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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_20260627_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)
=== ===== === ==== ==== === === === ====
Sat 06/27 18Z 0.85 3004  87  59  11 0.00
Sat 06/27 19Z 0.49 3105  85  58  12 0.03
Sat 06/27 20Z 0.30 3205  85  57  12 0.02
Sat 06/27 21Z 0.21 3305  86  52  12 0.01
Sat 06/27 22Z 0.11 3404  87  52  12 0.00
Sat 06/27 23Z 0.06 3404  87  58  12 0.00
Sun 06/28 00Z 0.05 3404  84  64  12 0.00
Sun 06/28 01Z 0.06 0004  81  67  12 0.00
Sun 06/28 02Z 0.14 0304  82  72  12 0.00
Sun 06/28 03Z 0.13 0303  84  69  12 0.00
Sun 06/28 04Z 0.10 0203  85  66  12 0.00
Sun 06/28 05Z 0.04 0003  84  59  11 0.00
Sun 06/28 06Z 0.05 0005  82  56  12 0.00
Sun 06/28 07Z 0.06 0005  78  48  12 0.00
Sun 06/28 08Z 0.11 0106  76  37  12 0.00
Sun 06/28 09Z 0.14 0206  76  35  11 0.00
Sun 06/28 10Z 0.16 0207  76  34  11 0.00
Sun 06/28 11Z 0.18 0207  76  35  11 0.00
Sun 06/28 12Z 0.21 0308  76  34  11 0.00
Sun 06/28 13Z 0.22 0308  78  28  11 0.00
Sun 06/28 14Z 0.22 0307  80  24  11 0.00
Sun 06/28 15Z 0.37 0205  83  23  11 0.00
Sun 06/28 16Z 0.67 0203  85  25  11 0.00
Sun 06/28 17Z 0.67 0202  83  31  11 0.02
Sun 06/28 18Z 0.31 0001  82  33  12 0.03
Sun 06/28 19Z 0.14 3402  81  26  12 0.01
Sun 06/28 20Z 0.12 3303  81  24  12 0.01
Sun 06/28 21Z 0.13 3303  81  27  13 0.01
Sun 06/28 22Z 0.13 3305  79  34  13 0.01
Sun 06/28 23Z 0.04 3404  76  33  13 0.01
Mon 06/29 00Z 0.04 3406  72  32  13 0.01
Mon 06/29 01Z 0.04 3507  69  20  13 0.00
Mon 06/29 02Z 0.14 0107  71  18  12 0.00
Mon 06/29 03Z 0.19 0207  76  20  12 0.00
Mon 06/29 04Z 0.13 0107  77  24  12 0.00
Mon 06/29 05Z 0.13 0107  76  24  12 0.00
Mon 06/29 06Z 0.16 0108  75  23  12 0.00
Mon 06/29 07Z 0.11 0008  74  18  12 0.00
Mon 06/29 08Z 0.09 0008  73  14  12 0.00
Mon 06/29 09Z 0.09 0009  74  11  11 0.00
Mon 06/29 10Z 0.13 0009  75   9  11 0.00
Mon 06/29 11Z 0.14 0010  76   7  11 0.00
Mon 06/29 12Z 0.18 0110  76   5  11 0.00
Mon 06/29 13Z 0.23 0109  77   4  11 0.00
Mon 06/29 14Z 0.44 0106  80   4  11 0.00
Mon 06/29 15Z 0.33 3504  82   5  11 0.00
Mon 06/29 16Z 0.24 3303  82  13  12 0.01
Mon 06/29 17Z 0.49 3104  80  25  12 0.02
Mon 06/29 18Z 0.65 3104  77  24  12 0.01
Mon 06/29 19Z 1.08 3005  71  14  13 0.00
Mon 06/29 20Z 1.15 3005  66  12  13 0.00
Mon 06/29 21Z 0.81 3006  65   9  13 0.00
Mon 06/29 22Z 0.45 3006  68   7  13 0.00
Mon 06/29 23Z 0.31 3006  71   5  13 0.00
Tue 06/30 00Z 0.34 3006  75   5  13 0.00
Tue 06/30 01Z 0.31 3006  78   5  12 0.00
Tue 06/30 02Z 0.32 2905  79   6  12 0.00
Tue 06/30 03Z 0.31 2805  80   8  12 0.00
Tue 06/30 04Z 0.36 2806  80  15  12 0.00
Tue 06/30 05Z 0.44 2707  82  19  12 0.00

Run total areal avg QPF for the Central_Greens is: 0.21 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