National Weather Service United States Department of Commerce

Heat Advisories in Effect for Today and Friday

Significant heat is expected to build today and Friday. Hot temperatures and high humidity will allow heat index values to reach into the lower to mid 90s this afternoon and again Friday afternoon in the Champlain Valley and Connecticut River Valley. Heat index values elsewhere will be in the upper 80s to low 90s. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260611_1200
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 06/11 12Z 0.31 2709  93  61  15 0.00
Thu 06/11 13Z 0.44 2713  92  42  15 0.00
Thu 06/11 14Z 0.61 2817  93  42  15 0.00
Thu 06/11 15Z 0.48 2915  95  47  15 0.01
Thu 06/11 16Z 0.34 3012  93  63  16 0.00
Thu 06/11 17Z 0.30 3008  92  68  16 0.00
Thu 06/11 18Z 0.48 2809  94  69  16 0.00
Thu 06/11 19Z 0.50 2710  95  71  17 0.01
Thu 06/11 20Z 0.58 2813  95  72  17 0.01
Thu 06/11 21Z 0.51 2813  91  72  18 0.00
Thu 06/11 22Z 0.49 2814  87  78  18 0.00
Thu 06/11 23Z 0.45 2812  87  76  18 0.00
Fri 06/12 00Z 0.44 2811  88  68  18 0.00
Fri 06/12 01Z 0.42 2812  84  60  18 0.00
Fri 06/12 02Z 0.44 2711  84  57  18 0.00
Fri 06/12 03Z 0.47 2613  80  66  18 0.00
Fri 06/12 04Z 0.55 2615  76  71  18 0.00
Fri 06/12 05Z 0.57 2614  73  62  18 0.00
Fri 06/12 06Z 0.59 2514  70  59  18 0.00
Fri 06/12 07Z 0.53 2512  75  52  18 0.00
Fri 06/12 08Z 0.41 2411  79  60  18 0.00
Fri 06/12 09Z 0.31 2310  86  71  18 0.00
Fri 06/12 10Z 0.21 2208  90  81  18 0.00
Fri 06/12 11Z 0.19 2307  93  88  18 0.01
Fri 06/12 12Z 0.12 2304  94  89  17 0.00
Fri 06/12 13Z 0.15 2504  95  90  17 0.00
Fri 06/12 14Z 0.18 2505  93  89  17 0.01
Fri 06/12 15Z 0.20 2405  88  89  17 0.00
Fri 06/12 16Z 0.22 2305  83  46  18 0.00
Fri 06/12 17Z 1.34 2507  84  19  17 0.00
Fri 06/12 18Z 2.47 2709  82  17  18 0.00
Fri 06/12 19Z 1.50 2707  80  15  18 0.00
Fri 06/12 20Z 1.13 2407  81  32  19 0.00
Fri 06/12 21Z 0.92 2310  87  77  18 0.02
Fri 06/12 22Z 0.65 2415  88  68  18 0.13
Fri 06/12 23Z 0.83 2619  93  57  18 0.02
Sat 06/13 00Z 0.74 2721  94  60  16 0.07
Sat 06/13 01Z 0.66 2822  74  53  16 0.01
Sat 06/13 02Z 0.57 2922  59  21  16 0.00
Sat 06/13 03Z 0.49 2922  65  10  15 0.00
Sat 06/13 04Z 0.44 3023  71   5  14 0.00
Sat 06/13 05Z 0.39 3023  72   5  14 0.00
Sat 06/13 06Z 0.38 3123  72   9  13 0.00
Sat 06/13 07Z 0.34 3124  65  10  13 0.00
Sat 06/13 08Z 0.34 3125  60  10  13 0.00
Sat 06/13 09Z 0.32 3125  56  14  13 0.00
Sat 06/13 10Z 0.30 3226  51  13  12 0.00
Sat 06/13 11Z 0.26 3225  49  13  12 0.00
Sat 06/13 12Z 0.21 3222  51  13  13 0.00
Sat 06/13 13Z 0.22 3221  57  11  12 0.00
Sat 06/13 14Z 0.25 3217  62  12  12 0.00
Sat 06/13 15Z 0.32 3113  62   9  12 0.00
Sat 06/13 16Z 0.89 3011  63   8  12 0.00
Sat 06/13 17Z 1.66 3010  67   6  12 0.00
Sat 06/13 18Z 2.38 2809  71   5  12 0.00
Sat 06/13 19Z 2.36 2708  73   6  13 0.00
Sat 06/13 20Z 2.23 2709  76  11  13 0.00
Sat 06/13 21Z 1.97 2709  77  14  13 0.00
Sat 06/13 22Z 1.32 2608  76  14  13 0.00
Sat 06/13 23Z 0.77 2509  75  18  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.30 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