NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260712_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)
=== ===== === ==== ==== === === === ====
Sun 07/12 00Z 0.22 0010  66  13  12 0.00
Sun 07/12 01Z 0.38 0211  68  15  11 0.00
Sun 07/12 02Z 0.46 0313  67  17  11 0.00
Sun 07/12 03Z 0.51 0413  66  20  11 0.00
Sun 07/12 04Z 0.48 0413  67  22  11 0.00
Sun 07/12 05Z 0.41 0412  63  21  11 0.00
Sun 07/12 06Z 0.39 0411  60  19  11 0.00
Sun 07/12 07Z 0.39 0410  58  17  11 0.00
Sun 07/12 08Z 0.43 0410  59  17  10 0.00
Sun 07/12 09Z 0.46 0409  61  18  10 0.00
Sun 07/12 10Z 0.52 0509  64  17  10 0.00
Sun 07/12 11Z 0.50 0508  65  16   9 0.00
Sun 07/12 13Z 0.71 0406  66  12   9 0.00
Sun 07/12 14Z 1.48 0404  68  10   9 0.00
Sun 07/12 15Z 0.96 0202  68  10  10 0.00
Sun 07/12 16Z 0.50 3502  69   9  10 0.00
Sun 07/12 17Z 0.29 3302  70   9  11 0.00
Sun 07/12 18Z 0.52 3102  72   9  11 0.00
Sun 07/12 19Z 0.67 3002  71   9  11 0.00
Sun 07/12 20Z 0.67 3102  70   8  12 0.00
Sun 07/12 21Z 0.78 2902  66   8  12 0.00
Sun 07/12 22Z 0.45 3002  62   8  12 0.00
Sun 07/12 23Z 0.16 2901  60   9  12 0.00
Mon 07/13 00Z 0.15 2501  60   5  12 0.00
Mon 07/13 01Z 0.24 2302  62   5  12 0.00
Mon 07/13 02Z 0.45 2404  66   6  12 0.00
Mon 07/13 03Z 0.50 2305  70  11  12 0.00
Mon 07/13 04Z 0.62 2407  72   9  11 0.00
Mon 07/13 05Z 0.71 2408  71   9  11 0.00
Mon 07/13 06Z 0.74 2410  69  12  11 0.00
Mon 07/13 07Z 0.90 2412  69  17  11 0.00
Mon 07/13 08Z 0.97 2514  68  24  11 0.00
Mon 07/13 09Z 1.00 2515  66  36  11 0.00
Mon 07/13 10Z 0.80 2514  66  43  11 0.00
Mon 07/13 11Z 0.69 2515  67  45  11 0.00
Mon 07/13 12Z 0.63 2614  67  49  12 0.00
Mon 07/13 13Z 0.54 2613  70  57  12 0.00
Mon 07/13 14Z 0.49 2511  72  61  12 0.00
Mon 07/13 15Z 0.50 2510  71  62  13 0.00
Mon 07/13 16Z 0.46 2409  67  65  13 0.00
Mon 07/13 17Z 0.52 2408  65  64  14 0.00
Mon 07/13 18Z 0.74 2308  65  58  14 0.00
Mon 07/13 19Z 1.48 2409  74  56  14 0.00
Mon 07/13 20Z 0.85 2510  80  57  14 0.00
Mon 07/13 21Z 0.48 2511  81  57  15 0.00
Mon 07/13 22Z 0.50 2512  79  60  15 0.00
Mon 07/13 23Z 0.62 2515  84  70  15 0.00
Tue 07/14 00Z 0.57 2515  83  76  15 0.00
Tue 07/14 01Z 0.68 2517  83  80  15 0.00
Tue 07/14 02Z 0.82 2620  86  77  14 0.00
Tue 07/14 03Z 0.70 2719  80  63  15 0.00
Tue 07/14 04Z 0.63 2618  63  53  15 0.00
Tue 07/14 05Z 0.59 2619  57  47  15 0.00
Tue 07/14 06Z 0.62 2719  68  45  15 0.00
Tue 07/14 07Z 0.58 2920  83  45  15 0.00
Tue 07/14 08Z 0.51 2918  85  33  15 0.00
Tue 07/14 09Z 0.47 2817  87  20  15 0.00
Tue 07/14 10Z 0.49 2818  87  22  16 0.00
Tue 07/14 11Z 0.53 2720  87  32  16 0.00

Run total areal avg QPF for the Central_Greens is: 0.00 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