Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261027_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)
=== ===== === ==== ==== === === === ====
Tue 10/27 00Z 0.46 3120  90  84   3 0.00
Tue 10/27 01Z 0.38 3223  91  69   2 0.00
Tue 10/27 02Z 0.32 3225  90  49   1 0.00
Tue 10/27 03Z 0.25 3326  85  31   0 0.00
Tue 10/27 04Z 0.15 3324  81  24   0 0.00
Tue 10/27 05Z 0.09 3422  79  16  -1 0.00
Tue 10/27 06Z 0.07 3421  78  11  -2 0.00
Tue 10/27 07Z 0.06 3421  74   8  -1 0.00
Tue 10/27 08Z 0.05 3421  69   4  -1 0.00
Tue 10/27 09Z 0.03 3421  64   1  -1 0.00
Tue 10/27 10Z 0.02 3520  59   1   0 0.00
Tue 10/27 11Z 0.02 3519  54   3   0 0.00
Tue 10/27 12Z 0.02 3518  50   5   0 0.00
Tue 10/27 13Z 0.01 3417  47   6   0 0.00
Tue 10/27 14Z 0.02 3415  43   7   0 0.00
Tue 10/27 15Z 0.04 3413  41   7   0 0.00
Tue 10/27 16Z 0.05 3312  40   7   0 0.00
Tue 10/27 17Z 0.06 3311  39   7   0 0.00
Tue 10/27 18Z 0.08 3310  39   7   0 0.00
Tue 10/27 19Z 0.10 3211  35   6   0 0.00
Tue 10/27 20Z 0.12 3213  30   6   0 0.00
Tue 10/27 21Z 0.12 3214  30   5   0 0.00
Tue 10/27 22Z 0.14 3215  35   5   0 0.00
Tue 10/27 23Z 0.12 3214  38   5   0 0.00
Wed 10/28 00Z 0.10 3314  38   5   1 0.00
Wed 10/28 01Z 0.06 3312  33   4   1 0.00
Wed 10/28 02Z 0.07 3311  29   4   2 0.00
Wed 10/28 03Z 0.07 3209  26   4   2 0.00
Wed 10/28 04Z 0.07 3208  24   3   1 0.00
Wed 10/28 05Z 0.07 3106  22   3   1 0.00
Wed 10/28 06Z 0.08 3005  20   3   1 0.00
Wed 10/28 07Z 0.08 2904  18   3   2 0.00
Wed 10/28 08Z 0.08 2704  16   3   2 0.00
Wed 10/28 09Z 0.10 2605  16   6   2 0.00
Wed 10/28 10Z 0.14 2606  17  21   2 0.00
Wed 10/28 11Z 0.18 2508  17  51   2 0.00
Wed 10/28 12Z 0.20 2609  16  90   2 0.00
Wed 10/28 13Z 0.21 2610  16  85   3 0.00
Wed 10/28 14Z 0.22 2611  18  91   4 0.00
Wed 10/28 15Z 0.21 2610  27  86   4 0.00
Wed 10/28 16Z 0.22 2611  31  81   4 0.00
Wed 10/28 17Z 0.25 2612  33  80   4 0.00
Wed 10/28 18Z 0.25 2612  35  83   4 0.00
Wed 10/28 19Z 0.25 2611  32  78   5 0.00
Wed 10/28 20Z 0.26 2612  30  83   6 0.00
Wed 10/28 21Z 0.27 2612  29  87   7 0.00
Wed 10/28 22Z 0.29 2614  33  86   7 0.00
Wed 10/28 23Z 0.31 2615  40  77   7 0.00
Thu 10/29 00Z 0.33 2615  56  73   7 0.00
Thu 10/29 01Z 0.33 2615  65  61   7 0.00
Thu 10/29 02Z 0.34 2615  72  46   7 0.00
Thu 10/29 03Z 0.35 2615  76  37   7 0.00
Thu 10/29 04Z 0.35 2514  79  40   7 0.00
Thu 10/29 05Z 0.36 2515  83  38   7 0.00
Thu 10/29 06Z 0.37 2515  85  36   7 0.00
Thu 10/29 07Z 0.36 2515  86  39   7 0.00
Thu 10/29 08Z 0.37 2415  88  33   7 0.00
Thu 10/29 09Z 0.40 2416  88  35   7 0.00
Thu 10/29 10Z 0.42 2417  88  43   7 0.00
Thu 10/29 11Z 0.43 2517  86  49   7 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