National Weather Service United States Department of Commerce

Extreme Heat Warnings and Heat Advisories are now in effect from Wednesday through Friday for the area

Significant heat is expected to build from Wednesday through Friday. Extreme Heat Warnings are now in effect for the entire Champlain Valley & eastern Windsor County in Vermont. Heat Advisories are now in effect for the remainder of the area in northern New York & Vermont. Heat index values are expected to peak around 105 degrees in warning areas, and mid 90s to lower 100s in advisory areas. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260630_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)
=== ===== === ==== ==== === === === ====
Tue 06/30 18Z 2.42 2208  78  83  15 0.00
Tue 06/30 19Z 1.06 2210  77  89  16 0.00
Tue 06/30 20Z 0.52 2210  78  87  16 0.00
Tue 06/30 21Z 0.69 2211  83  89  16 0.00
Tue 06/30 22Z 0.51 2414  85  87  16 0.02
Tue 06/30 23Z 0.42 2415  76  74  16 0.01
Wed 07/01 00Z 0.41 2516  78  79  17 0.01
Wed 07/01 01Z 0.41 2415  77  81  17 0.00
Wed 07/01 02Z 0.43 2220  75  75  18 0.00
Wed 07/01 03Z 0.45 2318  84  69  18 0.00
Wed 07/01 04Z 0.51 2518  90  71  17 0.01
Wed 07/01 05Z 0.52 2518  94  69  17 0.02
Wed 07/01 06Z 0.54 2518  95  67  18 0.01
Wed 07/01 07Z 0.55 2620  95  74  18 0.01
Wed 07/01 08Z 0.53 2620  92  62  18 0.09
Wed 07/01 09Z 0.59 2622  95  56  18 0.03
Wed 07/01 10Z 0.57 2621  95  46  18 0.01
Wed 07/01 11Z 0.48 2518  95  48  19 0.01
Wed 07/01 12Z 0.51 2619  95  44  19 0.01
Wed 07/01 13Z 0.51 2618  96  40  18 0.01
Wed 07/01 14Z 0.50 2616  96  43  18 0.01
Wed 07/01 15Z 0.49 2615  97  50  18 0.01
Wed 07/01 16Z 0.47 2614  96  50  19 0.01
Wed 07/01 17Z 0.49 2614  97  53  19 0.00
Wed 07/01 18Z 0.54 2615  94  57  19 0.00
Wed 07/01 19Z 0.55 2615  88  45  20 0.03
Wed 07/01 20Z 0.64 2416  92  41  20 0.00
Wed 07/01 21Z 0.68 2418  90  45  20 0.02
Wed 07/01 22Z 0.73 2522  94  37  20 0.02
Wed 07/01 23Z 0.69 2522  87  36  20 0.02
Thu 07/02 00Z 0.76 2724  89  40  20 0.01
Thu 07/02 01Z 0.65 2723  84  53  21 0.00
Thu 07/02 02Z 0.70 2726  85  55  21 0.00
Thu 07/02 03Z 0.66 2826  80  57  21 0.00
Thu 07/02 04Z 0.62 2826  79  61  21 0.00
Thu 07/02 05Z 0.60 2825  81  65  20 0.00
Thu 07/02 06Z 0.59 2925  86  55  20 0.00
Thu 07/02 07Z 0.54 2924  84  45  20 0.01
Thu 07/02 08Z 0.43 3022  79  30  20 0.01
Thu 07/02 09Z 0.32 3020  74  26  20 0.01
Thu 07/02 10Z 0.27 3018  67  22  21 0.01
Thu 07/02 11Z 0.27 3016  65  24  21 0.01
Thu 07/02 12Z 0.29 2916  62  27  21 0.00
Thu 07/02 13Z 0.32 2815  58  27  21 0.00
Thu 07/02 14Z 0.35 2816  54  27  21 0.00
Thu 07/02 15Z 0.39 2816  50  37  21 0.00
Thu 07/02 16Z 0.45 2817  51  43  21 0.00
Thu 07/02 17Z 0.44 2816  52  46  22 0.00
Thu 07/02 18Z 0.49 2815  57  52  21 0.00
Thu 07/02 19Z 0.72 2715  69  59  20 0.00
Thu 07/02 20Z 1.40 2615  71  46  20 0.00
Thu 07/02 21Z 1.94 2517  73  35  20 0.00
Thu 07/02 22Z 1.53 2518  79  46  20 0.00
Thu 07/02 23Z 1.92 2620  85  44  20 0.00
Fri 07/03 00Z 1.43 2622  84  59  20 0.00
Fri 07/03 01Z 1.27 2624  88  66  20 0.00
Fri 07/03 02Z 1.11 2727  89  64  19 0.01
Fri 07/03 03Z 1.05 2728  92  49  19 0.00
Fri 07/03 04Z 1.05 2731  93  51  19 0.01
Fri 07/03 05Z 0.90 2830  87  52  19 0.01

Run total areal avg QPF for the Central_Greens is: 0.46 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