NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261102_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)
=== ===== === ==== ==== === === === ====
Mon 11/02 12Z 0.49 2920  55  87   8 0.00
Mon 11/02 13Z 0.51 2920  57  85   8 0.00
Mon 11/02 14Z 0.52 2819  55  79   8 0.00
Mon 11/02 15Z 0.51 2818  54  72   8 0.00
Mon 11/02 16Z 0.53 2719  49  74   8 0.00
Mon 11/02 17Z 0.56 2719  50  72   8 0.00
Mon 11/02 18Z 0.57 2619  49  69   8 0.00
Mon 11/02 19Z 0.58 2619  43  69   9 0.00
Mon 11/02 20Z 0.59 2619  42  72   9 0.00
Mon 11/02 21Z 0.64 2621  42  75   9 0.00
Mon 11/02 22Z 0.63 2720  42  76   9 0.00
Mon 11/02 23Z 0.59 2720  43  77   9 0.00
Tue 11/03 00Z 0.54 2719  45  75   9 0.00
Tue 11/03 01Z 0.50 2718  47  75   9 0.00
Tue 11/03 02Z 0.49 2718  48  75   9 0.00
Tue 11/03 03Z 0.46 2717  48  79   9 0.00
Tue 11/03 04Z 0.46 2717  49  82   9 0.00
Tue 11/03 05Z 0.43 2716  50  89   9 0.00
Tue 11/03 06Z 0.41 2815  53  91   9 0.00
Tue 11/03 07Z 0.40 2814  55  88   9 0.00
Tue 11/03 08Z 0.37 2713  57  87   9 0.00
Tue 11/03 09Z 0.35 2712  58  85   9 0.00
Tue 11/03 10Z 0.35 2711  57  87   9 0.00
Tue 11/03 11Z 0.33 2710  59  92   9 0.00
Tue 11/03 12Z 0.34 2610  60  95   9 0.00
Tue 11/03 13Z 0.32 2609  59  98   9 0.00
Tue 11/03 14Z 0.36 2511  60  97   9 0.00
Tue 11/03 15Z 0.40 2412  61  98   9 0.00
Tue 11/03 16Z 0.45 2314  63  95   8 0.00
Tue 11/03 17Z 0.52 2317  64  96   8 0.00
Tue 11/03 18Z 0.55 2319  66  95   8 0.00
Tue 11/03 19Z 0.58 2320  74  97   9 0.00
Tue 11/03 20Z 0.61 2422  85  97   9 0.01
Tue 11/03 21Z 0.66 2424  83  96   9 0.02
Tue 11/03 22Z 0.66 2424  88  94  10 0.03
Tue 11/03 23Z 0.68 2525  90  85  10 0.02
Wed 11/04 00Z 0.67 2525  91  76  10 0.02
Wed 11/04 01Z 0.66 2624  91  58  10 0.01
Wed 11/04 02Z 0.63 2623  88  51  11 0.00
Wed 11/04 03Z 0.61 2523  86  52  11 0.00
Wed 11/04 04Z 0.66 2425  82  50  11 0.00
Wed 11/04 05Z 0.71 2427  81  53  11 0.00
Wed 11/04 06Z 0.74 2427  79  49  11 0.00
Wed 11/04 07Z 0.75 2428  76  51  11 0.00
Wed 11/04 08Z 0.74 2428  73  49  12 0.00
Wed 11/04 09Z 0.72 2527  71  45  12 0.00
Wed 11/04 10Z 0.73 2528  69  44  12 0.00
Wed 11/04 11Z 0.73 2627  68  38  12 0.00
Wed 11/04 12Z 0.70 2626  68  42  12 0.00
Wed 11/04 13Z 0.66 2625  66  46  12 0.00
Wed 11/04 14Z 0.60 2624  64  47  12 0.00
Wed 11/04 15Z 0.53 2622  64  45  12 0.00
Wed 11/04 16Z 0.47 2719  65  46  13 0.00
Wed 11/04 17Z 0.44 2717  68  46  12 0.00
Wed 11/04 18Z 0.42 2715  71  47  12 0.00
Wed 11/04 19Z 0.43 2715  73  47  12 0.00
Wed 11/04 20Z 0.42 2715  72  48  13 0.00
Wed 11/04 21Z 0.43 2715  71  46  13 0.00
Wed 11/04 22Z 0.44 2716  71  48  13 0.00
Wed 11/04 23Z 0.44 2616  71  50  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.11 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