NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260604_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)
=== ===== === ==== ==== === === === ====
Thu 06/04 00Z 0.20 3106  50  45  13 0.00
Thu 06/04 01Z 0.27 3006  49  41  13 0.00
Thu 06/04 02Z 0.27 2906  50  38  13 0.00
Thu 06/04 03Z 0.27 2805  53  37  13 0.00
Thu 06/04 04Z 0.35 2706  57  36  13 0.00
Thu 06/04 05Z 0.32 2807  59  36  13 0.00
Thu 06/04 06Z 0.25 2806  58  37  13 0.00
Thu 06/04 07Z 0.22 2705  56  39  13 0.00
Thu 06/04 08Z 0.22 2605  55  39  13 0.00
Thu 06/04 09Z 0.25 2506  54  36  13 0.00
Thu 06/04 10Z 0.32 2408  55  35  13 0.00
Thu 06/04 11Z 0.42 2511  56  35  13 0.00
Thu 06/04 12Z 0.48 2612  50  30  13 0.00
Thu 06/04 13Z 0.55 2713  48  26  13 0.00
Thu 06/04 14Z 0.63 2713  45  25  12 0.00
Thu 06/04 15Z 0.85 2713  44  20  13 0.00
Thu 06/04 16Z 2.03 2711  44  17  13 0.00
Thu 06/04 17Z 2.96 2610  46  17  13 0.00
Thu 06/04 18Z 4.02 2611  50  15  13 0.00
Thu 06/04 19Z 8.74 2613  54  17  13 0.00
Thu 06/04 20Z 8.65 2614  52  20  13 0.00
Thu 06/04 21Z 5.96 2714  48  22  13 0.00
Thu 06/04 22Z 2.94 2716  45  22  13 0.00
Thu 06/04 23Z 1.77 2718  48  25  13 0.00
Fri 06/05 00Z 1.45 2820  49  27  13 0.00
Fri 06/05 01Z 1.18 2922  50  23  13 0.00
Fri 06/05 02Z 1.08 2922  54  14  12 0.00
Fri 06/05 03Z 0.88 2923  54  10  12 0.00
Fri 06/05 04Z 0.78 2924  58  11  12 0.00
Fri 06/05 05Z 0.71 3023  63  11  12 0.00
Fri 06/05 06Z 0.68 3023  67   9  12 0.00
Fri 06/05 07Z 0.69 3023  69   5  11 0.00
Fri 06/05 08Z 0.71 3022  68   1  11 0.00
Fri 06/05 09Z 0.68 2919  67   1  11 0.00
Fri 06/05 10Z 0.52 2917  56   3  11 0.00
Fri 06/05 11Z 0.34 3015  45   4  12 0.00
Fri 06/05 12Z 0.28 3115  48   4  12 0.00
Fri 06/05 13Z 0.26 3214  57   4  11 0.00
Fri 06/05 14Z 0.32 3213  62   7  11 0.00
Fri 06/05 15Z 0.88 3111  63  10  11 0.00
Fri 06/05 16Z 2.30 3010  62  10  11 0.00
Fri 06/05 17Z 3.67 2909  60   4  12 0.00
Fri 06/05 18Z 4.50 2809  60   3  12 0.00
Fri 06/05 19Z 5.71 2609  65   5  13 0.00
Fri 06/05 20Z 6.13 2510  69   6  13 0.00
Fri 06/05 21Z 5.75 2413  71  13  13 0.00
Fri 06/05 22Z 3.96 2515  72  22  13 0.00
Fri 06/05 23Z 1.24 2516  69  12  13 0.00
Sat 06/06 00Z 1.82 2518  68  12  13 0.00
Sat 06/06 01Z 2.14 2620  71  11  13 0.00
Sat 06/06 02Z 2.03 2621  74  15  13 0.00
Sat 06/06 03Z 1.62 2621  76  19  13 0.00
Sat 06/06 04Z 1.39 2721  78  20  13 0.00
Sat 06/06 05Z 1.29 2622  82  25  12 0.00
Sat 06/06 06Z 1.16 2623  83  26  12 0.00
Sat 06/06 07Z 1.01 2623  86  32  12 0.00
Sat 06/06 08Z 0.91 2622  87  31  12 0.01
Sat 06/06 09Z 0.83 2622  89  26  12 0.00
Sat 06/06 10Z 0.77 2621  90  58  12 0.01
Sat 06/06 11Z 0.71 2619  89  60  12 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