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Subject: Changes to the Aviation Area Forecast (FA) and AIRMET Programs

References: WSOM Chapter D-20, Transmittal Issuance 91-3 dated May 3, 1991; WSOM Chapter D-22, Transmittal Issuance 91-7 dated may 22, 1991.

Supersedes: WSOM Chapter D-20, Sections 6.1, 6.2, 7, and 11.2.1 of Issuance 91-3 with regard to their application in the contiguous 48 states and Hawaii. WSOM Chapter D-22, Sections 2.2, 8 (regarding issuance times), 8.2, and 11.2.2 of Issuance 91-7.

Purpose. This Operations Manual Letter (OML) states the changes to National Weather Service procedures and policy as detailed below. It implements final versions of FA program changes that have been in effect, on a test basis, since November 16, 1992, and AIRMET issuance procedural changes.

Background. Issuance 91-3 initiated significant changes to the FA Program. Operational implementation of these changes revealed unintended or unnecessary impacts on pilot weather briefing (PWB) activities that had the potential to increase workload and/or reduce the quality of the information provided to pilots.

The Hazards section of the FA was intended as a "headline" service to alert weather briefers and other aviation users to conditions that required, or were expected to require, the issuance of In-flight Advisories. Its direct use in PWBs was noted and unintended. The use of this section of the FA, in of a full review of the existing In-flight Advisories, compromised safety.

In addition, the differences in scheduled issuance times between FAs and AIRMET bulletins resulted in numerous FA amendments issued solely to repeat information in, or about, newly issued advisories. AIRMET amendments were issued solely due to the issuance of new FAs. This was a redundancy that required use of limited resources with no measurable benefit to users.

As a result of these conditions and requests for program changes, two operational tests of proposed remedies to noted problems were conducted. An evaluation of these tests has resulted in the procedural changes for the contiguous United States and Hawaii detailed below. Changes to the procedures for FAs issued in Alaska are detailed in a separate OML.

1. Beginning at 0000 UTC on the effective date of this OML, elimination of the Hazards section of all FAs shall become permanent. In addition, for FAs issued in the contiguous United States and Hawaii, the following changes regarding the remaining Synopsis and VFR Clouds/Weather FA section shall also become Permanent:

a. The standard statements regarding the implications of thunderstorms and the height reference used in forecasts shall be moved from the Hazards section to the first text paragraph of the remaining FA section.

b. A single permanent statement referring users to the AIRMET SIERRA bulletin for information on any IFR conditions or mountain obscurations shall be added to the beginning of the first text paragraph of the remaining FA section.

c. Section 7 of reference Issuance 91-3 is amended to the extent that the only unscheduled updates made directly to the FA text shall be those required to keep forecasts of non-AIRMET conditions representative of existing or expected conditions. In addition, the number following "AMD" in the FA header shall be eliminated. The heading (states line) of the updated section(s) of the FA shall have n ...UPDT" appended to it.

d. Sections 11.2.1 of Issuance 91-3, and 11.2.2 of Issuance 91-7 are amended to change the location of the backup message appended to the Hazards section of FAs. The FA shall be amended to insert the message "BACKUP PROCEDURES IN EFFECT BEGINNING ddtttt...SEE AIRMET BULLETINS AND SIGMETS" in place of the AIRMET SIERRA statement mentioned in b. above. The additional message "BACKUP PROCEDURES IN EFFECT BEGINNING ddtttt...NO FA UPDT AVBL TIL (ddtttt OR FTHR NOTICE)..." shall continue to be appended to the end of the amended FA.

All updates addressing IFR or mountain obscuration conditions shall be made to the appropriate section (i.e., AIRMET or OUTLOOK) of the associated AIRMET bulletin. This bulletin will be prepared and should be used as a necessary extension of the FA, as are the turbulence and icing AIRMET bulletins. Examples of FAs in the new format are provided in the attachment to this OML.

2. Beginning at 0000 UTC on the effective date of this OML, the following changes shall be made regarding AIRMET bulletins, regardless of the issuing office. (See example below.)

a. The number following "AMD" in the bulletin header of unscheduled AIRMET updates and within the bulletin in the AIRMET line shall be eliminated. "AMD" on the AIRMET line shall be changed to "UPDT. n

b. Following the first scheduled issuance of each UTC day, each scheduled and unscheduled (i.e., UPDT) AIRMET update shall be issued with line 2 of the bulletin modified to include an update number. That is, the first scheduled issuance each UTC day shall not carry an update number. Each succeeding issuance that day shall be numbered sequentially beginning with number one (1). Corrections shall carry the same number as the issuance being corrected unless the update number itself is the item being corrected.

c. For unscheduled updates, the AIRMET within the bulletin describing the conditions that made the update necessary shall be placed at the beginning of the bulletin. The "AIRMET" line shall end with "...UPDT" to identify it as the bulletin element that has been updated.

ZCZC MKCWA4T ALL 242000
WAUS1 KDFW 241345
DFWT WA 241345
AIRMET TANGO UPDT 2 FOR TURBCSTG SFC WNDS AND LLWS VALID UNTIL
242000

AIRMET STG SFC WINDSTX
FROM CDS TO DFW TO SAT TO MAF TO CDS
AFT 18ZSUSTAINED SFC WINDS GTR THAN 30 KTS XPCD. CONDS CONTGBYD 2000Z

LLWS POTENTIAL N CNTRL TX TIL 16-18Z DUE TO LOW LVL JET AND
NIGHTTIME INVERSION.

OTLK VALID 2000-0200ZOK TX AR
MDT TURBC BLO 60 BGNG OVR OK/TX AND SPRDG INTO AR BY 2200-0200Z
CONTG ENTR AREA BYD 0200Z.
....NNNN

ZCZC MKCWA4T ALL 242000
WAUS1 KDFW 241650
DFWT WA 241650 AMD
AIRMET TANGO UPDT 3 FOR TURBCSTG SFC WINDS AND LLWS VALID UNTIL
242000

AIRMET TURBC...OK TX...UPDT
FROM OSW TO LRD TO PEQ TO 4ON DHT TO OSW
OCNL MDT TURBC BLO 60 DUE TO STG AND GUSTY LOW LVL WINDS.
CONDS CONTG BYD 2000Z.

AIRMET STG SFC WINDS...TX
FROM CDS TO DFW TO SAT TO MAF TO CDS
AFT 18Z...SUSTAINED SFC WINDS GTR THAN 30 KTS XPCD. CONDS CONTG
BYD 2000Z.

LLWS POTENTIAL N CNTRL TX DUE TO STG LOW LVL WNDS. LLWS ENDG BY 18Z.

OTLK VALID 2000-0200ZOK TX AR
MDT TURBC BLO 60 CONTG OVR OK/TX AND SPRDG INTO AR BY 2200-0200Z
CONTG ENTR AREA BYD 0200Z.
. . .
NNNN

d. Beginning with the first scheduled AIRMET bulletins after the change from Central daylight savings time to Central standard time in 1994, the valid time of the first scheduled AIRMET each day, during the standard time period, shall be 0300 UTC. The last AIRMET bulletins issued prior to the time change shall cover the 7-hour Period ending at 0300 UTC. The beginning valid time shall revert to 0200 UTC when the change to Central daylight savings time occurs.

e. AIRMET bulletins issued by the Weather Service Forecast Office in Honolulu, Hawaii, shall be issued with the first valid period each day beginning at 0400 UTC. Issuances for the contiguous United States shall continue to begin at 0200 UTC.

Elbert W. Friday, Jr:
Assistant Administrator
for Weather Services

SFOC FA 191045
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 200500
CLDS/WX VALID UNTIL 192300...0TLK VALID 192300-200500
WA OR CA AND CSTL WTRS

SEE AIRMET SIERRA FOR IFR CONDS AND MTN OBSCN. TSTMS IMPLY SVR OR GTR TURBC SVR ICG LLWS AND IFR CONDS. NON MSL HGTS DENOTED BY AGL OR CIG.

SYNOPSIS...WEAK CDFNT ALG CSTL SXNS MOVG TO CASCDS AND BCMG
STNRY. WK HI PRES BLDG INTO CSTL SXNS BY 02Z. ALF...MOIST WLY
FLO
WL CONT OVR WA OR AND GENLY WK SWLY FLOW OVR CA.

WA OR CASCDS WWD
WA NRN OR15-25 SCT-BKN 35-45 BKN-OVC 100-120. WDLY SCT RW-.
17-20Z BCMG 20 SCT-BKN 50 BKN 80-100. WDLY SCT RW-. TOPS 180.
OTLK...VFR.
SRN ORCLR. OTLKVFR.

WA OR E CASCDS
WA50-70 SCT 120 SCT. WRN SXNS WDLY SCT RW-. TOPS 180.
OTLK...VFR.
OR...CLR. OTLK...VFR.

CA
CSTL SXNS OF NRN CA10-15 BKN 25. AFT 21ZCLR. OTLK...VFR.
LAX BASIN15 BKN 25. VSBYS 3-5FH. AFT 16ZCLR. VSBYS LAX
BASIN 3-5FH. OTLK...MVFR CIG F.
RMNDR AREACLR. OTLK...VFR.

CSTL WTRS
ALG CST 10-25 SCT-BKN 30 OTHERWISE CLR. OTLK...MVFR CIG F.
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SLCC FA 141220 AMD
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 150500
CLDS/WX VALID UNTIL 142300...0TLK VALID
142300-150500
ID MT NV UT WY CO AZ NM

SEE AIRMET SIERRA FOR IFR CONDS AND MTN OBSCN. TSTMS IMPLY SVR OR GTR TURBC SVR ICG LLWS AND IFR CONDS. NON MSL HGTS DENOTED BY AGL OR CIG.

SYNOPSIS...HIGH PRES OVR NERN MT CONTG EWD GRDLY. LOW PRES OVR AZ NM AND WRN TX RMNG GENLY STNRY. ALF...TROF EXTDS FROM WRN MT INTO SRN AZ RMNG STNRY.

ID MT...UPDT
FROM YXH TO SHR TO 30SE BZN TO 60SE PIH TO LKT TO YXC TO
YXH
40-60 SCT-BKN 120-150. SCT TRW+. TOPS TSHWRS ABV 450.
OTLK...VFR.
RMNDR AREA...100-120 SCT. ISOLD TRW MNLY ERN PTNS AREA.
OTLK...VFR

UT NV
NRN80 SCT. WDLY SCT RW-. TOPS SHWRS 180. 15Z CLR. 18Z 100 SCT.
OTLK...VFR.
CNTRL/SRNCLR. 18Z 110 SCT. WDLY SCT RW-. ERN PTN AREA ISOLD
TRW-. CB TOPS 450. OTLK...VFR.
WY COUPDT
FROM 60SE BZN TO 60NE GCC TO 60SW BFF TO 6ONE AKO TO GLD TO 20S
ALS TO FMN TO DVC TO 30S RKS TO 30NE SLC TO 60SE BZN
70-90 BKN-OVC 150-200. OCNL VSBY 4-6R-F. AFT 20Z WDLY SCT TRW-.
CB TOPS 450. OTLK...VFR.
RMNDR COFROM GLD TO 60W LBL TO 20S ALS TO GLD80-100 BKN-OVC 150-200. OCNL VSBY 4-6R-F. SCT TRW-. CB TOPS
450.
OTLK...VFR.

NM
FROM 20S ALS TO TBE TO 30N PEQ TO ELP TO 20S ALS
90 SCT-BKN 120 BKN 150-200. l9Z 80 BKN. VSBY 3-5 IN SCT TRW-. CB
TOPS 450. OTLK...VFR.
RMNDR100 SCT 150 BKN. NWRN PTN WDLY SCT RW-. l9Z 110 BKN. WDLY
SCT TRW-. CB TOPS 450. OTLK...VFR.

AZ
80 SCT-BKN 150-200. WDLY SCT RW-/TRW-. CB TOPS 450. OTLK...VFR.
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CHIC FA 290945
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 300400
CLDS/WX VALID UNTIL 292200...0TLK VALID 292200-300400
ND SD NE KS MN IA MO WI LM LS MI LH IL IN KY

SEE AIRMET SIERRA FOR IFR CONDS AND MTN OBSCN. TSTMS IMPLY SVR OR GTR TURBC SVR ICG LLWS AND IFR CONDS. NON MSL HGTS DENOTED BY AGL OR CIG.

SYNOPSIS...CDFNT EXTDS FROM LOW OVR SRN ONT THRU NWRN MN AND INTO CNTRL NM. HI PRES RDG EXTDS FROM THE SRN PLAINS INTO WRN GRTLKS RUIN. SYSS ARE MOVG LTL. TSTMS ALG AND BHD FNTL SYS.

ND SD NE
FROM GFK TO FAR TO SUX TO GLD TO BFF TO 6ONW RAP TO GFK
CIG 20 BKN 50 BKN 180. WDLY SCT RW-/TRW-. CB TOPS 400. OTLK...VFR
NRN THIRD AREA AND MVFR CIG R F CNTRL/SRN THIRDS.

RMDR ND...AGL 50 SCT 80-100 BKN 180. ISOLD RW-/TRW- BCMG WDLY
SCT RW-/TRW- AFT 18-20Z. CB TOPS 350. OTLK...VFR.

MN
AGL 50 SCT 80-100 BKN 180. ISOLD RW-/TRW- BCMG WDLY SCT RW-/TRWAFT 18-20Z. CB TOPS 350. OTLK...VFR.

NE KS
FROM SUX TO PWE TO 40N GAG TO 60W LBL TO GLD TO SUX
AGL 50 SCT 80-100 BKN 180. WDLY SCT RW-/TRW-. CB TOPS 350 INCRG
TO 450 18-22Z. TSTMS PSBLY SVR AFT 18Z. OTLK...VFR.
RMNDR KSAREAS 300-BKN. AFT 15ZOCNL AGL 50 SCT. OTLK...VFR.

LM LS WI MO IL UPR MI IA
CLR OR SCT CI. OCNL 50 SCT DVLPG AFT 18Z. OTLK...VFR.

LH LWR MI
FROM SSM TO YVV TO 20S DTW TO 30NW SBN TO SSM
CIGS 20 BKN 80 BKN-OVC 160. OCNL R-. OTLK...VFR CIGS R F.

IN KY
FROM 30NW SBN TO 3 ONE FWA TO CVG TO 20W HNN TO 30W BKW TO 60W TRI
TO LOU TO 3ONW SBN.
10-20 BKN-OVC 40. CLDS OVR IN SXNS OCNLY SCT. OCNL VSBY 3-5FH
MNLY ERN SXNS. OTLK...MVFR CIG FH.
RMNDR...AREAS 200 SCT. AFT 1?-20ZOCNL 30-50 SCT-BKN 60 DVLPG.
OTLK...VFR.
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BOSC FA 081845
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 091300Z
CLDS/WX VALID UNTIL 090700...0TLK VALID 090700-091300Z
ME NH VT MA RI CT NY LO NJ PA OH LE WV MD DC DE VA AND CSTL, WTR.

SEE AIRMET SIERRA FOR IFR CONDS AND MTN OBSCN. TSTMS IMPLY SVR OR GTR TURBC SVR ICG LLWS AND IFR CONDS. NON MSL HGTS DENOTED BY AGL OR CIG.

SYNOPSIS...SFC HI PRES FROM NY TO CNTRL GULF STATES. WK UPR TROF CROSSING NEW ENG/NY RESPONSIBLE FOR CLDS/AREAS OF LGT SNOW.

ME NH VT
SXNS E OF BGR-CAR LN15 BKN-OVC 80. OCNL VSBY 3-5SW-.
02Z 40 BKN-SCT 80. OTLK...VFR.
ELSW35 SCT-BKN 100. ISOLD SW-. OTLK...VFR.

NY LO
30 SCT OCNL BKN 80 100 BKN 120. ISOLD SW- OVR NERN MTNS.
02Z 40 SCT 80 SCT-BKN 100. OTLK...VFR.

OH LE
NWRN OH/WRN LE15 BKN-SCT 40. OTLK...VFR.
ELSWCLR. OCNL 25 SCT SRN OH. OTLK...VFR.

MD DC DE VA
CHSPK BAY/EASTERN SHORE25 SCT100 SCT-BKN 120.00Z CLR.
OTLK...VFR.
ELSW...CLR. OTLK...VFR.

CSTL WTRS
CAPE COD NWD...20 BKN 60 80 BKN 120. 00Z 40 SCT-BKN 100.
OTLK...VFR.
S OF CAPE COD...30 SCT OCNL BKN 80. OTLK...VFR
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MIAC FA 081845
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 091300Z
CLDS/WX VALID UNTIL 090700...0TLK VALID 090700-091300Z
NC SC GA FL AND CSTL WTRS

SEE AIRMET SIERRA FOR IFR CONDS AND MTN OBSCN. TSTMS IMPLY SVR OR GTR TURBC SVR ICG LLWS AND IFR CONDS.
NON MSL HGTS DENOTED BY AGL OR CIG.

NC SC GA FL PNHDL CLR. OTLK...VFR.
FL PENINSULA
SCT-BKN CI. 06Z NRN SXNS VSBY 3-5F. OTLK...NRN SXNS MVFR CIG F.
EL.RW VFR