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_1800
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 18Z 0.64 2901  69  23  13 0.00
Sun 07/05 19Z 0.38 3301  67  22  14 0.00
Sun 07/05 20Z 0.23 3502  68  21  14 0.00
Sun 07/05 21Z 0.44 0202  70  22  14 0.00
Sun 07/05 22Z 0.52 0402  73  18  14 0.00
Sun 07/05 23Z 0.48 0504  75  17  13 0.00
Mon 07/06 00Z 0.50 0706  75  17  13 0.00
Mon 07/06 01Z 0.58 0808  73  15  13 0.00
Mon 07/06 02Z 0.62 0909  72  11  13 0.00
Mon 07/06 03Z 0.56 1010  76   9  13 0.00
Mon 07/06 04Z 0.44 1110  82   8  13 0.00
Mon 07/06 05Z 0.31 1211  87  10  13 0.00
Mon 07/06 06Z 0.26 1312  88  15  13 0.00
Mon 07/06 07Z 0.28 1313  89  19  13 0.00
Mon 07/06 08Z 0.26 1313  90  21  13 0.00
Mon 07/06 09Z 0.28 1314  93  23  12 0.00
Mon 07/06 10Z 0.34 1317  93  19  12 0.01
Mon 07/06 11Z 0.36 1319  78  12  12 0.01
Mon 07/06 12Z 0.39 1220  72   8  12 0.00
Mon 07/06 13Z 0.36 1220  64  15  12 0.00
Mon 07/06 14Z 0.33 1320  64  17  12 0.00
Mon 07/06 15Z 0.32 1318  67  12  12 0.00
Mon 07/06 16Z 0.38 1217  68   7  11 0.00
Mon 07/06 17Z 0.47 1217  69   5  11 0.00
Mon 07/06 18Z 0.63 1217  71   7  11 0.00
Mon 07/06 19Z 1.26 1217  75  11  10 0.00
Mon 07/06 20Z 1.48 1217  76  14  10 0.00
Mon 07/06 21Z 1.11 1118  73  16  11 0.00
Mon 07/06 22Z 0.74 1118  73  23  11 0.00
Mon 07/06 23Z 0.64 1119  72  26  11 0.00
Tue 07/07 00Z 0.52 1221  64  35  12 0.00
Tue 07/07 01Z 0.44 1221  63  44  12 0.00
Tue 07/07 02Z 0.38 1220  64  56  13 0.00
Tue 07/07 03Z 0.35 1220  65  59  13 0.00
Tue 07/07 04Z 0.32 1220  68  62  13 0.00
Tue 07/07 05Z 0.29 1219  73  57  13 0.00
Tue 07/07 06Z 0.28 1217  76  50  13 0.00
Tue 07/07 07Z 0.28 1217  78  45  13 0.00
Tue 07/07 08Z 0.28 1217  80  41  13 0.00
Tue 07/07 09Z 0.28 1217  78  38  13 0.00
Tue 07/07 10Z 0.30 1117  73  40  13 0.00
Tue 07/07 11Z 0.34 1117  72  43  13 0.00
Tue 07/07 12Z 0.37 1019  72  41  13 0.00
Tue 07/07 13Z 0.38 1019  72  38  13 0.00
Tue 07/07 14Z 0.40 1019  75  38  13 0.00
Tue 07/07 15Z 0.40 1017  78  39  13 0.00
Tue 07/07 16Z 0.44 1015  81  40  12 0.00
Tue 07/07 17Z 0.49 1014  81  36  12 0.00
Tue 07/07 18Z 0.64 1013  81  36  11 0.00
Tue 07/07 19Z 1.01 0912  82  32  11 0.00
Tue 07/07 20Z 0.97 1012  83  28  11 0.00
Tue 07/07 21Z 0.59 1013  82  21  12 0.00
Tue 07/07 22Z 0.38 1012  83  16  12 0.00
Tue 07/07 23Z 0.33 0911  82  16  12 0.00
Wed 07/08 00Z 0.29 0911  79  17  13 0.00
Wed 07/08 01Z 0.29 0811  77  18  13 0.00
Wed 07/08 02Z 0.25 0810  75  20  13 0.00
Wed 07/08 03Z 0.20 0908  75  22  13 0.00
Wed 07/08 04Z 0.17 0806  75  21  13 0.00
Wed 07/08 05Z 0.13 0705  74  19  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.02 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