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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 Northern_Greens

Model run: BTV_GRID_D2D_NAM3_20260627_1200
Using the MB925 to MB850 layer.
Assumes Northern_Greens are orthogonal to 290 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Northern_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Sat 06/27 12Z 0.29 3008  95  57   9 0.00
Sat 06/27 13Z 0.20 3006  93  50   9 0.00
Sat 06/27 14Z 0.17 3005  90  50  10 0.00
Sat 06/27 15Z 0.17 3005  89  52  10 0.00
Sat 06/27 16Z 0.17 3004  88  53  10 0.00
Sat 06/27 17Z 0.18 3103  87  53  10 0.00
Sat 06/27 18Z 0.21 3103  85  54  10 0.01
Sat 06/27 19Z 0.18 3102  84  53  11 0.01
Sat 06/27 20Z 0.16 3002  83  56  11 0.00
Sat 06/27 21Z 0.20 3102  83  63  11 0.00
Sat 06/27 22Z 0.17 3103  81  69  11 0.00
Sat 06/27 23Z 0.07 3401  79  66  11 0.00
Sun 06/28 00Z 0.06 3501  79  66  11 0.00
Sun 06/28 01Z 0.05 3300  78  62  11 0.00
Sun 06/28 02Z 0.04 3301  77  57  11 0.00
Sun 06/28 03Z 0.05 3401  75  58  11 0.00
Sun 06/28 04Z 0.05 3401  75  58  11 0.00
Sun 06/28 05Z 0.08 3302  75  61  11 0.00
Sun 06/28 06Z 0.10 3404  71  58  11 0.00
Sun 06/28 07Z 0.09 3505  67  53  11 0.00
Sun 06/28 08Z 0.11 3507  64  47  11 0.00
Sun 06/28 09Z 0.08 0008  67  35  11 0.00
Sun 06/28 10Z 0.09 0009  69  26  11 0.00
Sun 06/28 11Z 0.10 0009  68  22  11 0.00
Sun 06/28 12Z 0.10 0009  68  20  11 0.00
Sun 06/28 13Z 0.09 0008  69  20  11 0.00
Sun 06/28 14Z 0.12 3507  71  20  11 0.00
Sun 06/28 15Z 0.17 3505  76  20  10 0.00
Sun 06/28 16Z 0.27 3404  80  19  11 0.00
Sun 06/28 17Z 0.38 3505  82  16  11 0.00
Sun 06/28 18Z 0.52 3405  83  15  11 0.00
Sun 06/28 19Z 0.58 3305  83  13  11 0.00
Sun 06/28 20Z 0.59 3306  79  11  12 0.00
Sun 06/28 21Z 0.44 3306  76   9  12 0.00
Sun 06/28 22Z 0.24 3306  74   8  12 0.00
Sun 06/28 23Z 0.19 3407  71   8  12 0.00
Mon 06/29 00Z 0.17 3508  69  11  12 0.00
Mon 06/29 01Z 0.14 3509  69  13  12 0.00
Mon 06/29 02Z 0.08 0010  69  14  12 0.00
Mon 06/29 03Z 0.06 0009  68  14  12 0.00
Mon 06/29 04Z 0.05 0108  66  16  12 0.00
Mon 06/29 05Z 0.06 0007  63  19  12 0.00
Mon 06/29 06Z 0.07 0007  60  17  12 0.00
Mon 06/29 07Z 0.07 0008  61  18  12 0.00
Mon 06/29 08Z 0.07 0009  64  21  11 0.00
Mon 06/29 09Z 0.07 0110  69  22  11 0.00
Mon 06/29 10Z 0.05 0109  70  20  11 0.00
Mon 06/29 11Z 0.06 0108  72  18  11 0.00
Mon 06/29 12Z 0.09 0008  78  19  11 0.00
Mon 06/29 13Z 0.13 3507  83  23  11 0.00
Mon 06/29 14Z 0.21 3405  86  24  11 0.00
Mon 06/29 15Z 0.30 3304  87  27  11 0.00
Mon 06/29 16Z 0.32 3203  87  29  11 0.01
Mon 06/29 17Z 0.32 3203  86  27  12 0.02
Mon 06/29 18Z 0.43 3103  84  23  12 0.01
Mon 06/29 19Z 0.59 3003  82  19  12 0.01
Mon 06/29 20Z 0.40 2902  80  16  12 0.00
Mon 06/29 21Z 0.56 2803  79  14  13 0.00
Mon 06/29 22Z 0.34 2703  76  11  13 0.00
Mon 06/29 23Z 0.24 2604  70   8  13 0.00

Run total areal avg QPF for the Northern_Greens is: 0.07 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