NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260201_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)
=== ===== === ==== ==== === === === ====
Sun 02/01 00Z 0.01 3413  66  32 -13 0.00
Sun 02/01 01Z 0.02 3515  68  34 -13 0.00
Sun 02/01 02Z 0.03 3514  72  35 -14 0.00
Sun 02/01 03Z 0.05 0015  73  34 -13 0.00
Sun 02/01 04Z 0.08 0114  76  34 -13 0.00
Sun 02/01 05Z 0.09 0114  76  33 -12 0.00
Sun 02/01 06Z 0.10 0115  74  30 -11 0.00
Sun 02/01 07Z 0.13 0215  72  29 -11 0.00
Sun 02/01 08Z 0.16 0218  71  28 -11 0.00
Sun 02/01 09Z 0.16 0218  69  30 -10 0.00
Sun 02/01 10Z 0.13 0119  67  24 -10 0.00
Sun 02/01 11Z 0.17 0219  70  24 -10 0.00
Sun 02/01 12Z 0.16 0219  71  21 -10 0.00
Sun 02/01 13Z 0.18 0220  73  18 -10 0.00
Sun 02/01 14Z 0.17 0222  73  13 -10 0.00
Sun 02/01 15Z 0.17 0220  74  14 -10 0.00
Sun 02/01 16Z 0.16 0119  71  13 -10 0.00
Sun 02/01 17Z 0.14 0119  70  13 -10 0.00
Sun 02/01 18Z 0.13 0119  67  13  -9 0.00
Sun 02/01 20Z 0.12 0021  62  13  -8 0.00
Sun 02/01 21Z 0.14 0123  58  13  -8 0.00
Sun 02/01 22Z 0.14 0124  55  13  -8 0.00
Sun 02/01 23Z 0.14 0026  52  13  -8 0.00
Mon 02/02 00Z 0.16 0128  52  12  -8 0.00
Mon 02/02 01Z 0.15 0128  54  11  -8 0.00
Mon 02/02 02Z 0.15 0127  54  11  -8 0.00
Mon 02/02 03Z 0.16 0127  47  10  -8 0.00
Mon 02/02 04Z 0.13 0026  46  10  -8 0.00
Mon 02/02 05Z 0.09 0024  46  10  -9 0.00
Mon 02/02 06Z 0.07 0023  45  11  -8 0.00
Mon 02/02 07Z 0.06 0021  45  15  -8 0.00
Mon 02/02 08Z 0.04 3521  44  20  -8 0.00
Mon 02/02 09Z 0.03 3520  43  26  -8 0.00
Mon 02/02 10Z 0.02 3520  41  30  -7 0.00
Mon 02/02 11Z 0.03 3520  38  32  -7 0.00
Mon 02/02 12Z 0.02 3520  35  34  -7 0.00
Mon 02/02 13Z 0.02 3521  32  36  -7 0.00
Mon 02/02 14Z 0.02 3421  32  35  -7 0.00
Mon 02/02 15Z 0.02 3421  36  32  -7 0.00
Mon 02/02 16Z 0.03 3422  37  30  -7 0.00
Mon 02/02 17Z 0.04 3421  36  25  -7 0.00
Mon 02/02 18Z 0.04 3422  35  19  -7 0.00
Mon 02/02 19Z 0.05 3422  35  16  -8 0.00
Mon 02/02 20Z 0.06 3423  37  13  -8 0.00
Mon 02/02 21Z 0.07 3424  44  13  -9 0.00
Mon 02/02 22Z 0.07 3423  47  11  -9 0.00
Mon 02/02 23Z 0.06 3421  44  11  -8 0.00
Tue 02/03 00Z 0.05 3419  41  25  -8 0.00
Tue 02/03 01Z 0.04 3418  37  33  -8 0.00
Tue 02/03 02Z 0.03 3417  38  50  -8 0.00
Tue 02/03 03Z 0.02 3416  41  55  -8 0.00
Tue 02/03 04Z 0.03 3415  46  55  -8 0.00
Tue 02/03 05Z 0.03 3415  49  52  -8 0.00
Tue 02/03 06Z 0.06 3314  51  56  -8 0.00
Tue 02/03 07Z 0.08 3315  51  61  -8 0.00
Tue 02/03 08Z 0.10 3315  51  64  -8 0.00
Tue 02/03 09Z 0.11 3214  49  51  -8 0.00
Tue 02/03 10Z 0.11 3213  47  26  -8 0.00
Tue 02/03 11Z 0.10 3211  46  15  -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