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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_1200
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 12Z 0.95 2924  96  90   7 0.00
Sat 06/20 13Z 0.90 3026  98  90   7 0.02
Sat 06/20 14Z 0.90 3026  98  93   7 0.04
Sat 06/20 15Z 0.83 2925  97  92   8 0.03
Sat 06/20 16Z 0.81 3024  97  92   8 0.03
Sat 06/20 17Z 0.66 3021  97  90   9 0.04
Sat 06/20 18Z 0.69 3021  96  90   9 0.07
Sat 06/20 19Z 0.74 3021  96  84   9 0.10
Sat 06/20 20Z 0.93 3020  95  77   9 0.07
Sat 06/20 21Z 0.94 3019  94  79   9 0.12
Sat 06/20 22Z 0.82 2920  94  76   9 0.07
Sat 06/20 23Z 0.73 2921  92  68   9 0.07
Sun 06/21 00Z 0.76 2921  93  65   9 0.01
Sun 06/21 01Z 0.76 2921  92  65   9 0.00
Sun 06/21 02Z 0.62 2920  92  64   9 0.00
Sun 06/21 03Z 0.49 3018  92  65   9 0.00
Sun 06/21 04Z 0.47 2917  95  67   8 0.01
Sun 06/21 05Z 0.40 3015  94  72   8 0.01
Sun 06/21 06Z 0.34 3014  94  78   8 0.01
Sun 06/21 07Z 0.32 3013  95  76   8 0.01
Sun 06/21 08Z 0.33 3013  96  72   8 0.01
Sun 06/21 09Z 0.33 3013  95  61   8 0.01
Sun 06/21 10Z 0.30 3012  93  51   8 0.01
Sun 06/21 11Z 0.30 2912  92  52   8 0.00
Sun 06/21 12Z 0.29 2911  92  61   8 0.00
Sun 06/21 13Z 0.31 2911  92  73   8 0.00
Sun 06/21 14Z 0.30 2910  91  75   8 0.00
Sun 06/21 15Z 0.34 2909  91  73   8 0.00
Sun 06/21 16Z 0.74 2909  92  74   8 0.00
Sun 06/21 17Z 0.77 3009  92  71   8 0.00
Sun 06/21 18Z 0.67 3009  92  68   8 0.00
Sun 06/21 19Z 0.48 3009  92  67   9 0.00
Sun 06/21 20Z 0.40 3009  92  71   9 0.04
Sun 06/21 21Z 0.27 3110  87  65   9 0.02
Sun 06/21 22Z 0.22 3210  85  55  10 0.01
Sun 06/21 23Z 0.25 3110  86  55  10 0.00
Mon 06/22 00Z 0.29 3011  87  58   9 0.00
Mon 06/22 01Z 0.27 3112  86  57   9 0.00
Mon 06/22 02Z 0.28 3112  85  58   9 0.00
Mon 06/22 03Z 0.24 3111  87  50   9 0.00
Mon 06/22 04Z 0.15 3210  84  40  10 0.00
Mon 06/22 05Z 0.04 3408  77  31  10 0.00
Mon 06/22 06Z 0.04 3306  76  31  10 0.00
Mon 06/22 07Z 0.09 3105  80  38  10 0.00
Mon 06/22 08Z 0.12 2804  83  41   9 0.00
Mon 06/22 09Z 0.13 2503  85  38   9 0.00
Mon 06/22 10Z 0.11 2403  83  26   9 0.00
Mon 06/22 11Z 0.05 2002  79  22   9 0.00
Mon 06/22 12Z 0.02 1703  77  22  10 0.00
Mon 06/22 13Z 0.04 1706  78  22  10 0.00
Mon 06/22 14Z 0.10 1810  79  30  10 0.00
Mon 06/22 15Z 0.07 1712  79  89   9 0.00
Mon 06/22 16Z 0.09 1712  86  94   8 0.02
Mon 06/22 17Z 0.07 1611  88  81   8 0.04
Mon 06/22 18Z 0.13 1515  87  76   8 0.03
Mon 06/22 19Z 0.39 1420  88  98   8 0.03
Mon 06/22 20Z 0.79 1221  96  99   8 0.11
Mon 06/22 21Z 0.71 1225  98  99   9 0.28
Mon 06/22 22Z 0.56 1226  98  99   9 0.25
Mon 06/22 23Z 0.41 1325  98  98  10 0.20

Run total areal avg QPF for the Central_Greens is: 1.77 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