Plan a flight · Sun 10:47 pm PDT (05:47 UTC)

Boeing Fld/King County International to St. Louis Downtown Airport BFI → CPS

1,496 nautical miles (1,722 statute miles) east on a straight line, true course 099°, about 084° magnetic at the departure end (variation 15E). At 120 knots that is 9 h 35 min at the quickest height in today's winds (39,000 ft, a 36-knot tailwind), arriving about 10:22 am CDT (15:22 UTC). Right now BFI is VFR, wind calm; CPS is VFR, wind from the south-southeast (160°) at 4 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: 3 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

SIGMET 8C: thunderstorms (a convective SIGMET) up to 32,000 ft, moving from the southwest at 40 knots, until 11:55 pm PDT (06:55 UTC). Over the route from 778 to 828 nm out.

as issued

WSUS32 KKCI 120455
MKCC WST 120455
CONVECTIVE SIGMET 8C
VALID UNTIL 0655Z
NE SD WY
FROM 50WNW RAP-20SSW RAP-60NW BFF-40ENE DDY-50WNW RAP
DMSHG AREA TS MOV FROM 22040KT. TOPS TO FL320.

AIRMET TANGO 1W: moderate turbulence above 18,000 ft from 18,000 ft to 39,000 ft. Over the first 180 nm of the route.
AIRMET ZULU 2C: moderate icing up to 23,000 ft. Over the route from 120 to 539 nm out.
AIRMET SIERRA 1E: mountains obscured by cloud (due to mountains obscured by clouds, precipitation, mist). Over the route from 219 to 658 nm out.
AIRMET TANGO 1W: moderate turbulence above 18,000 ft from 18,000 ft to 36,000 ft. Over the route from 259 to 459 nm out.
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 route from 309 to 1008 nm out.
AIRMET ZULU 2C: moderate icing up to 23,000 ft. Over the route from 549 to 718 nm out.
AIRMET TANGO 4W: moderate turbulence below 18,000 ft up to 18,000 ft. Over the route from 589 to 758 nm out.
AIRMET TANGO 4W: moderate turbulence above 18,000 ft from 18,000 ft to 38,000 ft. Over the route from 609 to 828 nm out.
AIRMET TANGO 1W: low-level wind shear (due to air speed loss or gain of 20 knots or more below 2,000 ft above the ground). Over the route from 638 to 818 nm out.
AIRMET TANGO 3W: low-level wind shear (due to air speed loss or gain of 20 knots or more below 2,000 ft above the ground). Over the route from 948 to 1387 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 BFI.

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

CL30 at 4,200 ft, 35 nm north, 8:16 pm PDT (03:16 UTC): no icing, overcast above 4,200 ft, remarks: during the descent ils runway 12. 339 nm along the route, 35 nm north of the line.
as filed, and in English
```
MSO UA /OV MSO/TM 0316/FL042/TP CL30/SK OVC042/WX 2 1/2SM/IC NEG/RM DURD ILS RY 12
```
Report
a routine report filed through MSO
Where
over MSO
Time
03:16 UTC
Height
at 4,200 ft
Aircraft
CL30
Sky
overcast from 4,200 ft
Weather
2, 1/2SM
Icing
none
Remarks
during the descent ils runway 12
B737 , 4 nm northeast, 10:31 pm PDT (05:31 UTC): remarks: saw the light at 500FT braking good no icing. 469 nm along the route, 4 nm northeast of the line.
as filed, and in English
```
BZN UA /OV BZN/TM 0531/FLBURD/TP B737/RM SAW THE LIGHT AT 500FT. BRAKING GOOD. NEG ICING
```
Report
a routine report filed through BZN
Where
over BZN
Time
05:31 UTC
Height
at BURD
Aircraft
B737
Remarks
saw the light at 500FT braking good no icing
GLF5 descending, 4 nm northeast, 8:46 pm PDT (03:46 UTC): remarks: broke out 100-150FT above ground. 469 nm along the route, 4 nm northeast of the line.
as filed, and in English
```
BZN UA /OV BZN/TM 0346/FLDURD/TP GLF5/RM BROKE OUT 100-150FT AGL
```
Report
a routine report filed through BZN
Where
over BZN
Time
03:46 UTC
Height
during the descent
Aircraft
GLF5
Remarks
broke out 100-150FT above ground

Winds aloft along the route, and the time en route the forecast for use 02:00–09:00 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 15 forecast points nearest it (SEA, YKM, GEG, LWS, DLN, BIL, RAP, PIR, ONL, GRI, OMA, DSM, MKC, COU, STL). A plus sign is a headwind, a minus sign a tailwind.

Height	Average wind	Head- or tailwind	Temperature	Ground speed	Time en route	Arrival
5,500 ft	200° at 12 kt	+1 kt	15 °C	119 kt	12 h 34 min	1:21 pm CDT (18:21 UTC)
7,500 ft	210° at 9 kt	0	7 °C	120 kt	12 h 28 min	1:15 pm CDT (18:15 UTC)
9,500 ft	220° at 10 kt	−2 kt	3 °C	122 kt	12 h 16 min	1:03 pm CDT (18:03 UTC)
11,500 ft	220° at 14 kt	−4 kt	1 °C	124 kt	12 h 04 min	12:51 pm CDT (17:51 UTC)
13,500 ft	220° at 16 kt	−6 kt	-3 °C	126 kt	11 h 52 min	12:39 pm CDT (17:39 UTC)
15,500 ft	230° at 18 kt	−7 kt	-7 °C	127 kt	11 h 47 min	12:34 pm CDT (17:34 UTC)
17,500 ft	230° at 20 kt	−8 kt	-11 °C	128 kt	11 h 41 min	12:28 pm CDT (17:28 UTC)
18,000 ft FL180	230° at 20 kt	−9 kt	-12 °C	129 kt	11 h 36 min	12:23 pm CDT (17:23 UTC)
24,000 ft FL240	230° at 23 kt	−10 kt	-23 °C	130 kt	11 h 30 min	12:17 pm CDT (17:17 UTC)
30,000 ft FL300	240° at 31 kt	−19 kt	-35 °C	139 kt	10 h 46 min	11:33 am CDT (16:33 UTC)
34,000 ft FL340	250° at 42 kt	−32 kt	-39 °C	152 kt	9 h 51 min	10:38 am CDT (15:38 UTC)
39,000 ft FL390	250° at 47 kt	−36 kt	-45 °C	156 kt	9 h 35 min	10:22 am CDT (15:22 UTC)

Based on data from the 12th at 00:00 UTC; valid on the 12th at 06:00 UTC for use 02:00 to 09:00 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; 25 nm from the line	050/7	050/11 1°	050/12 -5°	030/31 -7°	010/61 -15°	010/69 -26°	360/73 -40°	360/62 -47°	330/21 -43°
YKM	used from 50 nm out; 45 nm from the line	070/10	040/15 -1°	020/27 -8°	030/25 -13°	020/48 -20°	010/83 -27°	010/77 -37°	010/49 -40°	350/14 -41°
GEG	used from 150 nm out; 44 nm from the line		080/16 -2°	050/17 -7°	080/9 -10°	190/33 -21°	180/31 -32°	L/V -35°	L/V -37°	270/8 -40°
LWS	used from 200 nm out; 26 nm from the line	070/10	080/12 -2°	030/12 -6°	080/7 -10°	170/34 -21°	160/46 -32°	200/33 -35°	220/22 -35°	230/18 -38°
DLN	used from 349 nm out; 66 nm from the line			090/6 -6°	240/22 -4°	210/34 -16°	210/62 -25°	210/66 -34°	210/82 -36°	220/77 -42°
BIL	used from 499 nm out; 64 nm from the line		080/13	180/9 -2°	210/38 0°	220/51 -11°	210/46 -22°	210/58 -35°	230/73 -39°	230/72 -45°
RAP	used from 698 nm out; 109 nm from the line		180/23 12°	200/38 13°	210/38 6°	220/28 -10°	230/34 -21°	230/37 -36°	250/52 -38°	250/59 -46°
PIR	used from 898 nm out; 92 nm from the line		170/22 19°	190/25 13°	210/32 6°	240/23 -9°	250/32 -21°	250/38 -36°	260/44 -40°	260/52 -47°
ONL	used from 948 nm out; 72 nm from the line		210/31 20°	230/27 13°	230/18 7°	220/19 -8°	240/26 -20°	250/44 -35°	270/52 -39°	260/57 -47°
GRI	used from 1097 nm out; 61 nm from the line		230/35 21°	230/23 13°	220/20 7°	240/25 -8°	240/37 -20°	250/49 -33°	260/57 -38°	260/58 -47°
OMA	used from 1147 nm out; 18 nm from the line	220/47	240/33 19°	250/18 11°	230/17 6°	260/29 -8°	250/33 -19°	250/51 -33°	260/61 -40°	270/62 -49°
DSM	used from 1247 nm out; 72 nm from the line	230/40	250/33 17°	250/18 12°	240/17 5°	260/28 -8°	270/34 -19°	260/41 -33°	260/55 -41°	270/62 -51°
MKC	used from 1297 nm out; 78 nm from the line	220/44	250/28 18°	250/18 13°	240/12 6°	280/24 -6°	240/34 -18°	260/47 -30°	260/51 -40°	270/58 -50°
COU	used from 1347 nm out; 50 nm from the line	230/31	230/30 15°	260/16 11°	270/14 6°	260/24 -6°	270/27 -18°	270/37 -32°	280/49 -41°	290/56 -51°
STL	used from 1447 nm out; 11 nm from the line	250/24	250/24 16°	260/23 9°	270/16 6°	260/25 -6°	270/29 -19°	290/34 -33°	290/48 -41°	290/54 -51°

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	calm	10+ mi	none	21 ft	9:53 pm PDT (04:53 UTC)
MWH Moses Lake, WA	120 nm out, 4 nm northeast of the line, tower	VFR Sky: overcast at 9,000 feet	from the northwest (310°) at 4 knots	10+ mi	9,000 ft	1,188 ft	04:52 UTC
PUW Pullman/Moscow, WA	219 nm out, 6 nm southwest of the line	VFR Sky: overcast at 5,500 feet	from the north-northeast (020°) at 5 knots	10+ mi	5,500 ft	2,566 ft	04:53 UTC
BTM Butte, MT	409 nm out, 6 nm southeast of the line	IFR Sky: a few clouds at 1,200 feet, overcast at 1,900 feet Weather: light snow, mist	from the west-northwest (300°) at 6 knots	1.5 mi	1,900 ft	5,550 ft	05:40 UTC
BZN Bozeman, MT	469 nm out, 4 nm northeast of the line, tower	low IFR Sky: a broken layer at 300 feet, overcast at 2,400 feet Weather: light snow, mist	from the south (180°) at 3 knots	2.5 mi	300 ft	4,473 ft	05:20 UTC
SHR Sheridan, WY	658 nm out, 3 nm north of the line	IFR Sky: overcast at 600 feet	from the north-northwest (340°) at 5 knots	10+ mi	600 ft	4,021 ft	05:04 UTC
RAP Rapid City, SD	828 nm out, 24 nm northeast of the line, tower	low IFR Sky: a broken layer at 300 feet, overcast at 700 feet Weather: mist	from the north-northeast (020°) at 3 knots	4 mi	300 ft	3,203 ft	05:37 UTC
ANW Ainsworth, NE	988 nm out, 1 nm south of the line	IFR Sky: overcast at 700 feet	from the east-northeast (060°) at 3 knots	7 mi	700 ft	2,588 ft	05:35 UTC
OMA Omaha, NE	1187 nm out, 12 nm north of the line, tower	VFR Sky: scattered clouds at 25,000 feet	from the south-southeast (160°) at 9 knots	10+ mi	none	984 ft	04:52 UTC
ICL Clarinda, IA	1237 nm out, 1 nm southwest of the line	VFR	from the south (190°) at 6 knots	10+ mi	none	995 ft	05:35 UTC
SUS St Louis, MO	1477 nm out, 8 nm southwest of the line, tower	VFR	from the west-southwest (240°) at 3 knots	10+ mi	none	463 ft	04:54 UTC
CPS Cahokia/St Louis, IL	destination	VFR	from the south-southeast (160°) at 4 knots	10+ mi	none	412 ft	11:53 pm CDT (04:53 UTC)

The highest airport on this list sits at 5,550 ft; the ground between airports is higher still. Check the sectional chart for the terrain and the minimum safe heights along the line.

At CPS when you get there the forecast at the estimated arrival, 10:22 am CDT (15:22 UTC)

Wind from the south at 5 knots, visibility more than 6 miles, scattered clouds at 25,000 feet VFR

The whole forecast for CPS

From Mon 1:00 am CDT (06:00 UTC): wind from the south at 5 knots, visibility more than 6 miles, scattered clouds at 25,000 feet
From Mon 11:00 am CDT (16:00 UTC): wind from the southwest at 10 knots, visibility more than 6 miles, clear skies

The forecast for BFI, the departure

From Sun 11:00 pm PDT (06:00 UTC): wind calm, visibility more than 6 miles, clear skies
From Mon 3:00 am PDT (10:00 UTC): wind calm, 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
From Mon 7:00 pm PDT (02:00 UTC): wind calm, visibility more than 6 miles, clear skies

Temporary flight restrictions on the line or within 25 nm of it

6/7634 CENTRALIA, MO, Monday, October 12, 2026 UTC 18 nm from the route, 1397 nm along the route · a hazard on the ground (fire-fighting, a chemical spill, rescue work) · today · ZKC

Daylight

Sunset at BFI 6:27 pm PDT (01:27 UTC), at CPS 6:27 pm CDT (23:27 UTC) (civil twilight ends 6:53 pm CDT (23:53 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 now, the northern Rockies · loop National Weather Service

Radar now, the upper Mississippi valley · 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, St. Louis Downtown Airport.