Plan a flight · Sun 7:02 pm PDT (02:02 UTC)

Boeing Fld/King County International to Joslin Fld/Magic Valley Regional BFI → TWF

449 nautical miles (517 statute miles) southeast on a straight line, true course 130°, about 115° magnetic at the departure end (variation 15E). At 120 knots that is 3 h 29 min at the quickest height in today's winds (5,500 ft, a 9-knot tailwind), arriving about 11:31 pm MDT (05:31 UTC), after sunset at the destination. Right now BFI is VFR, wind calm; TWF is VFR, wind from the southwest (230°) at 7 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: 9 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 TANGO 1W: moderate turbulence above 18,000 ft from 18,000 ft to 39,000 ft. Over the first 160 nm of the route.
AIRMET ZULU 2C: moderate icing up to 16,000 ft. Over the route from 110 to 249 nm out.
AIRMET SIERRA 1E: mountains obscured by cloud (due to mountains obscured by clouds, precipitation, mist). Over the route from 170 to 279 nm out.
AIRMET TANGO 4W: moderate turbulence above 18,000 ft from 18,000 ft to 36,000 ft. Over the last 120 nm of the route.
AIRMET ZULU 3C: moderate icing up to 22,000 ft. Over the last 110 nm of the route.

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 BFI.

Pilot reports along the route within 50 nm of the line, last three hours, the serious ones first

SB20 at 16,000 ft, 44 nm northeast, 6:52 pm PDT (01:52 UTC): remarks: zse. 20 nm along the route, 44 nm northeast of the line.
as filed, and in English
```
PAE UA /OV PAE075045/TM 0152/FL160/TP SB20/SK TOP120/RM ZSE
```
Report
a routine report filed through PAE
Where
45 nm east (075°) of PAE
Time
01:52 UTC
Height
at 16,000 ft
Aircraft
SB20
Sky
TOP120
Remarks
zse
A321 at 13,500 ft, 12 nm southwest, 6:54 pm PDT (01:54 UTC): remarks: zse. 50 nm along the route, 12 nm southwest of the line.
as filed, and in English
```
SEA UA /OV SEA120045/TM 0154/FL135/TP A321/SK TOP130/RM ZSE
```
Report
a routine report filed through SEA
Where
45 nm southeast (120°) of SEA
Time
01:54 UTC
Height
at 13,500 ft
Aircraft
A321
Sky
TOP130
Remarks
zse
PC12 at 15,000 ft, 12 nm southwest, 5:42 pm PDT (00:42 UTC): remarks: zse. 50 nm along the route, 12 nm southwest of the line.
as filed, and in English
```
YKM UA /OV YKM270050/TM 0042/FL150/TP PC12/SK TOP130/RM -ZSE
```
Report
a routine report filed through YKM
Where
50 nm west (270°) of YKM
Time
00:42 UTC
Height
at 15,000 ft
Aircraft
PC12
Sky
TOP130
Remarks
zse
PC12 at 13,000 ft, 12 nm southwest, 5:42 pm PDT (00:42 UTC): remarks: zse. 50 nm along the route, 12 nm southwest of the line.
as filed, and in English
```
YKM UA /OV YKM270050/TM 0042/FL130/TP PC12/SK TOP130/RM -ZSE
```
Report
a routine report filed through YKM
Where
50 nm west (270°) of YKM
Time
00:42 UTC
Height
at 13,000 ft
Aircraft
PC12
Sky
TOP130
Remarks
zse
C337 at 12,000 ft, 9 nm southwest, 6:18 pm PDT (01:18 UTC): light rime icing, -12 °C, remarks: zse. 110 nm along the route, 9 nm southwest of the line.
as filed, and in English
```
YKM UA /OV YKM155020/TM 0118/FL120/TP C337/TA M12/IC LGT RIME/RM ZSE
```
Report
a routine report filed through YKM
Where
20 nm southeast (155°) of YKM
Time
01:18 UTC
Height
at 12,000 ft
Aircraft
C337
Temperature
−12 °C
Icing
light rime
Remarks
zse
PC12 at 6,000 ft, 28 nm northeast, 5:56 pm PDT (00:56 UTC): overcast above 6,000 ft. 180 nm along the route, 28 nm northeast of the line.
as filed, and in English
```
ALW UA /OV ALW200015/TM 0056/FL060/TP PC12/SK OVC060
```
Report
a routine report filed through ALW
Where
15 nm south (200°) of ALW
Time
00:56 UTC
Height
at 6,000 ft
Aircraft
PC12
Sky
overcast from 6,000 ft
PC12 at 6,000 ft, 49 nm northeast, 6:09 pm PDT (01:09 UTC): scattered clouds up to 6,000 ft, remarks: multiple scattered layers during the descent runway 31. 409 nm along the route, 49 nm northeast of the line.
as filed, and in English
```
SUN UA /OV KSUN/TM 0109/FL060/TP PC12/SK SCT-TOP060/WX FV05SM/RM MULTIPLE SCT LAYERS DURD RY31
```
Report
a routine report filed through SUN
Where
over KSUN
Time
01:09 UTC
Height
at 6,000 ft
Aircraft
PC12
Sky
scattered clouds, tops 6,000 ft
Weather
flight visibility 5 miles
Remarks
multiple scattered layers during the descent runway 31
E550 at 21,000 ft, 49 nm northeast, 4:27 pm PDT (23:27 UTC): light turbulence, a few clouds above 7,000 ft, remarks: during the climb zlc. 409 nm along the route, 49 nm northeast of the line.
as filed, and in English
```
SUN UA /OV SUN/TM 2327/FL210/TP E550/SK FEW070/TB CONS LGT/RM DURC /ZLC
```
Report
a routine report filed through SUN
Where
over SUN
Time
23:27 UTC
Height
at 21,000 ft
Aircraft
E550
Sky
a few clouds from 7,000 ft
Turbulence
continuous light
Remarks
during the climb zlc

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 eastbound cruising heights for this course (VFR: odd thousands plus 500 ft; above 18,000 ft the forecast levels), with the wind averaged along the line from the 4 forecast points nearest it (SEA, YKM, LWS, BOI). A plus sign is a headwind, a minus sign a tailwind.

Height	Average wind	Head- or tailwind	Temperature	Ground speed	Time en route	Arrival
3,500 ft	020° at 13 kt	−4 kt		124 kt	3 h 37 min	11:39 pm MDT (05:39 UTC)
5,500 ft	360° at 13 kt	−9 kt	4 °C	129 kt	3 h 29 min	11:31 pm MDT (05:31 UTC)
7,500 ft	010° at 11 kt	−6 kt	-2 °C	126 kt	3 h 34 min	11:36 pm MDT (05:36 UTC)
9,500 ft	020° at 9 kt	−2 kt	-6 °C	122 kt	3 h 41 min	11:43 pm MDT (05:43 UTC)
11,500 ft	010° at 2 kt	−1 kt	-9 °C	121 kt	3 h 43 min	11:45 pm MDT (05:45 UTC)
13,500 ft	320° at 1 kt	−1 kt	-13 °C	121 kt	3 h 43 min	11:45 pm MDT (05:45 UTC)
15,500 ft	310° at 2 kt	−1 kt	-16 °C	121 kt	3 h 43 min	11:45 pm MDT (05:45 UTC)
17,500 ft	300° at 2 kt	−1 kt	-20 °C	121 kt	3 h 43 min	11:45 pm MDT (05:45 UTC)
18,000 ft FL180	300° at 2 kt	−1 kt	-21 °C	121 kt	3 h 43 min	11:45 pm MDT (05:45 UTC)
24,000 ft FL240	300° at 6 kt	−4 kt	-27 °C	124 kt	3 h 37 min	11:39 pm MDT (05:39 UTC)
30,000 ft FL300	240° at 10 kt	−2 kt	-35 °C	122 kt	3 h 41 min	11:43 pm MDT (05:43 UTC)
34,000 ft FL340	230° at 23 kt	−1 kt	-37 °C	121 kt	3 h 43 min	11:45 pm MDT (05:45 UTC)
39,000 ft FL390	240° at 28 kt	−6 kt	-41 °C	126 kt	3 h 34 min	11:36 pm MDT (05:36 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
SEA	used from 0 nm out; 22 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°
YKM	used from 50 nm out; 18 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°
LWS	used from 200 nm out; 93 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°
BOI	used from 249 nm out; 75 nm from the line		330/14 4°	230/5 -2°	220/20 -7°	210/37 -20°	200/59 -26°	200/67 -34°	210/73 -35°	220/62 -41°

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
BFI Seattle, WA	departure	VFR Sky: a few clouds at 6,000 feet	calm	10+ mi	none	21 ft	6:53 pm PDT (01:53 UTC)
PLU Puyallup, WA	20 nm out, 20 nm southwest of the line	VFR Weather: light drizzle	calm	10+ mi	none	537 ft	23:35 UTC
ESW Easton, WA	50 nm out, 17 nm northeast of the line	no report just now				2,226 ft
YKM Yakima, WA	90 nm out, 3 nm east of the line, tower	VFR Sky: overcast at 9,500 feet	from the west-northwest (290°) at 6 knots	10+ mi	9,500 ft	1,098 ft	01:53 UTC
HRI Hermiston, OR	160 nm out, 5 nm northeast of the line	VFR Sky: overcast at 9,500 feet	from the north (360°) at 3 knots	10+ mi	9,500 ft	644 ft	01:53 UTC
PDT Pendleton, OR	180 nm out, 10 nm northeast of the line, tower	VFR Sky: overcast at 7,000 feet	calm	10+ mi	7,000 ft	1,494 ft	01:53 UTC
BKE Baker City, OR	249 nm out, 3 nm north of the line	VFR Sky: a broken layer at 7,500 feet	from the northwest (310°) at 14 knots, gusting to 23	10+ mi	7,500 ft	3,373 ft	01:53 UTC
ONO Ontario, OR	309 nm out, 12 nm southwest of the line	VFR Sky: a broken layer at 7,500 feet	from the north-northwest (330°) at 18 knots, gusting to 28	10+ mi	7,500 ft	2,193 ft	01:53 UTC
BOI Boise, ID	349 nm out, 7 nm southwest of the line, tower	VFR Sky: a broken layer at 7,500 feet, overcast at 12,000 feet	from the southeast (130°) at 9 knots	10+ mi	7,500 ft	2,871 ft	01:53 UTC
GNG Gooding, ID	419 nm out, 10 nm northeast of the line	VFR Sky: overcast at 4,600 feet	calm	10+ mi	4,600 ft	3,732 ft	01:55 UTC
TWF Twin Falls, ID	destination	VFR Sky: overcast at 4,000 feet	from the southwest (230°) at 7 knots	10+ mi	4,000 ft	4,153 ft	7:53 pm MDT (01:53 UTC)

The highest airport on this list sits at 4,153 ft; the ground between airports is higher still. Check the sectional chart for the terrain and the minimum safe heights along the line.

At TWF when you get there the forecast at the estimated arrival, 11:31 pm MDT (05:31 UTC)

Wind from the southwest at 9 knots, visibility more than 6 miles, a broken layer at 4,000 feet VFR

The whole forecast for TWF

From Sun 6:00 pm MDT (00:00 UTC): wind from the west-southwest at 6 knots, visibility more than 6 miles, showers nearby, overcast at 4,000 feet
From Sun 8:00 pm MDT (02:00 UTC): wind from the southwest at 9 knots, visibility more than 6 miles, a broken layer at 4,000 feet
From Mon 2:00 am MDT (08:00 UTC): wind from the southwest at 7 knots, visibility 5 miles, light rain, mist, scattered clouds at 1,000 feet, overcast at 3,000 feet
From Mon 12:00 pm MDT (18:00 UTC): wind from the west-northwest at 8 knots, visibility 6 miles, light rain showers, mist, scattered clouds at 1,500 feet, a broken layer at 3,500 feet
From Mon 2:00 pm MDT (20:00 UTC): wind from the northwest at 6 knots, visibility more than 6 miles, showers nearby, scattered clouds at 5,000 feet, overcast at 10,000 feet

The forecast for BFI, the departure

From Sun 5:00 pm PDT (00:00 UTC): wind from the north-northwest at 8 knots, gusting to 18, visibility more than 6 miles, a few clouds at 5,000 feet
From Sun 7:00 pm PDT (02:00 UTC): wind light and variable, visibility more than 6 miles, clear skies
From Mon 3:00 am PDT (10:00 UTC): wind light and variable, 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 3 knots, visibility more than 6 miles, clear skies
From Mon 12:00 pm PDT (19:00 UTC): wind from the west-southwest at 3 knots, visibility more than 6 miles, clear skies
From Mon 2:00 pm PDT (21:00 UTC): wind from the west at 5 knots, visibility more than 6 miles, clear skies

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 BFI 6:27 pm PDT (01:27 UTC), at TWF 7:00 pm MDT (01:00 UTC) (civil twilight ends 7:29 pm MDT (01:29 UTC)). At 120 knots the arrival at TWF is after sunset there (7:02 pm MDT (01:02 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

Radar now, the Pacific Northwest · loop National Weather Service

Radar, the whole country · loop National Weather Service

Surface analysis now Weather Prediction Center

Forecast chart, 12 hours ahead Weather Prediction Center

Forecast chart, 24 hours ahead Weather Prediction Center

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: Boeing Fld/King County International, Joslin Fld/Magic Valley Regional.