085
UXUS97 KLKN 172057
SRGLKN
SOARING FORECAST
NATIONAL WEATHER SERVICE ELKO, NEVADA
1356 PDT WEDNESDAY, SEPTEMBER 17, 2025
DISCLAIMER: A SOARING FORECAST ATTEMPTS TO GAUGE THE POTENTIAL FOR THE
ATMOSPHERE TO PROVIDE A THERMAL LIFTING MECHANISM FOR GLIDERS OR HOT
AIR BALLOONISTS TO USE AS A SOURCE OF LIFT. A MORE UNSTABLE AIR MASS
BOTH IN THE LOW LEVELS AND ALOFT IS PREFERRED TO PRODUCE DESIRED
THERMAL ACTIVITY. THE FORECAST PRODUCT ISSUED BY MANY (BUT NOT ALL)
NWS OFFICES USES INDICES CALCULATED FROM AN UPPER AIR BALLOON SOUNDING.
THE DATA COLLECTED AT 12 UTC USUALLY SERVES AS THE INPUT TO THE FORECAST.
PLEASE NOTE THAT THIS IS NOT AN OFFICIAL FORECAST BUT CAN BE USED AS A
RESOURCE TO ASSIST PILOTS IN THEIR PRE-FLIGHT PLANNING. PILOTS CAN
COMPLETE THEIR REGULATORY-COMPLIANT PREFLIGHT BRIEFING BY USING OTHER
AUTOMATED RESOURCES OR FROM FLIGHT SERVICE AT WWW.1800WXBRIEF.COM OR
BY CALLING 1-800-WX-BRIEF.
THIS FORECAST IS FOR WEDNESDAY, SEPTEMBER 17, 2025:
IF THE TRIGGER TEMPERATURE OF 70.8 F/21.5 C IS REACHED...THEN
THERMAL SOARING INDEX....................... EXCELLENT
MAXIMUM RATE OF LIFT........................ 820 FT/MIN (4.2 M/S)
MAXIMUM HEIGHT OF THERMALS.................. 15729 FT MSL (10021 FT AGL)
FORECAST MAXIMUM TEMPERATURE................... 83.0 F/28.8 C
TIME OF TRIGGER TEMPERATURE.................... 1130 PDT
TIME OF OVERDEVELOPMENT........................ NONE
MIDDLE/HIGH CLOUDS DURING SOARING WINDOW....... NONE
SURFACE WINDS DURING SOARING WINDOW............ 20 MPH OR LESS
HEIGHT OF THE -3 THERMAL INDEX................. 13040 FT MSL (7333 FT AGL)
THERMAL SOARING OUTLOOK FOR THURSDAY 09/18..... GOOD
WAVE SOARING INDEX............................. POOR
WAVE SOARING INDEX TREND (TO 1800 PDT)......... GOOD
HEIGHT OF STABLE LAYER (12-18K FT MSL)......... NONE
WEAK PVA/NVA (THROUGH 1800 PDT)................ WEAK PVA
POTENTIAL HEIGHT OF WAVE....................... 28634 FT MSL (22926 FT AGL)
WAVE SOARING OUTLOOK FOR THURSDAY 09/18........ EXCELLENT
REMARKS...
SUNRISE/SUNSET.................... 06:26:19 / 18:48:23 PDT
TOTAL POSSIBLE SUNSHINE........... 12 HR 22 MIN 4 SEC (742 MIN 4 SEC)
ALTITUDE OF SUN AT 12:37:21 PDT... 50.74 DEGREES
UPPER AIR DATA FROM NUMERICAL MODEL FORECAST VALID ON 09/17/2025 AT 0600 PDT
FREEZING LEVEL.................. 14711 FT MSL (9003 FT AGL)
CONVECTIVE CONDENSATION LEVEL... 21310 FT MSL (15602 FT AGL)
LIFTED CONDENSATION LEVEL....... 19592 FT MSL (13884 FT AGL)
LIFTED INDEX.................... +3.5
K INDEX......................... -13.5
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 -62.9 -81.2 310 27 14 2.3 1.2 M M M M M
45000 -58.4 -73.1 305 39 20 4.4 2.4 M M M M M
40000 -51.7 -61.1 300 42 22 5.1 2.8 M M M M M
38000 -48.6 -55.5 300 40 21 5.1 2.8 M M M M M
36000 -45.5 -49.9 305 38 20 5.1 2.8 M M M M M
34000 -41.7 -43.1 305 38 19 6.7 3.7 M M M M M
32000 -37.7 -35.9 310 38 20 6.7 3.7 M M M M M
30000 -33.3 -27.9 315 40 20 7.7 4.2 41.9 107.5 10.3 M M
29000 -30.4 -22.7 315 41 21 7.7 4.2 41.0 105.7 9.7 M M
28000 -28.1 -18.6 320 42 22 7.7 4.2 40.3 104.6 9.3 M M
27000 -25.8 -14.4 320 40 21 7.7 4.2 39.4 102.9 8.7 M M
26000 -23.5 -10.3 320 39 20 7.7 4.2 38.6 101.5 8.2 M M
25000 -21.2 -6.2 325 37 19 7.6 4.2 37.9 100.3 7.8 M M
24000 -19.2 -2.6 325 33 17 6.5 3.5 36.7 98.1 6.9 M M
23000 -17.2 1.0 320 28 14 6.5 3.5 35.5 95.9 6.0 M M
22000 -15.3 4.5 315 23 12 6.6 3.6 34.4 94.0 5.1 M M
21000 -13.1 8.4 315 20 10 7.2 4.0 33.4 92.2 4.3 M M
20000 -11.0 12.2 310 17 9 7.2 4.0 32.6 90.6 3.6 M M
19000 -8.8 16.2 305 15 8 7.4 4.1 31.7 89.1 2.9 M M
18000 -6.5 20.3 305 14 7 7.1 3.9 31.0 87.7 2.3 M M
17000 -4.6 23.7 300 12 6 6.5 3.6 29.9 85.8 1.3 M M
16000 -2.7 27.1 300 11 6 6.5 3.6 28.8 83.8 0.3 M M
15000 -0.7 30.7 300 10 5 6.5 3.6 27.7 81.9 -0.7 762 3.9
14000 1.2 34.2 300 9 5 6.2 3.4 26.6 79.9 -1.7 675 3.4
13000 2.9 37.2 300 8 4 5.5 3.0 25.4 77.6 -2.9 593 3.0
12000 4.6 40.3 300 6 3 6.1 3.3 24.1 75.3 -4.2 514 2.6
11000 6.8 44.2 295 2 1 6.0 3.3 22.7 72.8 -5.7 409 2.1
10000 9.2 48.6 235 1 0 7.6 4.2 22.1 71.7 -6.4 310 1.6
9500 10.4 50.7 205 1 1 8.9 4.9 21.9 71.3 -6.6 259 1.3
9000 11.6 52.9 170 1 1 8.5 4.7 21.7 71.0 -6.9 207 1.1
8500 12.8 55.0 150 2 1 7.8 4.3 21.4 70.6 -7.2 156 0.8
8000 13.9 57.0 135 2 1 7.7 4.2 21.1 69.9 -7.6 108 0.6
7500 14.7 58.5 115 3 2 2.9 1.6 20.4 68.7 -8.3 70 0.4
7000 15.1 59.2 090 4 2 2.7 1.5 19.4 66.9 -9.4 43 0.2
6900 15.1 59.2 090 4 2 2.7 1.5 19.4 66.9 -9.4 43 0.2
6800 15.1 59.2 085 4 2 -2.3 -1.3 18.7 65.7 -10.2 35 0.2
6700 15.1 59.2 085 4 2 -2.3 -1.3 18.7 65.7 -10.2 35 0.2
6600 15.1 59.2 085 4 2 -2.3 -1.3 18.7 65.7 -10.2 35 0.2
6400 14.7 58.5 070 4 2 -7.2 -4.7 17.5 63.6 -11.4 40 0.2
6200 14.3 57.7 060 5 2 -1.2 -0.6 16.4 61.5 -12.5 46 0.2
6000 14.1 57.4 055 5 3 -10.4 -5.7 15.5 59.9 -13.5 44 0.2
5800 10.0 50.0 045 4 2 -99.0 -54.3 10.8 51.4 -18.3 158 0.8
5700 M M M M M M M M M M M M
________________________________________________________________________________
THIS PRODUCT IS ISSUED TWICE PER DAY, ONCE BY APPROXIMATELY 0630 PST/0730 PDT
(1330 UTC) AND AGAIN BY APPROXIMATELY 1830 PST/1930 PDT (0130 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 AT THE NATIONAL WEATHER SERVICE
OFFICE IN ELKO, NEVADA AT
NORTH LATITUDE: 40.84 DEGREES
WEST LONGITUDE: 115.60 DEGREES
ELEVATION: 5235 FEET (1595 METERS)
AND MAY NOT BE REPRESENTATIVE OF OTHER AREAS ACROSS NORTHERN AND CENTRAL
NEVADA. 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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