NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261101_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)
=== ===== === ==== ==== === === === ====
Sun 11/01 18Z 0.46 3017  68  17   2 0.00
Sun 11/01 19Z 0.46 3019  69  20   3 0.00
Sun 11/01 20Z 0.47 2918  67  21   3 0.00
Sun 11/01 21Z 0.59 2820  66  20   3 0.00
Sun 11/01 22Z 0.70 2823  67  17   4 0.00
Sun 11/01 23Z 0.74 2825  64  17   4 0.00
Mon 11/02 00Z 0.74 2826  59  17   5 0.00
Mon 11/02 01Z 0.75 2927  53  17   5 0.00
Mon 11/02 02Z 0.82 2827  46  16   5 0.00
Mon 11/02 03Z 0.84 2827  48  17   5 0.00
Mon 11/02 04Z 0.81 2827  49  34   6 0.00
Mon 11/02 05Z 0.83 2827  47  60   6 0.00
Mon 11/02 06Z 0.85 2727  50  67   6 0.00
Mon 11/02 07Z 0.92 2728  49  77   6 0.00
Mon 11/02 08Z 0.98 2728  49  84   6 0.00
Mon 11/02 09Z 0.95 2728  50  87   6 0.00
Mon 11/02 10Z 0.88 2727  50  87   7 0.00
Mon 11/02 11Z 0.83 2826  50  85   7 0.00
Mon 11/02 12Z 0.75 2825  50  82   8 0.00
Mon 11/02 13Z 0.70 2824  49  77   8 0.00
Mon 11/02 14Z 0.66 2823  48  75   8 0.00
Mon 11/02 15Z 0.64 2823  46  76   8 0.00
Mon 11/02 16Z 0.64 2823  45  79   8 0.00
Mon 11/02 17Z 0.66 2723  44  76   9 0.00
Mon 11/02 18Z 0.67 2722  43  76   9 0.00
Mon 11/02 19Z 0.66 2722  41  72   9 0.00
Mon 11/02 20Z 0.63 2721  38  68   9 0.00
Mon 11/02 21Z 0.63 2721  39  69   9 0.00
Mon 11/02 22Z 0.62 2620  42  67   9 0.00
Mon 11/02 23Z 0.58 2719  48  69   9 0.00
Tue 11/03 00Z 0.57 2720  53  76   9 0.00
Tue 11/03 01Z 0.56 2719  54  80   9 0.00
Tue 11/03 02Z 0.57 2720  56  83   9 0.00
Tue 11/03 03Z 0.50 2818  54  84   9 0.00
Tue 11/03 04Z 0.45 2817  56  84   9 0.00
Tue 11/03 05Z 0.43 2816  57  91   9 0.00
Tue 11/03 06Z 0.42 2815  56  88   9 0.00
Tue 11/03 07Z 0.39 2714  53  88   9 0.00
Tue 11/03 08Z 0.36 2813  52  89   9 0.00
Tue 11/03 09Z 0.32 2811  51  85  10 0.00
Tue 11/03 10Z 0.29 2811  52  79  10 0.00
Tue 11/03 11Z 0.26 2709  52  80  10 0.00
Tue 11/03 12Z 0.21 2707  50  79  10 0.00
Tue 11/03 13Z 0.20 2507  52  81   9 0.00
Tue 11/03 14Z 0.22 2407  53  82   9 0.00
Tue 11/03 15Z 0.27 2309  56  90   9 0.00
Tue 11/03 16Z 0.28 2309  61  87   9 0.00
Tue 11/03 17Z 0.31 2310  65  85   9 0.00
Tue 11/03 18Z 0.34 2311  64  97   9 0.00
Tue 11/03 19Z 0.39 2213  60  97   9 0.00
Tue 11/03 20Z 0.44 2214  61  95   8 0.00
Tue 11/03 21Z 0.45 2215  67  95   8 0.00
Tue 11/03 22Z 0.40 2216  75  97   8 0.00
Tue 11/03 23Z 0.39 2216  88  99   8 0.01
Wed 11/04 00Z 0.42 2317  92  99   9 0.04
Wed 11/04 01Z 0.40 2417  92  99  10 0.04
Wed 11/04 02Z 0.38 2516  94  95  10 0.02
Wed 11/04 03Z 0.39 2515  92  93  10 0.00
Wed 11/04 04Z 0.38 2515  91  87  10 0.00
Wed 11/04 05Z 0.39 2515  91  77  10 0.00

Run total areal avg QPF for the Central_Greens is: 0.11 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