NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260705_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)
=== ===== === ==== ==== === === === ====
Sun 07/05 12Z 0.08 0601  71  16  12 0.00
Sun 07/05 13Z 0.06 0600  73  12  12 0.00
Sun 07/05 14Z 0.08 1400  77  10  12 0.00
Sun 07/05 15Z 0.19 1600  81  12  12 0.00
Sun 07/05 16Z 0.23 2900  82  17  12 0.01
Sun 07/05 17Z 0.20 3000  83  18  13 0.01
Sun 07/05 18Z 0.20 3001  81  13  13 0.01
Sun 07/05 19Z 0.18 3201  80  12  13 0.00
Sun 07/05 20Z 0.14 3502  79  15  13 0.01
Sun 07/05 21Z 0.22 0102  79  18  14 0.00
Sun 07/05 22Z 0.25 0302  79  22  14 0.00
Sun 07/05 23Z 0.29 0603  80  28  13 0.01
Mon 07/06 00Z 0.34 0804  80  34  13 0.01
Mon 07/06 01Z 0.43 0806  78  32  13 0.00
Mon 07/06 02Z 0.52 0808  78  19  13 0.00
Mon 07/06 03Z 0.45 0909  82  11  13 0.00
Mon 07/06 04Z 0.41 1009  86   9  13 0.00
Mon 07/06 05Z 0.38 1111  87  11  13 0.00
Mon 07/06 06Z 0.33 1212  86  17  13 0.00
Mon 07/06 07Z 0.22 1413  90  28  13 0.00
Mon 07/06 08Z 0.19 1414  91  41  12 0.02
Mon 07/06 09Z 0.17 1515  88  50  12 0.02
Mon 07/06 10Z 0.18 1517  86  62  12 0.02
Mon 07/06 11Z 0.22 1417  78  71  12 0.02
Mon 07/06 12Z 0.27 1418  78  74  12 0.00
Mon 07/06 13Z 0.29 1319  79  73  12 0.01
Mon 07/06 14Z 0.30 1320  74  76  12 0.01
Mon 07/06 15Z 0.33 1321  70  80  11 0.00
Mon 07/06 16Z 0.36 1320  72  85  11 0.01
Mon 07/06 17Z 0.39 1320  77  85  11 0.00
Mon 07/06 18Z 0.42 1219  77  86  11 0.00
Mon 07/06 19Z 0.40 1218  78  88  11 0.00
Mon 07/06 20Z 0.42 1218  82  85  12 0.00
Mon 07/06 21Z 0.44 1219  82  78  12 0.00
Mon 07/06 22Z 0.45 1219  80  76  12 0.00
Mon 07/06 23Z 0.41 1219  77  71  12 0.00
Tue 07/07 00Z 0.39 1221  78  67  13 0.00
Tue 07/07 01Z 0.35 1221  77  63  13 0.00
Tue 07/07 02Z 0.35 1221  75  56  13 0.00
Tue 07/07 03Z 0.37 1221  75  55  13 0.00
Tue 07/07 04Z 0.36 1222  74  56  13 0.00
Tue 07/07 05Z 0.35 1222  75  58  13 0.00
Tue 07/07 06Z 0.35 1222  78  58  13 0.00
Tue 07/07 07Z 0.33 1221  81  60  13 0.00
Tue 07/07 08Z 0.33 1120  83  63  13 0.00
Tue 07/07 09Z 0.32 1119  84  71  13 0.00
Tue 07/07 10Z 0.33 1119  84  73  13 0.00
Tue 07/07 11Z 0.34 1018  83  74  13 0.00
Tue 07/07 12Z 0.34 1018  81  73  13 0.00
Tue 07/07 13Z 0.36 1018  79  72  13 0.00
Tue 07/07 14Z 0.39 0918  77  68  13 0.00
Tue 07/07 15Z 0.43 0916  78  69  12 0.00
Tue 07/07 16Z 0.51 0916  77  65  12 0.00
Tue 07/07 17Z 0.72 0914  79  65  11 0.00
Tue 07/07 18Z 1.40 0911  81  65  11 0.00
Tue 07/07 19Z 1.64 0910  80  56  11 0.00
Tue 07/07 20Z 2.13 0909  81  54  11 0.00
Tue 07/07 21Z 1.46 0808  81  47  11 0.00
Tue 07/07 22Z 0.70 0806  81  43  11 0.00
Tue 07/07 23Z 0.40 0805  82  32  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.17 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