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_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)
=== ===== === ==== ==== === === === ====
Mon 06/08 06Z 0.41 0615  72   4   8 0.00
Mon 06/08 07Z 0.41 0614  73   5   8 0.00
Mon 06/08 08Z 0.35 0712  74   5   7 0.00
Mon 06/08 09Z 0.35 0811  69   6   7 0.00
Mon 06/08 10Z 0.31 0810  64   7   7 0.00
Mon 06/08 11Z 0.27 0808  61   6   7 0.00
Mon 06/08 12Z 0.23 0806  60   6   7 0.00
Mon 06/08 13Z 0.19 0705  61   8   7 0.00
Mon 06/08 14Z 0.18 0604  65   9   7 0.00
Mon 06/08 15Z 0.17 0402  69  10   7 0.00
Mon 06/08 16Z 0.17 0401  73  11   8 0.00
Mon 06/08 17Z 0.14 0001  75  10   8 0.00
Mon 06/08 18Z 0.16 3401  76  10   9 0.00
Mon 06/08 19Z 0.21 3001  77   8   9 0.00
Mon 06/08 20Z 0.32 2802  76   7  10 0.00
Mon 06/08 21Z 0.27 2602  74   5  10 0.00
Mon 06/08 22Z 0.38 2504  69   5  10 0.00
Mon 06/08 23Z 0.26 2505  62   4  10 0.00
Tue 06/09 00Z 0.27 2506  54   4  11 0.00
Tue 06/09 01Z 0.39 2509  49   3  11 0.00
Tue 06/09 02Z 0.39 2610  48   2  11 0.00
Tue 06/09 03Z 0.41 2510  48   2  11 0.00
Tue 06/09 04Z 0.51 2613  58   2  11 0.00
Tue 06/09 05Z 0.57 2615  58   2  11 0.00
Tue 06/09 06Z 0.55 2716  60   2  11 0.00
Tue 06/09 07Z 0.53 2816  71   2  11 0.00
Tue 06/09 08Z 0.43 2814  78   2  10 0.00
Tue 06/09 09Z 0.34 2812  79   2  10 0.00
Tue 06/09 10Z 0.35 2713  76   2  11 0.00
Tue 06/09 11Z 0.29 2711  75   2  11 0.01
Tue 06/09 12Z 0.23 2608  77   2  11 0.01
Tue 06/09 13Z 0.25 2609  81   2  11 0.01
Tue 06/09 14Z 0.22 2608  79   2  11 0.01
Tue 06/09 15Z 0.19 2506  77   2  11 0.00
Tue 06/09 16Z 0.25 2507  79   2  11 0.00
Tue 06/09 17Z 0.32 2508  81   2  11 0.00
Tue 06/09 18Z 0.35 2508  80   2  12 0.00
Tue 06/09 19Z 0.38 2509  80   1  12 0.00
Tue 06/09 20Z 0.41 2510  78   1  13 0.00
Tue 06/09 21Z 0.40 2510  74   1  13 0.00
Tue 06/09 22Z 0.36 2610  70   0  14 0.00
Tue 06/09 23Z 0.35 2611  69   0  14 0.00
Wed 06/10 00Z 0.39 2613  74   0  14 0.00
Wed 06/10 01Z 0.38 2613  72   0  14 0.00
Wed 06/10 02Z 0.36 2613  70   0  15 0.00
Wed 06/10 03Z 0.31 2612  64   0  15 0.00
Wed 06/10 04Z 0.27 2611  59   1  16 0.00
Wed 06/10 05Z 0.22 2509  58   2  16 0.00
Wed 06/10 06Z 0.24 2410  62  12  16 0.00
Wed 06/10 07Z 0.24 2410  67  30  16 0.00
Wed 06/10 08Z 0.25 2410  76  40  15 0.00
Wed 06/10 09Z 0.25 2310  83  43  15 0.00
Wed 06/10 10Z 0.25 2211  86  57  15 0.00
Wed 06/10 11Z 0.29 2113  86  75  15 0.00
Wed 06/10 12Z 0.28 2114  84  80  15 0.00
Wed 06/10 13Z 0.23 2013  83  78  16 0.00
Wed 06/10 14Z 0.23 2014  83  73  16 0.00
Wed 06/10 15Z 0.20 1915  83  75  16 0.00
Wed 06/10 16Z 0.31 1914  85  88  15 0.00
Wed 06/10 17Z 0.30 1914  91  94  15 0.00

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