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_1200
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 12Z 0.20 2706  91  93  15 0.00
Sat 08/08 13Z 0.22 2706  89  90  15 0.00
Sat 08/08 14Z 0.25 2607  90  90  15 0.00
Sat 08/08 15Z 0.22 2506  90  85  15 0.00
Sat 08/08 16Z 0.22 2306  91  79  15 0.00
Sat 08/08 17Z 0.24 2207  90  73  15 0.00
Sat 08/08 18Z 0.48 2211  90  72  15 0.00
Sat 08/08 19Z 0.58 2312  87  61  16 0.00
Sat 08/08 20Z 0.63 2412  86  53  16 0.00
Sat 08/08 21Z 0.60 2412  89  42  16 0.00
Sat 08/08 22Z 0.52 2413  92  47  16 0.01
Sat 08/08 23Z 0.48 2513  89  60  16 0.18
Sun 08/09 00Z 0.47 2513  90  72  16 0.12
Sun 08/09 01Z 0.38 2610  88  65  16 0.04
Sun 08/09 02Z 0.43 2512  89  66  16 0.00
Sun 08/09 03Z 0.42 2513  85  53  16 0.01
Sun 08/09 04Z 0.46 2515  81  44  16 0.00
Sun 08/09 05Z 0.55 2517  86  31  16 0.00
Sun 08/09 06Z 0.58 2620  85  27  16 0.01
Sun 08/09 07Z 0.53 2620  81  27  16 0.00
Sun 08/09 08Z 0.53 2719  81  31  16 0.00
Sun 08/09 09Z 0.58 2620  83  19  16 0.00
Sun 08/09 10Z 0.59 2620  91  51  16 0.00
Sun 08/09 11Z 0.59 2620  89  46  15 0.01
Sun 08/09 12Z 0.61 2720  91  44  15 0.01
Sun 08/09 13Z 0.54 2819  91  34  15 0.01
Sun 08/09 14Z 0.48 2817  88  22  15 0.00
Sun 08/09 15Z 0.45 2815  86  15  15 0.00
Sun 08/09 16Z 0.49 2714  81   8  15 0.00
Sun 08/09 17Z 0.53 2715  75  12  15 0.01
Sun 08/09 18Z 0.59 2715  80  24  15 0.01
Sun 08/09 19Z 0.61 2816  84  36  15 0.01
Sun 08/09 20Z 0.63 2917  81  37  15 0.01
Sun 08/09 21Z 0.64 2917  75  26  14 0.00
Sun 08/09 22Z 0.55 3017  72  26  14 0.00
Sun 08/09 23Z 0.49 3018  69  32  14 0.00
Mon 08/10 00Z 0.46 3019  64  33  14 0.00
Mon 08/10 01Z 0.41 3019  57  33  15 0.00
Mon 08/10 02Z 0.30 3118  49  38  16 0.00
Mon 08/10 03Z 0.20 3116  44  44  17 0.00
Mon 08/10 04Z 0.14 3214  42  44  18 0.00
Mon 08/10 05Z 0.11 3212  41  42  17 0.00
Mon 08/10 06Z 0.11 3210  43  42  17 0.00
Mon 08/10 07Z 0.11 3209  44  47  17 0.00
Mon 08/10 08Z 0.08 3207  42  46  17 0.00
Mon 08/10 09Z 0.08 3004  42  43  16 0.00
Mon 08/10 10Z 0.07 2702  42  43  16 0.00
Mon 08/10 11Z 0.06 2102  42  49  16 0.00
Mon 08/10 12Z 0.07 2005  42  52  16 0.00
Mon 08/10 13Z 0.11 1907  43  60  16 0.00
Mon 08/10 14Z 0.15 1910  46  53  15 0.00
Mon 08/10 15Z 0.20 2010  47  38  15 0.00
Mon 08/10 16Z 0.30 2011  47  24  15 0.00
Mon 08/10 17Z 0.43 2012  46  17  15 0.00
Mon 08/10 18Z 0.59 2012  45  35  15 0.00
Mon 08/10 19Z 0.77 2115  52  76  15 0.00
Mon 08/10 20Z 0.64 2116  56  92  15 0.00
Mon 08/10 21Z 0.60 2115  64  75  15 0.01
Mon 08/10 22Z 0.68 2117  72  71  15 0.00
Mon 08/10 23Z 0.71 2118  77  69  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.45 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