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_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)
=== ===== === ==== ==== === === === ====
Mon 11/02 18Z 0.56 2716  55  76   8 0.00
Mon 11/02 19Z 0.58 2717  57  76   9 0.00
Mon 11/02 20Z 0.58 2717  54  74   9 0.00
Mon 11/02 21Z 0.66 2619  50  77   9 0.00
Mon 11/02 22Z 0.65 2618  49  76   9 0.00
Mon 11/02 23Z 0.67 2620  49  75   9 0.00
Tue 11/03 00Z 0.66 2620  48  75   9 0.00
Tue 11/03 01Z 0.62 2619  47  76   9 0.00
Tue 11/03 02Z 0.59 2619  47  81   9 0.00
Tue 11/03 03Z 0.59 2619  49  85   9 0.00
Tue 11/03 04Z 0.56 2718  51  83   9 0.00
Tue 11/03 05Z 0.48 2716  50  77  10 0.00
Tue 11/03 06Z 0.48 2716  48  84  10 0.00
Tue 11/03 07Z 0.46 2615  46  86  10 0.00
Tue 11/03 08Z 0.42 2713  43  84  10 0.00
Tue 11/03 09Z 0.37 2711  41  88  10 0.00
Tue 11/03 10Z 0.36 2711  45  93   9 0.00
Tue 11/03 11Z 0.38 2611  53  94   9 0.00
Tue 11/03 12Z 0.42 2612  55  95   9 0.00
Tue 11/03 13Z 0.40 2511  56  93   9 0.00
Tue 11/03 14Z 0.39 2411  58  90   9 0.00
Tue 11/03 15Z 0.39 2311  59  92   9 0.00
Tue 11/03 16Z 0.40 2313  57  89   9 0.00
Tue 11/03 17Z 0.44 2315  56  92   9 0.00
Tue 11/03 18Z 0.55 2317  65  93   9 0.00
Tue 11/03 19Z 0.60 2319  82  90   9 0.00
Tue 11/03 20Z 0.62 2322  93  86   9 0.00
Tue 11/03 21Z 0.59 2322  93  85   9 0.01
Tue 11/03 22Z 0.66 2425  93  81  10 0.01
Tue 11/03 23Z 0.70 2426  94  82  10 0.01
Wed 11/04 00Z 0.68 2526  93  72  10 0.01
Wed 11/04 01Z 0.64 2525  94  60  11 0.01
Wed 11/04 02Z 0.64 2625  94  45  11 0.01
Wed 11/04 03Z 0.67 2625  93  47  11 0.00
Wed 11/04 04Z 0.69 2527  88  46  11 0.00
Wed 11/04 05Z 0.73 2528  79  37  11 0.00
Wed 11/04 06Z 0.76 2529  76  34  11 0.00
Wed 11/04 07Z 0.78 2530  75  33  11 0.00
Wed 11/04 08Z 0.82 2532  73  40  11 0.00
Wed 11/04 09Z 0.81 2531  71  42  12 0.00
Wed 11/04 10Z 0.81 2531  69  48  11 0.00
Wed 11/04 11Z 0.76 2629  68  45  12 0.00
Wed 11/04 12Z 0.71 2628  69  47  12 0.00
Wed 11/04 13Z 0.65 2725  72  48  11 0.00
Wed 11/04 14Z 0.60 2723  73  46  11 0.00
Wed 11/04 15Z 0.56 2721  74  47  12 0.00
Wed 11/04 16Z 0.54 2720  74  50  12 0.00
Wed 11/04 17Z 0.52 2718  73  52  12 0.00
Wed 11/04 18Z 0.52 2717  71  51  12 0.00
Wed 11/04 19Z 0.52 2717  68  48  12 0.00
Wed 11/04 20Z 0.49 2716  67  55  12 0.00
Wed 11/04 21Z 0.49 2716  66  58  12 0.00
Wed 11/04 22Z 0.48 2716  65  49  13 0.00
Wed 11/04 23Z 0.46 2715  65  43  13 0.00
Thu 11/05 00Z 0.42 2715  65  43  13 0.00
Thu 11/05 01Z 0.37 2713  64  44  13 0.00
Thu 11/05 02Z 0.33 2712  62  63  13 0.00
Thu 11/05 03Z 0.27 2609  59  65  14 0.00
Thu 11/05 04Z 0.22 2408  57  60  14 0.00

Run total areal avg QPF for the Central_Greens is: 0.06 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