NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20250313_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)
=== ===== === ==== ==== === === === ====
Thu 03/13 00Z 0.02 3505  45  79  -4 0.00
Thu 03/13 01Z 0.02 3201  43  79  -4 0.00
Thu 03/13 02Z 0.05 2402  42  74  -4 0.00
Thu 03/13 03Z 0.06 2103  41  80  -4 0.00
Thu 03/13 04Z 0.08 2005  40  78  -4 0.00
Thu 03/13 05Z 0.11 2106  40  76  -4 0.00
Thu 03/13 06Z 0.10 2007  42  76  -5 0.00
Thu 03/13 07Z 0.12 2008  48  74  -5 0.00
Thu 03/13 08Z 0.13 2008  59  69  -5 0.00
Thu 03/13 09Z 0.15 2009  67  70  -5 0.00
Thu 03/13 10Z 0.20 2110  75  73  -5 0.00
Thu 03/13 11Z 0.20 2110  81  76  -5 0.00
Thu 03/13 12Z 0.17 2010  83  82  -5 0.00
Thu 03/13 13Z 0.13 1910  83  79  -5 0.00
Thu 03/13 14Z 0.11 1910  83  69  -5 0.00
Thu 03/13 15Z 0.09 1810  83  66  -5 0.00
Thu 03/13 16Z 0.10 1809  80  64  -5 0.00
Thu 03/13 17Z 0.11 1808  77  70  -4 0.00
Thu 03/13 18Z 0.13 1809  76  65  -4 0.00
Thu 03/13 19Z 0.09 1712  75  33  -3 0.00
Thu 03/13 20Z 0.10 1814  72  16  -2 0.00
Thu 03/13 21Z 0.11 1815  70   6  -2 0.00
Thu 03/13 22Z 0.14 1816  69   5  -2 0.00
Thu 03/13 23Z 0.14 1816  69   4  -2 0.00
Fri 03/14 00Z 0.18 1917  69   2  -2 0.00
Fri 03/14 01Z 0.30 2017  68   3  -2 0.00
Fri 03/14 02Z 0.32 2117  67   3  -1 0.00
Fri 03/14 03Z 0.34 2117  68   3  -1 0.00
Fri 03/14 04Z 0.30 2115  70   3  -1 0.00
Fri 03/14 05Z 0.29 2214  70   4  -1 0.00
Fri 03/14 06Z 0.27 2313  67   7   0 0.00
Fri 03/14 07Z 0.23 2311  63  14   0 0.00
Fri 03/14 08Z 0.23 2411  61  22   0 0.00
Fri 03/14 09Z 0.22 2410  59  29   0 0.00
Fri 03/14 10Z 0.21 2509  55  28   0 0.00
Fri 03/14 11Z 0.18 2608  52  27   0 0.00
Fri 03/14 12Z 0.17 2407  48  25   1 0.00
Fri 03/14 13Z 0.17 2308  46  28   1 0.00
Fri 03/14 14Z 0.18 2308  44  31   1 0.00
Fri 03/14 15Z 0.16 2307  42  33   2 0.00
Fri 03/14 16Z 0.16 2207  40  33   3 0.00
Fri 03/14 17Z 0.17 2207  40  31   3 0.00
Fri 03/14 18Z 0.19 2208  40  30   3 0.00
Fri 03/14 19Z 0.18 2108  40  27   4 0.00
Fri 03/14 20Z 0.20 2110  40  28   4 0.00
Fri 03/14 21Z 0.22 2112  40  29   5 0.00
Fri 03/14 22Z 0.27 2114  38  36   5 0.00
Fri 03/14 23Z 0.28 2215  33  35   6 0.00
Sat 03/15 00Z 0.27 2214  33  37   7 0.00
Sat 03/15 01Z 0.31 2316  37  31   7 0.00
Sat 03/15 02Z 0.30 2316  38  34   8 0.00
Sat 03/15 03Z 0.27 2216  35  30   8 0.00
Sat 03/15 04Z 0.29 2217  34  27   8 0.00
Sat 03/15 05Z 0.29 2118  32  27   8 0.00
Sat 03/15 06Z 0.30 2120  33  21   8 0.00
Sat 03/15 07Z 0.30 2120  36  17   8 0.00
Sat 03/15 08Z 0.31 2121  39  13   8 0.00
Sat 03/15 09Z 0.36 2123  43  26   8 0.00
Sat 03/15 10Z 0.37 2125  46  25   8 0.00
Sat 03/15 11Z 0.39 2126  47  27   8 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