NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260608_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)
=== ===== === ==== ==== === === === ====
Mon 06/08 00Z 0.15 0115  91  22   9 0.00
Mon 06/08 01Z 0.18 0118  87   3   9 0.00
Mon 06/08 02Z 0.33 0223  75   0   9 0.00
Mon 06/08 03Z 0.66 0327  66   0   8 0.00
Mon 06/08 04Z 0.81 0527  51   0   8 0.00
Mon 06/08 05Z 0.85 0525  45   1   8 0.00
Mon 06/08 06Z 0.90 0625  41   3   8 0.00
Mon 06/08 07Z 0.94 0724  40   4   8 0.00
Mon 06/08 08Z 0.87 0822  39   4   7 0.00
Mon 06/08 09Z 0.85 0820  40   5   7 0.00
Mon 06/08 10Z 0.69 0816  42   4   7 0.00
Mon 06/08 11Z 0.55 0813  44   6   7 0.00
Mon 06/08 12Z 0.47 0711  45  10   7 0.00
Mon 06/08 13Z 0.43 0609  47  13   7 0.00
Mon 06/08 14Z 0.46 0607  50  13   7 0.00
Mon 06/08 15Z 0.66 0404  54  12   7 0.00
Mon 06/08 16Z 0.65 0303  57  12   8 0.00
Mon 06/08 17Z 0.29 3101  61  12   8 0.00
Mon 06/08 18Z 0.36 2501  64  13   9 0.00
Mon 06/08 19Z 0.77 2502  66  13   9 0.00
Mon 06/08 20Z 0.79 2403  66  12  10 0.00
Mon 06/08 21Z 0.84 2405  65  10  10 0.00
Mon 06/08 22Z 0.60 2506  60  11  10 0.00
Mon 06/08 23Z 0.41 2607  57  12  10 0.00
Tue 06/09 00Z 0.38 2508  54  12  11 0.00
Tue 06/09 01Z 0.42 2510  49   9  11 0.00
Tue 06/09 02Z 0.45 2611  43   6  11 0.00
Tue 06/09 03Z 0.42 2511  47   5  11 0.00
Tue 06/09 04Z 0.49 2513  49   3  11 0.00
Tue 06/09 05Z 0.47 2514  50   3  12 0.00
Tue 06/09 06Z 0.50 2615  53   2  12 0.00
Tue 06/09 07Z 0.52 2616  60   3  11 0.00
Tue 06/09 08Z 0.53 2618  67   3  12 0.00
Tue 06/09 09Z 0.54 2620  74   3  12 0.00
Tue 06/09 10Z 0.49 2620  74   3  12 0.01
Tue 06/09 11Z 0.39 2717  71   3  12 0.01
Tue 06/09 12Z 0.39 2716  76   3  12 0.01
Tue 06/09 13Z 0.31 2713  74   2  12 0.01
Tue 06/09 14Z 0.21 2809  74   3  12 0.00
Tue 06/09 15Z 0.26 2708  74   5  12 0.00
Tue 06/09 16Z 0.30 2507  71   4  12 0.00
Tue 06/09 17Z 0.54 2408  72   5  12 0.00
Tue 06/09 18Z 0.66 2408  70   5  13 0.00
Tue 06/09 19Z 0.65 2409  68   5  13 0.00
Tue 06/09 20Z 0.66 2410  67   5  13 0.00
Tue 06/09 21Z 0.63 2412  67   5  14 0.00
Tue 06/09 22Z 0.63 2514  73   4  14 0.00
Tue 06/09 23Z 0.60 2515  76   4  14 0.00
Wed 06/10 00Z 0.62 2516  77   3  14 0.00
Wed 06/10 01Z 0.62 2617  76   2  14 0.00
Wed 06/10 02Z 0.55 2617  74   1  14 0.00
Wed 06/10 03Z 0.47 2616  69   1  15 0.00
Wed 06/10 04Z 0.36 2713  63   1  16 0.00
Wed 06/10 05Z 0.30 2611  60   1  16 0.00
Wed 06/10 06Z 0.25 2610  58   2  16 0.00
Wed 06/10 07Z 0.21 2408  58   4  16 0.00
Wed 06/10 08Z 0.18 2307  60  14  15 0.00
Wed 06/10 09Z 0.19 2208  64  43  15 0.00
Wed 06/10 10Z 0.20 2109  73  65  15 0.00
Wed 06/10 11Z 0.20 2109  80  69  14 0.00

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