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 Northern_Greens

Model run: BTV_GRID_D2D_NAM3_20260612_1200
Using the MB925 to MB850 layer.
Assumes Northern_Greens are orthogonal to 290 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Northern_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 06/12 12Z 0.13 2405  93  67  17 0.00
Fri 06/12 13Z 0.10 2305  92  67  16 0.00
Fri 06/12 14Z 0.06 2105  88  59  17 0.00
Fri 06/12 15Z 0.03 2005  87  51  17 0.00
Fri 06/12 16Z 0.18 2205  87  50  17 0.00
Fri 06/12 17Z 0.75 2407  86  40  17 0.00
Fri 06/12 18Z 1.10 2508  84  39  17 0.00
Fri 06/12 19Z 1.06 2607  79  24  18 0.00
Fri 06/12 20Z 1.08 2607  81  45  18 0.00
Fri 06/12 21Z 0.74 2611  89  82  18 0.03
Fri 06/12 22Z 0.35 2512  72  63  18 0.32
Fri 06/12 23Z 0.52 2513  65  11  18 0.05
Sat 06/13 00Z 0.82 2518  74   9  17 0.00
Sat 06/13 01Z 1.03 2523  89  20  16 0.00
Sat 06/13 02Z 1.04 2727  79  20  15 0.03
Sat 06/13 03Z 1.17 2829  78  11  13 0.01
Sat 06/13 04Z 1.13 2929  73  10  13 0.00
Sat 06/13 05Z 0.93 2928  81  14  12 0.00
Sat 06/13 06Z 0.82 3027  82  17  12 0.00
Sat 06/13 07Z 0.67 3025  80  12  12 0.00
Sat 06/13 08Z 0.58 3022  77  14  12 0.00
Sat 06/13 09Z 0.55 3022  78  13  12 0.00
Sat 06/13 10Z 0.53 3022  80  12  11 0.00
Sat 06/13 11Z 0.49 3021  74  13  11 0.00
Sat 06/13 12Z 0.48 3020  70  15  11 0.00
Sat 06/13 13Z 0.52 3019  72  15  11 0.00
Sat 06/13 14Z 0.53 3017  72  14  11 0.00
Sat 06/13 15Z 0.62 2916  74  15  11 0.00
Sat 06/13 16Z 0.69 2914  79  15  11 0.00
Sat 06/13 17Z 1.09 2713  85  14  11 0.00
Sat 06/13 18Z 1.57 2612  90  12  11 0.00
Sat 06/13 19Z 1.86 2613  90  14  11 0.00
Sat 06/13 20Z 4.01 2614  83  17  12 0.00
Sat 06/13 21Z 3.08 2714  76  15  12 0.00
Sat 06/13 22Z 1.91 2715  71  18  12 0.00
Sat 06/13 23Z 1.25 2715  69  26  13 0.00
Sun 06/14 00Z 1.77 2718  69  43  12 0.00
Sun 06/14 01Z 2.19 2820  73  77  12 0.00
Sun 06/14 02Z 0.88 2716  65  77  13 0.00
Sun 06/14 03Z 0.62 2616  59  66  13 0.00
Sun 06/14 04Z 0.65 2518  62  55  13 0.00
Sun 06/14 05Z 0.66 2520  63  57  13 0.00
Sun 06/14 06Z 0.62 2422  61  46  13 0.00
Sun 06/14 07Z 0.70 2427  50  69  14 0.00
Sun 06/14 08Z 1.27 2431  69  67  13 0.00
Sun 06/14 09Z 1.12 2435  77  55  12 0.01
Sun 06/14 10Z 1.27 2435  77  61  12 0.01
Sun 06/14 11Z 1.11 2532  77  69  13 0.00
Sun 06/14 12Z 0.85 2527  79  71  13 0.00
Sun 06/14 13Z 0.66 2424  75  53  14 0.00
Sun 06/14 14Z 0.59 2423  74  48  14 0.00
Sun 06/14 15Z 0.53 2321  72  39  14 0.00
Sun 06/14 16Z 0.44 2119  74  34  14 0.00
Sun 06/14 17Z 0.87 2119  75  37  14 0.00
Sun 06/14 18Z 0.46 2120  75  44  14 0.00
Sun 06/14 19Z 0.36 2120  74  41  15 0.00
Sun 06/14 20Z 0.22 2021  65  35  15 0.00
Sun 06/14 21Z 0.13 2023  62  26  15 0.00
Sun 06/14 22Z 0.11 1922  66  63  15 0.01
Sun 06/14 23Z 0.11 1928  80  77  15 0.04

Run total areal avg QPF for the Northern_Greens is: 0.51 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