Chapter 27, Forecasts 27-61
Figure 27-32. Aviation Watch (polygon) Compared to Public Watch (shaded) Example
The SPC will issue the SAW after the proposed convective watch area has been collaborated with the
impacted NWS WFOs defining the approximate areal outline of the watch.
SAWs are nonscheduled, event-driven products valid from the time of issuance to expiration or cancellation
time. Valid times are in UTC. SPC will correct watches for formatting and grammatical errors.
When tornadoes or severe thunderstorms have developed, the local NWS WFO will issue the warnings for
the storms.
27.17.4.1.1 Format and Example of a SAW
SPC forecasters may define the area as a rectangle or parallelogram (X mi les either side of the line from
point A to point B, or X miles north and south or east and west of the line from point A to point B). Distances
of the axis coordinates should be in statute miles. The aviation coordinates referencing VOR locations and
state distances will be in nautical miles. Valid times will be in UTC. The watch half width will be in statute
miles. The SAW will contain hail size in inches or half inches (forecaster discretion for tornado watches
associated with hurricanes) surface and aloft, surface convective wind gusts in knots, maximum cloud tops
and the Mean Storm Motion Vector, and replacement information, if necessary.
WWUS30 KWNS 271559
SAW2
SPC AWW 271559
WW 568 TORNADO AR LA MS 271605Z - 280000Z
AXIS..65 STATUTE MILES EAST AND WEST OF LINE..
Chapter 27, Forecasts 27-62
45ESE HEZ/NATCHEZ MS/ - 50N TUP/TUPELO MS/
..AVIATION COORDS.. 55NM E/W /18WNW MCB - 60E MEM/
HAIL SURFACE AND ALOFT..3 INCHES. WIND GUSTS..70 KNOTS. MAX TOPS TO 550. MEAN
STORM MOTION VECTOR 26030.
LAT...LON 31369169 34998991 34998762 31368948
THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
FOR WOU2.
Table 27-15. Decoding an Aviation Weather Watch Notification Message
Line(s) Content Description
1 WWUS30 KWNS 271559 Communication header with issuance
date/time
2 SAW2 NWS product type (SAW) and
issuance number (2)
SPC
AWW
Issuing office
Product type
Issuance date/time
WW 568
TORNADO
AR LA MS
271605Z - 280000Z
Watch number
Watch type
States affected
Valid date/time period
5 AXIS..65 STATUTE MILES EAST AND WEST
OF A LINE... Watch axis
6 45ESE HEZ/NATCHEZ MS/ - 50N
TUP/TUPELO MS/ Anchor points
7 …AVIATION COORDS..55NM E/W /18WNW MCB
- 60E MEM/ Aviation coordinates
8–9
HAIL SURFACE AND ALOFT…3 INCHES. WIND
GUSTS..70 KNOTS. MAX TOPS TO 550.
MEAN STORM MOTION VECTOR 26030.
Type, intensity, max tops and mean
storm motion using standard
contractions.
10 (blank line)
11 LAT...LON 31369169 34998991 4998762
31368948 Latitude and longitude coordinates
12 (blank line)
13–15
THIS IS AN APPROXIMATION TO THE WATCH
AREA. FOR A COMPLETE DEPICTION OF THE
WATCH SEE WOUS64 KWNS FOR WOU2.
Notice that this is an approximation
of the watch area and for users to
refer to the referenced product for the
actual area
27.17.4.2 Public Severe Thunderstorm Watch Notification Message
The SPC issues a Public Severe Thunderstorm Watch Notification Message when forecasting six or more
hail events of one inch (quarter-sized) diameter or greater or damaging winds of 50 kt (58 mph) or greater.
The forecast event minimum threshold is at least two hours over an area of at least 8,000 mi2. Below these
thresholds, the SPC, in collaboration with affected NWS offices, may issue a watch for smaller areas and
Chapter 27, Forecasts 27-63
for shorter periods of time when conditions warrant, and for convective watches along coastli nes, near the
Canadian border, and near the Mexican border.
A Public Severe Thunderstorm Watch Notification Message contains three bulleted blocks of information:
• The geographic area of the watch,
• The valid time of the watch, and
• A description of the primary threats anticipated within the watch.
A plain text watch summary is included beneath the bulleted information followed by a more detailed
description of the area and axis of the watch.
The SPC includes the term “adjacent coastal waters” when the watch affects coastal waters adjacent to the
Pacific/Atlantic coast, the Gulf of America, or the Great Lakes. Adjacent coastal waters refers to a WFO’s
near-shore responsibility (out to 20 NM for oceans), except for convective watches.
The SPC issues a watch cancellation message when no counties, parishes, independent cities, and/or marine
zones remaining are in the watch area prior to the expiration time. The text of the message will specify the
number and area of the cancelled watch.
27.17.4.3 Public Tornado Watch Notification Message
The SPC issues a Public Tornado Watch Notification Message when forecasting two or more tornadoes or
any tornado that could produce EF-2 or greater damage. The forecast event minimum thresholds are at least
two hours over an area at least 8,000 mi2. Below these thresholds, the SPC, in collaboration with affected
NWS offices, may issue a watch for smaller areas and for shorter periods of time when conditions warrant,
and for convective watches along coastlines, near the Canadian border, and near the Mexican border.
A Public Tornado Watch Notification Message contains the following:
• The area description and axis,
• The watch expiration time,
• The term “damaging tornadoes,”
• A description of the largest hail size and strongest thunderstorm wind gusts expected,
• The definition of the watch,
• A call-to-action statement,
• A list of other valid watches,
• A brief discussion of meteorological reasoning, and
• Technical information for the aviation community.
The SPC may enhance a Public Tornado Watch Notification Message by using the words “THIS IS A
PARTICULARLY DANGEROUS SITUATION” when there is a likelihood of multiple strong (damage of
EF-2 or EF-3) or violent (damage of EF-4 or EF-5) tornadoes.
The SPC includes the term “adjacent coastal waters” when the watch affects coastal waters adjacent to the
Pacific/Atlantic coast or the Gulf of America. Adjacent coastal waters refers to a WFO ’s near -shore
responsibility (out to 20 NM for oceans), which includes portions of the Great Lakes.
The SPC issues a watch cancellation message whenever it cancels a watch prior to the expiration time. The
text of the message will specify the number and area of the cancelled watch.
Chapter 27, Forecasts 27-64
27.17.5 Corridor Integrated Weather System (CIWS) and Consolidated Storm
Prediction for Aviation (CoSPA)
The CIWS and CoSPA are fully automated weather analysis and forecast systems developed for the FAA
by the Massachusetts Institute of Technology (MIT) Lincoln Laboratory. These systems combine data from
a wide variety of weather radars, satellites, surface observations, and numerical models to provide accurate,
rapidly updating weather information to air traffic controllers, air traffic flow managers, a nd airline users.
The state-of-the-art weather products allow managers to achieve more efficient tactical and strategic use of
the airspace, reduce controller workload, and significantly reduce delays.
The CIWS provides deterministic zero- to two-hour forecasts of precipitation, winter precipitation, and
echo tops. The deterministic forecast portrays storms in the same format as a radar detection. Thus, the
deterministic forecast is sometimes referred to as a “radar forward” depiction. The forecasts are provided
as gridded maps or contour overlays on the current weather. An animated loop is available with two hours
of past weather and forecasts out to two hours in the future, with five-minute granularity. This forecast
granularity can be set to five minutes, 10 minutes, 15 minutes, 30 minutes, or one hour, depending on the
user’s needs.
CoSPA provides deterministic zero- to eight-hr forecasts of precipitation, winter precipitation, and echo
tops. The animated loop allows the display of eight hours of past weather and forecasts out to eight hours
in the future, with 15 -minute granularity that can be set to 15 minutes, 30 minutes, or one hour. The first
two hours of the CoSPA forecasts are identical to the CIWS forecasts.
Figure 27-33. CIWS and CoSPA
27.18 Route Forecast (ROFOR)
The ROFOR product is no longer issued by the NWS and has been replaced by the GFA in the Pacific. See
Section 28.2 for information on the GFA.
Chapter 27, Forecasts 27-65
27.19 Aviation Forecast Discussion (AFD)
AFDs describe the weather conditions within a multistate or substate-sized area. They also may:
• Describe the weather conditions as they relate to a specific TAF or group of TAFs; and
• Provide additional aviation weather-related issues that cannot be encoded into the TAF, such as the
reasoning behind the forecast.
AFDs are a free-form plain language text product. Common or well -known aviation weather contractions
are used as well as local or regional geographic names, such as valleys, mountain ranges, and bodies of
water.
Technically, the AFD is not a discrete product ; it is the aviation section in the NWS WFO’s AFD. The
NWS AWC extracts the aviation section from the WFO’s AFD and makes it available o n the AWC’s
website under the Forecasts tab, titled “Avn. Forecast Disc.” The aviation section of the AFD can also be
found on the WFO’s website under “Forecaster Discussion.”
All WFOs in the CONUS, and most outside the CONUS, produce the aviation section of the AFD for their
area of responsibility (see Figure 27-34). They are issued roughly every six hours and correspond to the
issuance of TAFs from the respective NWS WFO. Each NWS office may tailor the format to meet the needs
of their local aviation users.
Figure 27-34. Map of NWS WFO’s Area of Responsibility
27.19.1 Example
NWS Boise, ID
COLD FRONT CURRENTLY OVER SW IDAHO WEST OF THE MAGIC VALLEY. IFR IN HEAVIER
RAIN/SNOW SHOWERS BEHIND THE FRONT MOSTLY IN THE MTNS UNTIL THIS EVENING.
OTHERWISE, LOW VFR THROUGH TOMORROW WITH ISOLATED SHOWERS INTO THE EVENING.
SURFACE WINDS...W TO NW WITH GUSTS 20-30 KTS...BECOMING 35-45 KTS IN THE UPPER
TREASURE AND MAGIC VALLEYS FOR A FEW HOURS THIS AFTERNOON...DROPPING DOWN TO
20-30 KTS OVERNIGHT INTO THE MORNING IN THE MAGIC VALLEY AND 5-10 KTS ELSEWHERE.
WINDS ALOFT NEAR 10K FT MSL...NW 30-40 KTS...40-50 KTS OVER THE UPPER TREASURE
AND MAGIC VALLEYS OVERNIGHT...BECOMING 20-30 KTS BY 15/12Z.
Chapter 27, Forecasts 27-66
27.20 Meteorological Impact Statement (MIS)
The MIS is a nontechnical plain language product intended primarily for FAA traffic managers and those
involved in planning aircraft routing. MISs are issued by the NWS CWSU.
MISs are available on the AWC’s website as well as CWSU’s websites.
The MIS valid times are determined according to local policy. The MIS is limited to a 48-hour valid period.
27.20.1 Example
ZAB MIS 02 VALID 281300-290300
...FOR ATC PLANNING PURPOSES ONLY...
AN UPPER-LVL DISTURBANCE OVER COLORADO COMBINED WITH A STRONG JET STREAM MOVING
ACROSS THE SWRN U.S. IS FCST TO PRODUCE AREAS OF TURBULENCE ACROSS PORTIONS OF
ZAB. THE TURBULENCE IS FCST TO SUBSIDE AFT 00Z AS THE DISTURBANCE AND JETSTREAM
MOVE FURTHER EAST.
27.21 Soaring Forecast
Select NWS WFOs issue soaring forecasts. These are automated forecasts primarily derived from the
radiosonde observation or model-generated soundings.
The content and format of soaring forecasts vary with the NWS WFO-provided forecast, based on the needs
of their soaring community. It is beyond the scope of this handbook to describe all of the many variations
of soaring forecasts and their content. Soaring pilots should consult with the NWS WFO in their soaring
area for more information.
27.21.1 Example
The following example is for Salt Lake City, Utah:
UXUS97 KSLC 091233
SRGSLC
Soaring Forecast
National Weather Service Salt Lake City, Utah
0633 MDT Tuesday, July 9, 2019
This forecast is for Tuesday, July 9, 2019:
If the trigger temperature of 81.4 F/27.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1239 ft/min (6.3 m/s)
Maximum height of thermals.................. 17411 ft MSL (13185 ft AGL)
Forecast maximum temperature................... 88.0 F/31.6 C
Time of trigger temperature.................... 1200 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10097 ft MSL (5872 ft AGL)
Thermal soaring outlook for Wednesday 07/10.... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:05:02 / 21:01:07 MDT
Chapter 27, Forecasts 27-67
Total possible sunshine........... 14 hr. 56 min 5 sec (896 min 5 sec)
Altitude of sun at 13:33:04 MDT... 70.27 degrees
Upper air data from rawinsonde observation taken on 07/09/2019 at 0600 MDT
Freezing level.................. 13975 ft MSL (9749 ft AGL)
Convective condensation level... 15400 ft MSL (11174 ft AGL)
Lifted condensation level....... 16064 ft MSL (11838 ft AGL)
Lifted index.................... -0.7
K index......................... +19.1
This product is issued once per day by approximately 0600 MST/ 0700 MDT (1300
UTC). This product is not continuously monitored nor updated after the initial
issuance.
The information contained herein is based on the 1200 UTC rawinsonde observation
at the Salt Lake City, Utah International Airport and/or numerical weather
prediction model data representative of the airport. These data may not be
representative of other areas along the Wasatch Front. Erroneous data such as
these should not be used.
The content and format of this report as well as the issuance times are subject
to change without prior notice.
27.22 Balloon Forecast
Select NWS WFOs issue balloon forecasts. These are automated forecasts primarily derived from the
radiosonde observation or model-generated soundings.
The content and format of balloon forecasts vary with the NWS WFO providing the forecast, based on the
needs of their ballooning community. It is beyond the scope of this handbook to describe all of the many
variations of balloon forecasts and their content. Balloon pilots should consult with the NWS WFO in their
area for more information.
27.22.1 Example
The following example is for St. Louis, Missouri:
SXUS43 KLSX 090850
RECSTL
Morning Hot Air Balloon Forecast
National Weather Service Saint Louis MO
350 AM CDT Tue Jul 9, 2019
...HERE IS THE MORNING HOT AIR BALLOON FORECAST
FOR THE SAINT LOUIS METROPOLITAN AREA...
.THIS MORNING...
Sunrise: 545 AM.
Surface Wind Forecast: 6 AM...110/05 mph.
8 AM...120/05 mph.
Latest Geostrophic Wind: 1 AM...160/15 mph.
Boundary Layer Wind: 7 AM...120/06 mph.
10 AM...160/12 mph.
NWS Doppler Winds (at 0334 AM): 1000ft...130/15 mph.
Chapter 27, Forecasts 27-68
2000ft...150/22 mph.
3000ft...160/20 mph.
Surface Lifted Index: 7 AM...+3.
10 AM...-1.
Density Altitude: 6 AM...1708 FT.
8 AM...1948 FT.
Additional Weather Info: Slight chance of thunderstorms.
.OUTLOOK FOR THIS EVENING...
Sunset: 829 PM.
Weather: Chance of thunderstorms.
Surface Wind: 6 PM...150/07 mph.
8 PM...150/06 mph.
Boundary Wind: 4 PM...160/14 mph.
7 PM...160/08 mph.
This forecast is not routinely updated or amended outside of scheduled
issuances.
&&
This forecast is also available at phone number 636-441-8467 ext. 5.
$$