NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260606_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)
=== ===== === ==== ==== === === === ====
Sat 06/06 00Z 0.06 3102  54  28  15 0.00
Sat 06/06 01Z 0.08 2801  53  24  15 0.00
Sat 06/06 02Z 0.09 2301  53  22  15 0.00
Sat 06/06 03Z 0.14 2103  54  23  15 0.00
Sat 06/06 04Z 0.25 2106  55  26  14 0.00
Sat 06/06 05Z 0.31 2207  56  36  14 0.00
Sat 06/06 06Z 0.34 2208  56  63  15 0.00
Sat 06/06 07Z 0.28 2008  54  73  15 0.00
Sat 06/06 08Z 0.35 2011  56  89  15 0.00
Sat 06/06 09Z 0.48 2114  66  94  14 0.01
Sat 06/06 10Z 0.45 2115  74  96  13 0.02
Sat 06/06 11Z 0.49 2118  75  91  13 0.01
Sat 06/06 12Z 0.47 2119  74  82  14 0.02
Sat 06/06 13Z 0.50 2217  74  58  14 0.00
Sat 06/06 14Z 0.62 2218  73  49  14 0.00
Sat 06/06 15Z 0.97 2219  76  61  14 0.00
Sat 06/06 16Z 0.75 2119  79  92  13 0.01
Sat 06/06 17Z 0.96 2122  77  98  14 0.00
Sat 06/06 18Z 1.69 2124  73  96  14 0.00
Sat 06/06 19Z 1.76 2126  82  90  14 0.01
Sat 06/06 20Z 5.38 2123  82  70  14 0.01
Sat 06/06 21Z 4.55 2123  81  71  14 0.01
Sat 06/06 22Z 2.45 2325  86  75  14 0.08
Sat 06/06 23Z 0.85 2425  82  50  15 0.07
Sun 06/07 00Z 0.86 2428  82  50  15 0.00
Sun 06/07 01Z 0.94 2430  89  66  14 0.00
Sun 06/07 02Z 0.96 2430  91  72  13 0.02
Sun 06/07 03Z 0.92 2530  95  68  12 0.01
Sun 06/07 04Z 0.95 2630  97  72  11 0.02
Sun 06/07 05Z 0.94 2629  98  84  10 0.03
Sun 06/07 06Z 0.94 2731  98  91  10 0.05
Sun 06/07 07Z 0.97 2832  97  93  10 0.09
Sun 06/07 08Z 0.96 2935  97  93  10 0.17
Sun 06/07 09Z 0.77 3032  97  82   9 0.08
Sun 06/07 10Z 0.73 3028  98  75  10 0.05
Sun 06/07 11Z 0.71 3028  97  61   9 0.03
Sun 06/07 12Z 0.70 3026  96  49   9 0.01
Sun 06/07 13Z 0.72 3024  96  55   8 0.01
Sun 06/07 14Z 0.78 3022  97  57   8 0.01
Sun 06/07 15Z 0.77 3021  97  60   8 0.01
Sun 06/07 16Z 0.82 2920  97  59   8 0.02
Sun 06/07 17Z 0.79 3020  98  62   8 0.02
Sun 06/07 18Z 0.71 3123  97  68   8 0.03
Sun 06/07 19Z 0.51 3225  98  74   7 0.04
Sun 06/07 20Z 0.34 3326  98  78   7 0.02
Sun 06/07 21Z 0.17 3327  97  87   6 0.01
Sun 06/07 22Z 0.07 3426  96  94   5 0.01
Sun 06/07 23Z 0.19 0023  97  94   4 0.01
Mon 06/08 00Z 0.46 0128  93  65   3 0.01
Mon 06/08 01Z 0.57 0232  82  23   4 0.00
Mon 06/08 02Z 0.46 0132  80   5   5 0.00
Mon 06/08 03Z 0.40 0130  81   3   5 0.00
Mon 06/08 04Z 0.39 0130  82   3   5 0.00
Mon 06/08 05Z 0.32 0031  84   2   5 0.00
Mon 06/08 06Z 0.40 0031  87   1   5 0.00
Mon 06/08 07Z 0.61 0132  82   2   4 0.00
Mon 06/08 08Z 0.62 0133  75   2   4 0.00
Mon 06/08 09Z 0.57 0133  72   2   4 0.00
Mon 06/08 10Z 0.55 0135  70   2   4 0.00
Mon 06/08 11Z 0.51 0235  64   3   5 0.00

Run total areal avg QPF for the Central_Greens is: 1.01 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