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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_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)
=== ===== === ==== ==== === === === ====
Fri 06/26 18Z 0.77 2310  95  53  10 0.00
Fri 06/26 19Z 0.98 2310  91  56  11 0.06
Fri 06/26 20Z 0.84 2510  87  61  11 0.23
Fri 06/26 21Z 0.96 2711  85  64  12 0.11
Fri 06/26 22Z 0.65 2911  86  63  12 0.15
Fri 06/26 23Z 0.30 3111  87  69  11 0.08
Sat 06/27 00Z 0.30 3112  88  63  11 0.03
Sat 06/27 01Z 0.24 3112  86  42  11 0.00
Sat 06/27 02Z 0.19 3110  82  36  11 0.00
Sat 06/27 03Z 0.17 3109  81  37  11 0.00
Sat 06/27 04Z 0.16 3108  82  39  11 0.00
Sat 06/27 05Z 0.19 3008  83  41  11 0.00
Sat 06/27 06Z 0.19 3009  81  38  11 0.00
Sat 06/27 07Z 0.19 3010  80  36  11 0.00
Sat 06/27 08Z 0.19 3010  80  40  11 0.00
Sat 06/27 09Z 0.19 3110  81  47  11 0.00
Sat 06/27 10Z 0.17 3111  80  56  11 0.00
Sat 06/27 11Z 0.10 3209  77  56  11 0.00
Sat 06/27 12Z 0.08 3207  77  52  11 0.00
Sat 06/27 13Z 0.07 3206  78  53  11 0.00
Sat 06/27 14Z 0.08 3205  80  53  11 0.00
Sat 06/27 15Z 0.09 3105  82  48  11 0.00
Sat 06/27 16Z 0.07 3204  84  44  11 0.00
Sat 06/27 17Z 0.11 3202  85  43  11 0.00
Sat 06/27 18Z 0.11 3202  85  48  11 0.01
Sat 06/27 19Z 0.15 3102  84  46  11 0.01
Sat 06/27 20Z 0.09 3202  84  48  12 0.00
Sat 06/27 21Z 0.07 3302  85  51  12 0.00
Sat 06/27 22Z 0.06 3202  84  52  12 0.00
Sat 06/27 23Z 0.05 3201  84  47  12 0.00
Sun 06/28 00Z 0.03 3301  83  48  12 0.00
Sun 06/28 01Z 0.03 3401  80  53  12 0.00
Sun 06/28 02Z 0.03 0200  79  54  12 0.00
Sun 06/28 03Z 0.03 3400  79  50  12 0.00
Sun 06/28 04Z 0.03 3200  80  46  12 0.00
Sun 06/28 05Z 0.04 3101  82  48  11 0.00
Sun 06/28 06Z 0.03 3202  80  51  11 0.00
Sun 06/28 07Z 0.04 3303  77  50  12 0.00
Sun 06/28 08Z 0.03 3304  76  45  12 0.00
Sun 06/28 09Z 0.03 3406  76  41  11 0.00
Sun 06/28 10Z 0.03 3406  74  37  11 0.00
Sun 06/28 11Z 0.02 3507  72  32  11 0.00
Sun 06/28 12Z 0.02 3507  71  34  11 0.00
Sun 06/28 13Z 0.02 3506  71  33  12 0.00
Sun 06/28 14Z 0.02 3406  73  33  11 0.00
Sun 06/28 15Z 0.02 3505  76  32  11 0.00
Sun 06/28 16Z 0.03 3505  80  29  11 0.00
Sun 06/28 17Z 0.05 3505  82  26  12 0.00
Sun 06/28 18Z 0.07 3504  82  24  12 0.01
Sun 06/28 19Z 0.13 3503  82  23  12 0.01
Sun 06/28 20Z 0.08 3404  82  25  12 0.01
Sun 06/28 21Z 0.08 3303  81  23  12 0.01
Sun 06/28 22Z 0.08 3304  78  19  12 0.01
Sun 06/28 23Z 0.06 3305  74  16  13 0.00
Mon 06/29 00Z 0.03 3407  68   8  13 0.00
Mon 06/29 01Z 0.04 3509  63   8  13 0.00
Mon 06/29 02Z 0.12 0009  61  10  12 0.00
Mon 06/29 03Z 0.14 0109  60  15  12 0.00
Mon 06/29 04Z 0.14 0108  60  18  12 0.00
Mon 06/29 05Z 0.13 0108  59  21  12 0.00

Run total areal avg QPF for the Central_Greens is: 0.73 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