NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261007_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)
=== ===== === ==== ==== === === === ====
Wed 10/07 06Z 0.20 2808  50  43   3 0.00
Wed 10/07 07Z 0.22 2708  51  45   3 0.00
Wed 10/07 08Z 0.23 2509  51  54   4 0.00
Wed 10/07 09Z 0.26 2411  46  65   4 0.00
Wed 10/07 10Z 0.29 2413  38  76   5 0.00
Wed 10/07 11Z 0.30 2414  34  85   6 0.00
Wed 10/07 12Z 0.33 2416  30  79   7 0.00
Wed 10/07 13Z 0.33 2317  25  84   8 0.00
Wed 10/07 14Z 0.33 2218  24  79   8 0.00
Wed 10/07 15Z 0.37 2221  31  82   8 0.00
Wed 10/07 16Z 0.44 2223  40  90   8 0.00
Wed 10/07 17Z 0.56 2124  45  96   7 0.00
Wed 10/07 18Z 0.63 2125  45  92   7 0.00
Wed 10/07 19Z 0.63 2124  47  84   8 0.00
Wed 10/07 20Z 0.66 2124  51  83   8 0.00
Wed 10/07 21Z 0.73 2124  56  76   7 0.00
Wed 10/07 22Z 0.79 2125  64  43   7 0.00
Wed 10/07 23Z 0.78 2226  70  72   7 0.00
Thu 10/08 00Z 0.77 2227  74  79   7 0.00
Thu 10/08 01Z 0.78 2328  77  74   7 0.00
Thu 10/08 02Z 0.71 2327  77  52   7 0.00
Thu 10/08 03Z 0.65 2327  76  60   8 0.00
Thu 10/08 04Z 0.69 2329  80  59   8 0.00
Thu 10/08 05Z 0.72 2329  87  69   8 0.00
Thu 10/08 06Z 0.69 2328  89  64   7 0.01
Thu 10/08 07Z 0.65 2326  90  51   7 0.01
Thu 10/08 08Z 0.68 2328  92  65   7 0.01
Thu 10/08 09Z 0.65 2329  94  87   8 0.06
Thu 10/08 10Z 0.68 2330  92  80   8 0.01
Thu 10/08 11Z 0.76 2431  93  56   8 0.01
Thu 10/08 12Z 0.87 2433  90  36   7 0.01
Thu 10/08 13Z 1.08 2533  88  22   6 0.02
Thu 10/08 14Z 1.26 2630  90  21   4 0.02
Thu 10/08 15Z 2.00 2629  93  22   3 0.01
Thu 10/08 16Z 2.22 2630  93  35   3 0.01
Thu 10/08 17Z 5.38 2730  90  32   3 0.02
Thu 10/08 18Z 9.50 2728  85  30   3 0.00
Thu 10/08 19Z 7.07 2726  86  39   3 0.00
Thu 10/08 20Z 5.00 2626  86  39   3 0.01
Thu 10/08 21Z 3.36 2626  87  35   3 0.00
Thu 10/08 22Z 1.86 2726  86  40   2 0.00
Thu 10/08 23Z 1.67 2726  90  54   2 0.01
Fri 10/09 00Z 1.25 2725  90  59   2 0.01
Fri 10/09 01Z 1.07 2725  91  56   2 0.01
Fri 10/09 02Z 0.99 2825  89  44   2 0.01
Fri 10/09 03Z 0.91 2726  88  53   2 0.00
Fri 10/09 04Z 0.90 2727  90  44   2 0.00
Fri 10/09 05Z 1.01 2731  92  47   1 0.00
Fri 10/09 06Z 1.08 2731  91  32   1 0.00
Fri 10/09 07Z 1.21 2732  90  33   1 0.00
Fri 10/09 08Z 1.22 2732  91  30   1 0.00
Fri 10/09 09Z 1.13 2831  91  22   1 0.00
Fri 10/09 10Z 1.13 2831  88  20   0 0.00
Fri 10/09 11Z 1.08 2831  87  29   0 0.00
Fri 10/09 12Z 1.07 2829  89  37   0 0.00
Fri 10/09 13Z 1.08 2827  92  40   0 0.00
Fri 10/09 14Z 1.19 2725  94  36   0 0.00
Fri 10/09 15Z 1.25 2722  96  34   0 0.00
Fri 10/09 16Z 1.34 2722  96  34   0 0.01
Fri 10/09 17Z 1.49 2722  96  32   0 0.01

Run total areal avg QPF for the Central_Greens is: 0.27 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