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Risks of Severe Thunderstorms and Excessive Rainfall; Fire Weather Concerns and Record Warmth

Severe thunderstorms and flash flooding risks increase across the center of the nation today. Meanwhile, ongoing thunderstorms and flash flooding will linger along the Gulf Coast states through the evening. The Great Basin and Intermountain West, warm temperatures and dry fuels with dry lightning may enhance fire weather potential. In addition, across interior Alaska, Red Flag Warning are posted. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260620_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)
=== ===== === ==== ==== === === === ====
Sat 06/20 06Z 1.07 2727  93  91   7 0.00
Sat 06/20 07Z 1.15 2731  95  92   7 0.05
Sat 06/20 08Z 1.10 2831  96  93   7 0.09
Sat 06/20 09Z 0.92 2831  97  90   7 0.09
Sat 06/20 10Z 0.82 2931  97  86   7 0.06
Sat 06/20 11Z 0.72 3031  97  84   7 0.04
Sat 06/20 12Z 0.64 3130  97  83   7 0.03
Sat 06/20 13Z 0.62 3128  97  84   7 0.03
Sat 06/20 14Z 0.71 3126  96  80   7 0.01
Sat 06/20 15Z 0.87 3022  97  76   8 0.01
Sat 06/20 16Z 1.38 2921  96  82   8 0.04
Sat 06/20 17Z 1.28 2923  96  81   8 0.06
Sat 06/20 18Z 1.83 2922  96  74   9 0.03
Sat 06/20 19Z 2.58 2922  95  72   9 0.02
Sat 06/20 20Z 3.20 2921  92  67   9 0.01
Sat 06/20 21Z 3.13 2922  90  69   9 0.01
Sat 06/20 22Z 1.95 2922  90  64   9 0.00
Sat 06/20 23Z 1.09 2922  92  65   9 0.00
Sun 06/21 00Z 0.91 2922  94  64   9 0.00
Sun 06/21 01Z 0.73 2921  94  62   9 0.01
Sun 06/21 02Z 0.64 2920  95  62   9 0.00
Sun 06/21 03Z 0.54 3018  96  63   9 0.01
Sun 06/21 04Z 0.47 3016  96  68   9 0.01
Sun 06/21 05Z 0.42 3015  96  73   9 0.01
Sun 06/21 06Z 0.35 3014  94  75   9 0.00
Sun 06/21 07Z 0.36 3014  94  79   8 0.00
Sun 06/21 08Z 0.34 2913  94  84   9 0.01
Sun 06/21 09Z 0.32 3013  94  79   8 0.01
Sun 06/21 10Z 0.30 3012  93  74   8 0.00
Sun 06/21 11Z 0.31 2911  93  68   8 0.00
Sun 06/21 12Z 0.28 2910  92  63   8 0.00
Sun 06/21 13Z 0.28 2909  91  62   9 0.00
Sun 06/21 14Z 0.33 2810  89  55   9 0.00
Sun 06/21 15Z 0.41 2809  89  44   9 0.00
Sun 06/21 16Z 1.10 2809  89  43   8 0.00
Sun 06/21 17Z 1.59 2808  89  34   9 0.00
Sun 06/21 18Z 1.48 2909  89  40   9 0.01
Sun 06/21 19Z 0.71 3009  88  47   9 0.06
Sun 06/21 20Z 0.47 3011  82  41   9 0.08
Sun 06/21 21Z 0.74 3010  83  38   9 0.01
Sun 06/21 22Z 0.48 3010  85  39   9 0.01
Sun 06/21 23Z 0.40 3011  81  32   9 0.05
Mon 06/22 00Z 0.36 3011  82  34   9 0.00
Mon 06/22 01Z 0.46 2913  89  41   9 0.00
Mon 06/22 02Z 0.31 3012  84  51   9 0.00
Mon 06/22 03Z 0.32 3014  82  57   9 0.00
Mon 06/22 04Z 0.24 3215  83  45   9 0.00
Mon 06/22 05Z 0.25 3114  82  46   9 0.00
Mon 06/22 06Z 0.19 3212  82  37   9 0.00
Mon 06/22 07Z 0.24 3111  83  31   9 0.00
Mon 06/22 08Z 0.16 3208  79  27   9 0.00
Mon 06/22 09Z 0.13 3106  76  26  10 0.00
Mon 06/22 10Z 0.19 2806  76  28   9 0.00
Mon 06/22 11Z 0.23 2606  77  29   9 0.00
Mon 06/22 12Z 0.25 2507  76  29   9 0.00
Mon 06/22 13Z 0.28 2407  78  31   9 0.00
Mon 06/22 14Z 0.21 2306  74  30   9 0.00
Mon 06/22 15Z 0.21 2205  71  29  10 0.00
Mon 06/22 16Z 0.14 1906  70  26  10 0.00
Mon 06/22 17Z 0.20 1908  74  39  10 0.00

Run total areal avg QPF for the Central_Greens is: 0.86 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