NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260806_0600
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)
=== ===== === ==== ==== === === === ====
Thu 08/06 06Z 0.41 2413  77  43  16 0.00
Thu 08/06 07Z 0.42 2412  79  44  16 0.00
Thu 08/06 08Z 0.40 2512  80  49  16 0.00
Thu 08/06 09Z 0.39 2511  81  61  16 0.00
Thu 08/06 10Z 0.34 2609  81  67  16 0.00
Thu 08/06 11Z 0.26 2707  81  69  16 0.00
Thu 08/06 12Z 0.17 2504  82  73  16 0.00
Thu 08/06 13Z 0.14 2303  83  77  16 0.00
Thu 08/06 14Z 0.13 2104  84  78  16 0.00
Thu 08/06 15Z 0.20 2104  86  82  16 0.00
Thu 08/06 16Z 0.23 2005  87  81  16 0.00
Thu 08/06 17Z 0.37 2106  88  75  16 0.00
Thu 08/06 18Z 0.46 2107  89  72  16 0.00
Thu 08/06 19Z 0.58 2208  89  78  17 0.00
Thu 08/06 20Z 0.53 2108  88  77  17 0.00
Thu 08/06 21Z 0.55 2208  88  79  17 0.00
Thu 08/06 22Z 0.45 2308  91  70  17 0.04
Thu 08/06 23Z 0.38 2409  90  68  17 0.13
Fri 08/07 00Z 0.42 2511  91  68  17 0.05
Fri 08/07 01Z 0.43 2512  90  65  17 0.06
Fri 08/07 02Z 0.45 2513  91  65  17 0.01
Fri 08/07 03Z 0.41 2613  86  63  18 0.00
Fri 08/07 04Z 0.41 2714  84  68  18 0.00
Fri 08/07 05Z 0.41 2714  82  64  17 0.00
Fri 08/07 06Z 0.43 2814  77  71  17 0.00
Fri 08/07 07Z 0.39 2814  71  73  17 0.00
Fri 08/07 08Z 0.32 2913  67  61  17 0.00
Fri 08/07 09Z 0.24 3010  64  62  17 0.00
Fri 08/07 10Z 0.24 2909  64  57  17 0.00
Fri 08/07 11Z 0.22 2908  67  58  16 0.00
Fri 08/07 12Z 0.21 2908  69  49  16 0.00
Fri 08/07 13Z 0.20 2908  74  36  16 0.00
Fri 08/07 14Z 0.21 2808  81  40  16 0.00
Fri 08/07 15Z 0.22 2807  85  43  16 0.00
Fri 08/07 16Z 0.25 2807  87  51  15 0.00
Fri 08/07 17Z 0.27 2806  87  49  16 0.00
Fri 08/07 18Z 0.24 2804  84  51  16 0.00
Fri 08/07 19Z 0.38 2804  83  56  16 0.00
Fri 08/07 20Z 0.47 2804  82  55  16 0.00
Fri 08/07 21Z 0.31 2805  81  53  16 0.00
Fri 08/07 22Z 0.21 2804  82  56  16 0.00
Fri 08/07 23Z 0.19 2805  82  57  17 0.00
Sat 08/08 00Z 0.20 2805  82  46  17 0.00
Sat 08/08 01Z 0.22 2706  86  34  17 0.00
Sat 08/08 02Z 0.18 2705  87  28  16 0.00
Sat 08/08 03Z 0.17 2704  85  22  17 0.00
Sat 08/08 04Z 0.19 2605  86  19  16 0.00
Sat 08/08 05Z 0.19 2605  88  21  16 0.00
Sat 08/08 06Z 0.18 2705  89  26  16 0.00
Sat 08/08 07Z 0.14 2704  88  33  16 0.00
Sat 08/08 08Z 0.13 2604  88  41  16 0.00
Sat 08/08 09Z 0.12 2603  86  48  16 0.00
Sat 08/08 10Z 0.12 2603  85  51  16 0.00
Sat 08/08 11Z 0.10 2403  84  52  16 0.00
Sat 08/08 12Z 0.09 2303  83  50  16 0.00
Sat 08/08 13Z 0.09 2203  81  45  17 0.00
Sat 08/08 14Z 0.09 2104  81  39  17 0.00
Sat 08/08 15Z 0.13 2105  81  32  17 0.00
Sat 08/08 16Z 0.25 2106  83  33  17 0.00
Sat 08/08 17Z 0.32 2206  84  40  16 0.00

Run total areal avg QPF for the Central_Greens is: 0.29 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