NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260814_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)
=== ===== === ==== ==== === === === ====
Fri 08/14 12Z 0.24 3216  81  52  10 0.00
Fri 08/14 13Z 0.25 3216  82  52  10 0.00
Fri 08/14 14Z 0.21 3213  83  55  10 0.00
Fri 08/14 15Z 0.25 3212  83  60  10 0.00
Fri 08/14 16Z 0.52 3211  82  62  10 0.00
Fri 08/14 17Z 0.67 3211  80  71  10 0.00
Fri 08/14 18Z 0.91 3311  78  79  10 0.00
Fri 08/14 19Z 0.53 3410  77  79  10 0.00
Fri 08/14 20Z 0.61 3311  77  84  10 0.00
Fri 08/14 21Z 0.22 3312  77  82  10 0.00
Fri 08/14 22Z 0.26 3213  78  76  10 0.03
Fri 08/14 23Z 0.18 3212  77  72  10 0.00
Sat 08/15 00Z 0.06 3413  77  59  10 0.00
Sat 08/15 01Z 0.05 3514  81  42   9 0.00
Sat 08/15 02Z 0.08 3515  84  34   9 0.00
Sat 08/15 03Z 0.06 3514  87  26   9 0.00
Sat 08/15 04Z 0.10 3512  88  19   9 0.00
Sat 08/15 05Z 0.07 3511  87  13   9 0.00
Sat 08/15 06Z 0.03 3408  87  11   8 0.00
Sat 08/15 07Z 0.12 3209  86  11   8 0.00
Sat 08/15 08Z 0.17 3211  81  10   8 0.00
Sat 08/15 09Z 0.16 3212  77   8   8 0.00
Sat 08/15 10Z 0.16 3313  79   7   8 0.00
Sat 08/15 11Z 0.16 3313  81   8   7 0.00
Sat 08/15 12Z 0.12 3416  87  11   7 0.00
Sat 08/15 13Z 0.06 3414  84  10   7 0.00
Sat 08/15 14Z 0.05 3410  78  11   8 0.00
Sat 08/15 15Z 0.08 3307  76  12   8 0.00
Sat 08/15 16Z 0.17 3208  77  13   8 0.00
Sat 08/15 17Z 0.19 3211  73  13   8 0.00
Sat 08/15 18Z 0.21 3212  67  14   8 0.00
Sat 08/15 19Z 0.14 3311  64  11   9 0.00
Sat 08/15 20Z 0.27 3311  67  10   9 0.00
Sat 08/15 21Z 0.27 3310  68   9   9 0.00
Sat 08/15 22Z 0.20 3310  67   9   9 0.00
Sat 08/15 23Z 0.17 3210  66  10   9 0.00
Sun 08/16 00Z 0.12 3310  61  10   9 0.00
Sun 08/16 01Z 0.08 3309  61   9   9 0.00
Sun 08/16 02Z 0.11 3309  67  11   9 0.00
Sun 08/16 03Z 0.03 3407  64  12  10 0.00
Sun 08/16 04Z 0.01 3405  59  12  10 0.00
Sun 08/16 05Z 0.02 3303  56  11  11 0.00
Sun 08/16 06Z 0.02 3101  53  10  11 0.00
Sun 08/16 07Z 0.09 2603  54   9  11 0.00
Sun 08/16 08Z 0.12 2404  58   8  10 0.00
Sun 08/16 09Z 0.15 2305  64   7  10 0.00
Sun 08/16 10Z 0.11 2204  65   6  10 0.00
Sun 08/16 11Z 0.10 2104  66   6  10 0.00
Sun 08/16 12Z 0.16 2108  73   5   9 0.00
Sun 08/16 13Z 0.22 2110  78   4   9 0.00
Sun 08/16 14Z 0.23 2110  82   4   9 0.00
Sun 08/16 15Z 0.29 2111  85   4   9 0.00
Sun 08/16 16Z 0.17 2009  81   4  10 0.00
Sun 08/16 17Z 0.13 1808  79   4  10 0.00
Sun 08/16 18Z 0.08 1709  81   5  10 0.00
Sun 08/16 19Z 0.07 1711  84   7  11 0.00
Sun 08/16 20Z 0.10 1712  87   8  11 0.00
Sun 08/16 21Z 0.09 1713  88  20  11 0.00
Sun 08/16 22Z 0.14 1713  88  37  11 0.00
Sun 08/16 23Z 0.20 1813  89  43  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.03 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