0.30 0813  27   1   7 0.00
Thu 09/24 09Z 0.28 0713  24   1   7 0.00
Thu 09/24 10Z 0.28 0713  21   1   7 0.00
Thu 09/24 11Z 0.29 0713  22   1   7 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