NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260427_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 04/27 06Z 0.20 0605  61  49   4 0.00
Mon 04/27 07Z 0.18 0504  61  47   4 0.00
Mon 04/27 08Z 0.16 0404  62  45   4 0.00
Mon 04/27 09Z 0.13 0304  62  46   4 0.00
Mon 04/27 10Z 0.14 0205  64  48   4 0.00
Mon 04/27 11Z 0.19 0306  65  47   4 0.00
Mon 04/27 12Z 0.22 0406  66  42   4 0.00
Mon 04/27 13Z 0.23 0505  66  36   4 0.00
Mon 04/27 14Z 0.43 0605  66  31   4 0.00
Mon 04/27 15Z 1.30 0705  66  27   4 0.00
Mon 04/27 16Z 2.47 0804  64  25   4 0.00
Mon 04/27 17Z 1.81 1003  62  24   5 0.00
Mon 04/27 18Z 0.52 1501  62  25   5 0.00
Mon 04/27 19Z 0.46 0400  64  26   5 0.00
Mon 04/27 20Z 0.30 0500  64  26   6 0.00
Mon 04/27 21Z 0.71 0901  64  24   6 0.00
Mon 04/27 22Z 0.52 1303  62  21   6 0.00
Mon 04/27 23Z 0.07 1603  62  22   6 0.00
Tue 04/28 00Z 0.12 1504  62  17   6 0.00
Tue 04/28 01Z 0.09 1606  60  13   6 0.00
Tue 04/28 02Z 0.08 1708  61  12   6 0.00
Tue 04/28 03Z 0.10 1709  61  12   5 0.00
Tue 04/28 04Z 0.06 1707  60  11   5 0.00
Tue 04/28 05Z 0.05 1608  58  10   6 0.00
Tue 04/28 06Z 0.10 1609  57  10   5 0.00
Tue 04/28 07Z 0.13 1511  58  10   5 0.00
Tue 04/28 08Z 0.16 1810  60   9   5 0.00
Tue 04/28 09Z 0.13 1810  60   9   5 0.00
Tue 04/28 10Z 0.09 1612  56   9   5 0.00
Tue 04/28 11Z 0.08 1614  54   8   5 0.00
Tue 04/28 12Z 0.15 1517  53   8   5 0.00
Tue 04/28 13Z 0.18 1519  55   8   4 0.00
Tue 04/28 14Z 0.46 1618  59   8   4 0.00
Tue 04/28 15Z 0.63 1617  60   8   4 0.00
Tue 04/28 16Z 0.95 1615  60   8   5 0.00
Tue 04/28 17Z 1.04 1615  59   7   5 0.00
Tue 04/28 18Z 0.98 1614  59   7   5 0.00
Tue 04/28 19Z 1.76 1614  61   7   6 0.00
Tue 04/28 20Z 0.87 1615  63   7   6 0.00
Tue 04/28 21Z 1.93 1516  65   7   5 0.00
Tue 04/28 22Z 0.54 1716  67  10   5 0.00
Tue 04/28 23Z 0.25 1717  70  14   5 0.00
Wed 04/29 00Z 0.19 1718  75  62   4 0.00
Wed 04/29 01Z 0.07 1718  77  88   4 0.00
Wed 04/29 02Z 0.10 1818  77  98   4 0.00
Wed 04/29 03Z 0.12 1817  79  97   4 0.00
Wed 04/29 04Z 0.18 1917  79  95   4 0.00
Wed 04/29 05Z 0.21 1917  79  91   3 0.00
Wed 04/29 06Z 0.22 1916  69  82   3 0.00
Wed 04/29 07Z 0.18 1915  62  77   4 0.00
Wed 04/29 08Z 0.22 2015  58  79   4 0.00
Wed 04/29 09Z 0.33 2018  60  85   4 0.00
Wed 04/29 10Z 0.40 2120  67  88   4 0.00
Wed 04/29 11Z 0.18 1916  64  80   6 0.00
Wed 04/29 12Z 0.15 1914  66  73   6 0.00
Wed 04/29 13Z 0.09 1813  67  50   6 0.00
Wed 04/29 14Z 0.07 1813  68  40   6 0.00
Wed 04/29 15Z 0.07 1812  68  39   6 0.00
Wed 04/29 16Z 0.17 1712  66  42   5 0.00
Wed 04/29 17Z 0.26 1611  65  38   5 0.00

Run total areal avg QPF for the Central_Greens is: 0.00 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