NAM3 EXPERIMENTAL Froude Number for the Northern Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Northern_Greens

Model run: BTV_GRID_D2D_NAM3_20240425_0600
Using the MB925 to MB850 layer.
Assumes Northern_Greens are orthogonal to 290 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Northern_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Thu 04/25 06Z 0.54 3321  58  12 -10 0.00
Thu 04/25 07Z 0.61 3323  59  12 -10 0.00
Thu 04/25 08Z 0.55 3322  60  14  -9 0.00
Thu 04/25 09Z 0.46 3321  57  14  -9 0.00
Thu 04/25 10Z 0.38 3320  52  12  -8 0.00
Thu 04/25 11Z 0.35 3219  49  12  -8 0.00
Thu 04/25 12Z 0.32 3217  47  14  -8 0.00
Thu 04/25 13Z 0.30 3215  46  14  -7 0.00
Thu 04/25 14Z 0.31 3213  45  15  -7 0.00
Thu 04/25 15Z 0.35 3212  44  15  -7 0.00
Thu 04/25 16Z 0.59 3211  44  16  -8 0.00
Thu 04/25 17Z 1.07 3110  43  16  -7 0.00
Thu 04/25 18Z 2.18 3109  44  15  -7 0.00
Thu 04/25 19Z 2.53 3109  44  14  -7 0.00
Thu 04/25 20Z 2.21 3110  45  11  -6 0.00
Thu 04/25 21Z 1.40 3110  45  10  -6 0.00
Thu 04/25 22Z 0.87 3110  45   9  -6 0.00
Thu 04/25 23Z 0.55 3111  44  11  -5 0.00
Fri 04/26 00Z 0.49 3111  44  15  -5 0.00
Fri 04/26 01Z 0.47 3112  44  18  -5 0.00
Fri 04/26 02Z 0.48 3112  46  25  -5 0.00
Fri 04/26 03Z 0.52 3113  47  29  -5 0.00
Fri 04/26 04Z 0.55 3113  47  25  -5 0.00
Fri 04/26 05Z 0.57 3113  47  22  -5 0.00
Fri 04/26 06Z 0.57 3213  46  22  -5 0.00
Fri 04/26 07Z 0.48 3212  45  27  -5 0.00
Fri 04/26 08Z 0.38 3311  43  32  -5 0.00
Fri 04/26 09Z 0.28 3309  40  41  -5 0.00
Fri 04/26 10Z 0.20 3407  38  42  -5 0.00
Fri 04/26 11Z 0.16 3406  36  46  -5 0.00
Fri 04/26 12Z 0.14 3405  34  47  -5 0.00
Fri 04/26 13Z 0.12 3404  37  43  -5 0.00
Fri 04/26 14Z 0.18 3302  41  42  -4 0.00
Fri 04/26 15Z 0.35 2901  43  42  -4 0.00
Fri 04/26 16Z 0.51 2801  44  41  -3 0.00
Fri 04/26 17Z 0.92 2802  46  43  -3 0.00
Fri 04/26 18Z 1.09 2803  48  43  -2 0.00
Fri 04/26 19Z 1.04 3003  50  38  -2 0.00
Fri 04/26 20Z 0.65 3103  51  35  -1 0.00
Fri 04/26 21Z 0.37 2903  51  33  -1 0.00
Fri 04/26 22Z 0.20 2903  49  27   0 0.00
Fri 04/26 23Z 0.17 3003  46  21   0 0.00
Sat 04/27 00Z 0.19 3004  43  18   0 0.00
Sat 04/27 01Z 0.14 3203  42  15   0 0.00
Sat 04/27 02Z 0.08 3402  42  12   0 0.00
Sat 04/27 03Z 0.07 3201  42  11   0 0.00
Sat 04/27 04Z 0.02 0100  41   9   0 0.00
Sat 04/27 05Z 0.07 1402  41   9   0 0.00
Sat 04/27 06Z 0.06 1702  41  10   0 0.00
Sat 04/27 07Z 0.07 1603  41  12   0 0.00
Sat 04/27 08Z 0.11 1705  42  12   0 0.00
Sat 04/27 09Z 0.10 1807  41  10   0 0.00
Sat 04/27 10Z 0.08 2108  41   9   0 0.00
Sat 04/27 11Z 0.13 2110  41   8   0 0.00
Sat 04/27 12Z 0.15 2111  41   8   0 0.00
Sat 04/27 13Z 0.14 2111  39   7   0 0.00
Sat 04/27 14Z 0.05 2009  40   6   0 0.00
Sat 04/27 15Z 0.09 1909  45   6   0 0.00
Sat 04/27 16Z 0.12 1908  50   5   0 0.00
Sat 04/27 17Z 0.49 1908  52   5   1 0.00

Run total areal avg QPF for the Northern_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