NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260804_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 08/04 06Z 0.70 3023  85   3  10 0.00
Tue 08/04 07Z 0.78 3024  80   0  10 0.00
Tue 08/04 08Z 0.65 3023  74   1  11 0.00
Tue 08/04 09Z 0.62 3023  70   1  11 0.00
Tue 08/04 10Z 0.66 3023  64   1  11 0.00
Tue 08/04 11Z 0.65 3023  57   1  12 0.00
Tue 08/04 12Z 0.63 3022  53   1  12 0.00
Tue 08/04 13Z 0.65 3022  52   1  12 0.00
Tue 08/04 14Z 0.72 2920  53   2  12 0.00
Tue 08/04 15Z 0.76 2918  54   2  12 0.00
Tue 08/04 16Z 0.76 2915  53   3  12 0.00
Tue 08/04 17Z 0.64 2912  54   4  13 0.00
Tue 08/04 18Z 0.68 2910  57   7  13 0.00
Tue 08/04 19Z 0.68 2808  62  10  13 0.00
Tue 08/04 20Z 0.58 2708  67  14  14 0.00
Tue 08/04 21Z 0.52 2607  71  19  14 0.00
Tue 08/04 22Z 0.36 2507  71  22  14 0.00
Tue 08/04 23Z 0.26 2407  65  29  16 0.00
Wed 08/05 00Z 0.25 2408  61  38  16 0.00
Wed 08/05 01Z 0.27 2309  59  42  16 0.00
Wed 08/05 02Z 0.25 2309  57  46  17 0.00
Wed 08/05 03Z 0.24 2309  53  47  17 0.00
Wed 08/05 04Z 0.23 2309  51  46  17 0.00
Wed 08/05 05Z 0.22 2408  51  44  17 0.00
Wed 08/05 06Z 0.21 2508  51  42  18 0.00
Wed 08/05 07Z 0.23 2509  51  43  17 0.00
Wed 08/05 08Z 0.22 2608  50  40  17 0.00
Wed 08/05 09Z 0.22 2608  47  35  17 0.00
Wed 08/05 10Z 0.20 2608  46  28  17 0.00
Wed 08/05 11Z 0.16 2706  45  19  17 0.00
Wed 08/05 12Z 0.18 2607  49  13  16 0.00
Wed 08/05 13Z 0.20 2707  55   6  16 0.00
Wed 08/05 14Z 0.19 2706  58   2  15 0.00
Wed 08/05 15Z 0.16 2505  58   1  15 0.00
Wed 08/05 16Z 0.16 2304  58   1  15 0.00
Wed 08/05 17Z 0.36 2206  59   1  15 0.00
Wed 08/05 18Z 0.51 2207  56   2  15 0.00
Wed 08/05 19Z 0.59 2208  54   2  16 0.00
Wed 08/05 20Z 0.36 2209  54   3  16 0.00
Wed 08/05 21Z 0.35 2310  55   5  17 0.00
Wed 08/05 22Z 0.39 2411  62  16  17 0.00
Wed 08/05 23Z 0.39 2412  70  31  17 0.00
Thu 08/06 00Z 0.39 2412  73  31  17 0.00
Thu 08/06 01Z 0.40 2413  76  41  17 0.00
Thu 08/06 02Z 0.39 2412  78  49  17 0.00
Thu 08/06 03Z 0.44 2414  78  56  16 0.00
Thu 08/06 04Z 0.46 2514  78  62  16 0.00
Thu 08/06 05Z 0.50 2515  80  67  16 0.00
Thu 08/06 06Z 0.49 2516  81  68  16 0.00
Thu 08/06 07Z 0.49 2516  81  60  16 0.00
Thu 08/06 08Z 0.49 2516  78  53  16 0.00
Thu 08/06 09Z 0.46 2615  79  55  16 0.00
Thu 08/06 10Z 0.39 2613  79  49  17 0.00
Thu 08/06 11Z 0.31 2711  79  36  17 0.00
Thu 08/06 12Z 0.25 2708  80  23  16 0.00
Thu 08/06 13Z 0.22 2607  82  19  16 0.00
Thu 08/06 14Z 0.21 2606  83  13  16 0.00
Thu 08/06 15Z 0.18 2505  83   9  16 0.00
Thu 08/06 16Z 0.21 2404  83  12  16 0.00
Thu 08/06 17Z 0.33 2405  82  16  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