NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260604_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)
=== ===== === ==== ==== === === === ====
Thu 06/04 12Z 0.31 2709  50  44  13 0.00
Thu 06/04 13Z 0.35 2810  49  46  13 0.00
Thu 06/04 14Z 0.38 2810  50  46  13 0.00
Thu 06/04 15Z 0.44 2710  51  44  13 0.00
Thu 06/04 16Z 0.63 2812  49  40  13 0.00
Thu 06/04 17Z 1.25 2812  48  33  13 0.00
Thu 06/04 18Z 2.02 2711  50  26  13 0.00
Thu 06/04 19Z 3.59 2711  55  23  13 0.00
Thu 06/04 20Z 6.65 2713  59  21  13 0.00
Thu 06/04 21Z 4.95 2713  58  20  13 0.00
Thu 06/04 22Z 1.83 2713  56  19  14 0.00
Thu 06/04 23Z 1.10 2814  52  21  14 0.00
Fri 06/05 00Z 0.99 2814  46  23  13 0.00
Fri 06/05 01Z 0.98 2817  45  23  13 0.00
Fri 06/05 02Z 0.88 2919  44  24  13 0.00
Fri 06/05 03Z 0.76 2921  41  22  13 0.00
Fri 06/05 04Z 0.70 3022  41  19  13 0.00
Fri 06/05 05Z 0.64 3022  51  15  13 0.00
Fri 06/05 06Z 0.64 3022  64  12  12 0.00
Fri 06/05 07Z 0.57 3121  64  10  12 0.00
Fri 06/05 08Z 0.57 3121  58   9  12 0.00
Fri 06/05 09Z 0.65 3021  59   8  12 0.00
Fri 06/05 10Z 0.76 3020  64   9  11 0.00
Fri 06/05 11Z 0.76 2919  61  10  12 0.00
Fri 06/05 12Z 0.76 2819  60   9  12 0.00
Fri 06/05 13Z 0.67 2817  56   8  12 0.00
Fri 06/05 14Z 0.76 2816  54   7  12 0.00
Fri 06/05 15Z 1.68 2915  56   6  12 0.00
Fri 06/05 16Z 3.35 2913  56   6  12 0.00
Fri 06/05 17Z 6.73 2812  63   6  12 0.00
Fri 06/05 18Z 7.55 2611  70   5  13 0.00
Fri 06/05 19Z 7.15 2512  73   8  13 0.00
Fri 06/05 20Z 6.02 2512  72   9  13 0.00
Fri 06/05 21Z 5.17 2412  71  10  13 0.00
Fri 06/05 22Z 3.58 2514  65  17  14 0.00
Fri 06/05 23Z 1.38 2515  58  21  14 0.00
Sat 06/06 00Z 1.18 2516  54  24  14 0.00
Sat 06/06 01Z 1.64 2519  58  21  14 0.00
Sat 06/06 02Z 1.59 2518  66  17  14 0.00
Sat 06/06 03Z 1.67 2520  71  20  13 0.00
Sat 06/06 04Z 1.39 2521  75  21  13 0.00
Sat 06/06 05Z 1.37 2522  80  20  12 0.00
Sat 06/06 06Z 1.32 2522  79  23  12 0.00
Sat 06/06 07Z 1.37 2521  80  26  12 0.00
Sat 06/06 08Z 1.14 2421  82  26  12 0.00
Sat 06/06 09Z 1.05 2423  84  22  12 0.00
Sat 06/06 10Z 1.08 2425  86  11  12 0.00
Sat 06/06 11Z 1.02 2325  84  13  12 0.00
Sat 06/06 12Z 0.93 2424  86  27  12 0.01
Sat 06/06 13Z 0.98 2324  89  73  12 0.01
Sat 06/06 14Z 0.95 2323  86  95  13 0.01
Sat 06/06 15Z 1.22 2324  91  97  13 0.06
Sat 06/06 16Z 1.25 2325  97  98  13 0.13
Sat 06/06 17Z 1.06 2528  98  97  12 0.16
Sat 06/06 18Z 1.04 2526  98  79  12 0.07
Sat 06/06 19Z 1.02 2724  98  43  13 0.04
Sat 06/06 20Z 0.90 2822  96  30  13 0.02
Sat 06/06 21Z 0.94 2821  94  44  13 0.01
Sat 06/06 22Z 0.99 2821  93  52  13 0.00
Sat 06/06 23Z 0.90 2721  94  58  13 0.01

Run total areal avg QPF for the Central_Greens is: 0.53 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