NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260730_0600
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)
=== ===== === ==== ==== === === === ====
Thu 07/30 06Z 0.59 1122  98  93  11 0.00
Thu 07/30 07Z 0.57 1020  97  93  11 0.01
Thu 07/30 08Z 0.49 1017  95  92  12 0.01
Thu 07/30 09Z 0.41 0914  93  90  12 0.00
Thu 07/30 10Z 0.36 0812  91  88  12 0.00
Thu 07/30 11Z 0.31 0611  90  88  12 0.00
Thu 07/30 12Z 0.27 0411  90  83  12 0.00
Thu 07/30 13Z 0.19 0211  88  80  12 0.00
Thu 07/30 14Z 0.18 0112  87  79  11 0.00
Thu 07/30 15Z 0.25 0111  89  79  11 0.00
Thu 07/30 16Z 0.45 0110  91  78  11 0.00
Thu 07/30 17Z 0.18 3508  92  78  12 0.00
Thu 07/30 18Z 0.17 3508  91  72  12 0.00
Thu 07/30 19Z 0.13 3509  90  70  12 0.01
Thu 07/30 20Z 0.09 3410  89  65  13 0.02
Thu 07/30 21Z 0.08 3511  88  66  13 0.00
Thu 07/30 22Z 0.06 3511  88  67  13 0.00
Thu 07/30 23Z 0.09 3513  88  76  13 0.00
Fri 07/31 00Z 0.10 0012  86  80  13 0.00
Fri 07/31 01Z 0.04 3513  84  82  13 0.00
Fri 07/31 02Z 0.03 3512  85  84  13 0.00
Fri 07/31 03Z 0.03 3412  88  90  13 0.01
Fri 07/31 04Z 0.04 3412  88  90  13 0.00
Fri 07/31 05Z 0.08 3312  89  91  12 0.00
Fri 07/31 06Z 0.16 3212  89  85  12 0.00
Fri 07/31 07Z 0.25 3113  92  83  12 0.01
Fri 07/31 08Z 0.25 3113  94  82  12 0.01
Fri 07/31 09Z 0.25 3114  95  78  12 0.01
Fri 07/31 10Z 0.21 3215  95  74  12 0.01
Fri 07/31 11Z 0.12 3316  95  69  12 0.01
Fri 07/31 12Z 0.07 3414  95  55  11 0.00
Fri 07/31 13Z 0.10 3313  95  50  11 0.00
Fri 07/31 14Z 0.05 3411  94  46  11 0.00
Fri 07/31 15Z 0.12 3310  95  50  11 0.00
Fri 07/31 16Z 0.15 3209  93  46  12 0.00
Fri 07/31 17Z 0.25 3109  93  45  12 0.00
Fri 07/31 18Z 0.35 3110  92  52  12 0.00
Fri 07/31 19Z 0.38 3010  91  61  12 0.03
Fri 07/31 20Z 0.39 3011  90  59  13 0.01
Fri 07/31 21Z 0.37 3112  86  58  13 0.00
Fri 07/31 22Z 0.32 3110  89  64  13 0.00
Fri 07/31 23Z 0.23 3109  92  79  13 0.01
Sat 08/01 00Z 0.22 3110  93  83  13 0.06
Sat 08/01 01Z 0.15 3310  90  72  13 0.01
Sat 08/01 02Z 0.14 3311  88  63  13 0.00
Sat 08/01 03Z 0.11 3310  86  49  13 0.00
Sat 08/01 04Z 0.13 3309  84  42  12 0.00
Sat 08/01 05Z 0.13 3308  82  38  13 0.00
Sat 08/01 06Z 0.08 3306  80  35  13 0.00
Sat 08/01 07Z 0.09 3306  81  36  13 0.00
Sat 08/01 08Z 0.19 3005  81  34  12 0.00
Sat 08/01 09Z 0.20 2905  81  27  12 0.00
Sat 08/01 10Z 0.17 2804  79  16  13 0.00
Sat 08/01 11Z 0.21 2504  78  12  13 0.00
Sat 08/01 12Z 0.24 2406  77  13  13 0.00
Sat 08/01 13Z 0.24 2306  75  14  13 0.00
Sat 08/01 14Z 0.24 2206  75  13  13 0.00
Sat 08/01 15Z 0.44 2205  75  14  13 0.00
Sat 08/01 16Z 0.44 2104  74  15  13 0.00
Sat 08/01 17Z 0.38 2003  73  16  14 0.00

Run total areal avg QPF for the Central_Greens is: 0.23 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