Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261103_0600
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)
=== ===== === ==== ==== === === === ====
Tue 11/03 06Z 0.40 2813  57  81   9 0.00
Tue 11/03 07Z 0.41 2813  56  81   9 0.00
Tue 11/03 08Z 0.36 2812  54  82  10 0.00
Tue 11/03 09Z 0.31 2710  54  80  10 0.00
Tue 11/03 10Z 0.32 2609  57  87  10 0.00
Tue 11/03 11Z 0.35 2610  61  88   9 0.00
Tue 11/03 12Z 0.39 2511  65  95   9 0.00
Tue 11/03 13Z 0.42 2412  64  94   9 0.00
Tue 11/03 14Z 0.41 2412  61  96   9 0.00
Tue 11/03 15Z 0.42 2313  59  95   9 0.00
Tue 11/03 16Z 0.47 2215  61  89   9 0.00
Tue 11/03 17Z 0.53 2317  64  87   9 0.00
Tue 11/03 18Z 0.55 2317  68  96   9 0.00
Tue 11/03 19Z 0.56 2218  74  98   8 0.00
Tue 11/03 20Z 0.62 2220  81  95   8 0.00
Tue 11/03 21Z 0.73 2323  83  91   9 0.00
Tue 11/03 22Z 0.68 2325  90  83   9 0.00
Tue 11/03 23Z 0.69 2425  91  77  10 0.01
Wed 11/04 00Z 0.65 2524  93  67  10 0.01
Wed 11/04 01Z 0.66 2624  93  53  10 0.01
Wed 11/04 02Z 0.63 2723  89  46  10 0.00
Wed 11/04 03Z 0.66 2624  86  44  10 0.00
Wed 11/04 04Z 0.68 2623  85  42  10 0.00
Wed 11/04 05Z 0.67 2523  83  40  10 0.00
Wed 11/04 06Z 0.72 2525  84  42  10 0.00
Wed 11/04 07Z 0.72 2525  78  41  11 0.00
Wed 11/04 08Z 0.71 2525  71  41  11 0.00
Wed 11/04 09Z 0.74 2526  69  60  11 0.00
Wed 11/04 10Z 0.74 2526  69  73  11 0.00
Wed 11/04 11Z 0.71 2526  70  69  11 0.00
Wed 11/04 12Z 0.71 2526  71  70  12 0.00
Wed 11/04 13Z 0.70 2526  67  74  12 0.00
Wed 11/04 14Z 0.65 2525  64  71  12 0.00
Wed 11/04 15Z 0.60 2523  61  65  12 0.00
Wed 11/04 16Z 0.54 2521  58  62  13 0.00
Wed 11/04 17Z 0.50 2519  53  61  13 0.00
Wed 11/04 18Z 0.48 2418  49  45  13 0.00
Wed 11/04 19Z 0.46 2418  49  40  13 0.00
Wed 11/04 20Z 0.46 2418  54  42  13 0.00
Wed 11/04 21Z 0.49 2419  58  44  13 0.00
Wed 11/04 22Z 0.51 2420  61  46  13 0.00
Wed 11/04 23Z 0.52 2421  63  40  13 0.00
Thu 11/05 00Z 0.49 2421  63  41  13 0.00
Thu 11/05 01Z 0.44 2419  59  43  14 0.00
Thu 11/05 02Z 0.42 2419  54  46  14 0.00
Thu 11/05 03Z 0.44 2420  50  51  14 0.00
Thu 11/05 04Z 0.48 2322  45  57  14 0.00
Thu 11/05 05Z 0.51 2324  39  57  14 0.00
Thu 11/05 06Z 0.53 2326  36  39  14 0.00
Thu 11/05 07Z 0.56 2328  38  30  14 0.00
Thu 11/05 08Z 0.55 2328  42  31  14 0.00
Thu 11/05 09Z 0.53 2228  45  34  14 0.00
Thu 11/05 10Z 0.52 2228  47  38  14 0.00
Thu 11/05 11Z 0.55 2230  47  41  14 0.00
Thu 11/05 12Z 0.61 2232  52  57  14 0.00
Thu 11/05 13Z 0.65 2234  58  66  13 0.00
Thu 11/05 14Z 0.61 2233  68  63  13 0.00
Thu 11/05 15Z 0.57 2230  74  76  13 0.00
Thu 11/05 16Z 0.58 2229  82  90  12 0.00
Thu 11/05 17Z 0.66 2229  96  92  11 0.01

Run total areal avg QPF for the Central_Greens is: 0.04 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