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_1800
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 18Z 2.09 2307  75  17  14 0.00
Wed 08/05 19Z 1.41 2308  72  14  15 0.00
Wed 08/05 20Z 0.86 2308  71  13  15 0.00
Wed 08/05 21Z 0.49 2208  68  14  16 0.00
Wed 08/05 22Z 0.46 2208  69  16  16 0.00
Wed 08/05 23Z 0.37 2209  73  17  16 0.00
Thu 08/06 00Z 0.38 2210  75  14  16 0.00
Thu 08/06 01Z 0.39 2310  75  12  16 0.00
Thu 08/06 02Z 0.42 2311  75  14  16 0.00
Thu 08/06 03Z 0.44 2312  76  20  16 0.00
Thu 08/06 04Z 0.47 2314  81  32  16 0.00
Thu 08/06 05Z 0.51 2415  83  43  16 0.00
Thu 08/06 06Z 0.48 2414  85  50  16 0.00
Thu 08/06 07Z 0.46 2514  87  51  16 0.00
Thu 08/06 08Z 0.36 2511  86  47  16 0.00
Thu 08/06 09Z 0.27 2509  83  38  16 0.00
Thu 08/06 10Z 0.20 2507  80  39  17 0.00
Thu 08/06 11Z 0.15 2405  78  45  17 0.00
Thu 08/06 12Z 0.14 2206  78  51  17 0.00
Thu 08/06 13Z 0.13 2206  80  52  16 0.00
Thu 08/06 14Z 0.13 2205  83  50  16 0.00
Thu 08/06 15Z 0.13 2104  86  51  16 0.00
Thu 08/06 16Z 0.15 2104  87  51  16 0.00
Thu 08/06 17Z 0.17 2103  86  64  16 0.00
Thu 08/06 18Z 0.33 2304  84  79  16 0.00
Thu 08/06 19Z 0.33 2204  81  81  17 0.00
Thu 08/06 20Z 0.31 2303  81  76  17 0.00
Thu 08/06 21Z 0.15 2003  81  73  17 0.00
Thu 08/06 22Z 0.12 2003  83  71  17 0.00
Thu 08/06 23Z 0.14 2005  84  68  17 0.00
Fri 08/07 00Z 0.22 2205  84  71  17 0.00
Fri 08/07 01Z 0.22 2306  83  67  17 0.00
Fri 08/07 02Z 0.26 2208  81  71  18 0.00
Fri 08/07 03Z 0.33 2311  82  72  18 0.00
Fri 08/07 04Z 0.38 2412  86  70  18 0.00
Fri 08/07 05Z 0.40 2412  90  71  17 0.00
Fri 08/07 06Z 0.40 2512  93  75  17 0.01
Fri 08/07 07Z 0.38 2611  95  75  17 0.01
Fri 08/07 08Z 0.37 2711  95  69  17 0.02
Fri 08/07 09Z 0.27 2809  94  67  17 0.01
Fri 08/07 10Z 0.21 3009  92  63  17 0.00
Fri 08/07 11Z 0.17 3109  93  44  16 0.00
Fri 08/07 12Z 0.14 3107  93  30  16 0.00
Fri 08/07 13Z 0.14 3107  92  39  16 0.00
Fri 08/07 14Z 0.15 3007  89  43  16 0.00
Fri 08/07 15Z 0.14 3006  83  45  16 0.00
Fri 08/07 16Z 0.15 2906  78  34  17 0.00
Fri 08/07 17Z 0.15 3006  73  22  17 0.00
Fri 08/07 18Z 0.22 3006  72  23  17 0.00
Fri 08/07 19Z 0.27 3006  74  24  17 0.00
Fri 08/07 20Z 0.20 3005  76  24  17 0.00
Fri 08/07 21Z 0.19 2905  76  21  18 0.00
Fri 08/07 22Z 0.18 2905  77  24  18 0.00
Fri 08/07 23Z 0.18 2805  80  27  17 0.00
Sat 08/08 00Z 0.20 2705  83  28  17 0.00
Sat 08/08 01Z 0.23 2706  86  26  17 0.00
Sat 08/08 02Z 0.20 2605  86  26  17 0.00
Sat 08/08 03Z 0.21 2505  86  27  17 0.00
Sat 08/08 04Z 0.16 2304  85  25  17 0.00
Sat 08/08 05Z 0.23 2207  85  34  17 0.00

Run total areal avg QPF for the Central_Greens is: 0.05 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