NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260708_1800
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)
=== ===== === ==== ==== === === === ====
Wed 07/08 18Z 1.73 2804  74  14  14 0.00
Wed 07/08 19Z 2.12 2805  69   6  15 0.00
Wed 07/08 20Z 1.73 2704  67   9  15 0.00
Wed 07/08 21Z 1.26 2505  68  16  15 0.00
Wed 07/08 22Z 1.04 2507  73  21  15 0.00
Wed 07/08 23Z 0.71 2509  79  16  15 0.00
Thu 07/09 00Z 0.63 2511  81  26  15 0.00
Thu 07/09 01Z 0.63 2511  83  23  15 0.00
Thu 07/09 02Z 0.69 2512  83  22  15 0.00
Thu 07/09 03Z 0.73 2514  83  28  15 0.00
Thu 07/09 04Z 0.78 2515  86  16  14 0.00
Thu 07/09 05Z 0.74 2516  87   9  14 0.00
Thu 07/09 06Z 0.71 2516  88  20  14 0.00
Thu 07/09 07Z 0.74 2618  87  18  14 0.00
Thu 07/09 08Z 0.65 2619  85  14  15 0.00
Thu 07/09 09Z 0.54 2718  78  14  15 0.00
Thu 07/09 10Z 0.46 2817  71  28  16 0.00
Thu 07/09 11Z 0.35 2813  74  45  16 0.00
Thu 07/09 12Z 0.28 2910  75  45  16 0.00
Thu 07/09 13Z 0.25 2808  78  48  15 0.00
Thu 07/09 14Z 0.25 2706  81  41  15 0.00
Thu 07/09 15Z 0.30 2605  85  36  15 0.00
Thu 07/09 16Z 0.51 2506  85  38  15 0.00
Thu 07/09 17Z 0.55 2405  84  31  15 0.00
Thu 07/09 18Z 0.91 2406  82  28  16 0.00
Thu 07/09 19Z 1.16 2406  82  41  16 0.00
Thu 07/09 20Z 1.43 2408  85  56  16 0.00
Thu 07/09 21Z 0.79 2409  89  55  16 0.01
Thu 07/09 22Z 0.46 2409  90  62  16 0.00
Thu 07/09 23Z 0.49 2412  91  73  16 0.03
Fri 07/10 00Z 0.61 2515  94  87  16 0.08
Fri 07/10 01Z 0.63 2717  94  76  16 0.03
Fri 07/10 02Z 0.46 2915  91  71  15 0.03
Fri 07/10 03Z 0.40 2913  92  69  15 0.00
Fri 07/10 04Z 0.38 2812  92  71  15 0.00
Fri 07/10 05Z 0.39 2712  94  68  15 0.00
Fri 07/10 06Z 0.49 2714  95  67  15 0.00
Fri 07/10 07Z 0.51 2715  94  73  15 0.00
Fri 07/10 08Z 0.56 2717  94  76  15 0.00
Fri 07/10 09Z 0.50 2816  93  74  15 0.00
Fri 07/10 10Z 0.46 2816  92  73  15 0.00
Fri 07/10 11Z 0.40 2916  92  76  15 0.00
Fri 07/10 12Z 0.29 3012  91  72  15 0.00
Fri 07/10 13Z 0.20 3110  92  63  14 0.00
Fri 07/10 14Z 0.17 3109  93  63  14 0.00
Fri 07/10 15Z 0.15 3207  93  71  14 0.00
Fri 07/10 16Z 0.14 3206  91  74  14 0.00
Fri 07/10 17Z 0.24 3106  90  79  14 0.00
Fri 07/10 18Z 0.31 3106  89  79  14 0.00
Fri 07/10 19Z 0.25 3106  88  80  14 0.00
Fri 07/10 20Z 0.23 3206  88  76  14 0.00
Fri 07/10 21Z 0.12 3308  87  81  14 0.00
Fri 07/10 22Z 0.06 3409  87  80  14 0.01
Fri 07/10 23Z 0.08 3509  86  79  14 0.00
Sat 07/11 00Z 0.12 0009  84  68  14 0.01
Sat 07/11 01Z 0.19 0111  83  56  14 0.00
Sat 07/11 02Z 0.24 0112  81  50  14 0.00
Sat 07/11 03Z 0.31 0212  81  53  14 0.00
Sat 07/11 04Z 0.33 0312  81  51  13 0.00
Sat 07/11 05Z 0.29 0211  81  49  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.20 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