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_1200
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 12Z 0.20 0803  69  44   4 0.00
Mon 04/27 13Z 0.22 0903  70  40   4 0.00
Mon 04/27 14Z 0.45 0904  70  34   4 0.00
Mon 04/27 15Z 0.99 0903  71  31   4 0.00
Mon 04/27 16Z 1.36 1002  71  30   4 0.00
Mon 04/27 17Z 1.48 1103  70  29   5 0.00
Mon 04/27 18Z 0.90 1302  68  30   5 0.00
Mon 04/27 19Z 0.62 1401  68  31   5 0.00
Mon 04/27 20Z 0.36 1400  68  35   6 0.00
Mon 04/27 21Z 0.44 0901  69  33   6 0.00
Mon 04/27 22Z 0.72 1104  66  24   6 0.00
Mon 04/27 23Z 0.48 1305  64  21   6 0.00
Tue 04/28 00Z 0.31 1407  63  20   6 0.00
Tue 04/28 01Z 0.21 1508  63  16   6 0.00
Tue 04/28 02Z 0.07 1610  62  14   5 0.00
Tue 04/28 03Z 0.15 1811  61  15   5 0.00
Tue 04/28 04Z 0.06 1710  57  11   6 0.00
Tue 04/28 05Z 0.08 1710  56   9   6 0.00
Tue 04/28 06Z 0.11 1611  56   9   5 0.00
Tue 04/28 07Z 0.19 1513  52   8   5 0.00
Tue 04/28 08Z 0.11 1712  52   9   5 0.00
Tue 04/28 09Z 0.09 1713  51   7   5 0.00
Tue 04/28 10Z 0.11 1514  51   7   5 0.00
Tue 04/28 11Z 0.09 1616  53   7   4 0.00
Tue 04/28 12Z 0.22 1519  56   7   4 0.00
Tue 04/28 13Z 0.17 1520  62   6   4 0.00
Tue 04/28 14Z 0.25 1521  64   6   4 0.00
Tue 04/28 15Z 0.17 1618  67   5   4 0.00
Tue 04/28 16Z 0.48 1617  67   5   3 0.00
Tue 04/28 17Z 0.90 1616  66   6   3 0.00
Tue 04/28 18Z 1.66 1515  65   6   4 0.00
Tue 04/28 19Z 1.77 1517  64   7   4 0.00
Tue 04/28 20Z 0.74 1615  66   7   4 0.00
Tue 04/28 21Z 0.56 1616  69  12   4 0.00
Tue 04/28 22Z 0.36 1617  72  50   4 0.00
Tue 04/28 23Z 0.23 1619  74  77   3 0.00
Wed 04/29 00Z 0.09 1621  72  92   3 0.00
Wed 04/29 01Z 0.04 1720  71  94   4 0.00
Wed 04/29 02Z 0.09 1720  73  93   4 0.00
Wed 04/29 03Z 0.19 1820  75  93   4 0.00
Wed 04/29 04Z 0.19 1919  78  90   3 0.00
Wed 04/29 05Z 0.20 1919  75  88   4 0.00
Wed 04/29 06Z 0.28 2019  73  84   4 0.00
Wed 04/29 07Z 0.41 2121  79  86   3 0.00
Wed 04/29 08Z 0.35 2119  89  79   5 0.00
Wed 04/29 09Z 0.20 2113  90  58   7 0.00
Wed 04/29 10Z 0.19 2212  92  44   7 0.00
Wed 04/29 11Z 0.18 2211  92  36   7 0.00
Wed 04/29 12Z 0.13 2109  92  31   7 0.00
Wed 04/29 13Z 0.06 1906  89  28   7 0.00
Wed 04/29 14Z 0.06 1808  90  28   7 0.00
Wed 04/29 15Z 0.03 1709  89  27   6 0.00
Wed 04/29 16Z 0.03 1710  88  31   6 0.00
Wed 04/29 17Z 0.06 1710  86  34   6 0.00
Wed 04/29 18Z 0.06 1611  85  33   6 0.00
Wed 04/29 19Z 0.30 1613  84  33   6 0.00
Wed 04/29 20Z 0.33 1615  84  35   6 0.00
Wed 04/29 21Z 0.13 1617  85  32   6 0.00
Wed 04/29 22Z 0.13 1621  87  30   6 0.00
Wed 04/29 23Z 0.15 1624  87  33   6 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