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Severe Weather and Flooding Threats for the Central U.S.; Fire Weather Concerns for the Western U.S.

Severe weather and flooding threats will continue for portions of the central U.S. through Thursday, focused from the central High Plains to the Mid-Mississippi Valley. Hot and dry conditions will fuel fire weather concerns for the Intermountain West, and dry thunderstorms may spark additional wildfires. Dangerous heat will build across the southern U.S. Friday into the weekend. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260625_0000
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)
=== ===== === ==== ==== === === === ====
Thu 06/25 00Z 0.85 2916  79  58  10 0.00
Thu 06/25 01Z 1.14 2919  77  52  10 0.00
Thu 06/25 02Z 1.20 2920  78  46  10 0.00
Thu 06/25 03Z 1.08 2921  80  51  10 0.00
Thu 06/25 04Z 0.80 2920  80  55  10 0.00
Thu 06/25 05Z 0.72 2920  76  60  10 0.00
Thu 06/25 06Z 0.69 2919  73  60  10 0.00
Thu 06/25 07Z 0.66 3018  69  59  10 0.00
Thu 06/25 08Z 0.63 2916  66  44  10 0.00
Thu 06/25 09Z 0.57 2915  65  38  10 0.00
Thu 06/25 10Z 0.55 3014  64  40  10 0.00
Thu 06/25 11Z 0.47 3012  64  48  10 0.00
Thu 06/25 12Z 0.37 3009  64  52  10 0.00
Thu 06/25 13Z 0.32 2907  63  52  10 0.00
Thu 06/25 14Z 0.37 2805  63  53  10 0.00
Thu 06/25 15Z 0.81 2505  65  54  10 0.00
Thu 06/25 16Z 1.58 2505  65  53  10 0.00
Thu 06/25 17Z 2.76 2405  65  47  11 0.00
Thu 06/25 18Z 3.38 2406  65  44  11 0.00
Thu 06/25 19Z 3.52 2306  65  48  11 0.00
Thu 06/25 20Z 2.97 2207  66  53  11 0.00
Thu 06/25 21Z 1.83 2107  67  56  11 0.00
Thu 06/25 22Z 1.23 2107  67  61  11 0.00
Thu 06/25 23Z 0.49 2107  67  64  11 0.00
Fri 06/26 00Z 0.29 2009  65  71  11 0.00
Fri 06/26 01Z 0.29 2010  66  76  11 0.00
Fri 06/26 02Z 0.27 1912  68  81  11 0.00
Fri 06/26 03Z 0.20 1913  69  83  11 0.00
Fri 06/26 04Z 0.19 1914  73  86  11 0.00
Fri 06/26 05Z 0.20 1916  77  87  11 0.00
Fri 06/26 06Z 0.20 1918  82  90  10 0.01
Fri 06/26 07Z 0.20 1919  88  95  10 0.03
Fri 06/26 08Z 0.15 1919  92  94  10 0.08
Fri 06/26 09Z 0.10 1820  93  95  11 0.03
Fri 06/26 10Z 0.15 1920  94  96  10 0.07
Fri 06/26 11Z 0.20 1920  94  95  10 0.14
Fri 06/26 12Z 0.20 1919  94  92  10 0.07
Fri 06/26 13Z 0.25 2016  97  87  10 0.08
Fri 06/26 14Z 0.27 2113  98  78  10 0.03
Fri 06/26 15Z 0.25 2210  97  71  10 0.01
Fri 06/26 16Z 0.23 2307  97  49  10 0.00
Fri 06/26 17Z 0.27 2407  97  49  10 0.00
Fri 06/26 18Z 0.34 2507  96  55  10 0.00
Fri 06/26 19Z 0.34 2505  94  51  11 0.00
Fri 06/26 20Z 0.41 2605  94  51  11 0.00
Fri 06/26 21Z 0.35 2605  93  58  11 0.01
Fri 06/26 22Z 0.27 2505  93  75  11 0.07
Fri 06/26 23Z 0.29 2706  91  59  11 0.06
Sat 06/27 00Z 0.30 2807  93  65  11 0.02
Sat 06/27 01Z 0.27 2807  91  65  11 0.02
Sat 06/27 02Z 0.28 2807  90  66  11 0.01
Sat 06/27 03Z 0.25 2807  92  56  11 0.00
Sat 06/27 04Z 0.28 2808  95  49  11 0.00
Sat 06/27 05Z 0.28 2808  95  45  11 0.01
Sat 06/27 06Z 0.22 2806  94  46  11 0.01
Sat 06/27 07Z 0.20 2806  93  48  10 0.01
Sat 06/27 08Z 0.13 2904  93  47  10 0.01
Sat 06/27 09Z 0.11 2903  94  43  10 0.01
Sat 06/27 10Z 0.06 3002  93  40  10 0.00
Sat 06/27 11Z 0.05 3101  93  42  10 0.00

Run total areal avg QPF for the greens is: 0.79 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