Subject: NAM3 EXPERIMENTAL Froude Number for the Northern_Greens

Model run: BTV_GRID_D2D_NAM3_20260627_1200
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)
=== ===== === ==== ==== === === === ====
Sat 06/27 12Z 0.29 3008  95  57   9 0.00
Sat 06/27 13Z 0.20 3006  93  50   9 0.00
Sat 06/27 14Z 0.17 3005  90  50  10 0.00
Sat 06/27 15Z 0.17 3005  89  52  10 0.00
Sat 06/27 16Z 0.17 3004  88  53  10 0.00
Sat 06/27 17Z 0.18 3103  87  53  10 0.00
Sat 06/27 18Z 0.21 3103  85  54  10 0.01
Sat 06/27 19Z 0.18 3102  84  53  11 0.01
Sat 06/27 20Z 0.16 3002  83  56  11 0.00
Sat 06/27 21Z 0.20 3102  83  63  11 0.00
Sat 06/27 22Z 0.17 3103  81  69  11 0.00
Sat 06/27 23Z 0.07 3401  79  66  11 0.00
Sun 06/28 00Z 0.06 3501  79  66  11 0.00
Sun 06/28 01Z 0.05 3300  78  62  11 0.00
Sun 06/28 02Z 0.04 3301  77  57  11 0.00
Sun 06/28 03Z 0.05 3401  75  58  11 0.00
Sun 06/28 04Z 0.05 3401  75  58  11 0.00
Sun 06/28 05Z 0.08 3302  75  61  11 0.00
Sun 06/28 06Z 0.10 3404  71  58  11 0.00
Sun 06/28 07Z 0.09 3505  67  53  11 0.00
Sun 06/28 08Z 0.11 3507  64  47  11 0.00
Sun 06/28 09Z 0.08 0008  67  35  11 0.00
Sun 06/28 10Z 0.09 0009  69  26  11 0.00
Sun 06/28 11Z 0.10 0009  68  22  11 0.00
Sun 06/28 12Z 0.10 0009  68  20  11 0.00
Sun 06/28 13Z 0.09 0008  69  20  11 0.00
Sun 06/28 14Z 0.12 3507  71  20  11 0.00
Sun 06/28 15Z 0.17 3505  76  20  10 0.00
Sun 06/28 16Z 0.27 3404  80  19  11 0.00
Sun 06/28 17Z 0.38 3505  82  16  11 0.00
Sun 06/28 18Z 0.52 3405  83  15  11 0.00
Sun 06/28 19Z 0.58 3305  83  13  11 0.00
Sun 06/28 20Z 0.59 3306  79  11  12 0.00
Sun 06/28 21Z 0.44 3306  76   9  12 0.00
Sun 06/28 22Z 0.24 3306  74   8  12 0.00
Sun 06/28 23Z 0.19 3407  71   8  12 0.00
Mon 06/29 00Z 0.17 3508  69  11  12 0.00
Mon 06/29 01Z 0.14 3509  69  13  12 0.00
Mon 06/29 02Z 0.08 0010  69  14  12 0.00
Mon 06/29 03Z 0.06 0009  68  14  12 0.00
Mon 06/29 04Z 0.05 0108  66  16  12 0.00
Mon 06/29 05Z 0.06 0007  63  19  12 0.00
Mon 06/29 06Z 0.07 0007  60  17  12 0.00
Mon 06/29 07Z 0.07 0008  61  18  12 0.00
Mon 06/29 08Z 0.07 0009  64  21  11 0.00
Mon 06/29 09Z 0.07 0110  69  22  11 0.00
Mon 06/29 10Z 0.05 0109  70  20  11 0.00
Mon 06/29 11Z 0.06 0108  72  18  11 0.00
Mon 06/29 12Z 0.09 0008  78  19  11 0.00
Mon 06/29 13Z 0.13 3507  83  23  11 0.00
Mon 06/29 14Z 0.21 3405  86  24  11 0.00
Mon 06/29 15Z 0.30 3304  87  27  11 0.00
Mon 06/29 16Z 0.32 3203  87  29  11 0.01
Mon 06/29 17Z 0.32 3203  86  27  12 0.02
Mon 06/29 18Z 0.43 3103  84  23  12 0.01
Mon 06/29 19Z 0.59 3003  82  19  12 0.01
Mon 06/29 20Z 0.40 2902  80  16  12 0.00
Mon 06/29 21Z 0.56 2803  79  14  13 0.00
Mon 06/29 22Z 0.34 2703  76  11  13 0.00
Mon 06/29 23Z 0.24 2604  70   8  13 0.00

Run total areal avg QPF for the Northern_Greens is: 0.07 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