Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) (Line 4) Concerning the Oakland Oceanic Flight Information Region (FIR), frequent thunderstorms observed and forecast within 200 nautical miles of 30 degrees and 6 minutes north; 140 degrees and 12 minutes west; to 20 degrees and 12 minutes north, 150 degrees and 16 minutes west, cumulonimbus tops to flight level 400 moving west at 10 knots, weakening.
6.1.5.4 SIGMETs for Volcanic Ash A SIGMET for volcanic ash cloud is issued for volcanic eruptions. A volcanic eruption is any volcanic activity including the emission of volcanic ash, regardless of the eruption’s magnitude.
Initial Volcanic Ash SIGMETs may be issued based on credible pilot reports in the absence of a Volcanic Ash Advisory (VAA), but are updated once a VAA is issued. Volcanic ash SIGMETs will continue to be issued until the ash cloud is no longer occurring or expected to occur over the area of responsibility.
SIGMETs for volcanic ash cloud are valid up to six (6) hours and provide an observed or forecast location of the ash cloud at the beginning of the SIGMET. A six-hour forecast position for the ash cloud, valid at the end of the validity period of the SIGMET message, is also included. SIGMETs are reissued at least every six (6) hours while the volcanic ash cloud hazard exists or is expected to exist.
6.1.5.5 SIGMETs for Tropical Cyclone A SIGMET for a tropical cyclone may be issued for non-frontal synoptic-scale cyclones meeting the following criteria.
• Originates over tropical or sub-tropical waters with organized convection and definite cyclonic surface wind circulation.
• Wind speeds reach 35 knots independent of the wind averaging time used by the Tropical Cyclone Advisory Center (TCAC).
SIGMETs for tropical cyclones will be valid up to six (6) hours. SIGMETs for tropical cyclones will include two positions. The first position included will be the TCAC advisory position. The second position will be the forecast position valid at the end of the SIGMET period.
In addition to the two storm positions, SIGMETs will include associated convection when applicable. SIGMETs will be reissued at least every six (6) hours while the tropical cyclone wind remains or are expected to remain above 34 knots.
6.1.5.6 SIGMET Cancellation– Outside the Conterminous U.S. (O-CONUS) SIGMETs are cancelled when the phenomena is no longer occurring or expected to occur in the area of responsibility.
6.1.5.7 SIGMET Amendments– Outside the Conterminous U.S. (O-CONUS) SIGMET amendments will NOT be issued. Instead, the next SIGMET in the series is issued to accomplish the update. The valid time of the new SIGMET is reset to reflect the new 4-hour valid period (6-hour for VA and TC SIGMETs).
6.1.5.8 SIGMET Corrections– Outside the Conterminous U.S. (O-CONUS) Corrections to SIGMETs are issued as necessary. This is done by issuing a new SIGMET in the series which advances the SIGMET number and cancels the previous SIGMET.
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-17
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
6.1.5.9 SIGMET Example– Outside the Conterminous U.S. (O-CONUS)
WSPA07 PHFO 010358 SIGPAT KZOA SIGMET TANGO 1 VALID 010400/010800 PHFO- OAKLAND OCEANIC FIR. EMBD TS OBS BY SATELLITE WITHIN AREA BOUNDED BY N2055 W15000 - N1950 W14945 - N1922 W15130 - N2027 W15048 – N2055 W15000. CB TO TOP FL400. MOV W 10KT. WKN.
SIGMET (SWPA07) issued by the Meteorological Watch Office (Weather Forecast Office) in Honolulu, Hawaii (PHFO) on the 1st day of the month at 0358 UTC. The National Weather Service AWIPS communication header for this product is SIGPAT. This SIGMET concerns the Oakland Oceanic FIR. This is the first (1) issuance of SIGMET series Tango valid from the 1st day of the month at 0400 UTC until the 1st day of the month at 0800 UTC. Within the WFO Honolulu portion of the Oakland Oceanic FIR, embedded thunderstorms observed by satellite within an area bounded by 20 degrees/55 minutes north, 150 degrees/00 minutes west to 19 degrees/50 minutes north, 14 degrees/45 minutes west to 19 degrees/22 minutes north, 151 degrees/30 minutes west to 20 degrees/27 minutes north, 150 degrees/48 minutes west to 20 degrees/55 minutes north, 150 degrees/00 minutes west. Cumulonimbus tops to flight level 400 (approximately 40,000 feet MSL). The thunderstorms are moving west at 10 knots and weakening.
6.1.5.9.1 SIGMET for Volcanic Ash Example
WVNT06 KKCI 082030 TJZS SIGMET FOXTROT 2 VALID 082030/090230 KKCI- SAN JUAN FIR VA FROM SOUFRIERE HILLS LOC 1642N06210W VA CLD OBS AT 2030Z SFC/060 WI N1730 W06400 - N1700 W06300 - N1650 W06300 - N1710 W06400 - N1730 W06400. MOV W 15KT. FCST 0230Z VA CLD APRX N1730 W06500 - N1700 W06300 - N1650 W06300 - N1710 W06500 - N1730 W06500.
The ICAO communication header for this product is WVNT06. It is a SIGMET issued by the Aviation Weather Center (KCCI) in Kansas City, Missouri on the 8th day of the month at 2030 UTC. This is the second (2) issuance of SIGMET series Foxtrot valid from the 8th day of the month at 2030 UTC until the 9th day of the month at 0230 UTC. Within the San Juan Oceanic FIR, volcanic ash from Soufriere Hills volcano located at 16 degrees/42 minutes north, 62 degrees/10 minutes west. Volcanic ash cloud observed at 2030 UTC from the surface to 6,000 feet MSL within an area bounded by 17 degrees/30 minutes north, 64 degrees/00 minutes west to 17 degrees/00 minutes north, 63 degrees/00 minutes west to 16 degrees/50 minutes north, 63 degrees/00 minutes west to 17 degrees/10 minutes north, 64 degrees/00 minutes west to 17 degrees/30 minutes north, 64 degrees/00 minutes west. Moving to the west at 15 knots.
Forecast at 0230 UTC, volcanic ash cloud located approximately at 17 degrees/30 minutes north, 65 degrees/00 minutes west to 17 degrees/00 minutes north, 63 degrees/00 minutes west to 16 degrees/50 minutes north, 63 degrees/00 minutes west to 17 degrees/10 minutes north, 65 degrees/00 minutes west to 17 degrees/30 minutes north, 65 degrees/00 minutes west.
6.1.5.9.2 SIGMET for Tropical Cyclone Example
WSNT03 KKCI 081451 SIGA0C AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-18
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) KZNY SIGMET CHARLIE 11 VALID 081500/082100 KKCI- NEW YORK OCEANIC FIR TC KYLE OBS N3106 W07118 AT 1500Z CB TOP FL500 WI 120NM OF CENTER MOV WSW 5 KT NC FCST 2100Z TC CENTER N3142 W07012
The ICAO communication header for this product is WSNT03. It is a SIGMET issued by the Aviation Weather Center (KCCI) in Kansas City, Missouri on the 8th day of the month at 1451 UTC. The National Weather Service AWIPS communication header for this product is SIGPAT.
This is the eleventh (11) issuance of SIGMET series Charlie valid from the 8th day of the month at 1500 UTC until the 8th day of the month at 2100 UTC. Within the New York Oceanic FIR, Tropical Cyclone Kyle observed at 31 degrees/6 minutes north, 71 degrees/18 minutes west at 1500 UTC, cumulonimbus tops to flight level 500 (approximately 50,000 feet MSL), within 120 nautical miles of the center, moving from west-southwest at 5 knots, no change in intensity is forecast, at 2100 UTC the tropical cyclone center will be at 31 degrees/42 minutes north, 70 degrees/12 minutes west.
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-19
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
6.2 Airmen’s Meteorological Information (AIRMET) An AIRMET is a concise description of the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of aircraft operations, but at intensities lower than those which require the issuance of a SIGMET. AIRMETs are intended for dissemination to all pilots in flight to enhance safety and are of particular concern to operators and pilots of aircraft sensitive to the phenomena described and to pilots without instrument ratings. AIRMETs are issued by the responsible Meteorological Watch Office (MWO) to give notice to operators and aircrews of potentially hazardous en route conditions.
• AIRMETs are available for the conterminous U.S. (CONUS) on the Aviation Digital Data Service (ADDS) web site at: http://adds.aviationweather.noaa.gov/airmets/
• AIRMETs are available for Alaska on the Alaska Aviation Weather Unit (AAWU) web site at:
http://aawu.arh.noaa.gov/
• AIRMETs are available for Hawaii on the NWS WFO Honolulu web site at:
http://www.prh.noaa.gov/hnl/pages/aviation.php
6.2.1 AIRMET Issuance AIRMETs are issued from the three Meteorological Watch Offices (MWO) located at the Aviation Weather Center (AWC), the Alaska Aviation Weather Unit (AAWU), and the Weather Forecast Office (WFO) in Honolulu. Their areas of responsibility are:
• AWC: The conterminous U.S. and adjacent coastal waters (CONUS) (Figure 6-8)
• AAWU: Alaska and adjacent coastal waters (Figure 6-9)
• WFO Honolulu: Hawaii and adjacent waters (Figure 6-10)
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-20
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-8 AWC AIRMET Areas of Responsibility – Conterminous U.S.
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-21
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-9. AAWU Flight Advisory and Area Forecast Zones - Alaska
Table 6-4. AAWU Flight Advisory and Area Forecast Zones – Alaska 1 Arctic Coast Coastal 14 Southern Southeast Alaska 2 North Slopes of the Brooks Range 15 Coastal Southeast Alaska 3 Upper Yukon Valley 16 Eastern Gulf Coast 4 Koyukuk and Upper Kobuk Valley 17 Copper River Basin 5 Northern Seward Peninsula-Lower Kobuk Valley 18 Cook Inlet-Susitna Valley 6 Southern Seward Peninsula-Eastern Norton Sound 19 Central Gulf Coast 7 Tanana Valley 20 Kodiak Island 8 Lower Yukon Valley 21 Alaska Peninsula-Port Heiden to Unimak Pass 9 Kuskowim Valley 22 Unimak Pass to Adak 10 Yukon-Kuskowim Delta 23 St. Lawrence Island-Bering Sea Coast 11 Bristol Bay 24 Adak to Attu 12 Lynn Canal and Glacier Bay 25 Pribilof Islands and Southeast Bering Sea 13 Central Southeast Alaska
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-22
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-10. WFO Honolulu AIRMET Areas of Responsibility - Hawaii
6.2.2 AIRMET Issuance Criteria An AIRMET may be issued when any of the following weather phenomena are occurring or expected to occur over an area of at least 3,000 square miles:
• Ceiling less than 1,000 feet and/or visibility less than 3 statute miles (IFR)
o Weather phenomena restricting the visibility including, but not limited to, precipitation (PCPN), smoke (FU), haze (HZ), mist (BR), fog (FG), and blowing snow (BS).
• Widespread mountain obscuration (MTN OBSCN)
o Weather phenomena causing the obscurement are included, but limited to clouds (CLDS), precipitation (PCPN), smoke (FU), haze (HZ), mist (BR), and fog (FG).
• Moderate turbulence (MOD TURB)
o Top and bottom of MOD TURB layer are specified.
• Sustained surface wind greater than 30 knots (STG SFC WND)
• Moderate icing (MOD ICE)
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-23
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) o Top and bottom of MOD ICE are specified.
o The range of freezing level altitudes is given when the bottom altitude of MOD ICE is the freezing level (FRZLVL).
o Areas with multiple freezing levels are specified.
o Range of freezing levels over the area is specified.
o Lowest freezing levels above ground level (AGL) at intervals of 4,000 feet AMSL (or SFC as appropriate) are specified.
• Non-convective low-level wind shear potential below 2,000 feet AGL (LLWS POTENTIAL).
6.2.3 AIRMET Standardization All AIRMETs follow these standards:
• All heights or altitudes are referenced to above mean sea level (AMSL), unless otherwise noted, and annotated using the height in hundreds of feet, consisting of three digits (e.g., 040). For heights at or above 18,000 feet, the level is preceded by FL to represent flight levels (e.g., FL180).
• Messages are prepared in abbreviated plain language using contractions from the Federal Aviation Administration (FAA) Order 7340.1Z. A limited number of nonabbreviated words, geographical names and numerical values of a self-explanatory nature may also be used.
• Weather and obstructions to visibility are described using the weather abbreviations for surface weather observations (METAR/SPECI). See the Federal Meteorological Handbook (FMH) No. 1 – Surface Observations or Section 3.1 of this document.
Note: Refer to Appendix A for definitions of common terms used in AIRMETs.
6.2.4 AIRMET Bulletins, Issuance Times, and Valid Period AIRMETs are issued as bulletins containing one or more AIRMET messages following the schedule listed below. Unscheduled AIRMETs are issued when conditions are occurring or expected to occur, but were not forecast.
Table 6-5. AIRMET Issuance Schedule 1st Scheduled Issuance (UTC) 2nd Scheduled Issuance (UTC) 3rd Scheduled Issuance (UTC) 4th Scheduled Issuance (UTC) CONUS 0245 0845 1445 2045 Alaska 0145 (DT)/ 0245 (ST) 0745 (DT)/ 0845 (ST) 1345 (DT)/ 1445 (ST) 1945 (DT)/ 2045 (ST) Hawaii 0400 1000 1600 2200 Note: DT - Daylight Time, ST - Standard Time
AIRMETs are valid for no more than 6 hours. The valid period of an AIRMET message cannot exceed the valid time of the AIRMET bulletin. However, note that each AIRMET contains remarks concerning the continuance of the phenomenon during the six (6) hours following the AIRMET ending time. Also, AIRMET bulletins can contain a separate outlook when conditions AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-24
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) meeting AIRMET criteria are expected to occur during the 6-hour period after the valid time of the AIRMET bulletin.
6.2.5 AIRMET Format An AIRMET message includes the following information as appropriate and in the order indicated:
• Reference to appropriate active SIGMETs affecting the area at the time of AIRMET issuance (e.g., SEE SIGMET BRAVO SERIES).
• Beginning time of the AIRMET phenomenon if different from the AIRMET beginning valid time.
• AIRMET name (SIERRA, TANGO or ZULU), update number, weather phenomenon, and ending valid time (Note: the AIRMET number is reset to one (1) after 0000 UTC each day).
o AIRMET Sierra describes IFR conditions and/or extensive mountain obscurations
o AIRMET Tango describes moderate turbulence, sustained surface winds of 30 knots or greater and non-convective low-level wind shear.
o AIRMET Zulu describes moderate icing and provides freezing level heights
• List of affected states (CONUS only).
• Location of phenomenon using VORs or other well known geographic features.
• Description of phenomenon for the AIRMET issuance.
• Vertical extent (bases and tops), as appropriate.
• Ending time of phenomenon if different from the AIRMET ending time.
• Remarks concerning the continuance of the phenomenon during the six (6) hours following the AIRMET ending time.
• CONUS and Hawaii AIRMETs: A separate AIRMET outlook is included in the AIRMET bulletin when conditions meeting AIRMET criteria are expected to occur during the 6- hour period after the valid time of the AIRMET bulletin.
• Alaska AIRMETs: Outlook information is included in the appropriate Area Forecast zone when conditions are expected to occur during the 6-hour period after the valid time of the AIRMET bulletin.
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-25
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) LINE 1 BOSS WA 211945 2 AIRMET SIERRA UPDT 3 FOR IFR AND MIN OBSCN VALID UNTIL 220200 ЗА AIRMET IFR..ME NH VT MA CT RI NY NJ AND CSTL WTRS 4A FROM CAR TO YSJ TO 150E ACK TO EWR TO YOW TO CAR SA OCNL CIG BLW 010/VIS BLW 3SM PCPN/BR. CONDS CONT BYD 02Z THRU 082.
ЗВ AIRMET MIN OBSCN..ME NH VT MA NY PA 4B FROM CAR TO MLT TO CON TO SLT TO SYR TO CAR 5B MINS ONLY OBSCD BY CLDS/PCPN/BR. CONDS CONT BYD 02Z THRU 08Z.
Figure 6-11. AIRMET Bulletin Decoding Example Table 6-6. Decoding an AIRMET Bulletin Line Content Description 1 BOS AIRMET area identifier S AIRMET series WA Product type 211945 Issuance UTC date/time 2 AIRMET Product type SIERRA AIRMET series UPDT 3 Update number FOR IFR AND MTN OBSCN Product description VALID UNTIL 220200 Ending UTC date/time ЗА AIRMET IFR..ME NH VI MA CT RI NY Product type/series...
NJ AND CSTL WTRS Phenomenon location ЗВ AIRMET MIN OBSCN..ME NH VT MA NY (states) 4A FROM CAR TO YSJ TO 150E ACK TO EWR Phenomenon location TO YOW TO CAR (VOR locations) 4B FROM CAR TO MLT TO CON TO SIT TO
SYR TO CAR 5A CIG BLW 010/VIS BLW 3SM PCPN/BR. Phenomenon description CONDS CONT BYD 02Z THRU 08Z.
5B MINS OBSCD BY CLDS/PCPN/BR. CONDS CONT BYD 02Z THRU 08Z.
The AIRMET bulletin in Figure 6-11 is decoded as follows:
(Line 1) AIRMET SIERRA issued for the Boston area at 1945Z on the 21s day of the month.
"SIERRA" contains information on Instrument Flight Rules (IFR) and/or mountain obscurations.
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-26
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) (Line 2) This is the third updated issuance of this Boston AIRMET series as indicated by “SIERRA UPDT 3” and is valid until 0200Z on the 22nd.
(Line 3A) The affected states within the BOS area are: Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New York, New Jersey, and coastal waters.
(Line 3B) The affected states within the BOS area are: Maine, New Hampshire, Vermont, Massachusetts, New York, and Pennsylvania.
(Line 4A) Within an area bounded by: Caribou, ME; to Saint Johns, New Brunswick; to 150 nautical miles east of Nantucket, MA; to Newark, NJ; to Ottawa, Ontario; to Caribou, ME
(Line 4B) Within an area bounded by: Caribou, ME to Millinocket, ME to Concord, NH to Slate Run, PA to Syracuse, NY to Caribou, ME
(Line 5A) Ceiling below 1,000 feet/visibility below 3 statute miles, precipitation/mist. Conditions continuing beyond 0200Z through 0800Z.
(Line 5B) Mountains Obscured by clouds, precipitation and mist. Conditions continuing beyond 0200Z through 0800Z.
6.2.5.1 AIRMET Updates and Amendments If an AIRMET is amended, AMD is added after the date/time group on the FAA product line.
The update number will be incremented, UPDT is added to end of the line containing the list of affected states (CONUS only). The issuance time of the AIRMET bulletin is updated to reflect the time of the amendment. The ending valid time remains unchanged.
6.2.5.2 AIRMET Corrections AIRMETs containing errors are corrected by adding COR after the date/time group on the FAA product line. The issuance time of the AIRMET bulletin is updated to reflect the time of the correction. The ending valid time remains unchanged.
6.2.6 AIRMET Examples
6.2.6.1 CONUS AIRMET Example
WAUS43 KKCI 091445 CHIZ WA 091445 AIRMET ZULU UPDT 4 FOR ICE AND FRZLVL VALID UNTIL 092100 AIRMET ICE...KS IA MO IL FROM 30WSW FOD TO DBQ TO 50NW DEC TO 50SW FAM TO OSW TO MKC TO 30WSW FOD MOD ICE BTN FRZLVL AND FL200. FRZLVL 060-100. CONDS ENDG BY 21Z.
.
OTLK VALID 2100-0300Z...ICE IA MO WI IL IN KY BOUNDED BY BAE-BVT-PXV-50SW FAM-50NW DEC-DBQ-BAE MOD ICE BTN FRZLVL AND FL200. FRZLVL 080-100. CONDS CONTG THRU 03Z.
.
FRZLVL...RANGING FROM SFC-120 ACRS AREA MULT FRZLVL 015-085 BOUNDED BY 40W INL-YQT-SSM-70NNE AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-27
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) ASP-YVV-DXO-40NE FWA-40SSE BJI-40W INL SFC ALG 50NNW ISN-70W FAR-GFK-40NE ODI-40SW DXO 040 ALG ISN-70S BIS-30W ABR-30E ABR-60S FAR-30SW BRD-30NE FWA 080 ALG GLD-SLN-30W BDF-50S JOT-40SE IND-30SW CVG-40SW LOZ
AIRMET (WAUS43) issued by the Meteorological Watch Office (Aviation Weather Center) in Kansas City, Missouri on the 9th day of the month at 1445 UTC. This AIRMET (WA) is the Zulu series bulletin for the Chicago Area Forecast region (CHIZ) issued on the 9th day of the month at 1445 UTC. This is the 4th update to the Zulu series bulletin for icing and freezing levels and is valid until the 9th day of the month at 2100 UTC.
The first (and only) AIRMET noted within the bulletin is for icing affecting Kansas, Iowa, Missouri and Illinois. Within an area bounded from 30 nautical miles west-southwest of Fort Dodge, Iowa (FOD) to Dubuque, Iowa (DBQ) to 50 nautical miles northwest of Decatur, Illinois (DEC) to 50 nautical miles southwest of Farmington, Missouri (FAM) to Oswego, Kansas (OSW) to Kansas City, Missouri (MKC) to 30 nautical miles west-southwest of Fort Dodge, Iowa (FOD). Moderate icing between the freezing level and flight level 200 (approximately 20,000 feet MSL). The freezing level is between 6,000 feet MSL and 10,000 feet MSL. Conditions ending by 2100 UTC.
An outlook for icing between 2100 UTC to 0300 UTC exists over: Iowa, Missouri, Wisconsin, Illinois, Indiana and Kentucky. Within an area bounded by Milwaukee, Wisconsin (BAE) to Lafayette, Indiana (BVT) to Pocket City, Indiana (PXV) to 50 nautical miles southwest of Farmington, Missouri (FAM) to 50 nautical miles northwest of Decatur, Illinois (DEC) to Dubuque, Iowa (DBQ) to Milwaukee, Wisconsin (BAE). Moderate icing between the freezing level and flight level 200 (approximately 20,000 feet MSL). The freezing level is between 8,000 feet MSL and 10,000 feet MSL. Conditions continuing through 0300 UTC.
The freezing level ranges from the surface to 12,000 feet MSL across the Chicago Area Forecast region. Multiple freezing levels exist between 1,500 feet MSL and 8,500 feet MSL within an area bounded by 40 nautical miles west of International Falls, Minnesota (INL) to Thunder Bay, Ontario, Canada to Sault Saint Marie, Michigan (SSM) to 70 nautical miles northnortheast of Oscoda, Michigan (ASP) to Wiarton, Ontario, Canada to Detroit, Michigan (DXO) to 40 nautical miles northeast of Fort Wayne, Indiana (FWA) to 40 nautical miles south-southeast of Bemidji, Minnesota (BJI) to 40 nautical miles west of International Falls, Minnesota (INL).
The freezing level is at the surface along a line from 50 nautical miles north-northwest of Williston, North Dakota (ISN) to 70 nautical miles west of Fargo, North Dakota (FAR) to Grand Forks, North Dakota (GFK) to 40 nautical miles northeast of Nodine, Minnesota (ODI) to 40 nautical miles southwest of Detroit, Michigan (DXO). The freezing level is at 4,000 feet MSL along a line from Williston, North Dakota (ISN) to 70 nautical miles south of Bismarck, North Dakota (BIS) to 30 nautical miles west of Aberdeen, South Dakota (ABR) to 30 nautical miles east of Aberdeen, South Dakota (ABR) to 60 nautical miles south of Fargo, North Dakota (FAR) to 30 nautical miles southwest of Brainerd, Minnesota (BRD) to 30 nautical miles northeast of Fort Wayne, Indiana. The freezing level is 8,000 feet MSL along a line from Goodland, Kansas (GLD) to Salina, Kansas (SLN) to 30 nautical miles west of Bradford, Illinois (BDF) to 50 nautical miles south of Joliet, Illinois to 40 nautical miles southeast of Indianapolis, Indiana (IND) to 30 nautical miles southwest of Covington, Kentucky (CVG) to 40 nautical miles southwest of London, Kentucky (LOZ).
6.2.6.2 Hawaii AIRMET Example
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-28