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_1200
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 12Z 0.23 1209  88   5   3 0.00
Tue 09/22 13Z 0.26 1110  85   5   3 0.00
Tue 09/22 14Z 0.26 1110  84   5   3 0.00
Tue 09/22 15Z 0.28 1109  84   4   2 0.00
Tue 09/22 16Z 0.33 1109  85   5   2 0.00
Tue 09/22 17Z 0.43 0906  86   5   2 0.00
Tue 09/22 18Z 1.32 0805  87   5   2 0.00
Tue 09/22 19Z 1.82 0705  87   5   3 0.00
Tue 09/22 20Z 1.79 0706  87   5   3 0.00
Tue 09/22 21Z 1.39 0707  87   6   3 0.00
Tue 09/22 22Z 0.90 0608  87   7   3 0.00
Tue 09/22 23Z 0.60 0609  86   8   3 0.00
Wed 09/23 00Z 0.55 0611  86  10   3 0.00
Wed 09/23 01Z 0.53 0612  84  11   3 0.00
Wed 09/23 02Z 0.53 0713  82  11   3 0.00
Wed 09/23 03Z 0.53 0714  78  12   3 0.00
Wed 09/23 04Z 0.62 0815  74  11   3 0.00
Wed 09/23 05Z 0.70 0917  73  10   3 0.00
Wed 09/23 06Z 0.69 0918  69  10   3 0.00
Wed 09/23 07Z 0.63 0919  62   9   3 0.00
Wed 09/23 08Z 0.56 0819  58   7   4 0.00
Wed 09/23 09Z 0.52 0818  54   6   4 0.00
Wed 09/23 10Z 0.49 0818  50   7   4 0.00
Wed 09/23 11Z 0.49 0818  49  12   4 0.00
Wed 09/23 12Z 0.48 0818  50  19   4 0.00
Wed 09/23 13Z 0.46 0818  50  25   4 0.00
Wed 09/23 14Z 0.45 0817  51  25   4 0.00
Wed 09/23 15Z 0.44 0816  51  21   4 0.00
Wed 09/23 16Z 0.45 0714  55  13   4 0.00
Wed 09/23 17Z 0.49 0812  59   7   3 0.00
Wed 09/23 18Z 0.67 0810  61   5   3 0.00
Wed 09/23 19Z 0.73 0809  63   5   4 0.00
Wed 09/23 20Z 0.68 0709  63   5   4 0.00
Wed 09/23 21Z 0.53 0709  62   6   4 0.00
Wed 09/23 22Z 0.47 0610  61   6   4 0.00
Wed 09/23 23Z 0.48 0611  61   5   4 0.00
Thu 09/24 00Z 0.46 0611  60   4   4 0.00
Thu 09/24 01Z 0.45 0613  58   4   5 0.00
Thu 09/24 02Z 0.43 0614  54   4   5 0.00
Thu 09/24 03Z 0.40 0714  48   3   6 0.00
Thu 09/24 04Z 0.39 0714  44   3   6 0.00
Thu 09/24 05Z 0.37 0714  41   2   6 0.00
Thu 09/24 06Z 0.34 0714  35   2   6 0.00
Thu 09/24 07Z 0.33 0714  32   1   7 0.00
Thu 09/24 08Z 0.32 0714  32   2   7 0.00
Thu 09/24 09Z 0.29 0713  34   2   7 0.00
Thu 09/24 10Z 0.27 0712  33   2   7 0.00
Thu 09/24 11Z 0.25 0612  30   2   7 0.00
Thu 09/24 12Z 0.27 0613  28   3   8 0.00
Thu 09/24 13Z 0.27 0613  27   3   8 0.00
Thu 09/24 14Z 0.25 0612  29   3   8 0.00
Thu 09/24 15Z 0.23 0610  32   4   7 0.00
Thu 09/24 16Z 0.25 0610  33   4   7 0.00
Thu 09/24 17Z 0.26 0609  33   4   7 0.00
Thu 09/24 18Z 0.28 0709  32   4   7 0.00
Thu 09/24 19Z 0.27 0608  33   4   8 0.00
Thu 09/24 20Z 0.29 0608  36   4   8 0.00
Thu 09/24 21Z 0.29 0608  39   4   8 0.00
Thu 09/24 22Z 0.29 0609  40   4   8 0.00
Thu 09/24 23Z 0.29 0510  39   4   8 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