NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260907_0000
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)
=== ===== === ==== ==== === === === ====
Mon 09/07 00Z 0.08 3516  77   7   7 0.00
Mon 09/07 01Z 0.14 3417  73   4   7 0.00
Mon 09/07 02Z 0.19 3318  76   9   7 0.00
Mon 09/07 03Z 0.20 3319  81  15   8 0.00
Mon 09/07 04Z 0.26 3320  82  14   8 0.00
Mon 09/07 05Z 0.27 3321  82  14   8 0.00
Mon 09/07 06Z 0.20 3321  81  15   8 0.00
Mon 09/07 07Z 0.12 3420  79  17   8 0.00
Mon 09/07 08Z 0.11 3420  77  22   8 0.00
Mon 09/07 09Z 0.13 3321  74  27   8 0.00
Mon 09/07 10Z 0.14 3322  72  29   8 0.00
Mon 09/07 11Z 0.15 3424  67  26   8 0.00
Mon 09/07 12Z 0.14 3425  65  24   8 0.00
Mon 09/07 13Z 0.18 3425  66  22   8 0.00
Mon 09/07 14Z 0.13 3424  64  19   8 0.00
Mon 09/07 15Z 0.14 3424  64  13   8 0.00
Mon 09/07 16Z 0.31 3420  65  10   8 0.00
Mon 09/07 17Z 0.80 3417  67   9   9 0.00
Mon 09/07 18Z 1.76 3318  66   7   9 0.00
Mon 09/07 19Z 2.48 3319  65   5   9 0.00
Mon 09/07 20Z 1.91 3315  64   3   9 0.00
Mon 09/07 21Z 2.01 3214  67   4   9 0.00
Mon 09/07 22Z 0.88 3215  69   5   9 0.00
Mon 09/07 23Z 1.03 3117  71   7   9 0.00
Tue 09/08 00Z 1.15 3119  75  13   9 0.00
Tue 09/08 01Z 1.04 3120  78  24   9 0.00
Tue 09/08 02Z 0.67 3221  78  38   9 0.00
Tue 09/08 03Z 0.48 3221  79  50   9 0.00
Tue 09/08 04Z 0.41 3322  79  56   9 0.00
Tue 09/08 05Z 0.36 3322  79  55   9 0.00
Tue 09/08 06Z 0.30 3319  79  51   9 0.00
Tue 09/08 07Z 0.29 3217  79  53  10 0.00
Tue 09/08 08Z 0.35 3218  80  62  10 0.00
Tue 09/08 09Z 0.40 3118  81  69  10 0.00
Tue 09/08 10Z 0.45 3120  84  79  10 0.00
Tue 09/08 11Z 0.45 3121  88  77   9 0.00
Tue 09/08 12Z 0.45 3121  89  83  10 0.00
Tue 09/08 13Z 0.40 3120  90  87  10 0.00
Tue 09/08 14Z 0.32 3118  92  87  10 0.00
Tue 09/08 15Z 0.28 3117  90  89  10 0.00
Tue 09/08 16Z 0.25 3216  89  84  10 0.00
Tue 09/08 17Z 0.27 3115  89  91  10 0.00
Tue 09/08 18Z 0.26 3214  90  89  10 0.00
Tue 09/08 19Z 0.21 3213  86  87  10 0.00
Tue 09/08 20Z 0.19 3212  83  77  10 0.00
Tue 09/08 21Z 0.18 3210  82  80  11 0.00
Tue 09/08 22Z 0.20 3109  83  87  11 0.00
Tue 09/08 23Z 0.20 3108  85  80  11 0.00
Wed 09/09 00Z 0.24 2908  88  81  11 0.00
Wed 09/09 01Z 0.26 2908  91  80  11 0.00
Wed 09/09 02Z 0.26 2807  92  81  11 0.00
Wed 09/09 03Z 0.28 2607  94  76  11 0.00
Wed 09/09 04Z 0.27 2407  96  71  11 0.00
Wed 09/09 05Z 0.25 2208  97  72  11 0.00
Wed 09/09 06Z 0.26 2110  97  74  11 0.00
Wed 09/09 07Z 0.28 2111  96  73  11 0.00
Wed 09/09 08Z 0.35 2114  95  73  11 0.00
Wed 09/09 09Z 0.40 2116  92  69  11 0.00
Wed 09/09 10Z 0.52 2219  91  62  11 0.00
Wed 09/09 11Z 0.45 2119  83  60  11 0.00

Run total areal avg QPF for the Central_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