NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261001_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 10/01 00Z 0.26 2609  91  43  11 0.00
Thu 10/01 01Z 0.28 2710  87  38  11 0.00
Thu 10/01 02Z 0.30 2610  87  39  11 0.00
Thu 10/01 03Z 0.34 2611  92  50  11 0.00
Thu 10/01 04Z 0.37 2612  91  53  11 0.00
Thu 10/01 05Z 0.40 2713  88  42  11 0.00
Thu 10/01 06Z 0.37 2712  84  36  11 0.00
Thu 10/01 07Z 0.36 2611  87  40  11 0.00
Thu 10/01 08Z 0.38 2512  90  43  11 0.00
Thu 10/01 09Z 0.43 2513  93  56  11 0.00
Thu 10/01 10Z 0.45 2414  95  32  11 0.01
Thu 10/01 11Z 0.45 2315  95  28  11 0.01
Thu 10/01 12Z 0.47 2316  94  45  11 0.01
Thu 10/01 13Z 0.51 2318  94  71  11 0.01
Thu 10/01 14Z 0.54 2319  93  88  12 0.01
Thu 10/01 15Z 0.59 2320  93  92  12 0.01
Thu 10/01 16Z 0.64 2322  94  91  12 0.01
Thu 10/01 17Z 0.74 2323  91  84  12 0.00
Thu 10/01 18Z 0.79 2323  85  89  12 0.00
Thu 10/01 19Z 0.79 2424  94  96  13 0.01
Thu 10/01 20Z 0.75 2426  97  98  13 0.06
Thu 10/01 21Z 0.76 2527  95  96  14 0.06
Thu 10/01 22Z 0.78 2529  91  89  14 0.04
Thu 10/01 23Z 0.79 2529  91  90  15 0.02
Fri 10/02 00Z 0.82 2429  89  70  14 0.02
Fri 10/02 01Z 0.84 2430  90  59  15 0.01
Fri 10/02 02Z 0.88 2332  91  33  15 0.01
Fri 10/02 03Z 0.98 2337  95  43  15 0.02
Fri 10/02 04Z 1.05 2337  94  34  15 0.03
Fri 10/02 05Z 1.06 2338  93  59  15 0.01
Fri 10/02 06Z 1.10 2439  94  73  15 0.01
Fri 10/02 07Z 1.14 2439  93  73  15 0.01
Fri 10/02 08Z 1.12 2440  89  73  15 0.01
Fri 10/02 09Z 1.10 2439  91  73  15 0.01
Fri 10/02 10Z 1.11 2439  92  78  15 0.01
Fri 10/02 11Z 1.09 2437  94  75  15 0.03
Fri 10/02 12Z 1.05 2535  95  93  14 0.15
Fri 10/02 13Z 0.82 2726  98  95  13 0.14
Fri 10/02 14Z 0.68 2923  98  98  12 0.11
Fri 10/02 15Z 0.64 2921  97  95  11 0.07
Fri 10/02 16Z 0.62 2919  91  90  11 0.02
Fri 10/02 17Z 0.70 2819  88  87  11 0.00
Fri 10/02 18Z 0.75 2719  92  74  11 0.01
Fri 10/02 19Z 0.60 2819  94  68  11 0.03
Fri 10/02 20Z 0.51 2920  94  49  10 0.03
Fri 10/02 21Z 0.39 3021  91  40  10 0.02
Fri 10/02 22Z 0.35 3122  80   6   9 0.01
Fri 10/02 23Z 0.29 3122  71   2   8 0.00
Sat 10/03 00Z 0.29 3222  68   1   7 0.00
Sat 10/03 01Z 0.24 3323  62   1   6 0.00
Sat 10/03 02Z 0.20 3323  62   1   5 0.00
Sat 10/03 03Z 0.19 3322  74   1   5 0.00
Sat 10/03 04Z 0.22 3322  79   1   4 0.00
Sat 10/03 05Z 0.17 3321  78   1   4 0.00
Sat 10/03 06Z 0.08 3419  78   0   4 0.00
Sat 10/03 07Z 0.12 3419  77   1   3 0.00
Sat 10/03 08Z 0.16 3318  76   2   3 0.00
Sat 10/03 09Z 0.14 3318  72   1   3 0.00
Sat 10/03 10Z 0.12 3418  71   1   3 0.00
Sat 10/03 11Z 0.10 3417  72   1   3 0.00

Run total areal avg QPF for the Central_Greens is: 1.03 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