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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_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)
=== ===== === ==== ==== === === === ====
Fri 06/26 12Z 0.22 2012  97  86  10 0.00
Fri 06/26 13Z 0.23 2111  97  86  10 0.00
Fri 06/26 14Z 0.28 2211  97  91  11 0.01
Fri 06/26 15Z 0.31 2310  98  93  11 0.00
Fri 06/26 16Z 0.28 2308  97  88  11 0.02
Fri 06/26 17Z 0.29 2407  97  74  11 0.01
Fri 06/26 18Z 0.30 2407  94  74  11 0.00
Fri 06/26 19Z 0.37 2307  87  61  12 0.00
Fri 06/26 20Z 0.42 2306  88  61  11 0.03
Fri 06/26 21Z 0.40 2306  86  68  12 0.23
Fri 06/26 22Z 0.36 2707  86  62  12 0.24
Fri 06/26 23Z 0.23 3111  85  64  12 0.21
Sat 06/27 00Z 0.25 3112  83  36  12 0.02
Sat 06/27 01Z 0.18 3211  81  39  12 0.00
Sat 06/27 02Z 0.15 3210  79  41  12 0.00
Sat 06/27 03Z 0.20 3110  81  40  11 0.00
Sat 06/27 04Z 0.17 3109  83  39  11 0.00
Sat 06/27 05Z 0.17 3008  84  40  11 0.00
Sat 06/27 06Z 0.19 3008  84  38  11 0.00
Sat 06/27 07Z 0.21 3009  85  38  11 0.00
Sat 06/27 08Z 0.20 3008  86  38  11 0.00
Sat 06/27 09Z 0.19 3009  87  41  11 0.00
Sat 06/27 10Z 0.15 3108  88  41  11 0.00
Sat 06/27 11Z 0.14 3108  90  40  11 0.00
Sat 06/27 12Z 0.11 3207  91  35  10 0.00
Sat 06/27 13Z 0.11 3106  93  35  10 0.00
Sat 06/27 14Z 0.10 3206  95  36  10 0.00
Sat 06/27 15Z 0.05 3304  94  37  10 0.00
Sat 06/27 16Z 0.08 3002  94  40  10 0.00
Sat 06/27 17Z 0.12 2702  92  38  11 0.01
Sat 06/27 18Z 0.17 2703  90  39  11 0.01
Sat 06/27 19Z 0.25 2803  89  40  11 0.01
Sat 06/27 20Z 0.22 2803  88  36  11 0.01
Sat 06/27 21Z 0.20 3004  87  37  12 0.00
Sat 06/27 22Z 0.12 3104  87  40  12 0.00
Sat 06/27 23Z 0.06 3203  87  45  12 0.00
Sun 06/28 00Z 0.05 3302  86  46  12 0.00
Sun 06/28 01Z 0.03 3402  84  49  12 0.00
Sun 06/28 02Z 0.03 0002  83  47  12 0.00
Sun 06/28 03Z 0.03 0002  83  46  11 0.00
Sun 06/28 04Z 0.05 0103  82  46  11 0.00
Sun 06/28 05Z 0.02 0003  82  48  11 0.00
Sun 06/28 06Z 0.02 3503  81  41  11 0.00
Sun 06/28 07Z 0.02 3503  80  40  11 0.00
Sun 06/28 08Z 0.02 3504  78  27  11 0.00
Sun 06/28 09Z 0.02 3404  77  24  11 0.00
Sun 06/28 10Z 0.03 3405  77  23  11 0.00
Sun 06/28 11Z 0.02 3406  75  22  11 0.00
Sun 06/28 12Z 0.02 3406  73  25  11 0.00
Sun 06/28 13Z 0.02 3506  72  25  11 0.00
Sun 06/28 14Z 0.03 0005  73  27  11 0.00
Sun 06/28 15Z 0.05 0004  76  30  11 0.00
Sun 06/28 16Z 0.06 0104  79  32  11 0.00
Sun 06/28 17Z 0.09 0103  80  30  11 0.00
Sun 06/28 18Z 0.13 0004  79  26  11 0.00
Sun 06/28 19Z 0.14 3504  80  22  12 0.00
Sun 06/28 20Z 0.15 3504  81  22  12 0.00
Sun 06/28 21Z 0.10 3404  81  24  12 0.01
Sun 06/28 22Z 0.06 3405  80  27  12 0.01
Sun 06/28 23Z 0.06 3506  78  19  12 0.01

Run total areal avg QPF for the Central_Greens is: 0.84 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