880
UXUS97 KPUB 251219
SRGPUB
SOARING FORECAST
NATIONAL WEATHER SERVICE PUEBLO, COLORADO
0619 MDT FRIDAY, APRIL 25, 2025
THIS FORECAST IS FOR VILLA GROVE, CO FOR FRIDAY, APRIL 25, 2025:
IF THE TRIGGER TEMPERATURE OF 50.7 F/10.4 C IS REACHED...THEN
THERMAL SOARING INDEX....................... EXCELLENT
MAXIMUM RATE OF LIFT........................ 1148 FT/MIN (5.8 M/S)
MAXIMUM HEIGHT OF THERMALS.................. 21051 FT MSL (12075 FT AGL)
FORECAST MAXIMUM TEMPERATURE................... 64.0 F/18.2 C
TIME OF TRIGGER TEMPERATURE.................... 0945 MDT
TIME OF OVERDEVELOPMENT........................ 1100 MDT
MIDDLE/HIGH CLOUDS DURING SOARING WINDOW....... NONE
SURFACE WINDS DURING SOARING WINDOW............ 20 MPH OR LESS
HEIGHT OF THE -3 THERMAL INDEX................. 18464 FT MSL (9487 FT AGL)
THERMAL SOARING OUTLOOK FOR SATURDAY 04/26..... EXCELLENT
WAVE SOARING INDEX............................. NOT AVAILABLE
REMARKS...
SUNRISE/SUNSET.................... 06:13:28 / 19:49:26 MDT
TOTAL POSSIBLE SUNSHINE........... 13 HR 35 MIN 59 SEC (815 MIN 59 SEC)
ALTITUDE OF SUN AT 13:01:27 MDT... 65.19 DEGREES
UPPER AIR DATA FROM NUMERICAL MODEL FORECAST VALID ON 04/25/2025 AT 0600 MDT
FREEZING LEVEL.................. 11673 FT MSL (2697 FT AGL)
CONVECTIVE CONDENSATION LEVEL... 15808 FT MSL (6832 FT AGL)
LIFTED CONDENSATION LEVEL....... 18181 FT MSL (9204 FT AGL)
LIFTED INDEX.................... -2.8
K INDEX......................... +0.2
HEIGHT TEMPERATURE WIND WIND SPD LAPSE RATE CONVECTIONT THERMAL LIFT RATE
FT MSL DEG C DEG F DIR KT M/S C/KM F/KFT DEG C DEG F INDEX FPM M/S
--------------------------------------------------------------------------------
50000 -59.6 -75.3 255 38 19 -1.1 -0.6 M M M M M
45000 -61.3 -78.3 260 48 25 -0.2 -0.1 M M M M M
40000 -61.7 -79.1 255 53 27 -0.1 -0.0 M M M M M
38000 -58.7 -73.7 250 53 27 7.1 3.9 M M M M M
36000 -54.4 -65.9 250 51 26 7.1 3.9 M M M M M
34000 -49.9 -57.8 245 49 25 8.2 4.5 M M M M M
32000 -45.0 -49.0 245 47 24 8.2 4.5 M M M M M
30000 -39.6 -39.3 240 43 22 7.7 4.2 24.3 75.8 5.2 M M
29000 -37.3 -35.1 240 41 21 7.7 4.2 23.5 74.4 4.6 M M
28000 -35.0 -31.0 235 39 20 7.7 4.2 22.9 73.1 4.1 M M
27000 -32.8 -27.0 235 38 20 7.3 4.0 22.1 71.7 3.5 M M
26000 -30.6 -23.1 235 37 19 7.3 4.0 21.1 69.9 2.7 M M
25000 -28.4 -19.1 235 37 19 7.3 4.0 20.2 68.4 2.0 M M
24000 -26.1 -15.0 240 37 19 8.5 4.7 19.5 67.2 1.4 M M
23000 -23.6 -10.5 240 37 19 8.4 4.6 19.0 66.2 1.0 M M
22000 -21.1 -6.0 240 38 19 8.4 4.6 18.6 65.4 0.6 M M
21000 -18.8 -1.8 240 38 20 6.1 3.3 17.8 64.1 -0.0 1147 5.8
20000 -17.0 1.4 240 39 20 6.2 3.4 16.6 61.8 -1.1 1062 5.4
19500 -16.1 3.0 235 40 21 6.2 3.4 16.0 60.8 -1.7 1020 5.2
19000 -15.2 4.6 235 41 21 6.3 3.5 15.4 59.8 -2.2 977 5.0
18500 -14.3 6.3 235 41 21 5.1 2.8 14.8 58.6 -2.8 938 4.8
18000 -13.6 7.5 230 41 21 5.4 3.0 14.0 57.2 -3.6 901 4.6
17500 -12.8 9.0 225 40 21 7.1 3.9 13.3 56.0 -4.3 863 4.4
17000 -11.6 11.1 225 39 20 8.3 4.6 13.1 55.6 -4.6 811 4.1
16500 -10.3 13.5 225 37 19 8.3 4.6 12.9 55.2 -4.8 759 3.9
16000 -9.2 15.4 225 34 18 7.2 4.0 12.5 54.6 -5.1 710 3.6
15500 -8.1 17.4 225 31 16 7.2 3.9 12.2 53.9 -5.5 661 3.4
15000 -6.2 20.8 230 28 14 8.9 4.9 11.8 53.3 -5.9 583 3.0
14500 -4.9 23.2 230 26 13 8.0 4.4 11.7 53.1 -6.0 528 2.7
14000 -3.7 25.3 230 24 12 8.2 4.5 11.3 52.4 -6.4 479 2.4
13500 -2.5 27.5 225 21 11 8.5 4.6 11.1 51.9 -6.6 428 2.2
13000 -1.6 29.1 220 18 9 5.2 2.9 10.6 51.0 -7.2 385 2.0
12500 -0.7 30.7 210 14 7 6.8 3.7 10.0 50.0 -7.8 344 1.7
12000 -0.2 31.6 190 11 6 1.6 0.9 9.1 48.4 -8.8 313 1.6
11750 -0.0 32.0 180 11 6 3.8 2.1 8.6 47.5 -9.4 302 1.5
11500 0.2 32.4 165 11 6 4.3 2.3 8.2 46.7 -9.9 287 1.5
11250 0.5 32.9 155 12 6 4.5 2.5 7.7 45.9 -10.5 273 1.4
11000 0.7 33.3 150 13 7 4.8 2.6 7.4 45.2 -10.9 257 1.3
10750 1.0 33.8 145 13 7 4.9 2.7 7.0 44.6 -11.4 241 1.2
10500 1.4 34.5 140 13 7 5.8 3.2 6.6 43.9 -11.8 223 1.1
10250 1.7 35.1 135 13 7 4.0 2.2 6.3 43.4 -12.3 205 1.0
10000 1.9 35.4 130 12 6 1.9 1.1 5.8 42.4 -12.9 193 1.0
9750 2.0 35.6 125 11 6 2.3 1.3 5.2 41.3 -13.5 182 0.9
9500 2.2 36.0 115 10 5 3.5 1.9 4.7 40.4 -14.1 169 0.9
9250 2.5 36.5 100 8 4 4.9 2.7 4.2 39.6 -14.5 152 0.8
9000 2.7 36.9 080 5 3 -1.2 -0.7 3.7 38.7 -15.1 139 0.7
8750 M M M M M M M M M M M M
8500 M M M M M M M M M M M M
8250 M M M M M M M M M M M M
8000 M M M M M M M M M M M M
* * * * * * NUMERICAL WEATHER PREDICTION MODEL FORECAST DATA VALID * * * * * *
04/25/2025 AT 0900 MDT | 04/25/2025 AT 1200 MDT
|
CAPE... +10.0 LI... +2.0 | CAPE... +148.3 LI... +0.2
CINH... -2.2 K INDEX... -2.7 | CINH... -21.9 K INDEX... -11.4
|
HEIGHT TEMPERATURE WND WNDSPD LAPSE RATE | TEMPERATURE WND WNDSPD LAPSE RATE
FT MSL DEG C DEG F DIR KT M/S C/KM F/KFT | DEG C DEG F DIR KT M/S C/KM F/KFT
--------------------------------------------------------------------------------
50000 -59.8 -75.6 250 40 21 -1.2 -0.6 | -58.9 -74.0 240 43 22 -0.9 -0.5
45000 -61.4 -78.5 250 48 25 0.8 0.4 | -60.3 -76.5 240 57 30 -1.3 -0.7
40000 -60.5 -76.9 240 55 28 0.7 0.4 | -62.2 -80.0 240 58 30 -1.2 -0.6
38000 -57.9 -72.2 235 55 28 5.9 3.2 | -59.6 -75.3 240 57 30 6.8 3.7
36000 -54.3 -65.7 235 53 27 5.9 3.2 | -55.5 -67.9 240 56 29 6.8 3.7
34000 -50.4 -58.7 235 52 27 7.8 4.3 | -51.3 -60.3 240 55 28 7.5 4.1
32000 -45.7 -50.3 235 52 27 7.8 4.3 | -46.2 -51.2 240 55 28 7.5 4.1
30000 -40.4 -40.7 240 50 26 7.8 4.3 | -41.2 -42.2 240 51 26 9.1 5.0
29000 -38.1 -36.6 240 49 25 7.9 4.3 | -38.5 -37.3 240 46 24 9.1 5.0
28000 -35.7 -32.3 240 48 25 7.9 4.3 | -35.8 -32.4 240 42 22 9.1 5.0
27000 -33.4 -28.1 240 46 24 7.9 4.4 | -33.1 -27.6 240 40 21 9.0 4.9
26000 -31.0 -23.8 240 43 22 8.0 4.4 | -30.4 -22.7 235 40 21 9.0 4.9
25000 -28.6 -19.5 240 41 21 8.0 4.4 | -27.7 -17.9 230 40 21 9.0 4.9
24000 -26.2 -15.2 240 39 20 8.6 4.7 | -25.1 -13.2 230 41 21 7.9 4.3
23000 -23.5 -10.3 235 38 19 8.7 4.8 | -22.7 -8.9 225 41 21 8.1 4.4
22000 -20.9 -5.6 235 37 19 8.7 4.7 | -20.2 -4.4 225 41 21 8.0 4.4
21000 -18.6 -1.5 230 37 19 6.4 3.5 | -18.0 -0.4 225 41 21 6.4 3.5
20000 -16.7 1.9 230 37 19 6.4 3.5 | -16.0 3.2 225 39 20 6.5 3.6
19500 -15.7 3.7 225 37 19 6.5 3.6 | -15.0 5.0 225 39 20 6.5 3.6
19000 -14.7 5.5 225 38 19 6.6 3.6 | -14.0 6.8 220 38 20 6.7 3.7
18500 -13.9 7.0 220 38 19 5.0 2.7 | -13.4 7.9 220 37 19 2.4 1.3
18000 -13.2 8.2 215 37 19 5.3 2.9 | -13.0 8.6 220 36 19 3.0 1.6
17500 -12.4 9.7 210 38 19 7.5 4.1 | -12.5 9.5 215 35 18 6.4 3.5
17000 -11.1 12.0 205 36 18 8.7 4.7 | -11.3 11.7 215 33 17 8.3 4.6
16500 -9.8 14.4 200 34 18 8.7 4.8 | -10.1 13.8 210 32 16 8.6 4.7
16000 -8.6 16.5 200 32 17 8.1 4.5 | -8.8 16.2 210 30 15 8.7 4.8
15500 -7.4 18.7 200 30 15 8.2 4.5 | -7.5 18.5 210 28 14 8.8 4.8
15000 -5.5 22.1 200 26 14 8.2 4.5 | -6.3 20.7 210 27 14 7.9 4.3
14500 -4.3 24.3 200 24 12 6.4 3.5 | -4.5 23.9 205 26 13 7.8 4.3
14000 -3.3 26.1 195 22 12 8.5 4.7 | -3.4 25.9 200 26 13 6.6 3.6
13500 -2.1 28.2 190 22 11 8.2 4.5 | -2.4 27.7 195 26 13 6.8 3.7
13000 -1.2 29.8 185 19 10 5.7 3.1 | -1.6 29.1 190 22 11 5.0 2.7
12500 -0.2 31.6 180 16 8 7.3 4.0 | -0.9 30.4 185 17 9 6.4 3.5
12000 0.6 33.1 170 12 6 4.0 2.2 | -0.2 31.6 180 13 7 4.5 2.5
11750 1.0 33.8 165 11 6 5.1 2.8 | 0.1 32.2 175 12 6 6.5 3.6
11500 1.4 34.5 155 10 5 6.7 3.7 | 0.6 33.1 170 11 6 7.2 4.0
11250 1.8 35.2 145 9 4 1.7 0.9 | 1.0 33.8 160 10 5 6.3 3.5
11000 1.5 34.7 140 8 4 -3.6 -2.0 | 1.4 34.5 155 10 5 4.8 2.6
10750 1.2 34.2 135 9 4 -3.6 -2.0 | 1.7 35.1 150 10 5 6.5 3.6
10500 0.7 33.3 130 9 4 -7.8 -4.3 | 2.3 36.1 145 9 4 8.3 4.6
10250 0.1 32.2 120 9 4 0.7 0.4 | 2.9 37.2 135 8 4 8.2 4.5
10000 0.6 33.1 115 8 4 9.1 5.0 | 3.5 38.3 125 7 4 8.2 4.5
9750 1.1 34.0 105 8 4 6.9 3.8 | 4.1 39.4 115 6 3 8.2 4.5
9500 1.7 35.1 100 7 4 9.0 5.0 | 4.8 40.6 100 6 3 11.3 6.2
9250 2.4 36.3 085 6 3 12.7 7.0 | 5.9 42.6 090 6 3 20.5 11.2
9000 3.6 38.5 075 5 3 20.3 11.2 | 7.9 46.2 085 6 3 32.2 17.6
8750 M M M M M M M | M M M M M M M
8500 M M M M M M M | M M M M M M M
8250 M M M M M M M | M M M M M M M
8000 M M M M M M M | M M M M M M M
04/25/2025 AT 1500 MDT | 04/25/2025 AT 1800 MDT
|
CAPE... +204.6 LI... -0.8 | CAPE... +25.2 LI... -0.3
CINH... -14.7 K INDEX... +3.6 | CINH... -43.4 K INDEX... +15.1
|
HEIGHT TEMPERATURE WND WNDSPD LAPSE RATE | TEMPERATURE WND WNDSPD LAPSE RATE
FT MSL DEG C DEG F DIR KT M/S C/KM F/KFT | DEG C DEG F DIR KT M/S C/KM F/KFT
--------------------------------------------------------------------------------
50000 -59.6 -75.3 245 47 24 -0.8 -0.4 | -60.3 -76.5 245 43 22 -0.1 -0.0
45000 -60.9 -77.6 250 66 34 -1.0 -0.6 | -60.4 -76.7 250 58 30 -0.5 -0.3
40000 -62.4 -80.3 245 61 31 -0.9 -0.5 | -61.1 -78.0 250 72 37 -0.4 -0.2
38000 -59.7 -75.5 245 57 29 6.8 3.7 | -58.6 -73.5 250 69 35 6.2 3.4
36000 -55.6 -68.1 240 53 27 6.8 3.7 | -54.9 -66.8 245 62 32 6.2 3.4
34000 -51.2 -60.2 240 49 25 8.4 4.6 | -50.8 -59.4 245 56 29 8.0 4.4
32000 -46.1 -51.0 235 44 22 8.4 4.6 | -45.4 -49.7 240 50 26 8.0 4.4
30000 -40.4 -40.7 235 41 21 8.5 4.6 | -40.6 -41.1 240 46 23 8.0 4.4
29000 -37.9 -36.2 235 42 22 8.5 4.6 | -38.2 -36.8 240 44 23 8.0 4.4
28000 -35.4 -31.7 235 43 22 8.5 4.7 | -35.8 -32.4 240 42 22 8.0 4.4
27000 -32.8 -27.0 235 44 23 8.6 4.7 | -33.4 -28.1 240 41 21 8.0 4.4
26000 -30.2 -22.4 235 46 24 8.6 4.7 | -31.0 -23.8 240 41 21 8.0 4.4
25000 -27.7 -17.9 235 48 25 8.6 4.7 | -28.6 -19.5 240 40 21 8.0 4.4
24000 -25.1 -13.2 235 48 25 8.9 4.9 | -26.2 -15.2 240 40 20 7.9 4.4
23000 -22.4 -8.3 235 46 24 8.9 4.9 | -23.8 -10.8 240 39 20 8.0 4.4
22000 -19.7 -3.5 235 44 23 8.8 4.9 | -21.4 -6.5 240 38 20 7.9 4.3
21000 -17.5 0.5 235 43 22 5.5 3.0 | -19.2 -2.6 235 38 19 6.5 3.6
20000 -15.8 3.6 235 44 23 5.5 3.0 | -17.2 1.0 225 37 19 6.7 3.7
19500 -15.0 5.0 230 45 23 5.5 3.0 | -16.3 2.7 225 37 19 6.8 3.7
19000 -14.2 6.4 230 46 23 5.6 3.1 | -15.3 4.5 220 37 19 6.9 3.8
18500 -13.5 7.7 230 45 23 3.8 2.1 | -14.2 6.4 220 36 19 8.5 4.7
18000 -12.9 8.8 225 42 22 4.2 2.3 | -12.9 8.8 215 35 18 8.4 4.6
17500 -12.3 9.9 225 40 21 6.4 3.5 | -11.7 10.9 215 34 18 9.0 4.9
17000 -11.2 11.8 220 38 20 7.6 4.2 | -10.3 13.5 210 33 17 9.3 5.1
16500 -10.1 13.8 220 36 18 7.8 4.3 | -8.9 16.0 210 32 17 9.3 5.1
16000 -8.9 16.0 215 33 17 8.4 4.6 | -7.5 18.5 210 31 16 9.3 5.1
15500 -7.7 18.1 215 31 16 8.4 4.6 | -6.1 21.0 210 31 16 9.3 5.1
15000 -6.4 20.5 215 29 15 8.9 4.9 | -4.7 23.5 210 30 15 9.3 5.1
14500 -5.2 22.6 210 26 14 9.3 5.1 | -2.6 27.3 210 29 15 8.8 4.8
14000 -3.4 25.9 205 23 12 10.0 5.5 | -1.3 29.7 205 27 14 9.2 5.1
13500 -2.0 28.4 200 21 11 9.3 5.1 | 0.0 32.0 205 25 13 8.9 4.9
13000 -0.8 30.6 200 19 10 8.8 4.8 | 1.3 34.3 205 23 12 9.5 5.2
12500 0.7 33.3 195 17 9 10.7 5.9 | 2.9 37.2 205 22 12 11.0 6.0
12000 1.6 34.9 190 15 8 3.9 2.1 | 4.0 39.2 200 21 11 5.2 2.9
11750 2.1 35.8 185 13 7 7.4 4.1 | 4.5 40.1 200 19 10 5.9 3.3
11500 2.6 36.7 180 12 6 7.8 4.3 | 4.9 40.8 195 17 9 7.2 4.0
11250 3.1 37.6 175 11 6 6.3 3.5 | 5.3 41.5 190 16 8 2.4 1.3
11000 3.5 38.3 160 10 5 3.4 1.9 | 5.1 41.2 185 13 7 -5.5 -3.0
10750 3.8 38.8 150 9 5 6.8 3.7 | 4.6 40.3 170 11 6 -2.7 -1.5
10500 4.4 39.9 135 8 4 10.5 5.7 | 4.5 40.1 155 9 5 -0.5 -0.3
10250 5.2 41.4 120 8 4 9.2 5.1 | 4.4 39.9 130 8 4 2.0 1.1
10000 5.8 42.4 110 8 4 8.6 4.7 | 4.7 40.5 115 8 4 5.6 3.1
9750 6.5 43.7 100 8 4 9.0 4.9 | 5.1 41.2 105 8 4 5.9 3.2
9500 7.2 45.0 095 9 4 10.8 5.9 | 5.7 42.3 090 8 4 9.1 5.0
9250 8.3 46.9 090 9 5 20.5 11.2 | 6.6 43.9 080 9 4 16.5 9.0
9000 10.8 51.4 090 7 4 53.9 29.6 | 8.3 46.9 075 7 3 31.6 17.4
8750 M M M M M M M | M M M M M M M
8500 M M M M M M M | M M M M M M M
8250 M M M M M M M | M M M M M M M
8000 M M M M M M M | M M M M M M M
________________________________________________________________________________
THIS PRODUCT IS ISSUED TWICE PER DAY, ONCE BY APPROXIMATELY 0630 MST/0730 MDT
(1330 UTC). IT IS NOT CONTINUOUSLY MONITORED NOR UPDATED AFTER ITS INITIAL
ISSUANCE.
THE INFORMATION CONTAINED HEREIN IS BASED ON RAWINSONDE OBSERVATION AND/OR
NUMERICAL WEATHER PREDICTION MODEL DATA TAKEN NEAR VILLA GROVE, COLORADO AT:
NORTH LATITUDE: 38 DEG 16 MIN 03 SEC
WEST LONGITUDE: 105 DEG 53 MIN 37 SEC
ELEVATION: 7986 FEET (2434 METERS)
AND MAY NOT BE REPRESENTATIVE OF OTHER AREAS ALONG THE FRONT RANGE OF THE
COLORADO ROCKY MOUNTAINS. NOTE THAT SOME ELEVATIONS IN NUMERICAL WEATHER
PREDICTION MODELS DIFFER FROM ACTUAL STATION ELEVATIONS, WHICH CAN LEAD TO
DATA WHICH APPEAR TO BE BELOW GROUND. ERRONEOUS DATA SUCH AS THESE SHOULD
NOT BE USED.
THE CONTENT AND FORMAT OF THIS REPORT AS WELL AS THE ISSUANCE TIMES ARE SUBJECT
TO CHANGE WITHOUT PRIOR NOTICE. COMMENTS AND SUGGESTIONS ARE WELCOME AND SHOULD
BE DIRECTED TO ONE OF THE ADDRESSES OR PHONE NUMBERS SHOWN AT THE BOTTOM OF THIS
PAGE. TO EXPEDITE A RESPONSE TO COMMENTS, BE SURE TO MENTION YOUR INTEREST IN
THE SOARING FORECAST.
DEFINITIONS:
CAPE (CONVECTIVE AVAILABLE POTENTIAL ENERGY) - AN INTEGRATED MEASURE OF THE
ENERGY AVAILABLE FOR CONVECTIVE DEVELOPMENT, ALSO KNOWN AS THE POSITIVE
AREA ON A THERMODYNAMIC DIAGRAM. UNITS ARE JOULES PER KILOGRAM. LARGER
VALUES ARE INDICATIVE OF GREATER INSTABILITY AND THE POSSIBILITY OF
STRONGER CONVECTIVE ACTIVITY, INCLUDING THUNDERSTORMS. VALUES AROUND OR
GREATER THAN 1000 SUGGEST THE POSSIBILITY OF SEVERE WEATHER SHOULD
CONVECTIVE ACTIVITY DEVELOP.
CIN (CONVECTIVE INHIBITION) - AN INTEGRATED MEASURE OF THE AMOUNT OF ENERGY
NEEDED TO INITIATE CONVECTIVE ACTIVITY, ALSO KNOWN AS THE NEGATIVE AREA ON
A THERMODYNAMIC DIAGRAM. UNITS ARE JOULES PER KILOGRAM. THE MORE NEGATIVE
THIS NUMBER, THE MORE ENERGY IS REQUIRED TO INITIATE CONVECTION. THIS
INHIBITIVE ENERGY CAN BE OVERCOME THROUGH SURFACE HEATING, COOLING ALOFT,
LIFTING MECHANISMS (OROGRAPHIC, FRONTAL, GRAVITY WAVES, ETC.)
CONVECTIVE CONDENSATION LEVEL - THE HEIGHT TO WHICH AN AIR PARCEL POSSESSING THE
AVERAGE SATURATION MIXING RATIO IN THE LOWEST 4000 FEET OF THE AIRMASS,
IF HEATED SUFFICIENTLY FROM BELOW, WILL RISE DRY ADIABATICALLY UNTIL IT
JUST BECOMES SATURATED. IT ESTIMATES THE BASE OF CUMULUS CLOUDS THAT ARE
PRODUCED BY SURFACE HEATING ONLY.
CONVECTION TEMPERATURE (CONVECTIONT) - THE SURFACE TEMPERATURE REQUIRED TO MAKE
THE AIRMASS DRY ADIABATIC UP TO THE GIVEN LEVEL. IT CAN BE CONSIDERED A
"TRIGGER TEMPERATURE" FOR THAT LEVEL.
FREEZING LEVEL - THE HEIGHT WHERE THE TEMPERATURE IS ZERO DEGREES CELSIUS.
HEIGHT OF STABLE LAYER - THE HEIGHT (BETWEEN 12,000 AND 18,000 FEET ABOVE
MEAN SEA LEVEL) WHERE THE SMALLEST LAPSE RATE EXISTS. THE LOCATION AND
EXISTENCE OF THIS FEATURE IS IMPORTANT IN THE GENERATION OF MOUNTAIN
WAVES.
K INDEX - A MEASURE OF STABILITY WHICH COMBINES THE TEMPERATURE DIFFERENCE
BETWEEN APPROXIMATELY 5,000 AND 18,000 FEET ABOVE THE SURFACE, THE AMOUNT
OF MOISTURE AT APPROXIMATELY 5,000 FEET ABOVE THE SURFACE, AND A MEASURE
OF THE DRYNESS AT APPROXIMATELY 10,000 FEET ABOVE THE SURFACE. LARGER
POSITIVE NUMBERS INDICATE MORE INSTABILITY AND A GREATER LIKELIHOOD OF
THUNDERSTORM DEVELOPMENT. ONE INTERPRETATION OF K INDEX VALUES REGARDING
SOARING IN THE WESTERN UNITED STATES IS GIVEN IN WMO TECHNICAL NOTE 158
AND IS REPRODUCED IN THE FOLLOWING TABLE:
BELOW -10 NO OR WEAK THERMALS
-10 TO 5 DRY THERMALS OR 1/8 CUMULUS WITH MODERATE THERMALS
5 TO 15 GOOD SOARING CONDITIONS
15 TO 20 GOOD SOARING CONDITIONS WITH OCCASIONAL SHOWERS
20 TO 30 EXCELLENT SOARING CONDITIONS, BUT INCREASING
PROBABILITY OF SHOWERS AND THUNDERSTORMS
ABOVE 30 MORE THAN 60 PERCENT PROBABILITY OF THUNDERSTORMS
LAPSE RATE - THE CHANGE WITH HEIGHT OF THE TEMPERATURE. NEGATIVE VALUES INDICATE
INVERSIONS.
LIFTED CONDENSATION LEVEL - THE HEIGHT TO WHICH AN AIR PARCEL POSSESSING THE
AVERAGE DEW POINT IN THE LOWEST 4000 FEET OF THE AIRMASS AND THE FORECAST
MAXIMUM TEMPERATURE MUST BE LIFTED DRY ADIABATICALLY TO ATTAIN SATURATION.
LIFTED INDEX (LI) - THE DIFFERENCE BETWEEN THE ENVIRONMENTAL TEMPERATURE AT A
LEVEL APPROXIMATELY 18,000 FEET ABOVE THE SURFACE AND THE TEMPERATURE OF
AN AIR PARCEL LIFTED DRY ADIABATICALLY FROM THE SURFACE TO ITS LIFTED
CONDENSATION LEVEL AND THEN PSEUDOADIABATICALLY THEREAFTER TO THIS SAME
LEVEL. THE PARCEL'S INITIAL TEMPERATURE IS THE FORECAST MAXIMUM
TEMPERATURE AND ITS DEW POINT IS THE AVERAGE DEW POINT IN THE LOWEST 4000
FEET OF THE AIRMASS. NEGATIVE VALUES ARE INDICATIVE OF INSTABILITY WITH
POSITIVE VALUES SHOWING STABLE CONDITIONS.
LIFT RATE - AN EXPERIMENTAL ESTIMATE OF THE STRENGTH OF THERMALS. IT IS
COMPUTED THE SAME WAY AS THE MAXIMUM RATE OF LIFT BUT USES THE ACTUAL
LEVEL RATHER THAN THE MAXIMUM HEIGHT OF THERMALS IN THE CALCULATION.
ALSO, NONE OF THE EMPIRICAL ADJUSTMENTS BASED ON CLOUDINESS AND K-INDEX
ARE APPLIED TO THESE CALCULATIONS.
MAXIMUM HEIGHT OF THERMALS - THE HEIGHT WHERE THE DRY ADIABAT THROUGH THE
FORECAST MAXIMUM TEMPERATURE INTERSECTS THE ENVIRONMENTAL TEMPERATURE.
MAXIMUM RATE OF LIFT - AN ESTIMATE OF THE MAXIMUM STRENGTH OF THERMALS. IT
IS COMPUTED FROM AN EMPIRICAL FORMULA WHICH COMBINES THE EXPECTED MAXIMUM
HEIGHT OF THERMALS WITH THE DIFFERENCE IN THE ENVIRONMENTAL TEMPERATURES
BETWEEN THE MAXIMUM HEIGHT OF THERMALS AND THE TEMPERATURE 4,000 FEET
ABOVE THE GROUND. AFTER THIS COMPUTATION, FURTHER EMPIRICAL ADJUSTMENTS
ARE MADE BASED ON THE VALUE OF THE K-INDEX AND THE AMOUNT AND OPACITY OF
MIDDLE AND HIGH LEVEL CLOUDINESS EXPECTED BETWEEN THE TIME OF TRIGGER
TEMPERATURE AND THE TIME OF OVERDEVELOPMENT.
MIDDLE/HIGH CLOUDS - THE AMOUNT AND OPACITY OF MIDDLE (ALTOSTRATUS, ALTOCUMULUS)
OR HIGH (CIRRUS, CIRROSTRATUS, CIRROCUMULUS) CLOUDS. BROKEN MEANS THAT
BETWEEN 60% AND 90% OF THE SKY IS COVERED BY THE CLOUD, WITH OVERCAST
CONDITIONS OCCURRING WHEN MORE THAN 90% OF THE SKY IS COVERED BY THE CLOUD.
THIN IMPLIES THAT THE CLOUDS ARE PREDOMINANTLY TRANSPARENT, MEANING THAT
SOME SUNLIGHT IS REACHING THE GROUND, IN CONTRAST TO OPAQUE WHICH SUGGESTS
THAT LITTLE SUNLIGHT IS REACHING THE GROUND.
POTENTIAL HEIGHT OF WAVE - THE MINIMUM OF THE FOLLOWING TWO HEIGHTS:
1. LEVEL ABOVE THE HEIGHT OF STABLE LAYER (OR 14,000 FEET IF NONE EXISTS)
WHERE THE WIND DIRECTION CHANGES BY 30 DEGREES OR MORE
2. LEVEL ABOVE THE HEIGHT OF STABLE LAYER (OR 14,000 FEET IF NONE EXISTS)
WHERE THE WIND SPEED NO LONGER INCREASES WITH HEIGHT
PVA/NVA - POSITIVE VORTICITY ADVECTION (PVA)/NEGATIVE VORTICITY ADVECTION (NVA)
ON THE 500 MILLIBAR ISOBARIC SURFACE (APPROXIMATELY 18,000 FEET ABOVE MEAN
SEA LEVEL). WEAK PVA HAS BEEN SHOWN TO ASSIST IN MOUNTAIN WAVE SOARING.
SOARING WINDOW - THE TIME BETWEEN THE TIME THE TRIGGER TEMPERATURE IS REACHED
AND THE TIME OF OVERDEVELOPMENT.
THERMAL INDEX - THE DIFFERENCE BETWEEN THE ENVIRONMENTAL TEMPERATURE AND THE
TEMPERATURE AT A PARTICULAR LEVEL DETERMINED BY FOLLOWING THE DRY ADIABAT
THROUGH THE FORECAST MAXIMUM TEMPERATURE UP TO THAT LEVEL. NEGATIVE VALUES
ARE INDICATIVE OF THERMAL LIFT.
THERMAL SOARING INDEX - AN ADJECTIVE RATING (FOR SAILPLANES) BASED ON THE
COMPUTED MAXIMUM RATE OF LIFT, AND THE WIND SPEED AND MIDDLE AND HIGH
CLOUD COVER EXPECTED DURING THE SOARING WINDOW (THE TIME OF THE TRIGGER
TEMPERATURE AND THE TIME OF OVERDEVELOPMENT) ACCORDING TO THE FOLLOWING:
MAXIMUM RATE OF LIFT ADJECTIVE RATING
>= 800 FPM EXCELLENT
>= 400 AND < 800 FPM GOOD
>= 200 AND < 400 FPM FAIR
< 200 FPM POOR
TIME OF OVERDEVELOPMENT - THE TIME ONE OR MORE OF THE FOLLOWING PHENOMENA,
WHICH ESSENTIALLY SHUT OFF THERMAL LIFT, IS EXPECTED TO OCCUR:
1. FORMATION OF BROKEN TO OVERCAST CONVECTIVE CLOUD COVER
2. FORMATION OF SCATTERED TO NUMEROUS DOWNBURSTS
3. INITIATION OF WIDESPREAD PRECIPITATION
TIME OF TRIGGER TEMPERATURE - THE TIME THE SURFACE TEMPERATURE IS EXPECTED TO
REACH THE TRIGGER TEMPERATURE.
TRIGGER TEMPERATURE - THE SURFACE TEMPERATURE REQUIRED TO MAKE THE FIRST 4000
FEET OF THE ATMOSPHERE DRY ADIABATIC.
WAVE SOARING INDEX - AN EMPIRICAL, ADJECTIVE RATING (FOR SAILPLANES) WHICH
ATTEMPTS TO COMBINE A VARIETY OF PHENOMENA IMPORTANT IN MOUNTAIN WAVE
SOARING INTO A SINGLE INDEX NUMBER. OBJECTIVE POINTS ARE ASSIGNED TO
THESE PHENOMENA: WIND SPEED AND DIRECTION AT 14,000 FT MSL, THE STATIC
STABILITY IN THE 12,000-18,000 FT MSL LAYER, THE WIND SPEED GRADIENT ABOVE
THE STABLE LAYER, JET STREAM LOCATION AND FRONTAL AND UPPER TROUGH
MOVEMENTS.
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