NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260806_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 08/06 00Z 0.32 2409  80  42  16 0.00
Thu 08/06 01Z 0.38 2410  77  55  16 0.00
Thu 08/06 02Z 0.41 2411  77  62  16 0.00
Thu 08/06 03Z 0.43 2412  77  61  16 0.00
Thu 08/06 04Z 0.41 2312  76  54  16 0.00
Thu 08/06 05Z 0.41 2312  76  48  16 0.00
Thu 08/06 06Z 0.39 2411  76  57  16 0.00
Thu 08/06 07Z 0.37 2411  75  65  16 0.00
Thu 08/06 08Z 0.36 2411  76  72  16 0.00
Thu 08/06 09Z 0.29 2409  73  77  16 0.00
Thu 08/06 10Z 0.25 2408  73  81  16 0.00
Thu 08/06 11Z 0.21 2407  74  80  16 0.00
Thu 08/06 12Z 0.17 2306  75  78  16 0.00
Thu 08/06 13Z 0.16 2106  76  76  16 0.00
Thu 08/06 14Z 0.17 2206  79  78  16 0.00
Thu 08/06 15Z 0.20 2305  82  79  16 0.00
Thu 08/06 16Z 0.24 2205  82  81  16 0.00
Thu 08/06 17Z 0.39 2205  81  82  16 0.00
Thu 08/06 18Z 0.80 2205  81  83  17 0.00
Thu 08/06 19Z 0.85 2205  82  80  17 0.00
Thu 08/06 20Z 0.81 2205  85  80  17 0.00
Thu 08/06 21Z 0.66 2206  88  82  17 0.02
Thu 08/06 22Z 0.43 2205  89  84  17 0.17
Thu 08/06 23Z 0.28 2604  88  79  17 0.25
Fri 08/07 00Z 0.15 3006  88  81  17 0.18
Fri 08/07 01Z 0.20 2705  86  72  17 0.12
Fri 08/07 02Z 0.22 2707  85  77  17 0.00
Fri 08/07 03Z 0.23 2808  84  73  17 0.00
Fri 08/07 04Z 0.22 2908  84  62  17 0.00
Fri 08/07 05Z 0.21 2908  86  51  17 0.00
Fri 08/07 06Z 0.22 2908  89  47  17 0.00
Fri 08/07 07Z 0.21 2908  91  54  17 0.00
Fri 08/07 08Z 0.19 3008  92  60  17 0.00
Fri 08/07 09Z 0.14 3107  92  50  16 0.00
Fri 08/07 10Z 0.15 3006  92  43  16 0.00
Fri 08/07 11Z 0.15 2905  89  33  16 0.00
Fri 08/07 12Z 0.13 2905  86  36  16 0.00
Fri 08/07 13Z 0.13 2905  85  37  16 0.00
Fri 08/07 14Z 0.13 2904  84  34  16 0.00
Fri 08/07 15Z 0.15 2804  83  34  15 0.00
Fri 08/07 16Z 0.15 2603  82  37  16 0.00
Fri 08/07 17Z 0.21 2604  80  43  16 0.00
Fri 08/07 18Z 0.35 2603  76  46  16 0.00
Fri 08/07 19Z 0.60 2704  75  45  16 0.00
Fri 08/07 20Z 0.52 2805  73  46  16 0.00
Fri 08/07 21Z 0.27 2803  72  50  17 0.00
Fri 08/07 22Z 0.19 2703  73  59  17 0.00
Fri 08/07 23Z 0.16 2703  74  54  17 0.00
Sat 08/08 00Z 0.18 2603  76  56  16 0.00
Sat 08/08 01Z 0.19 2404  80  53  16 0.00
Sat 08/08 02Z 0.25 2405  82  72  16 0.00
Sat 08/08 03Z 0.27 2406  85  78  16 0.00
Sat 08/08 04Z 0.31 2407  87  81  16 0.00
Sat 08/08 05Z 0.32 2308  88  79  16 0.00
Sat 08/08 06Z 0.34 2309  87  76  16 0.00
Sat 08/08 07Z 0.36 2311  87  76  16 0.00
Sat 08/08 08Z 0.38 2311  89  79  16 0.00
Sat 08/08 09Z 0.31 2210  88  80  16 0.00
Sat 08/08 10Z 0.32 2211  90  83  16 0.00
Sat 08/08 11Z 0.34 2212  90  82  16 0.00

Run total areal avg QPF for the Central_Greens is: 0.74 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