NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260807_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)
=== ===== === ==== ==== === === === ====
Fri 08/07 06Z 0.15 2905  88  81  17 0.00
Fri 08/07 07Z 0.22 2908  89  85  17 0.00
Fri 08/07 08Z 0.22 2908  90  82  17 0.00
Fri 08/07 09Z 0.21 2908  87  72  17 0.00
Fri 08/07 10Z 0.18 3008  82  63  17 0.00
Fri 08/07 11Z 0.13 3107  78  62  17 0.00
Fri 08/07 12Z 0.10 3208  80  60  16 0.00
Fri 08/07 13Z 0.05 3307  82  54  16 0.00
Fri 08/07 14Z 0.04 3406  84  51  16 0.00
Fri 08/07 15Z 0.04 3504  86  47  16 0.00
Fri 08/07 16Z 0.04 0002  88  45  16 0.00
Fri 08/07 17Z 0.06 3501  87  47  16 0.03
Fri 08/07 18Z 0.12 2100  86  48  16 0.04
Fri 08/07 19Z 0.23 2602  85  49  17 0.03
Fri 08/07 20Z 0.18 2601  84  48  17 0.02
Fri 08/07 21Z 0.15 2702  84  49  17 0.01
Fri 08/07 22Z 0.13 2502  83  51  17 0.00
Fri 08/07 23Z 0.06 2201  80  51  17 0.00
Sat 08/08 00Z 0.06 2101  78  52  17 0.00
Sat 08/08 01Z 0.03 1901  78  53  17 0.00
Sat 08/08 02Z 0.04 1901  79  57  17 0.00
Sat 08/08 03Z 0.05 1902  79  57  17 0.00
Sat 08/08 04Z 0.09 1903  79  63  17 0.00
Sat 08/08 05Z 0.07 1903  79  67  17 0.00
Sat 08/08 06Z 0.08 1903  80  71  16 0.00
Sat 08/08 07Z 0.03 1704  81  80  16 0.01
Sat 08/08 08Z 0.08 1505  78  86  16 0.00
Sat 08/08 09Z 0.06 1505  78  94  17 0.00
Sat 08/08 10Z 0.03 1707  80  92  17 0.00
Sat 08/08 11Z 0.12 1908  82  88  16 0.00
Sat 08/08 12Z 0.24 2109  88  83  16 0.00
Sat 08/08 13Z 0.30 2210  93  76  16 0.00
Sat 08/08 14Z 0.40 2213  97  81  16 0.01
Sat 08/08 15Z 0.45 2215  93  73  16 0.01
Sat 08/08 16Z 0.59 2317  89  47  16 0.00
Sat 08/08 17Z 0.61 2417  79  47  16 0.00
Sat 08/08 18Z 0.79 2518  85  61  16 0.00
Sat 08/08 19Z 0.96 2519  90  45  16 0.00
Sat 08/08 20Z 0.94 2519  89  37  16 0.01
Sat 08/08 21Z 1.01 2518  87  40  16 0.00
Sat 08/08 22Z 1.00 2617  88  59  16 0.00
Sat 08/08 23Z 0.93 2616  88  60  16 0.00
Sun 08/09 00Z 0.81 2615  87  68  16 0.00
Sun 08/09 01Z 0.70 2615  86  72  16 0.00
Sun 08/09 02Z 0.59 2614  85  73  16 0.00
Sun 08/09 03Z 0.49 2613  87  83  16 0.03
Sun 08/09 04Z 0.39 2612  87  77  16 0.12
Sun 08/09 05Z 0.39 2712  92  80  16 0.00
Sun 08/09 06Z 0.38 2813  92  72  16 0.01
Sun 08/09 07Z 0.38 2814  90  57  16 0.01
Sun 08/09 08Z 0.34 2813  87  32  16 0.00
Sun 08/09 09Z 0.34 2713  83  41  16 0.00
Sun 08/09 10Z 0.39 2715  84  47  16 0.00
Sun 08/09 11Z 0.39 2715  84  44  16 0.01
Sun 08/09 12Z 0.43 2716  89  39  16 0.01
Sun 08/09 13Z 0.47 2716  92  49  15 0.01
Sun 08/09 14Z 0.48 2715  95  47  15 0.02
Sun 08/09 15Z 0.53 2715  95  35  15 0.01
Sun 08/09 16Z 0.63 2814  97  42  14 0.01
Sun 08/09 17Z 0.65 2714  96  42  15 0.05

Run total areal avg QPF for the Central_Greens is: 0.46 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