NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260805_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)
=== ===== === ==== ==== === === === ====
Wed 08/05 12Z 0.29 2609  73  34  15 0.00
Wed 08/05 13Z 0.27 2708  71  34  15 0.00
Wed 08/05 14Z 0.22 2606  67  33  15 0.00
Wed 08/05 15Z 0.29 2505  66  30  15 0.00
Wed 08/05 16Z 0.44 2205  64  25  15 0.00
Wed 08/05 17Z 0.78 2206  63  17  15 0.00
Wed 08/05 18Z 1.12 2308  62   8  15 0.00
Wed 08/05 19Z 0.94 2208  61   2  16 0.00
Wed 08/05 20Z 0.84 2209  59   3  16 0.00
Wed 08/05 21Z 0.67 2209  61   8  16 0.00
Wed 08/05 22Z 0.67 2310  66  16  16 0.00
Wed 08/05 23Z 0.71 2311  74  23  15 0.00
Thu 08/06 00Z 0.66 2312  78  29  15 0.00
Thu 08/06 01Z 0.67 2312  79  38  15 0.00
Thu 08/06 02Z 0.64 2313  80  38  15 0.00
Thu 08/06 03Z 0.64 2314  83  31  15 0.00
Thu 08/06 04Z 0.54 2315  85  31  16 0.00
Thu 08/06 05Z 0.51 2315  87  36  16 0.00
Thu 08/06 06Z 0.49 2316  88  57  16 0.01
Thu 08/06 07Z 0.45 2415  87  74  16 0.01
Thu 08/06 08Z 0.41 2414  88  68  16 0.01
Thu 08/06 09Z 0.37 2412  87  57  16 0.00
Thu 08/06 10Z 0.33 2411  87  52  16 0.00
Thu 08/06 11Z 0.26 2309  86  58  16 0.00
Thu 08/06 12Z 0.21 2208  85  74  16 0.00
Thu 08/06 13Z 0.19 2207  86  79  16 0.00
Thu 08/06 14Z 0.21 2207  88  82  16 0.00
Thu 08/06 15Z 0.25 2306  90  76  16 0.00
Thu 08/06 16Z 0.31 2306  90  71  16 0.00
Thu 08/06 17Z 0.42 2207  90  72  16 0.00
Thu 08/06 18Z 0.58 2308  89  68  16 0.00
Thu 08/06 19Z 0.63 2207  87  73  17 0.00
Thu 08/06 20Z 0.55 2307  85  73  17 0.00
Thu 08/06 21Z 0.49 2308  85  73  17 0.00
Thu 08/06 22Z 0.34 2209  85  68  18 0.00
Thu 08/06 23Z 0.47 2311  90  73  17 0.00
Fri 08/07 00Z 0.52 2313  96  73  17 0.09
Fri 08/07 01Z 0.46 2413  90  64  17 0.13
Fri 08/07 02Z 0.48 2614  86  39  17 0.02
Fri 08/07 03Z 0.47 2716  86  44  18 0.01
Fri 08/07 04Z 0.46 2717  83  49  18 0.01
Fri 08/07 05Z 0.46 2717  74  61  18 0.00
Fri 08/07 06Z 0.47 2717  70  74  17 0.00
Fri 08/07 07Z 0.46 2817  69  69  17 0.00
Fri 08/07 08Z 0.42 2917  71  66  17 0.00
Fri 08/07 09Z 0.34 2915  72  60  17 0.00
Fri 08/07 10Z 0.30 3014  75  67  17 0.00
Fri 08/07 11Z 0.27 3013  79  69  16 0.00
Fri 08/07 12Z 0.25 3113  82  76  16 0.00
Fri 08/07 13Z 0.22 3113  84  79  16 0.00
Fri 08/07 14Z 0.19 3111  85  78  16 0.00
Fri 08/07 15Z 0.18 3109  83  79  16 0.00
Fri 08/07 16Z 0.18 3107  83  79  16 0.00
Fri 08/07 17Z 0.24 3005  83  77  16 0.00
Fri 08/07 18Z 0.43 2905  83  79  16 0.00
Fri 08/07 19Z 0.64 2705  82  81  16 0.00
Fri 08/07 20Z 0.49 2705  81  74  16 0.00
Fri 08/07 21Z 0.34 2605  80  71  17 0.00
Fri 08/07 22Z 0.31 2506  83  71  17 0.00
Fri 08/07 23Z 0.30 2407  82  72  17 0.00

Run total areal avg QPF for the Central_Greens is: 0.29 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