NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260610_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)
=== ===== === ==== ==== === === === ====
Wed 06/10 00Z 0.38 2509  73   0  16 0.00
Wed 06/10 01Z 0.48 2512  73   0  16 0.00
Wed 06/10 02Z 0.53 2613  71   0  16 0.00
Wed 06/10 03Z 0.47 2712  68   0  16 0.00
Wed 06/10 04Z 0.45 2812  64   1  16 0.00
Wed 06/10 05Z 0.45 2811  64   2  15 0.00
Wed 06/10 06Z 0.45 2911  67   4  15 0.00
Wed 06/10 07Z 0.42 2810  71   7  15 0.00
Wed 06/10 08Z 0.39 2809  74  14  15 0.00
Wed 06/10 09Z 0.32 2607  78  27  15 0.00
Wed 06/10 10Z 0.29 2407  81  46  15 0.00
Wed 06/10 11Z 0.32 2309  84  75  15 0.00
Wed 06/10 12Z 0.29 2210  89  92  15 0.00
Wed 06/10 13Z 0.29 2211  93  85  15 0.03
Wed 06/10 14Z 0.26 2209  92  80  15 0.01
Wed 06/10 15Z 0.28 2110  89  84  15 0.00
Wed 06/10 16Z 0.30 2009  88  79  16 0.00
Wed 06/10 17Z 0.46 1908  89  79  16 0.00
Wed 06/10 18Z 0.68 1909  87  86  16 0.01
Wed 06/10 19Z 1.56 2110  85  85  16 0.01
Wed 06/10 20Z 1.08 1910  85  91  16 0.00
Wed 06/10 21Z 0.62 1911  88  80  16 0.00
Wed 06/10 22Z 0.42 2014  93  81  16 0.04
Wed 06/10 23Z 0.45 2216  94  76  16 0.12
Thu 06/11 00Z 0.50 2120  97  82  16 0.01
Thu 06/11 01Z 0.47 2119  98  84  16 0.07
Thu 06/11 02Z 0.52 2219  98  81  16 0.29
Thu 06/11 03Z 0.46 2216  93  81  16 0.18
Thu 06/11 04Z 0.57 2320  91  88  16 0.20
Thu 06/11 05Z 0.53 2418  93  89  16 0.08
Thu 06/11 06Z 0.55 2419  96  84  16 0.02
Thu 06/11 07Z 0.55 2518  96  85  16 0.02
Thu 06/11 08Z 0.56 2619  96  88  15 0.02
Thu 06/11 09Z 0.53 2718  96  75  15 0.01
Thu 06/11 10Z 0.52 2718  97  66  15 0.01
Thu 06/11 11Z 0.50 2717  95  59  15 0.01
Thu 06/11 12Z 0.47 2817  94  63  16 0.01
Thu 06/11 13Z 0.47 2816  94  62  15 0.00
Thu 06/11 14Z 0.42 2814  96  57  15 0.01
Thu 06/11 15Z 0.36 2914  96  49  16 0.01
Thu 06/11 16Z 0.26 3012  94  35  16 0.00
Thu 06/11 17Z 0.26 2909  90  36  17 0.00
Thu 06/11 18Z 0.44 2711  90  59  17 0.00
Thu 06/11 19Z 0.52 2712  90  62  17 0.00
Thu 06/11 20Z 0.58 2613  95  78  17 0.00
Thu 06/11 21Z 0.62 2614  97  79  17 0.02
Thu 06/11 22Z 0.74 2718  94  73  17 0.10
Thu 06/11 23Z 0.75 2917  92  68  16 0.03
Fri 06/12 00Z 0.77 2917  92  72  16 0.00
Fri 06/12 01Z 0.61 2815  93  67  16 0.01
Fri 06/12 02Z 0.62 2715  93  69  15 0.00
Fri 06/12 03Z 0.38 2811  92  59  16 0.00
Fri 06/12 04Z 0.39 2812  94  43  16 0.00
Fri 06/12 05Z 0.35 2811  95  42  15 0.00
Fri 06/12 06Z 0.28 2911  97  48  15 0.01
Fri 06/12 07Z 0.23 3009  97  67  15 0.01
Fri 06/12 08Z 0.26 2910  97  84  15 0.01
Fri 06/12 09Z 0.25 2910  98  89  15 0.01
Fri 06/12 10Z 0.29 2911  99  94  15 0.06
Fri 06/12 11Z 0.27 2911  97  91  15 0.03

Run total areal avg QPF for the Central_Greens is: 1.46 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