Helena Regional to Seattle-Tacoma International HLN → SEA
425 nautical miles (490 statute miles) west on a straight line, true course 281°, about 269° magnetic at the departure end (variation 12E). At 120 knots that is 3 h 13 min at the quickest height in today's winds (8,500 ft, a 12-knot tailwind), arriving about 8:47 pm PDT (03:47 UTC), after sunset at the destination. Right now HLN is low IFR, wind from the west-northwest (290°) at 5 knots; SEA is VFR, wind from the north-northwest (340°) at 10 knots. For planning, not a briefing: the legal preflight briefing comes from Flight Service (1-800-WX-BRIEF) or the FAA's own tools. Airlines fly this pair: 721 flights in the DOT's last twelve reported months, the route's page.
The route the straight line, the warnings crossed, restrictions, pilot reports and the airports along the way · click a mark for its words
Green, blue, red and purple airport dots are the flying conditions reported there now (VFR, marginal VFR, IFR, low IFR); grey means no report. Red areas are SIGMETs, orange areas AIRMETs, hatched red areas temporary flight restrictions. Map tiles: OpenFreeMap, data © OpenStreetMap contributors.
Warnings the route crosses SIGMETs and AIRMETs whose area the line passes through or comes within 25 nm of
- AIRMET SIERRA 4E: low cloud or poor visibility (IFR conditions) (due to ceilings below 1,000 ft, visibility below 3 miles, precipitation, mist). Over the first 158 nm of the route.
- AIRMET TANGO 4W: moderate turbulence above 18,000 ft from 18,000 ft to 36,000 ft. Over the first 168 nm of the route.
- AIRMET SIERRA 1E: mountains obscured by cloud (due to mountains obscured by clouds, precipitation, mist). Over the first 228 nm of the route.
- AIRMET ZULU 2C: moderate icing up to 14,000 ft. Over the route from 79 to 307 nm out.
A SIGMET warns of weather hazardous to all aircraft; an AIRMET of weather that matters to small aircraft and to flying without instruments. "From 60 to 180 nm out" is measured along the route from HLN.
Pilot reports along the route within 50 nm of the line, last three hours, the serious ones first
- E75L at 14,000 ft, 20 nm south, 5:22 pm MDT (23:22 UTC): moderate turbulence from 14,000 ft to 21,000 ft, remarks: during the climb zlc. 79 nm along the route, 20 nm south of the line.
as filed, and in English
MSO UA /OV 32S/TM 2322/FL140/TP E75L/TB MOD 140-210/RM DURC /ZLC
- Report
- a routine report filed through MSO
- Where
- over 32S
- Time
- 23:22 UTC
- Height
- at 14,000 ft
- Aircraft
- E75L
- Turbulence
- moderate from 14,000 ft to 21,000 ft
- Remarks
- during the climb zlc
- B738 at 24,000 ft, 41 nm south, 5:13 pm MDT (23:13 UTC): remarks: snow top flight level at 24,000 ft zlc. At the departure end, 41 nm south of the line.
as filed, and in English
BZN UA /OV BZN270030/TM 2313/FL240/TP B738/RM SN TOP FL 240 /ZLC
- Report
- a routine report filed through BZN
- Where
- 30 nm west (270°) of BZN
- Time
- 23:13 UTC
- Height
- at 24,000 ft
- Aircraft
- B738
- Remarks
- snow top flight level at 24,000 ft zlc
- B739 at 3,700 ft, 3 nm northeast, 3:58 pm MDT (21:58 UTC): overcast above 3,700 ft, remarks: during the descent ils runway 12. 89 nm along the route, 3 nm northeast of the line.
as filed, and in English
MSO UA /OV MSO/TM 2158/FL037/TP B739/SK OVC037/RM DURD ILS RY 12
- Report
- a routine report filed through MSO
- Where
- over MSO
- Time
- 21:58 UTC
- Height
- at 3,700 ft
- Aircraft
- B739
- Sky
- overcast from 3,700 ft
- Remarks
- during the descent ils runway 12
- C172 at 5,500 ft, 32 nm south, 4:17 pm MDT (22:17 UTC): a trace of rime icing, 0 °C, remarks: zse. 247 nm along the route, 32 nm south of the line.
as filed, and in English
PUW UA /OV PUW250030/TM 2217/FL055/TP C172/TA 00/IC TRACE RIME/RM -ZSE
- Report
- a routine report filed through PUW
- Where
- 30 nm west (250°) of PUW
- Time
- 22:17 UTC
- Height
- at 5,500 ft
- Aircraft
- C172
- Temperature
- 0 °C
- Icing
- trace rime
- Remarks
- zse
Winds aloft along the route, and the time en route the forecast for use 20:00–03:00 UTC · at 120 knots true airspeed
The westbound cruising heights for this course (VFR: even thousands plus 500 ft; above 18,000 ft the forecast levels), with the wind averaged along the line from the 6 forecast points nearest it (GTF, GPI, LWS, GEG, YKM, SEA). A plus sign is a headwind, a minus sign a tailwind.
| Height | Average wind | Head- or tailwind | Temperature | Ground speed | Time en route | Arrival |
|---|---|---|---|---|---|---|
| 4,500 ft | 050° at 16 kt | −10 kt | -2 °C | 130 kt | 3 h 16 min | 8:50 pm PDT (03:50 UTC) |
| 6,500 ft | 050° at 16 kt | −11 kt | -3 °C | 131 kt | 3 h 15 min | 8:49 pm PDT (03:49 UTC) |
| 8,500 ft | 050° at 16 kt | −12 kt | -7 °C | 132 kt | 3 h 13 min | 8:47 pm PDT (03:47 UTC) |
| 10,500 ft | 050° at 11 kt | −8 kt | -9 °C | 128 kt | 3 h 19 min | 8:53 pm PDT (03:53 UTC) |
| 12,500 ft | 060° at 6 kt | −5 kt | -11 °C | 125 kt | 3 h 24 min | 8:58 pm PDT (03:58 UTC) |
| 14,500 ft | 090° at 4 kt | −4 kt | -14 °C | 124 kt | 3 h 26 min | 9:00 pm PDT (04:00 UTC) |
| 16,500 ft | 140° at 4 kt | −4 kt | -18 °C | 124 kt | 3 h 26 min | 9:00 pm PDT (04:00 UTC) |
| 18,000 ft FL180 | 160° at 6 kt | −4 kt | -21 °C | 124 kt | 3 h 26 min | 9:00 pm PDT (04:00 UTC) |
| 24,000 ft FL240 | 210° at 7 kt | +1 kt | -28 °C | 119 kt | 3 h 34 min | 9:08 pm PDT (04:08 UTC) |
| 30,000 ft FL300 | 210° at 25 kt | +9 kt | -37 °C | 111 kt | 3 h 50 min | 9:24 pm PDT (04:24 UTC) |
| 34,000 ft FL340 | 230° at 26 kt | +17 kt | -40 °C | 103 kt | 4 h 08 min | 9:42 pm PDT (04:42 UTC) |
| 39,000 ft FL390 | 250° at 22 kt | +18 kt | -42 °C | 102 kt | 4 h 10 min | 9:44 pm PDT (04:44 UTC) |
Based on data from the 11th at 18:00 UTC; valid on the 12th at 00:00 UTC for use 20:00 to 03:00 UTC; temperatures above 24,000 ft are below zero. Heights are above sea level; a height is left out when the forecast has no wind for it over most of the line (the ground is higher). Ground speed is the airspeed less the headwind; the time en route is for the straight line and ignores climb, descent and routing around weather.
The forecast points as issued
| Point | From | 3,000 | 6,000 | 9,000 | 12,000 | 18,000 | 24,000 | 30,000 | 34,000 | 39,000 |
|---|---|---|---|---|---|---|---|---|---|---|
| GTF | used from 0 nm out; 69 nm from the line | 070/21 | 080/18 -6° | 120/5 -5° | 180/30 -14° | 200/53 -24° | 210/80 -38° | 220/83 -44° | 230/68 -46° | |
| GPI | used from 49 nm out; 92 nm from the line | 060/19 -3° | 110/11 -8° | 130/6 -8° | 200/40 -19° | 190/58 -28° | 200/101 -39° | 220/73 -43° | 230/41 -43° | |
| LWS | used from 148 nm out; 55 nm from the line | 010/5 | 050/14 -2° | 040/12 -6° | 160/7 -10° | 190/30 -22° | 200/54 -27° | 200/48 -35° | 210/40 -37° | 230/32 -41° |
| GEG | used from 198 nm out; 28 nm from the line | 050/18 -2° | 060/19 -8° | L/V -11° | 160/11 -24° | 190/17 -31° | 200/19 -35° | 220/14 -37° | 250/11 -41° | |
| YKM | used from 297 nm out; 56 nm from the line | 030/16 | 020/18 0° | 030/30 -8° | 030/23 -13° | 020/40 -23° | 010/73 -29° | 010/54 -36° | 360/29 -37° | 330/16 -40° |
| SEA | used from 396 nm out; 15 nm from the line | 360/9 | 350/10 1° | 010/10 -5° | 030/20 -11° | 020/60 -17° | 010/86 -26° | 360/90 -40° | 010/68 -42° | 360/31 -43° |
The weather now: both ends and the airports along the way public airports with a weather report within 25 nm of the line, one for each stretch
| Airport | Where | Conditions | Wind | Visibility | Ceiling | Elevation | Reported |
|---|---|---|---|---|---|---|---|
| HLN Helena, MT | departure | low IFR Sky: scattered clouds at 500 feet, overcast at 1,300 feet Weather: snow, freezing fog | from the west-northwest (290°) at 5 knots | 0.5 mi | 1,300 ft | 3,877 ft | 6:06 pm MDT (00:06 UTC) |
| MSO Missoula, MT | 89 nm out, 4 nm north of the line, tower | marginal VFR Sky: overcast at 3,200 feet Weather: light rain | from the south (180°) at 3 knots | 4 mi | 3,200 ft | 3,205 ft | 23:53 UTC |
| PUW Pullman/Moscow, WA | 208 nm out, 24 nm south of the line | VFR Sky: overcast at 5,500 feet | from the north-northeast (030°) at 9 knots | 10+ mi | 5,500 ft | 2,566 ft | 23:53 UTC |
| MWH Moses Lake, WA | 307 nm out, 7 nm southeast of the line, tower | VFR Sky: a broken layer at 10,000 feet | from the east-northeast (070°) at 14 knots | 10+ mi | 10,000 ft | 1,188 ft | 23:52 UTC |
| ESW Easton, WA | 376 nm out, 9 nm southwest of the line | no report just now | 2,226 ft | ||||
| SEA Seattle, WA | destination | VFR Sky: a few clouds at 2,000 feet, a few clouds at 5,000 feet | from the north-northwest (340°) at 10 knots | 10+ mi | none | 432 ft | 4:53 pm PDT (23:53 UTC) |
The highest airport on this list sits at 3,877 ft; the ground between airports is higher still. Check the sectional chart for the terrain and the minimum safe heights along the line.
At SEA when you get there the forecast at the estimated arrival, 8:47 pm PDT (03:47 UTC)
Wind from the northeast at 6 knots, visibility more than 6 miles, clear skies VFR
The whole forecast for SEA
- From Sun 5:00 pm PDT (00:00 UTC): wind from the north at 12 knots, gusting to 20, visibility more than 6 miles, a few clouds at 2,000 feet, a few clouds at 5,000 feet
- From Sun 8:00 pm PDT (03:00 UTC): wind from the northeast at 6 knots, visibility more than 6 miles, clear skies
- From Mon 3:00 am PDT (10:00 UTC): wind from the southeast at 4 knots, visibility more than 6 miles, patches of fog, clear skies
- From Mon 9:00 am PDT (16:00 UTC): wind from the south-southeast at 4 knots, visibility more than 6 miles, clear skies
- From Mon 11:00 am PDT (18:00 UTC): wind from the west at 6 knots, visibility more than 6 miles, clear skies
- From Mon 8:00 pm PDT (03:00 UTC): wind from the northwest at 5 knots, visibility more than 6 miles, scattered clouds at 25,000 feet
The forecast for HLN, the departure
- From Sun 6:00 pm MDT (00:00 UTC): wind from the north-northwest at 12 knots, gusting to 24, visibility ¾ mile, light snow, mist, scattered clouds at 800 feet, overcast at 1,600 feet
- From Mon 12:00 am MDT (06:00 UTC): wind from the northwest at 14 knots, gusting to 30, visibility 1½ miles, light snow, mist, scattered clouds at 800 feet, overcast at 1,500 feet
- From Mon 4:00 am MDT (10:00 UTC): wind from the west-northwest at 10 knots, visibility 3 miles, light snow, mist, scattered clouds at 1,000 feet, overcast at 2,500 feet
- From Mon 7:00 am MDT (13:00 UTC): wind light and variable, visibility more than 6 miles, overcast at 2,500 feet
- From Mon 1:00 pm MDT (19:00 UTC): wind light and variable, visibility more than 6 miles, scattered clouds at 3,500 feet
Temporary flight restrictions on the line or within 25 nm of it
No temporary flight restriction on or near this route right now.
Daylight
Sunset at HLN 6:46 pm MDT (00:46 UTC), at SEA 6:27 pm PDT (01:27 UTC) (civil twilight ends 6:58 pm PDT (01:58 UTC)). At 120 knots the arrival at SEA is after sunset there (6:29 pm PDT (01:29 UTC)).
Each restriction opens the FAA's own page with the exact area, heights and times. Ordinary notices to air missions (closed runways, lights out) are not shown: the FAA's notice search is not open to sites like this one at this time.
Radar and forecast charts for the regions crossed government pictures, the latest each time the page loads
Sources: the Aviation Weather Center's data service (SIGMETs, AIRMETs, graphical AIRMETs, pilot reports, winds and temperatures aloft, observations and terminal forecasts), the National Weather Service radar, the Weather Prediction Center's charts, the FAA's temporary flight restriction list and shapes, and the FAA's airport file for the positions, elevations and magnetic variation. Fetched when the page is viewed and kept a few minutes. Each leg is the straight line between its two airports; airways, terrain and airspace are not considered. The airports in detail: Helena Regional, Seattle-Tacoma International.