052
UXUS97 KPUB 301212
SRGPUB
SOARING FORECAST
NATIONAL WEATHER SERVICE PUEBLO, COLORADO
0611 MDT THURSDAY, APRIL 30, 2026
THIS FORECAST IS FOR VILLA GROVE, CO FOR THURSDAY, APRIL 30, 2026:
IF THE TRIGGER TEMPERATURE OF 39.7 F/4.3 C IS REACHED...THEN
THERMAL SOARING INDEX....................... GOOD
MAXIMUM RATE OF LIFT........................ 556 FT/MIN (2.8 M/S)
MAXIMUM HEIGHT OF THERMALS.................. 16894 FT MSL (7896 FT AGL)
FORECAST MAXIMUM TEMPERATURE................... 46.0 F/8.2 C
TIME OF TRIGGER TEMPERATURE.................... 0845 MDT
TIME OF OVERDEVELOPMENT........................ NONE
MIDDLE/HIGH CLOUDS DURING SOARING WINDOW....... OVERCAST OPAQUE HIGH
SURFACE WINDS DURING SOARING WINDOW............ 20 MPH OR LESS
HEIGHT OF THE -3 THERMAL INDEX................. 13274 FT MSL (4276 FT AGL)
THERMAL SOARING OUTLOOK FOR FRIDAY 05/01....... POOR
WAVE SOARING INDEX............................. NOT AVAILABLE
REMARKS...
SUNRISE/SUNSET.................... 06:07:36 / 19:53:55 MDT
TOTAL POSSIBLE SUNSHINE........... 13 HR 46 MIN 19 SEC (826 MIN 19 SEC)
ALTITUDE OF SUN AT 13:00:46 MDT... 66.69 DEGREES
UPPER AIR DATA FROM NUMERICAL MODEL FORECAST VALID ON 04/30/2026 AT 0600 MDT
FREEZING LEVEL.................. ENTIRE AIRMASS BELOW 32 F / 0 C
CONVECTIVE CONDENSATION LEVEL... 12739 FT MSL (3741 FT AGL)
LIFTED CONDENSATION LEVEL....... 14325 FT MSL (5327 FT AGL)
LIFTED INDEX.................... -0.1
K INDEX......................... +9.0
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 -58.8 -73.8 275 49 25 1.5 0.8 M M M M M
45000 -56.6 -69.9 270 68 35 1.2 0.7 M M M M M
40000 -55.1 -67.2 270 100 51 0.9 0.5 M M M M M
38000 -53.3 -63.9 265 105 54 4.7 2.6 M M M M M
36000 -50.5 -58.9 265 105 54 4.7 2.6 M M M M M
34000 -47.7 -53.9 260 104 54 4.2 2.3 M M M M M
32000 -45.2 -49.4 260 91 47 4.2 2.3 M M M M M
30000 -42.6 -44.7 260 77 40 4.1 2.3 23.0 73.4 11.9 M M
29000 -41.1 -42.0 260 66 34 4.1 2.3 20.1 68.2 9.8 M M
28000 -39.9 -39.8 260 57 29 4.1 2.3 18.0 64.5 8.2 M M
27000 -38.7 -37.7 255 48 25 5.7 3.1 16.1 61.0 6.8 M M
26000 -36.4 -33.5 260 45 23 7.6 4.2 15.2 59.3 6.1 M M
25000 -34.1 -29.4 260 42 22 7.6 4.2 14.4 57.9 5.5 M M
24000 -31.8 -25.2 260 39 20 7.4 4.1 13.8 56.8 5.0 M M
23000 -29.9 -21.8 260 35 18 6.2 3.4 12.5 54.5 4.0 M M
22000 -28.1 -18.6 255 31 16 6.2 3.4 11.3 52.3 3.0 M M
21000 -26.2 -15.2 255 26 14 7.4 4.1 10.2 50.3 2.0 M M
20000 -23.8 -10.8 260 25 13 8.0 4.4 9.5 49.1 1.5 M M
19500 -22.6 -8.7 260 25 13 8.0 4.4 9.2 48.6 1.2 M M
19000 -21.4 -6.5 260 25 13 8.0 4.4 9.0 48.1 1.0 M M
18500 -20.2 -4.4 260 24 12 8.2 4.5 8.7 47.7 0.8 M M
18000 -19.0 -2.2 265 24 12 8.5 4.6 8.5 47.3 0.6 M M
17500 -17.7 0.1 265 24 12 8.5 4.7 8.3 46.9 0.4 M M
17000 -16.5 2.3 265 23 12 8.0 4.4 8.0 46.5 0.1 M M
16500 -15.3 4.5 265 23 12 8.1 4.4 7.8 46.0 -0.2 727 3.7
16000 -14.2 6.4 265 22 11 7.6 4.2 7.5 45.4 -0.5 678 3.4
15500 -12.6 9.3 270 18 10 7.4 4.1 6.9 44.4 -1.1 607 3.1
15000 -11.4 11.5 275 16 8 8.4 4.6 6.6 43.9 -1.4 559 2.8
14500 -10.2 13.6 275 12 6 7.8 4.3 6.4 43.5 -1.7 509 2.6
14000 -9.4 15.1 280 9 5 5.9 3.2 5.8 42.5 -2.3 468 2.4
13500 -8.4 16.9 280 5 3 6.4 3.5 5.3 41.5 -2.8 425 2.2
13000 -7.6 18.3 270 2 1 5.4 2.9 4.7 40.5 -3.4 384 2.0
12500 -6.9 19.6 070 1 1 4.9 2.7 4.0 39.2 -4.2 348 1.8
12000 -6.2 20.8 075 4 2 4.5 2.5 3.2 37.8 -5.0 312 1.6
11750 -5.8 21.6 075 6 3 4.9 2.7 2.8 37.1 -5.4 295 1.5
11500 -5.4 22.3 080 7 3 5.5 3.0 2.5 36.5 -5.7 276 1.4
11250 -5.0 23.0 080 7 4 5.3 2.9 2.1 35.9 -6.1 257 1.3
11000 -4.7 23.5 080 8 4 5.3 2.9 1.8 35.3 -6.5 238 1.2
10750 -4.3 24.3 080 9 5 5.1 2.8 1.5 34.6 -6.8 220 1.1
10500 -3.9 25.0 080 10 5 4.9 2.7 1.1 34.0 -7.2 201 1.0
10250 -3.6 25.5 085 10 5 5.0 2.7 0.7 33.3 -7.6 183 0.9
10000 -3.2 26.2 085 10 5 5.2 2.8 0.4 32.7 -8.0 165 0.8
9750 -2.8 27.0 085 10 5 5.3 2.9 0.0 32.1 -8.4 146 0.7
9500 -2.4 27.7 085 9 4 6.4 3.5 -0.3 31.5 -8.7 127 0.6
9250 -1.9 28.6 085 7 4 7.8 4.3 -0.5 31.2 -8.9 104 0.5
9000 -1.5 29.3 085 3 2 2.3 1.3 -0.7 30.7 -9.3 84 0.4
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 * * * * * *
04/30/2026 AT 0900 MDT | 04/30/2026 AT 1200 MDT
|
CAPE... +23.4 LI... -0.6 | CAPE... +290.8 LI... -2.7
CINH... -43.0 K INDEX... +12.4 | CINH... -1.2 K INDEX... +12.5
|
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 -60.9 -77.6 305 18 9 2.2 1.2 | -60.4 -76.7 270 20 10 3.3 1.8
45000 -57.9 -72.2 325 21 11 -0.8 -0.4 | -56.2 -69.2 295 24 12 -2.4 -1.3
40000 -59.1 -74.4 360 45 23 -0.9 -0.5 | -59.9 -75.8 360 49 25 -2.7 -1.5
38000 -56.4 -69.5 005 50 26 6.1 3.3 | -57.1 -70.8 005 52 27 6.6 3.6
36000 -52.7 -62.9 010 55 28 6.1 3.3 | -53.1 -63.6 010 51 26 6.6 3.6
34000 -48.7 -55.7 015 57 29 7.6 4.2 | -48.6 -55.5 015 50 26 8.6 4.7
32000 -44.1 -47.4 020 55 28 7.6 4.2 | -43.5 -46.3 020 48 25 8.6 4.7
30000 -39.7 -39.5 025 52 27 7.0 3.8 | -38.2 -36.8 025 44 22 7.2 3.9
29000 -37.1 -34.8 025 47 24 7.0 3.8 | -36.0 -32.8 025 41 21 7.2 3.9
28000 -35.0 -31.0 025 44 23 7.0 3.9 | -33.9 -29.0 020 37 19 7.2 3.9
27000 -32.7 -26.9 025 41 21 7.9 4.3 | -31.7 -25.1 020 35 18 7.2 4.0
26000 -30.4 -22.7 025 39 20 7.9 4.3 | -29.5 -21.1 020 33 17 7.2 4.0
25000 -28.0 -18.4 025 38 19 7.9 4.3 | -27.4 -17.3 015 32 16 7.2 4.0
24000 -25.6 -14.1 030 35 18 8.0 4.4 | -25.1 -13.2 015 30 16 8.3 4.6
23000 -23.2 -9.8 030 32 17 8.0 4.4 | -22.6 -8.7 015 29 15 8.3 4.5
22000 -20.8 -5.4 030 29 15 8.0 4.4 | -20.1 -4.2 015 28 14 8.2 4.5
21000 -18.6 -1.5 025 26 13 6.9 3.8 | -17.8 -0.0 015 26 13 7.4 4.0
20000 -16.5 2.3 025 22 11 6.9 3.8 | -15.6 3.9 015 22 11 7.3 4.0
19500 -15.5 4.1 025 20 11 6.9 3.8 | -14.5 5.9 015 21 11 7.3 4.0
19000 -14.5 5.9 020 19 10 6.9 3.8 | -13.4 7.9 015 19 10 7.3 4.0
18500 -13.4 7.9 020 17 9 7.5 4.1 | -12.3 9.9 015 18 9 7.1 3.9
18000 -12.3 9.9 020 16 8 7.5 4.1 | -11.2 11.8 015 17 9 7.2 3.9
17500 -11.2 11.8 020 15 8 6.8 3.7 | -10.2 13.6 015 16 8 6.4 3.5
17000 -10.3 13.5 020 14 7 6.5 3.6 | -9.3 15.3 015 15 8 6.2 3.4
16500 -9.3 15.3 020 14 7 6.5 3.6 | -8.4 16.9 015 14 7 6.2 3.4
16000 -8.3 17.1 015 12 6 6.6 3.6 | -7.4 18.7 010 13 7 6.3 3.5
15500 -7.4 18.7 015 11 6 6.7 3.7 | -6.5 20.3 010 12 6 6.3 3.4
15000 -6.4 20.5 015 10 5 6.3 3.5 | -5.1 22.8 005 11 6 6.8 3.7
14500 -5.5 22.1 010 9 5 6.3 3.5 | -4.1 24.6 360 10 5 6.1 3.3
14000 -4.1 24.6 005 7 4 5.9 3.3 | -3.2 26.2 355 10 5 6.7 3.7
13500 -3.2 26.2 360 7 3 5.9 3.3 | -2.2 28.0 350 9 5 6.3 3.5
13000 -2.4 27.7 360 6 3 6.3 3.4 | -1.4 29.5 345 8 4 6.2 3.4
12500 -1.5 29.3 355 5 3 6.8 3.7 | -0.5 31.1 335 8 4 7.0 3.9
12000 -0.5 31.1 355 5 2 7.4 4.1 | 0.4 32.7 325 7 3 7.4 4.0
11750 0.1 32.2 350 5 2 8.6 4.7 | 1.1 34.0 320 6 3 10.0 5.5
11500 0.7 33.3 350 5 2 8.9 4.9 | 1.8 35.2 315 5 3 10.4 5.7
11250 1.4 34.5 345 5 2 8.4 4.6 | 2.5 36.5 305 5 2 9.7 5.3
11000 1.9 35.4 340 5 3 8.0 4.4 | 3.2 37.8 300 5 2 8.7 4.7
10750 2.5 36.5 335 6 3 8.2 4.5 | 3.8 38.8 300 4 2 10.0 5.5
10500 3.1 37.6 330 7 4 8.5 4.7 | 4.6 40.3 300 4 2 11.3 6.2
10250 3.7 38.7 330 8 4 6.2 3.4 | 5.4 41.7 300 4 2 10.3 5.7
10000 4.0 39.2 330 9 5 4.0 2.2 | 6.2 43.2 300 4 2 9.7 5.3
9750 4.4 39.9 325 10 5 5.4 2.9 | 6.9 44.4 295 4 2 9.7 5.3
9500 4.8 40.6 325 11 5 5.6 3.1 | 7.6 45.7 295 4 2 11.3 6.2
9250 5.0 41.0 320 9 5 -0.1 -0.0 | 8.7 47.7 295 3 2 18.3 10.1
9000 4.3 39.7 295 5 3 -18.4 -10.1 | 10.5 50.9 290 3 2 32.2 17.7
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
04/30/2026 AT 1500 MDT | 04/30/2026 AT 1800 MDT
|
CAPE... +160.7 LI... -1.4 | CAPE... +65.5 LI... -0.5
CINH... -3.4 K INDEX... +19.8 | CINH... -2.8 K INDEX... +17.5
|
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 -62.0 -79.6 280 26 14 2.2 1.2 | -62.9 -81.2 280 27 14 1.7 0.9
45000 -59.2 -74.6 305 33 17 -0.9 -0.5 | -60.7 -77.3 305 32 17 -0.5 -0.3
40000 -60.6 -77.1 355 38 20 -1.5 -0.8 | -61.5 -78.7 330 36 18 -1.4 -0.8
38000 -57.3 -71.1 360 40 21 6.8 3.7 | -57.6 -71.7 335 36 18 7.7 4.2
36000 -53.3 -63.9 360 41 21 6.8 3.7 | -53.0 -63.4 340 35 18 7.7 4.2
34000 -48.7 -55.7 005 40 21 8.6 4.7 | -48.2 -54.8 340 34 18 8.3 4.6
32000 -43.5 -46.3 005 38 20 8.6 4.7 | -43.2 -45.8 345 33 17 8.3 4.6
30000 -38.0 -36.4 010 35 18 7.7 4.2 | -37.5 -35.5 350 30 16 8.5 4.7
29000 -35.6 -32.1 010 32 17 7.7 4.2 | -34.9 -30.8 350 29 15 8.5 4.7
28000 -33.3 -27.9 010 30 15 7.7 4.2 | -32.4 -26.3 355 28 15 8.6 4.7
27000 -30.9 -23.6 010 29 15 8.1 4.5 | -29.9 -21.8 355 28 14 7.9 4.3
26000 -28.5 -19.3 005 30 15 8.1 4.5 | -27.6 -17.7 355 28 14 7.8 4.3
25000 -26.0 -14.8 360 31 16 8.1 4.5 | -25.2 -13.4 350 28 15 7.8 4.3
24000 -23.7 -10.7 360 31 16 7.5 4.1 | -22.9 -9.2 355 28 14 7.6 4.2
23000 -21.4 -6.5 360 30 16 7.5 4.1 | -20.6 -5.1 355 26 13 7.6 4.2
22000 -19.2 -2.6 005 29 15 7.6 4.1 | -18.3 -0.9 360 25 13 7.6 4.2
21000 -16.9 1.6 005 28 14 8.0 4.4 | -16.1 3.0 360 23 12 7.2 3.9
20000 -14.4 6.1 010 26 13 8.1 4.4 | -14.0 6.8 360 20 10 7.2 3.9
19500 -13.2 8.2 010 25 13 8.0 4.4 | -12.9 8.8 360 19 10 7.2 3.9
19000 -12.0 10.4 015 24 12 7.9 4.3 | -11.9 10.6 355 17 9 7.4 4.0
18500 -11.0 12.2 015 23 12 6.4 3.5 | -10.7 12.7 355 17 9 8.3 4.5
18000 -10.0 14.0 010 21 11 6.5 3.6 | -9.4 15.1 350 17 9 8.3 4.5
17500 -9.1 15.6 010 19 10 5.4 3.0 | -8.3 17.1 345 17 9 7.2 3.9
17000 -8.3 17.1 010 17 9 5.1 2.8 | -7.2 19.0 345 17 9 6.9 3.8
16500 -7.6 18.3 005 15 8 5.1 2.8 | -6.2 20.8 340 17 9 6.3 3.5
16000 -6.8 19.8 360 13 7 5.0 2.7 | -5.4 22.3 340 17 9 4.6 2.5
15500 -6.1 21.0 350 12 6 4.9 2.7 | -4.7 23.5 335 16 8 4.7 2.6
15000 -4.9 23.2 335 11 6 6.8 3.7 | -3.8 25.2 330 14 7 5.2 2.8
14500 -4.0 24.8 320 11 6 6.7 3.7 | -3.2 26.2 325 13 7 5.5 3.0
14000 -2.9 26.8 310 10 5 9.1 5.0 | -2.2 28.0 320 11 6 8.8 4.8
13500 -1.7 28.9 295 8 4 8.4 4.6 | -1.0 30.2 315 10 5 8.1 4.5
13000 -0.5 31.1 285 8 4 9.5 5.2 | 0.2 32.4 310 9 5 9.4 5.1
12500 1.0 33.8 280 7 4 9.9 5.4 | 1.6 34.9 305 9 5 9.9 5.5
12000 2.4 36.3 275 7 4 9.2 5.0 | 2.8 37.0 305 9 4 7.4 4.1
11750 3.1 37.6 275 7 3 10.1 5.6 | 3.5 38.3 300 8 4 10.0 5.5
11500 3.8 38.8 275 7 3 10.1 5.5 | 4.2 39.6 300 8 4 9.9 5.5
11250 4.6 40.3 275 6 3 9.9 5.5 | 4.9 40.8 295 8 4 9.2 5.1
11000 5.3 41.5 270 6 3 9.6 5.3 | 5.6 42.1 290 8 4 8.0 4.4
10750 6.0 42.8 270 6 3 10.1 5.5 | 6.2 43.2 285 8 4 8.8 4.9
10500 6.8 44.2 270 6 3 10.6 5.8 | 6.9 44.4 280 7 4 9.7 5.3
10250 7.6 45.7 270 6 3 10.3 5.7 | 7.6 45.7 275 7 4 9.0 5.0
10000 8.4 47.1 270 6 3 10.2 5.6 | 8.2 46.8 270 7 4 8.6 4.7
9750 9.1 48.4 265 5 3 10.3 5.7 | 8.9 48.0 265 7 3 8.6 4.7
9500 9.9 49.8 265 5 3 10.6 5.8 | 9.5 49.1 260 6 3 9.3 5.1
9250 10.8 51.4 265 5 3 15.4 8.5 | 10.1 50.2 255 6 3 6.0 3.3
9000 12.6 54.7 260 5 3 38.9 21.3 | 9.7 49.5 240 4 2 -21.6 -11.9
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.
042613
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