NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260811_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 08/11 00Z 0.71 2216  81  72  15 0.00
Tue 08/11 01Z 0.69 2218  82  69  15 0.00
Tue 08/11 02Z 0.75 2321  80  67  15 0.00
Tue 08/11 03Z 0.93 2526  90  73  15 0.00
Tue 08/11 04Z 1.00 2628  93  80  15 0.01
Tue 08/11 05Z 0.88 2826  93  67  14 0.04
Tue 08/11 06Z 0.73 2825  87  51  15 0.01
Tue 08/11 07Z 0.60 2923  88  40  14 0.00
Tue 08/11 08Z 0.67 2824  92  42  14 0.01
Tue 08/11 09Z 0.72 2925  93  44  13 0.01
Tue 08/11 10Z 0.64 2925  91  40  12 0.01
Tue 08/11 11Z 0.60 3025  87  34  12 0.00
Tue 08/11 12Z 0.51 3024  82  27  12 0.00
Tue 08/11 13Z 0.48 3124  79  25  12 0.00
Tue 08/11 14Z 0.51 3122  82  23  11 0.00
Tue 08/11 15Z 0.62 3119  84  21  11 0.00
Tue 08/11 16Z 2.69 3017  86  20  11 0.00
Tue 08/11 17Z 6.40 3015  82  21  11 0.00
Tue 08/11 18Z 5.58 3116  76  21  11 0.00
Tue 08/11 19Z 5.30 3114  71  19  12 0.00
Tue 08/11 20Z 4.48 3114  69  18  12 0.00
Tue 08/11 21Z 3.35 3011  70  18  12 0.00
Tue 08/11 22Z 2.40 2911  73  25  12 0.00
Tue 08/11 23Z 0.82 2811  77  47  12 0.00
Wed 08/12 00Z 0.82 2912  77  45  12 0.00
Wed 08/12 01Z 0.59 2912  77  48  12 0.00
Wed 08/12 02Z 0.52 2912  76  39  12 0.00
Wed 08/12 03Z 0.51 2911  77  30  12 0.00
Wed 08/12 04Z 0.47 2911  77  27  12 0.00
Wed 08/12 05Z 0.42 2911  78  27  12 0.00
Wed 08/12 06Z 0.36 3011  78  23  12 0.00
Wed 08/12 07Z 0.34 3111  79  20  11 0.00
Wed 08/12 08Z 0.29 3111  79  23  11 0.00
Wed 08/12 09Z 0.24 3110  78  21  11 0.00
Wed 08/12 10Z 0.23 3109  77  21  11 0.00
Wed 08/12 11Z 0.18 3108  76  18  11 0.00
Wed 08/12 12Z 0.14 3207  77  18  11 0.00
Wed 08/12 13Z 0.18 3106  80  19  11 0.00
Wed 08/12 14Z 0.39 3104  81  21  11 0.00
Wed 08/12 15Z 0.73 3104  80  24  11 0.00
Wed 08/12 16Z 0.70 3204  78  27  11 0.00
Wed 08/12 17Z 0.62 3205  75  32  12 0.01
Wed 08/12 18Z 0.52 3306  71  39  12 0.00
Wed 08/12 19Z 0.66 3307  70  51  12 0.00
Wed 08/12 20Z 0.47 3307  69  59  12 0.00
Wed 08/12 21Z 0.50 3208  69  65  12 0.00
Wed 08/12 22Z 0.24 3307  70  74  12 0.00
Wed 08/12 23Z 0.18 3208  70  74  12 0.00
Thu 08/13 00Z 0.17 3208  70  75  12 0.00
Thu 08/13 01Z 0.17 3208  71  60  12 0.00
Thu 08/13 02Z 0.24 3209  73  53  12 0.00
Thu 08/13 03Z 0.27 3210  76  48  11 0.00
Thu 08/13 04Z 0.26 3209  79  51  11 0.00
Thu 08/13 05Z 0.30 3210  82  59  11 0.00
Thu 08/13 06Z 0.29 3211  84  66  11 0.00
Thu 08/13 07Z 0.29 3211  84  79  10 0.00
Thu 08/13 08Z 0.27 3211  84  81  10 0.00
Thu 08/13 09Z 0.14 3310  83  78  10 0.00
Thu 08/13 10Z 0.12 3310  81  84  10 0.00
Thu 08/13 11Z 0.10 3310  78  74  10 0.00

Run total areal avg QPF for the Central_Greens is: 0.10 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