NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260808_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 08/08 00Z 0.12 1703  80  75  17 0.00
Sat 08/08 01Z 0.20 2105  83  81  16 0.07
Sat 08/08 02Z 0.24 2207  82  81  16 0.02
Sat 08/08 03Z 0.22 2207  77  87  17 0.00
Sat 08/08 04Z 0.19 2207  75  84  17 0.00
Sat 08/08 05Z 0.18 2107  76  84  17 0.00
Sat 08/08 06Z 0.20 2108  74  79  16 0.00
Sat 08/08 07Z 0.25 2109  77  87  16 0.00
Sat 08/08 08Z 0.30 2209  83  93  16 0.00
Sat 08/08 09Z 0.26 2209  87  84  16 0.00
Sat 08/08 10Z 0.25 2308  90  78  16 0.00
Sat 08/08 11Z 0.27 2309  91  81  16 0.00
Sat 08/08 12Z 0.23 2308  89  84  16 0.00
Sat 08/08 13Z 0.24 2308  90  90  16 0.00
Sat 08/08 14Z 0.25 2308  89  92  16 0.00
Sat 08/08 15Z 0.24 2308  88  89  16 0.00
Sat 08/08 16Z 0.22 2207  88  78  16 0.00
Sat 08/08 17Z 0.28 2208  89  64  16 0.00
Sat 08/08 18Z 0.46 2309  92  64  15 0.00
Sat 08/08 19Z 0.53 2410  92  57  15 0.00
Sat 08/08 20Z 0.50 2410  91  48  16 0.00
Sat 08/08 21Z 0.59 2513  92  52  16 0.00
Sat 08/08 22Z 0.59 2516  91  50  16 0.06
Sat 08/08 23Z 0.44 2613  90  39  17 0.03
Sun 08/09 00Z 0.44 2613  88  45  16 0.01
Sun 08/09 01Z 0.45 2713  88  60  16 0.01
Sun 08/09 02Z 0.42 2713  87  64  16 0.01
Sun 08/09 03Z 0.43 2714  88  67  16 0.01
Sun 08/09 04Z 0.41 2814  87  55  16 0.01
Sun 08/09 05Z 0.41 2815  83  45  16 0.00
Sun 08/09 06Z 0.42 2815  81  52  16 0.00
Sun 08/09 07Z 0.42 2815  82  60  16 0.00
Sun 08/09 08Z 0.39 2814  85  65  16 0.00
Sun 08/09 09Z 0.40 2713  88  68  16 0.00
Sun 08/09 10Z 0.48 2616  92  71  15 0.00
Sun 08/09 11Z 0.55 2617  95  71  15 0.01
Sun 08/09 12Z 0.59 2518  96  34  15 0.02
Sun 08/09 13Z 0.55 2617  94  30  15 0.02
Sun 08/09 14Z 0.53 2717  92  33  15 0.01
Sun 08/09 15Z 0.55 2716  92  28  14 0.01
Sun 08/09 16Z 0.51 2814  88  18  15 0.01
Sun 08/09 17Z 0.49 2814  82  17  15 0.01
Sun 08/09 18Z 0.54 2814  80  10  15 0.01
Sun 08/09 19Z 0.81 2914  79  10  15 0.00
Sun 08/09 20Z 1.92 2913  78  12  14 0.00
Sun 08/09 21Z 1.29 2914  73  18  14 0.00
Sun 08/09 22Z 0.94 2914  68  23  14 0.00
Sun 08/09 23Z 0.67 2915  65  26  14 0.00
Mon 08/10 00Z 0.79 2917  64  31  14 0.00
Mon 08/10 01Z 0.56 3017  61  32  14 0.00
Mon 08/10 02Z 0.41 3016  58  32  15 0.00
Mon 08/10 03Z 0.29 3115  54  28  15 0.00
Mon 08/10 04Z 0.21 3114  51  32  16 0.00
Mon 08/10 05Z 0.19 3215  50  36  16 0.00
Mon 08/10 06Z 0.10 3313  50  35  15 0.00
Mon 08/10 07Z 0.07 3412  53  43  15 0.00
Mon 08/10 08Z 0.05 3411  57  41  14 0.00
Mon 08/10 09Z 0.07 3409  59  46  14 0.00
Mon 08/10 10Z 0.09 3308  62  45  14 0.00
Mon 08/10 11Z 0.11 3206  63  36  14 0.00

Run total areal avg QPF for the Central_Greens is: 0.33 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