NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260608_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)
=== ===== === ==== ==== === === === ====
Mon 06/08 12Z 0.16 0404  73   6   7 0.00
Mon 06/08 13Z 0.17 0305  75   7   7 0.00
Mon 06/08 14Z 0.17 0204  78   8   7 0.00
Mon 06/08 15Z 0.30 0203  80   8   8 0.00
Mon 06/08 16Z 0.22 3502  82   8   8 0.00
Mon 06/08 17Z 0.19 3101  83   7   8 0.00
Mon 06/08 18Z 0.38 2903  84   6   9 0.00
Mon 06/08 19Z 0.49 2903  82   6   9 0.00
Mon 06/08 20Z 0.61 2903  78   5  10 0.00
Mon 06/08 21Z 0.60 2804  73   5  10 0.00
Mon 06/08 22Z 0.39 2803  66   5  10 0.00
Mon 06/08 23Z 0.28 2705  59   4  11 0.00
Tue 06/09 00Z 0.35 2708  59   4  11 0.00
Tue 06/09 01Z 0.49 2610  65   3  11 0.00
Tue 06/09 02Z 0.45 2710  65   3  11 0.00
Tue 06/09 03Z 0.42 2709  66   2  11 0.00
Tue 06/09 04Z 0.36 2709  69   2  11 0.00
Tue 06/09 05Z 0.47 2611  67   3  11 0.00
Tue 06/09 06Z 0.55 2613  67   2  11 0.00
Tue 06/09 07Z 0.58 2615  70   2  11 0.00
Tue 06/09 08Z 0.66 2617  75   2  10 0.00
Tue 06/09 09Z 0.60 2618  78   2  10 0.00
Tue 06/09 10Z 0.50 2617  81   2  10 0.00
Tue 06/09 11Z 0.36 2714  78   2  11 0.01
Tue 06/09 12Z 0.30 2712  78   2  11 0.01
Tue 06/09 13Z 0.24 2609  75   2  11 0.01
Tue 06/09 14Z 0.25 2509  74   2  11 0.00
Tue 06/09 15Z 0.24 2508  70   2  11 0.00
Tue 06/09 16Z 0.28 2608  72   2  11 0.00
Tue 06/09 17Z 0.36 2608  75   2  11 0.00
Tue 06/09 18Z 0.40 2607  74   2  12 0.00
Tue 06/09 19Z 0.48 2609  74   2  13 0.00
Tue 06/09 20Z 0.50 2610  73   2  13 0.00
Tue 06/09 21Z 0.55 2611  72   3  13 0.00
Tue 06/09 22Z 0.57 2513  72   2  13 0.00
Tue 06/09 23Z 0.53 2513  77   2  14 0.00
Wed 06/10 00Z 0.62 2516  80   2  13 0.00
Wed 06/10 01Z 0.59 2616  83   1  14 0.00
Wed 06/10 02Z 0.55 2616  81   1  14 0.00
Wed 06/10 03Z 0.45 2715  74   1  15 0.00
Wed 06/10 04Z 0.45 2615  74   1  15 0.00
Wed 06/10 05Z 0.46 2615  74   1  14 0.00
Wed 06/10 06Z 0.38 2713  73   2  15 0.00
Wed 06/10 07Z 0.32 2611  71   8  15 0.00
Wed 06/10 08Z 0.29 2510  72  36  15 0.00
Wed 06/10 09Z 0.25 2409  73  57  15 0.00
Wed 06/10 10Z 0.22 2408  75  58  15 0.00
Wed 06/10 11Z 0.22 2308  75  79  15 0.00
Wed 06/10 12Z 0.18 2208  75  76  15 0.00
Wed 06/10 13Z 0.19 2209  75  72  15 0.00
Wed 06/10 14Z 0.20 2110  76  79  15 0.00
Wed 06/10 15Z 0.23 2110  81  79  15 0.00
Wed 06/10 16Z 0.30 2110  86  73  15 0.00
Wed 06/10 17Z 0.44 2010  87  78  15 0.00
Wed 06/10 18Z 0.46 2010  86  78  15 0.00
Wed 06/10 19Z 0.35 2011  86  83  15 0.00
Wed 06/10 20Z 0.33 2010  86  87  15 0.00
Wed 06/10 21Z 0.38 2010  88  80  15 0.00
Wed 06/10 22Z 0.43 2112  91  84  15 0.00
Wed 06/10 23Z 0.31 2012  91  94  15 0.01

Run total areal avg QPF for the Central_Greens is: 0.04 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