NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260214_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)
=== ===== === ==== ==== === === === ====
Sat 02/14 00Z 0.40 2613  70  32  -9 0.00
Sat 02/14 01Z 0.52 2518  70  30 -10 0.00
Sat 02/14 02Z 0.53 2619  72  45 -10 0.00
Sat 02/14 03Z 0.51 2620  72  61 -10 0.00
Sat 02/14 04Z 0.44 2718  64  44 -10 0.00
Sat 02/14 05Z 0.38 2718  59  49  -9 0.00
Sat 02/14 06Z 0.37 2818  67  70  -9 0.00
Sat 02/14 07Z 0.39 2819  74  75 -10 0.00
Sat 02/14 08Z 0.39 2818  85  75 -10 0.00
Sat 02/14 09Z 0.33 2815  88  70 -10 0.00
Sat 02/14 10Z 0.37 2816  91  71 -10 0.00
Sat 02/14 11Z 0.37 2816  92  75 -10 0.00
Sat 02/14 12Z 0.37 2815  92  76 -10 0.00
Sat 02/14 13Z 0.38 2816  92  77 -10 0.00
Sat 02/14 14Z 0.42 2817  92  70 -10 0.00
Sat 02/14 15Z 0.45 2816  95  58 -10 0.00
Sat 02/14 16Z 0.49 2816  96  45 -10 0.00
Sat 02/14 17Z 0.49 2915  94  33 -10 0.00
Sat 02/14 18Z 0.53 2914  93  26 -10 0.00
Sat 02/14 19Z 0.62 2914  94  21 -10 0.00
Sat 02/14 20Z 0.70 2814  96  18 -10 0.00
Sat 02/14 21Z 0.75 2716  96  18  -9 0.00
Sat 02/14 22Z 0.77 2718  94  18  -9 0.00
Sat 02/14 23Z 0.71 2819  90  18  -9 0.00
Sun 02/15 00Z 0.60 2921  85  18  -9 0.00
Sun 02/15 01Z 0.52 2922  78  18  -9 0.00
Sun 02/15 02Z 0.48 3024  72  18  -9 0.00
Sun 02/15 03Z 0.47 3025  71  18  -9 0.00
Sun 02/15 04Z 0.44 3125  75  18 -10 0.00
Sun 02/15 05Z 0.38 3125  77  19 -10 0.00
Sun 02/15 06Z 0.35 3125  79  19 -10 0.00
Sun 02/15 07Z 0.26 3224  71  20 -10 0.00
Sun 02/15 08Z 0.22 3224  59  19  -9 0.00
Sun 02/15 09Z 0.15 3323  45  20  -9 0.00
Sun 02/15 10Z 0.09 3323  32  25  -8 0.00
Sun 02/15 11Z 0.06 3421  26  27  -8 0.00
Sun 02/15 12Z 0.03 3418  24  28  -8 0.00
Sun 02/15 13Z 0.03 3515  23  27  -8 0.00
Sun 02/15 14Z 0.04 3511  23  29  -8 0.00
Sun 02/15 15Z 0.02 3507  24  32  -8 0.00
Sun 02/15 16Z 0.04 0105  24  40  -7 0.00
Sun 02/15 17Z 0.05 0303  24  54  -7 0.00
Sun 02/15 18Z 0.05 0601  26  54  -6 0.00
Sun 02/15 19Z 0.03 1401  27  46  -6 0.00
Sun 02/15 20Z 0.02 1503  28  25  -6 0.00
Sun 02/15 21Z 0.02 1705  29  25  -6 0.00
Sun 02/15 22Z 0.05 1807  27  40  -6 0.00
Sun 02/15 23Z 0.07 1809  27  54  -5 0.00
Mon 02/16 00Z 0.07 1810  27  56  -5 0.00
Mon 02/16 01Z 0.10 1911  31  52  -5 0.00
Mon 02/16 02Z 0.12 1912  38  61  -6 0.00
Mon 02/16 03Z 0.13 1912  48  71  -6 0.00
Mon 02/16 04Z 0.13 1912  53  83  -6 0.00
Mon 02/16 07Z 0.07 1909  82  89  -5 0.00
Mon 02/16 08Z 0.05 1809  90  90  -5 0.00
Mon 02/16 09Z 0.05 1809  92  92  -5 0.00
Mon 02/16 10Z 0.04 1808  94  93  -5 0.00
Mon 02/16 11Z 0.04 1808  94  94  -5 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