NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260607_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 06/07 18Z 0.18 3321  98  94  10 0.00
Sun 06/07 19Z 0.12 3422  97  92  10 0.02
Sun 06/07 20Z 0.11 3521  97  85   9 0.02
Sun 06/07 21Z 0.15 3522  97  86   9 0.01
Sun 06/07 22Z 0.22 0023  97  82   9 0.01
Sun 06/07 23Z 0.29 0125  90  70   9 0.00
Mon 06/08 00Z 0.37 0226  80  42   9 0.00
Mon 06/08 01Z 0.46 0326  79  17   9 0.00
Mon 06/08 02Z 0.55 0425  72   4   9 0.00
Mon 06/08 03Z 0.62 0524  66   1   8 0.00
Mon 06/08 04Z 0.65 0622  63   1   8 0.00
Mon 06/08 05Z 0.65 0621  57   2   8 0.00
Mon 06/08 06Z 0.67 0720  52   2   8 0.00
Mon 06/08 07Z 0.70 0720  42   3   7 0.00
Mon 06/08 08Z 0.79 0720  37   3   7 0.00
Mon 06/08 09Z 0.68 0717  40   4   7 0.00
Mon 06/08 10Z 0.55 0713  44   6   7 0.00
Mon 06/08 11Z 0.49 0611  47   9   7 0.00
Mon 06/08 12Z 0.42 0609  49  12   7 0.00
Mon 06/08 13Z 0.32 0407  52  12   7 0.00
Mon 06/08 14Z 0.47 0306  56  12   7 0.00
Mon 06/08 15Z 0.59 0403  59  13   7 0.00
Mon 06/08 16Z 0.32 0102  61  13   8 0.00
Mon 06/08 17Z 0.35 3001  64  13   8 0.00
Mon 06/08 18Z 0.57 2902  66  12   9 0.00
Mon 06/08 19Z 0.86 2703  68  11   9 0.00
Mon 06/08 20Z 0.75 2803  67  10  10 0.00
Mon 06/08 21Z 0.80 2705  62   9  10 0.00
Mon 06/08 22Z 0.51 2706  56   8  10 0.00
Mon 06/08 23Z 0.34 2707  53   7  11 0.00
Tue 06/09 00Z 0.38 2709  49   5  11 0.00
Tue 06/09 01Z 0.39 2710  50   5  11 0.00
Tue 06/09 02Z 0.39 2710  49   4  11 0.00
Tue 06/09 03Z 0.38 2709  51   3  11 0.00
Tue 06/09 04Z 0.55 2614  52   3  11 0.00
Tue 06/09 05Z 0.50 2613  55   3  11 0.00
Tue 06/09 06Z 0.61 2615  60   4  11 0.00
Tue 06/09 07Z 0.54 2715  66   3  11 0.00
Tue 06/09 08Z 0.46 2715  71   3  11 0.00
Tue 06/09 09Z 0.34 2713  71   2  12 0.00
Tue 06/09 10Z 0.33 2713  69   2  12 0.00
Tue 06/09 11Z 0.29 2612  66   1  12 0.00
Tue 06/09 12Z 0.24 2609  69   1  11 0.00
Tue 06/09 13Z 0.20 2607  71   1  11 0.00
Tue 06/09 14Z 0.21 2507  70   1  11 0.00
Tue 06/09 15Z 0.25 2606  70   1  11 0.00
Tue 06/09 16Z 0.52 2507  71   2  11 0.00
Tue 06/09 17Z 0.69 2608  68   2  12 0.00
Tue 06/09 18Z 0.56 2607  62   2  12 0.00
Tue 06/09 19Z 0.55 2607  59   1  13 0.00
Tue 06/09 20Z 0.48 2607  61   2  14 0.00
Tue 06/09 21Z 0.41 2608  65   2  14 0.00
Tue 06/09 22Z 0.40 2509  71   2  14 0.00
Tue 06/09 23Z 0.37 2510  75   1  14 0.00
Wed 06/10 00Z 0.40 2612  74   1  15 0.00
Wed 06/10 01Z 0.41 2613  75   1  15 0.00
Wed 06/10 02Z 0.37 2612  73   2  15 0.00
Wed 06/10 03Z 0.31 2611  69   3  15 0.00
Wed 06/10 04Z 0.22 2507  67   3  15 0.00
Wed 06/10 05Z 0.19 2506  69   2  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.06 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