NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260822_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)
=== ===== === ==== ==== === === === ====
Sat 08/22 06Z 0.16 1204  73  18  11 0.00
Sat 08/22 07Z 0.15 1305  73  19  11 0.00
Sat 08/22 08Z 0.17 1305  74  20  10 0.00
Sat 08/22 09Z 0.19 1407  76  21  10 0.00
Sat 08/22 10Z 0.21 1408  77  21  10 0.00
Sat 08/22 11Z 0.25 1410  76  22  10 0.00
Sat 08/22 12Z 0.28 1312  77  23  10 0.00
Sat 08/22 13Z 0.29 1314  78  22  10 0.00
Sat 08/22 14Z 0.36 1315  80  22  10 0.00
Sat 08/22 15Z 0.47 1315  80  22  10 0.00
Sat 08/22 16Z 1.16 1315  81  22  10 0.00
Sat 08/22 17Z 2.07 1412  82  24  10 0.00
Sat 08/22 18Z 1.67 1413  82  25  10 0.00
Sat 08/22 19Z 1.75 1413  81  29  10 0.00
Sat 08/22 20Z 0.68 1414  84  36  11 0.00
Sat 08/22 21Z 0.27 1414  87  42  11 0.00
Sat 08/22 22Z 0.22 1416  90  52  11 0.00
Sat 08/22 23Z 0.21 1417  90  64  12 0.00
Sun 08/23 00Z 0.23 1418  89  61  12 0.00
Sun 08/23 01Z 0.24 1419  90  46  12 0.00
Sun 08/23 02Z 0.24 1419  92  51  12 0.00
Sun 08/23 03Z 0.23 1420  95  47  12 0.01
Sun 08/23 04Z 0.20 1420  96  47  12 0.01
Sun 08/23 05Z 0.18 1519  96  51  12 0.01
Sun 08/23 06Z 0.15 1517  95  59  11 0.01
Sun 08/23 07Z 0.14 1516  94  65  11 0.01
Sun 08/23 08Z 0.16 1415  93  67  11 0.01
Sun 08/23 09Z 0.18 1417  93  73  11 0.01
Sun 08/23 10Z 0.21 1418  93  77  11 0.01
Sun 08/23 11Z 0.24 1420  93  78  11 0.01
Sun 08/23 12Z 0.27 1419  93  74  12 0.01
Sun 08/23 13Z 0.27 1419  93  79  12 0.01
Sun 08/23 14Z 0.23 1417  93  84  12 0.01
Sun 08/23 15Z 0.21 1415  95  87  12 0.01
Sun 08/23 16Z 0.18 1414  96  88  12 0.01
Sun 08/23 17Z 0.09 1513  97  89  12 0.01
Sun 08/23 18Z 0.05 1612  95  78  12 0.01
Sun 08/23 19Z 0.02 1713  96  77  12 0.00
Sun 08/23 20Z 0.03 1712  95  72  13 0.00
Sun 08/23 21Z 0.05 1714  94  73  13 0.00
Sun 08/23 22Z 0.10 1817  94  66  13 0.00
Sun 08/23 23Z 0.14 1819  95  54  13 0.01
Mon 08/24 00Z 0.24 1823  96  44  13 0.01
Mon 08/24 01Z 0.31 1924  98  49  13 0.01
Mon 08/24 02Z 0.67 2221  91  64  12 0.14
Mon 08/24 03Z 0.61 2419  90  49  12 0.04
Mon 08/24 04Z 0.57 2418  91  56  11 0.01
Mon 08/24 05Z 0.52 2318  91  44  11 0.00
Mon 08/24 06Z 0.49 2318  85  39  12 0.00
Mon 08/24 07Z 0.45 2317  83  31  11 0.00
Mon 08/24 08Z 0.43 2318  83  24  11 0.00
Mon 08/24 09Z 0.47 2319  83  24  11 0.00
Mon 08/24 10Z 0.49 2319  87  25  11 0.00
Mon 08/24 11Z 0.45 2219  86  23  10 0.01
Mon 08/24 12Z 0.41 2217  85  25  10 0.00
Mon 08/24 13Z 0.39 2215  89  26  10 0.00
Mon 08/24 14Z 0.36 2213  91  30   9 0.00
Mon 08/24 15Z 0.33 2112  92  44   9 0.00
Mon 08/24 16Z 0.44 2112  92  68   8 0.00
Mon 08/24 17Z 0.60 2013  92  69   8 0.00

Run total areal avg QPF for the Central_Greens is: 0.39 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