NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260204_1200
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)
=== ===== === ==== ==== === === === ====
Wed 02/04 12Z 0.76 2815  87  74 -15 0.00
Wed 02/04 13Z 0.65 2917  92  70 -15 0.00
Wed 02/04 14Z 0.58 2918  92  73 -16 0.00
Wed 02/04 15Z 0.43 3017  90  73 -15 0.00
Wed 02/04 16Z 0.37 3016  87  67 -15 0.00
Wed 02/04 17Z 0.43 3016  86  52 -14 0.00
Wed 02/04 18Z 0.45 3115  86  36 -14 0.00
Wed 02/04 19Z 0.43 3114  85  30 -14 0.00
Wed 02/04 20Z 0.55 3014  86  35 -14 0.00
Wed 02/04 21Z 0.60 2915  87  35 -13 0.00
Wed 02/04 22Z 0.56 2916  87  32 -13 0.00
Wed 02/04 23Z 0.44 3017  87  27 -13 0.00
Thu 02/05 00Z 0.28 3117  85  23 -12 0.00
Thu 02/05 01Z 0.27 3117  87  24 -12 0.00
Thu 02/05 02Z 0.28 3016  88  28 -12 0.00
Thu 02/05 03Z 0.27 3015  87  29 -12 0.00
Thu 02/05 04Z 0.27 2914  86  30 -12 0.00
Thu 02/05 05Z 0.30 2914  86  31 -12 0.00
Thu 02/05 06Z 0.29 2915  84  32 -12 0.00
Thu 02/05 07Z 0.29 2915  84  34 -12 0.00
Thu 02/05 08Z 0.30 2916  85  28 -13 0.00
Thu 02/05 09Z 0.33 2916  86  36 -13 0.00
Thu 02/05 10Z 0.34 2916  87  52 -14 0.00
Thu 02/05 11Z 0.34 3017  88  63 -14 0.00
Thu 02/05 12Z 0.33 3017  87  46 -14 0.00
Thu 02/05 13Z 0.33 3017  88   5 -15 0.00
Thu 02/05 14Z 0.28 3117  86   4 -15 0.00
Thu 02/05 15Z 0.25 3116  84   3 -15 0.00
Thu 02/05 16Z 0.25 3115  83   3 -15 0.00
Thu 02/05 17Z 0.25 3114  82   4 -15 0.00
Thu 02/05 18Z 0.23 3113  77   3 -15 0.00
Thu 02/05 19Z 0.22 3113  71   4 -14 0.00
Thu 02/05 20Z 0.19 3214  64   4 -13 0.00
Thu 02/05 21Z 0.16 3214  60   4 -13 0.00
Thu 02/05 22Z 0.12 3214  57   4 -12 0.00
Thu 02/05 23Z 0.10 3314  54   5 -12 0.00
Fri 02/06 00Z 0.08 3313  52   5 -11 0.00
Fri 02/06 01Z 0.06 3311  51   6 -11 0.00
Fri 02/06 02Z 0.05 3309  49   7 -11 0.00
Fri 02/06 03Z 0.04 3306  44   8 -10 0.00
Fri 02/06 04Z 0.03 3305  40  10 -10 0.00
Fri 02/06 05Z 0.04 3205  37  12  -9 0.00
Fri 02/06 06Z 0.04 3103  36  15  -9 0.00
Fri 02/06 07Z 0.05 2603  38  22 -10 0.00
Fri 02/06 08Z 0.06 2104  41  28 -10 0.00
Fri 02/06 09Z 0.07 2105  40  33 -10 0.00
Fri 02/06 10Z 0.08 2205  37  32 -10 0.00
Fri 02/06 11Z 0.08 2205  34  28  -9 0.00
Fri 02/06 12Z 0.10 2306  33  19  -9 0.00
Fri 02/06 13Z 0.09 2206  35  13 -10 0.00
Fri 02/06 14Z 0.08 2106  38  10 -10 0.00
Fri 02/06 15Z 0.08 2007  39  10 -10 0.00
Fri 02/06 16Z 0.11 2008  42   7 -10 0.00
Fri 02/06 17Z 0.12 2008  42  18 -10 0.00
Fri 02/06 18Z 0.12 2008  46  69 -10 0.00
Fri 02/06 19Z 0.14 2008  53  85 -10 0.00
Fri 02/06 20Z 0.19 2009  58  87 -11 0.00
Fri 02/06 21Z 0.19 2010  56  85 -10 0.00
Fri 02/06 22Z 0.16 1911  59  87 -10 0.00
Fri 02/06 23Z 0.16 1912  64  83 -11 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