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

Extremely critical fire weather conditions are expected to develop across the Great Basin and Southwest today, and exceptionally dry and windy conditions will promote rapid wildfire spread through the weekend. Scattered severe thunderstorms and heavy rain are possible across parts of the Ozark Plateau into lower Ohio Valley and parts of the northern Rockies into adjacent Great Plains. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260626_0600
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)
=== ===== === ==== ==== === === === ====
Fri 06/26 06Z 0.28 2020  87  97  11 0.00
Fri 06/26 07Z 0.33 2019  89  95  11 0.00
Fri 06/26 08Z 0.37 2119  93  88  10 0.00
Fri 06/26 09Z 0.34 2117  93  92  11 0.00
Fri 06/26 10Z 0.36 2118  97  92  11 0.02
Fri 06/26 11Z 0.39 2218  98  90  11 0.21
Fri 06/26 12Z 0.40 2217  98  86  11 0.08
Fri 06/26 13Z 0.42 2217  96  87  11 0.07
Fri 06/26 14Z 0.40 2215  98  75  11 0.07
Fri 06/26 15Z 0.40 2312  98  70  11 0.07
Fri 06/26 16Z 0.41 2411  96  78  11 0.01
Fri 06/26 17Z 0.42 2410  95  65  11 0.00
Fri 06/26 18Z 0.47 2309  94  54  11 0.00
Fri 06/26 19Z 0.50 2208  94  75  11 0.02
Fri 06/26 20Z 0.55 2509  87  73  12 0.34
Fri 06/26 21Z 0.53 2814  85  64  11 0.14
Fri 06/26 22Z 0.44 2914  85  50  11 0.03
Fri 06/26 23Z 0.37 3012  88  48  11 0.00
Sat 06/27 00Z 0.34 3012  91  50  11 0.01
Sat 06/27 01Z 0.24 3112  90  59  11 0.00
Sat 06/27 02Z 0.21 3110  90  52  11 0.00
Sat 06/27 03Z 0.22 3110  89  49  11 0.00
Sat 06/27 04Z 0.22 3110  87  46  11 0.00
Sat 06/27 05Z 0.27 3012  88  46  11 0.00
Sat 06/27 06Z 0.28 3013  88  48  11 0.00
Sat 06/27 07Z 0.31 3013  90  51  10 0.00
Sat 06/27 08Z 0.31 3013  92  56  10 0.00
Sat 06/27 09Z 0.29 3012  94  43  10 0.00
Sat 06/27 10Z 0.30 3013  94  48  10 0.00
Sat 06/27 11Z 0.28 3013  92  46  10 0.00
Sat 06/27 12Z 0.23 3112  90  47  10 0.00
Sat 06/27 13Z 0.19 3112  89  45  10 0.00
Sat 06/27 14Z 0.16 3211  89  45  10 0.00
Sat 06/27 15Z 0.14 3210  89  44  10 0.00
Sat 06/27 16Z 0.14 3208  89  46  10 0.00
Sat 06/27 17Z 0.16 3208  87  44  10 0.00
Sat 06/27 18Z 0.25 3208  85  43  10 0.00
Sat 06/27 19Z 0.24 3207  82  43  10 0.00
Sat 06/27 20Z 0.20 3307  80  41  10 0.00
Sat 06/27 21Z 0.16 3307  80  41  11 0.00
Sat 06/27 22Z 0.09 3306  80  38  11 0.00
Sat 06/27 23Z 0.06 3406  80  37  11 0.00
Sun 06/28 00Z 0.10 0006  80  38  11 0.00
Sun 06/28 01Z 0.05 0005  80  41  11 0.00
Sun 06/28 02Z 0.03 3506  79  40  11 0.00
Sun 06/28 03Z 0.06 0007  76  41  12 0.00
Sun 06/28 04Z 0.07 0106  74  41  12 0.00
Sun 06/28 05Z 0.08 0106  72  42  12 0.00
Sun 06/28 06Z 0.06 0105  69  42  12 0.00
Sun 06/28 07Z 0.06 0106  68  41  11 0.00
Sun 06/28 08Z 0.08 0107  67  39  11 0.00
Sun 06/28 09Z 0.08 0107  67  38  11 0.00
Sun 06/28 10Z 0.10 0108  65  33  11 0.00
Sun 06/28 11Z 0.10 0108  66  30  11 0.00
Sun 06/28 12Z 0.14 0210  67  28  11 0.00
Sun 06/28 13Z 0.18 0211  70  26  11 0.00
Sun 06/28 14Z 0.22 0311  73  24  11 0.00
Sun 06/28 15Z 0.22 0309  75  25  11 0.00
Sun 06/28 16Z 0.23 0306  76  25  10 0.00
Sun 06/28 17Z 0.62 0305  76  23  10 0.00

Run total areal avg QPF for the Central_Greens is: 1.07 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