National Weather Service United States Department of Commerce

Heat Advisories Today for Portions of the Champlain and Connecticut River Valleys

Heat index values near 95 are expected for the central and southern Champlain Valley and portions of the Connecticut River Valley today. Heat Advisories have been issued for these locations, valid from noon to 8 PM today. The highest heat index values will occur between 1 PM and 5 PM. Read More >

Subject: BTV4 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_BTV4_20220521_1200
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Sat 05/21 12Z 0.48 2519  91  68  15 0.00
Sat 05/21 13Z 0.49 2518  90  66  16 0.00
Sat 05/21 14Z 0.50 2616  88  63  16 0.00
Sat 05/21 15Z 0.47 2514  85  53  17 0.00
Sat 05/21 16Z 0.50 2413  82  47  17 0.00
Sat 05/21 17Z 0.60 2313  80  44  17 0.00
Sat 05/21 18Z 0.72 2315  80  42  17 0.00
Sat 05/21 19Z 0.98 2317  81  42  17 0.00
Sat 05/21 20Z 1.12 2318  83  48  17 0.00
Sat 05/21 21Z 1.07 2320  85  50  17 0.01
Sat 05/21 22Z 1.14 2423  82  61  17 0.01
Sat 05/21 23Z 0.62 2318  77  59  18 0.05
Sun 05/22 00Z 0.60 2321  79  79  17 0.03
Sun 05/22 01Z 0.59 2419  88  78  17 0.26
Sun 05/22 02Z 0.81 2622  90  72  16 0.15
Sun 05/22 03Z 0.58 2516  88  79  16 0.08
Sun 05/22 04Z 0.78 2418  91  76  16 0.09
Sun 05/22 05Z 0.86 2821  92  82  14 0.43
Sun 05/22 06Z 0.35 2612  75  80  16 0.10
Sun 05/22 07Z 0.39 2513  73  75  15 0.00
Sun 05/22 08Z 0.35 2412  76  72  15 0.00
Sun 05/22 09Z 0.36 2413  77  65  15 0.00
Sun 05/22 10Z 0.38 2415  74  60  16 0.00
Sun 05/22 11Z 0.41 2416  71  61  16 0.00
Sun 05/22 12Z 0.43 2316  69  63  15 0.00
Sun 05/22 13Z 0.48 2318  72  69  15 0.00
Sun 05/22 14Z 0.56 2320  74  67  15 0.00
Sun 05/22 15Z 0.66 2222  73  63  16 0.00
Sun 05/22 16Z 1.05 2222  71  60  16 0.00
Sun 05/22 17Z 2.10 2222  73  56  16 0.00
Sun 05/22 18Z 2.70 2223  76  58  16 0.00
Sun 05/22 19Z 4.19 2223  78  62  16 0.00
Sun 05/22 20Z 5.86 2321  80  78  16 0.03
Sun 05/22 21Z 3.68 2321  74  73  16 0.04
Sun 05/22 22Z 2.31 2619  81  79  16 0.04
Sun 05/22 23Z 3.15 2835  94  90  12 0.36
Mon 05/23 00Z 0.63 2928  92  87  12 0.25
Mon 05/23 01Z 0.55 3026  92  85  10 0.04
Mon 05/23 02Z 0.47 3124  92  62   8 0.03
Mon 05/23 03Z 0.45 3123  94  42   7 0.02
Mon 05/23 04Z 0.41 3223  93  28   5 0.01
Mon 05/23 05Z 0.38 3223  92  20   5 0.01
Mon 05/23 06Z 0.34 3223  89  16   4 0.01
Mon 05/23 07Z 0.30 3223  85  13   4 0.01
Mon 05/23 08Z 0.26 3322  79  12   4 0.00
Mon 05/23 09Z 0.23 3322  74  12   3 0.00
Mon 05/23 10Z 0.19 3322  69  12   3 0.00
Mon 05/23 11Z 0.15 3421  64  11   3 0.00
Mon 05/23 12Z 0.11 3421  61  11   3 0.00
Mon 05/23 13Z 0.08 3520  60  12   3 0.00
Mon 05/23 14Z 0.06 3520  58  13   2 0.00
Mon 05/23 15Z 0.05 3518  60  14   2 0.00
Mon 05/23 16Z 0.11 3517  63  15   1 0.00
Mon 05/23 17Z 0.40 3516  65  16   1 0.00
Mon 05/23 18Z 0.64 3515  65  16   1 0.00
Mon 05/23 19Z 0.74 3515  65  16   2 0.00
Mon 05/23 20Z 0.92 3515  65  15   2 0.00
Mon 05/23 21Z 0.81 3514  66  15   2 0.00
Mon 05/23 22Z 0.61 3514  68  15   2 0.00
Mon 05/23 23Z 0.24 3514  68  16   1 0.00
Tue 05/24 00Z 0.15 3515  67  16   1 0.00
Tue 05/24 01Z 0.12 0016  65  16   1 0.00
Tue 05/24 02Z 0.09 0015  64  16   1 0.00
Tue 05/24 03Z 0.10 0014  64  15   1 0.00
Tue 05/24 04Z 0.14 0112  64  15   1 0.00
Tue 05/24 05Z 0.19 0111  63  14   1 0.00
Tue 05/24 06Z 0.24 0211  61  15   1 0.00
Tue 05/24 07Z 0.31 0310  60  15   1 0.00
Tue 05/24 08Z 0.37 0410  61  15   1 0.00
Tue 05/24 09Z 0.38 0410  59  15   1 0.00
Tue 05/24 10Z 0.37 0510  55  15   1 0.00
Tue 05/24 11Z 0.35 0609  52  16   1 0.00
Tue 05/24 12Z 0.32 0708  51  16   1 0.00
Tue 05/24 13Z 0.35 0807  53  16   1 0.00
Tue 05/24 14Z 0.65 1006  57  16   1 0.00
Tue 05/24 15Z 1.92 1105  59  17   1 0.00
Tue 05/24 16Z 2.69 1306  60  17   2 0.00
Tue 05/24 17Z 2.22 1506  60  19   2 0.00
Tue 05/24 18Z 2.10 1508  60  20   3 0.00
Tue 05/24 19Z 1.69 1609  60  22   4 0.00
Tue 05/24 20Z 0.89 1710  61  24   4 0.00
Tue 05/24 21Z 0.70 1711  62  26   4 0.00
Tue 05/24 22Z 0.67 1712  64  29   4 0.00
Tue 05/24 23Z 0.39 1715  66  32   4 0.00

Run total areal avg QPF for the greens is: 2.06 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