NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260823_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)
=== ===== === ==== ==== === === === ====
Sun 08/23 00Z 0.30 1316  91  45  11 0.00
Sun 08/23 01Z 0.27 1317  88  36  12 0.00
Sun 08/23 02Z 0.19 1417  86  26  12 0.01
Sun 08/23 03Z 0.15 1417  83  24  13 0.01
Sun 08/23 04Z 0.09 1517  83  31  12 0.01
Sun 08/23 05Z 0.07 1617  84  40  12 0.01
Sun 08/23 06Z 0.08 1618  87  51  12 0.01
Sun 08/23 07Z 0.09 1619  90  59  11 0.01
Sun 08/23 08Z 0.07 1619  92  64  11 0.01
Sun 08/23 09Z 0.07 1617  93  62  11 0.01
Sun 08/23 10Z 0.06 1616  93  58  11 0.01
Sun 08/23 11Z 0.03 1615  92  53  11 0.01
Sun 08/23 12Z 0.03 1614  91  56  11 0.00
Sun 08/23 13Z 0.03 1614  90  60  12 0.00
Sun 08/23 14Z 0.03 1614  90  63  12 0.00
Sun 08/23 15Z 0.05 1615  93  67  12 0.00
Sun 08/23 16Z 0.04 1615  95  76  12 0.01
Sun 08/23 17Z 0.05 1713  95  75  12 0.00
Sun 08/23 18Z 0.05 1713  96  71  12 0.00
Sun 08/23 19Z 0.04 1713  96  68  13 0.00
Sun 08/23 20Z 0.04 1714  95  70  13 0.00
Sun 08/23 21Z 0.05 1616  95  63  13 0.01
Sun 08/23 22Z 0.07 1619  95  60  13 0.01
Sun 08/23 23Z 0.11 1721  96  72  13 0.01
Mon 08/24 00Z 0.19 1823  96  51  13 0.01
Mon 08/24 01Z 0.34 1923  95  31  13 0.01
Mon 08/24 02Z 0.59 2319  88  81  11 0.25
Mon 08/24 03Z 0.61 2519  85  40  12 0.08
Mon 08/24 04Z 0.50 2417  84  33  11 0.00
Mon 08/24 05Z 0.49 2516  86  32  11 0.00
Mon 08/24 06Z 0.42 2415  85  31  11 0.00
Mon 08/24 07Z 0.39 2414  85  42  11 0.00
Mon 08/24 08Z 0.34 2413  85  35  11 0.00
Mon 08/24 09Z 0.31 2312  83  39  11 0.00
Mon 08/24 10Z 0.30 2312  83  42  10 0.00
Mon 08/24 11Z 0.29 2311  83  43  10 0.00
Mon 08/24 12Z 0.26 2311  83  46  10 0.00
Mon 08/24 13Z 0.26 2210  84  51  10 0.00
Mon 08/24 14Z 0.21 2109  86  47  10 0.00
Mon 08/24 15Z 0.20 2009  87  45   9 0.00
Mon 08/24 16Z 0.41 2110  88  49   9 0.00
Mon 08/24 17Z 0.69 2111  87  58   9 0.00
Mon 08/24 18Z 1.04 2211  84  59   9 0.00
Mon 08/24 19Z 1.60 2211  82  60   9 0.00
Mon 08/24 20Z 1.99 2212  81  52   9 0.00
Mon 08/24 21Z 1.08 2311  83  57   9 0.00
Mon 08/24 22Z 0.68 2311  83  46   9 0.00
Mon 08/24 23Z 0.54 2312  80  31   9 0.00
Tue 08/25 00Z 0.51 2513  77  26   9 0.00
Tue 08/25 01Z 0.58 2514  78  28   9 0.00
Tue 08/25 02Z 0.63 2615  82  26   9 0.00
Tue 08/25 03Z 0.56 2614  83  43   9 0.00
Tue 08/25 04Z 0.54 2614  83  50   9 0.00
Tue 08/25 05Z 0.50 2514  81  52   9 0.00
Tue 08/25 06Z 0.44 2513  82  59   9 0.00
Tue 08/25 07Z 0.39 2512  83  67   9 0.00
Tue 08/25 08Z 0.34 2511  83  67   9 0.00
Tue 08/25 09Z 0.32 2411  85  69   8 0.00
Tue 08/25 10Z 0.36 2412  88  80   8 0.00
Tue 08/25 11Z 0.37 2413  88  85   8 0.00

Run total areal avg QPF for the Central_Greens is: 0.49 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