NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260707_0600
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 07/07 06Z 0.26 1215  81  51  13 0.00
Tue 07/07 07Z 0.31 1217  82  58  13 0.00
Tue 07/07 08Z 0.32 1218  81  61  13 0.00
Tue 07/07 09Z 0.35 1220  74  59  12 0.01
Tue 07/07 10Z 0.42 1222  72  53  12 0.01
Tue 07/07 11Z 0.42 1222  76  59  12 0.00
Tue 07/07 12Z 0.42 1222  79  64  11 0.01
Tue 07/07 13Z 0.45 1223  80  68  11 0.02
Tue 07/07 14Z 0.46 1223  75  68  11 0.01
Tue 07/07 15Z 0.45 1223  70  67  11 0.01
Tue 07/07 16Z 0.48 1221  69  64  11 0.01
Tue 07/07 17Z 0.49 1117  69  62  11 0.00
Tue 07/07 18Z 0.52 1116  66  61  11 0.00
Tue 07/07 19Z 0.61 1115  64  59  12 0.00
Tue 07/07 20Z 0.60 1115  63  51  12 0.00
Tue 07/07 21Z 0.51 1114  62  43  12 0.00
Tue 07/07 22Z 0.48 1114  61  37  12 0.00
Tue 07/07 23Z 0.42 1114  60  30  13 0.00
Wed 07/08 00Z 0.34 1112  59  29  13 0.00
Wed 07/08 01Z 0.31 1011  58  31  13 0.00
Wed 07/08 02Z 0.27 1010  56  28  13 0.00
Wed 07/08 03Z 0.27 1009  53  18  13 0.00
Wed 07/08 04Z 0.24 1008  53  14  13 0.00
Wed 07/08 05Z 0.17 1005  51   8  12 0.00
Wed 07/08 06Z 0.13 0703  51   7  12 0.00
Wed 07/08 07Z 0.06 0202  51   6  12 0.00
Wed 07/08 08Z 0.08 0203  51   3  12 0.00
Wed 07/08 09Z 0.07 0004  52   3  12 0.00
Wed 07/08 10Z 0.04 3405  54   8  12 0.00
Wed 07/08 11Z 0.06 3505  53  11  13 0.00
Wed 07/08 12Z 0.06 0004  53  13  13 0.00
Wed 07/08 13Z 0.05 3503  55  16  12 0.00
Wed 07/08 14Z 0.06 3402  58  17  12 0.00
Wed 07/08 15Z 0.19 3002  61  14  13 0.00
Wed 07/08 16Z 0.65 2803  62  13  13 0.00
Wed 07/08 17Z 0.82 2704  59  12  13 0.00
Wed 07/08 18Z 0.97 2605  56  12  14 0.00
Wed 07/08 19Z 1.03 2606  55  12  14 0.00
Wed 07/08 20Z 0.74 2707  55   8  14 0.00
Wed 07/08 21Z 0.51 2607  56   7  15 0.00
Wed 07/08 22Z 0.53 2609  59   9  15 0.00
Wed 07/08 23Z 0.61 2610  66  21  14 0.00
Thu 07/09 00Z 0.65 2512  73  17  14 0.00
Thu 07/09 01Z 0.76 2515  76  16  14 0.00
Thu 07/09 02Z 0.85 2517  78  13  14 0.00
Thu 07/09 03Z 0.79 2518  80  13  14 0.00
Thu 07/09 04Z 0.82 2620  82  17  14 0.00
Thu 07/09 05Z 0.73 2620  80  18  15 0.00
Thu 07/09 06Z 0.71 2721  81  18  14 0.00
Thu 07/09 07Z 0.63 2821  79  22  14 0.00
Thu 07/09 08Z 0.57 2821  81  21  14 0.00
Thu 07/09 09Z 0.52 2920  84  22  14 0.00
Thu 07/09 10Z 0.45 2919  85  21  14 0.00
Thu 07/09 11Z 0.41 2917  86  30  14 0.00
Thu 07/09 12Z 0.35 2915  84  34  14 0.00
Thu 07/09 13Z 0.33 2913  85  46  14 0.00
Thu 07/09 14Z 0.34 2912  84  52  14 0.00
Thu 07/09 15Z 0.31 2909  81  55  14 0.00
Thu 07/09 16Z 0.42 2708  80  57  14 0.00
Thu 07/09 17Z 0.90 2608  80  63  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.08 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