Chapter 27, Forecasts 27-19
14008KT Wind 140° true at 8 kt.
P6SM Visibility greater than 6 SM.
SCT040 OVC080 4,000 ft scattered, ceiling 8,000 ft overcast.
TEMPO 1204/1208 Temporary conditions between the 12 th day of the month at
0400 UTC and the 12th day of the month at 0800 UTC.
3SM Visibility 3 SM.
TSRA Thunderstorms with moderate rain showers.
OVC030CB Ceiling 3,000 ft overcast with cumulonimbus.
TAF AMD
KEYW 131555Z 1316/1412 VRB03KT P6SM VCTS SCT025CB BKN250
TEMPO 1316/1318 2SM TSRA BKN020CB
FM131800 VRB03KT P6SM SCT025 BKN250 TEMPO 1320/1324 1SM TSRA OVC010CB
FM140000 VRB03KT P6SM VCTS SCT020CB BKN120 TEMPO 1408/1412 BKN020CB
TAF AMD Amended Terminal Aerodrome Forecast.
KEYW Key West, Florida.
131555Z Prepared on the 13th day of the month at 1555 UTC.
1316/1412 Valid from the 13 th day of the month at 1600 UTC until the
14th day of the month at 1200 UTC
VRB03KT Wind variable at 3 kt.
P6SM Visibility greater than 6 SM.
VCTS Thunderstorms in the vicinity.
SCT025CB BKN250 2,500 ft scattered with cumulonimbus, ceiling 25,000 ft
broken.
TEMPO 1316/1318 Temporary conditions between the 13 th day of the month at
1600 UTC and the 13th day of the month at 1800 UTC.
2SM Visibility 2 SM.
TSRA Thunderstorms with moderate rain showers.
BKN020CB Ceiling 2,000 ft broken with cumulonimbus.
FM131800 From the 13th day of the month at 1800 UTC.
VRB03KT Wind variable at 3 kt.
P6SM Visibility greater than 6 SM.
SCT025 BKN250 2,500 ft scattered, ceiling 25,000 ft broken.
TEMPO 1320/1324 Temporary conditions between the 13 th day of the month at
2000 UTC and the 14th day of the month at 0000 UTC.
1SM Visibility 1 SM.
TSRA Thunderstorms with moderate rain showers.
Chapter 27, Forecasts 27-20
OVC010CB Ceiling 1,000 ft overcast with cumulonimbus.
FM140000 From the 14th day of the month at 0000 UTC.
VRB03KT Variable wind at 3 kt.
P6SM Visibility greater than 6 SM.
VCTS Thunderstorms in the vicinity.
SCT020CB BKN120 2,000 ft scattered with cumulonimbus, ceiling 12,000 ft
broken.
TEMPO 1408/1412 Temporary conditions between the 14 th day of the month at
0800 UTC and the 14th day of the month at 1200 UTC.
BKN020CB Ceiling 2,000 ft broken with cumulonimbus.
27.4.4 Issuance
Scheduled TAFs prepared by NWS offices are issued at least four times a day, every six hours. Some
locations have amendments routinely issued three hours after the initial issuance. The issuance schedule is
shown in Table 27-7.The issuance of a new TAF cancels any previous TAF for the same location.
Table 27-7. TAF Issuance Schedule
Scheduled Issuance Valid Period End Time for
30 Hour Issuance Window
0000 UTC 0000 to 0000 0600 UTC 2320 to 2340 UTC
0300 UTC (AMD) 0300 to 0000 UTC 0600 UTC
0600 UTC 0600 to 0600 1200 UTC 0520 to 0540 UTC
0900 UTC (AMD) 0900 to 0600 UTC 1200 UTC
1200 UTC 1200 to 1200 1800 UTC 1120 to 1140 UTC
1500 UTC (AMD) 1500 to 1200 UTC 1800 UTC
1800 UTC 1800 to 1800 0000 UTC 1720 to 1740 UTC
2100 UTC (AMD) 2100 to 1800 UTC 0000 UTC
27.4.4.1 Minimum Observational Criteria for Routine TAF Issuance and Continuation
The NWS forecaster must have certain information for the preparation and scheduled issuance of each
individual TAF. Although integral to the TAF writing process, a complete surface (METAR/SPECI)
observation is not needed. Forecasters use the “total observation concept” to write TAFs with data including
nearby surface observations, radar, satellite, radiosonde, model data, aircraft, and other sources.
If information sources, such as surface observations, are missing, unreliable, or not complete, forecasters
will append AMD NOT SKED to the end of a TAF. The use of AMD NOT SKED indicates the forecaster
has enough data, using the total observation concept, to issue a forecast, but will not provide updates. This
allows airport operations to continue using a valid TAF.
Chapter 27, Forecasts 27-21
In rare situations where observations have been missing for extended periods of time (i.e., more than one
TAF cycle of six hours) and the total observation concept cannot provide sufficient information, the TAF
may be suspended by the use of NIL TAF.
27.4.4.2 Sites with Scheduled Part-Time Observations
For TAFs with less than 24 -hour observational coverage, the TAF will be valid to the end of the routine
scheduled forecast period even if observations cease prior to that time. The time observations are scheduled
to end and/or resume will be indicated by e xpanding the AMD NOT SKED statement. Expanded
statements will include the observation ending time (AFT Y1Y1HHmm, e.g., AFT 120200), the scheduled
observation resumption time ( TIL Y 1Y1HHmm, e.g., TIL 171200Z) or the period of observation
unavailability ( Y1Y1HH/YeYehh, e.g., 2502-2512). TIL will be used only when the beginning of the
scheduled TAF valid period coincides with the time of the last observation or when observations are
scheduled to resume prior to the next scheduled issuance time. When used, these remarks will immediately
follow the last forecast group. If a routine TAF issuance is scheduled to be made after observations have
ceased, but before they resume, the remark AMD NOT SKED will immediately follow the valid period
group of the scheduled issuance. After sufficient data using the total observation concept has been received,
the AMD NOT SKED remark will be removed.
Examples of Scheduled Part-Time Observations TAFs:
TAF AMD
KRWF 150202Z 1502/1524 {TAF text}
AMD NOT SKED 1505Z-1518Z=
No amendments will be available between the 15th day of the month at 0500 UTC and the 15th day of the
month at 1800 UTC due to lack of a complete observational set between those times.
TAF AMD
KPSP 190230Z 1903/1924 {TAF text}
AMD NOT SKED=
Amendments are not scheduled.
27.4.4.3 Automated Observing Sites Requiring Part-Time Augmentation
TAFs for automated stations without present weather and obstruction to vision information and have no
augmentation or only part -time augmentation are prepared using the procedures for part -time manual
observation sites detailed in the previous section, with one exception. This exception is the remark used
when the automated system is unattended. Specifically, the time an augmented automated system is
scheduled to go into unattended operation and/or the time augmentation resumes is included in a remark
unique to automated observing sites: AMD LTD TO CLD VIS AND WIND (AFT YYHHmm, or TIL
YYhhmm, or YYHH-YYhh), where YY is the date, HHmm is the time, in hours and minutes, of last
augmented observation, and hhmm is the time, in hours and minutes, the second complete observation is
expected to be received. This remark, which does not preclude amendments for other forecast elements, is
appended to the last scheduled TAF issued prior to the last augmented observation. It will also be appended
to all subsequent amendments until augmentation resumes.
The AMD LTD TO (elements specified) remark is a flag for users and differs from the AMD NOT SKED
AFT Z remark for part -time manual observation sites. AMD LTD TO means users should expect
amendments only for those elements and the times specified.
Example:
TAF AMD
KCOE 150202Z 1502/1524 text
AMD LTD TO CLD VIS AND WIND 1505-1518=
Chapter 27, Forecasts 27-22
The amended forecast indicates that amendments will only be issued for wind, visibility, and clouds,
between the 15th day of the month at 0500Z and the 15th day of the month at 1800Z.
An amendment includes forecasts for all appropriate TAF elements, even those not reported when the
automated site is not augmented. If unreported elements are judged to be crucial to the TAF and cannot be
adequately determined (e.g., fog versus moderate snow), the TAF will be suspended (i.e., an amended TAF
stating “AMD NOT SKED”).
AWOS systems with part -time augmentation, which the forecaster suspects are providing unreliable
information when not augmented, will be reported for maintenance and treated the same as part -time
manual observation sites. In such cases, the AMD NOT SKED AFT YY/aaZ remark will be used.
27.4.4.4 Non-Augmented Automated Observing Sites
The TAF issued for automated observing stations with no augmentation may be suspended in the event the
forecaster is notified of, or strongly suspects, an outage or unrepresentative data. Forecasters may also
suspend TAF amendments when an element the fore caster judges to be critical is missing from the
observation and cannot be obtained using the total observation concept. The term AMD NOT SKED will
be appended, on a separate line and indented five spaces, to the end of an amendment to the existing TAF
when appropriate.
27.5 Aviation Surface Forecast and Aviation Clouds Forecast
The Aviation Surface Forecast and Aviation Clouds Forecast graphics are snapshot images derived from a
subset of the aviation weather forecasts within the GFA Tool (see Chapter 28, Aviation Weather Tools). A
CONUS view is available as well as several regional views. Forecasts are prov ided for 3, 6, 9, 12, 15 ,
and 18 hours.
The Aviation Surface Forecast (see Figure 27-1) provides obscurations, visibility, weather phenomena, and
winds (including wind gusts) with AIRMET Sierra for IFR conditions and AIRMET Tango for sustained
surface winds of 30 kt or more overlaid. The Aviation Clouds Forecast (see Figure 27-2) provides cloud
coverage, bases, layers, and tops with AIRMET Sierra for mountain obscuration and AIRMET Zulu for
icing overlaid.
The Aviation Clouds Forecast graphic provides a forecast of cloud coverage and height (in hundreds of feet
MSL). Tops of the highest broken (BKN) or overcast (OVC) layer are shown when bases are below FL180.
Overlays of AIRMETs for icing and mountain obscuration are included when applicable.
Both of these products are updated every three hours and provide forecast snapsh ots for 3, 6, 9, 12, 15,
and 18 hours in the future.
These forecasts are presented on regional maps as well as a CONUS map. The regional maps provide more
detail than the CONUS map. The NWS plans to expand the coverage beyond the CONUS.
Complete product information can be found on the AWC’s website.
Chapter 27, Forecasts 27-23
Figure 27-1. Aviation Surface Forecast Example
Figure 27-2. Aviation Clouds Forecast Example
Chapter 27, Forecasts 27-24
27.6 Area Forecasts (FA)
An FA is an abbreviated plain language (text) forecast concerning the occurrence or expected occurrence
of specified en route weather phenomena. FAs cover an 18- to 24-hour period, depending on the region, are
issued three to four times daily, depending on the region, and are updated as needed. The exact phenomenon
contained in FAs also varies by region.
Text FAs are produced by the NWS for Alaska. They are available at https://aviationweather.gov. Text FAs
for the CONUS , Hawaii, the Gulf of America, and the Caribbean have been retired and replaced by the
NWS’ GFA Tool (see Chapter 28) and the Aviation Surface Forecast and Aviation Clouds Forecast graphics
(see Section 27.5). The NWS will continue producing text FAs for Alaska for the foreseeable future.
27.6.1 FA Standardization
Alaska FAs follow these standards:
• All heights or altitudes are referenced to MSL, unless otherwise noted (i.e., prefaced by AGL or
CIG), and annotated using the height in hundreds of feet, consisting of three digits (e.g., 040). For
heights at or above 18,000 ft, the level is preceded by “FL” to represent flight levels (e.g., FL180).
Tops are always referenced to MSL.
• References to latitude and longitude are in whole degrees and minutes following the model:
Nnn[nn] or Snn[nn], Wnnn[nn], or Ennn[nn] with a space between latitude and longitude and a
hyphen between successive points (e.g., N3106 W07118 – N3011 W7209).
• Messages are prepared in abbreviated plain language using contractions from Order JO 7340.2,
Contractions, for domestic products, and from ICAO Doc 8400, ICAO Abbreviations and Codes,
for products issued for Oceanic FIR s. A limited number of non -abbreviated 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 Section 24.3).
27.6.2 FA Issuance Schedule
FAs for Alaska are scheduled products issued at the times listed in Table 27-8 below.
Table 27-8. FA Issuance Schedule
Alaska
(UTC)
1st Issuance 0415 (DT)/0515 (ST)
2nd Issuance 1215 (DT)/1315 (ST)
3rd Issuance 2015 (DT)/2115 (ST)
4th Issuance None
Note: DT—During Alaska Daylight Time; ST—During Alaska Standard Time;
UTC—Coordinated Universal Time.
Chapter 27, Forecasts 27-25
27.6.3 FA Amendments and Corrections
Amendments are issued whenever the weather significantly improves or deteriorates based upon the
judgment of the forecaster. AMD is included after the date/time group. The date/time group on the WMO
and FAA lines is updated to indicate the time of the correction. The ending valid time remains unchanged.
FAs containing errors will be corrected. COR is included after the date/time group.
27.6.4 Alaska FA
27.6.4.1 Alaska FA Issuance
Issued by t he AAWU . There are s even FAs containing a total of 25 zones (see Table 27-9), covering
separate geographical areas of Alaska and the adjacent coastal waters, including the Pribilof Island s and
Southeast Bering Sea (see Figure 27-3).
FAs issued for Alaska cover the airspace between the surface and 45,000 ft MSL and include the following
elements:
1. Synopsis: A brief description of the significant synoptic weather affecting the FA area
during the first 18 hours of the forecast period.
2. Significant Clouds and Weather: A description of the significant clouds and weather for
each geographical zone during the first 12 hours of the forecast period, including the
following elements:
• AIRMET information for IFR ceiling and visibility, mountain obscuration, and strong surface
winds.
• Cloud amount (SCT, BKN, or OVC) with bases and tops.
• Visibility below 7 SM and obstruction(s) to visibility.
• Precipitation and thunderstorms.
• Surface wind greater than 20 kt.
• Mountain pass conditions using categorical terms (for selected zones only).
• Categorical outlook (VFR, MVFR, and IFR) for 12 to 18 hours.
3. Icing and Freezing Level: A description of expected icing conditions, including the
following elements:
• AIRMET information for icing and freezing precipitation.
• Icing not meeting SIGMET or AIRMET criteria during the six-hour to 12-hour period.
• Freezing level.
• If no significant icing is forecast, NIL SIG will be entered, followed by the freezing level.
4. Turbulence: A description of expected turbulence conditions, including the following
elements:
• AIRMET information for turbulence or LLWS.
• Turbulence not meeting SIGMET or AIRMET criteria during the six-hour to 12-hour period.
• If no significant turbulence is forecast, NIL SIG will be entered.
Chapter 27, Forecasts 27-26
Figure 27-3. AAWU Flight Advisory and FA Zones—Alaska
Table 27-9. AAWU Area Forecast (FA) 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 Kuskokwim Valley 22 Unimak Pass to Adak
10 Yukon-Kuskokwim 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
Chapter 27, Forecasts 27-27
27.6.4.2 FA—Alaska Example
FAAK47 PAWU 222010 (ICAO product header)
FA7H (NWS AWIPS Communication header)
JNUH FA 222015 (Area Forecast region, product type, issuance date/time)
EASTERN GULF COAST AND SE AK...
.
AIRMETS VALID UNTIL 230415
CB IMPLY POSSIBLE SEV OR GREATER TURB SEV ICE LLWS AND IFR CONDS.
NON MSL HEIGHTS NOTED BY AGL OR CIG.
.
SYNOPSIS VALID UNTIL 231400
989 MB LOW 275 NM SE KODIAK IS WILL MOV SE WARD TO ABOUT 350 NM S
PASI BY 14Z WHILE FILLING TO 998 MB. ASSOCD OCFNT ARCING E AND SE FM
LOW WILL MOV ONSHR SE AK AND DSIPT BY END OF PD.
.
LYNN CANAL AND GLACIER BAY JB...VALID UNTIL 230800
...CLOUDS/WX...
FEW025 SCT050 BKN100 TOP 120.
OTLK VALID 230800-231400...VFR.
PASSES...WHITE...CHILKOOT...VFR.
...TURB...
NIL SIG.
...ICE AND FZLVL...
NIL SIG. FZLVL 020.
.
CNTRL SE AK JC...VALID UNTIL 230800
...CLOUDS/WX...
FEW025 SCT050 BKN100 TOP 120.
AFT 03Z ISOL BKN050 -SHRA.
OTLK VALID 230800-231400...VFR.
...TURB...
AFT 05Z SW PAFE ISOL MOD TURB BLW 040.
...ICE AND FZLVL...
NIL SIG. FZLVL 025.
.
SRN SE AK JD...VALID UNTIL 230800
...CLOUDS/WX...
FEW025 SCT050 BKN100 TOP 120.
AFT 00Z OCNL BKN050 -RA. ISOL BKN025 -RA.
AFT 03Z SFC WND SE 25G35KT.
OTLK VALID 230800-231400...VFR.
...TURB...
AFT 02Z CLARENCE STRAIT SW ISOL MOD TURB BLW 040.
...ICE AND FZLVL...
AFT 02Z OUTER CST PAHY S ISOL MOD ICEIC 040-100. FZLVL 025.
27.7 Alaska Graphical Forecasts
The NWS AAWU produces a series of graphical forecasts to complement the text -based FA for Alaska
(see Section 27.6.4.1). These forecasts are available from the AAWU’s website. Forecasts include: