1. MIN/MAX:
(Alternatively labeled as MAX/MIN for morning issuance)
A forecast of minimum or maximum temperatures in degrees Fahrenheit
(F). The MAX temperature is valid for the period 7:00 a.m. through
7:00 p.m. local standard time, and MIN is valid for 7:00 p.m. through
8:00 a.m. local standard time (note that due to a 3-hour minimum time resolution,
this element is right justified in the column beneath the approximate ending
time of the MAX/MIN period). The nighttime MIN and daytime MAX may be displayed
as single integer (e.g., -2, 8, 53, 102) as a range (e.g., 54 56 60) if
the MAX/MIN temperatures are expected to vary across the area. In area
forecasts, the middle number within the range is the representative single
digit value for that area. MAX/MIN is forecast out through Day 7.
2. TEMP:
TEMP is a snapshot of the expected temperature in degrees F valid at
the indicated hour. The temperature is right justified in the column below
the hour to which it refers. TEMP is forecast at 3-hour intervals through
60 hours, then 6-hour intervals through Day 7.
3. DEWPT:
DEWPT is a snapshot of the expected dew point temperature in degrees
F for the same time periods as its corresponding temperature forecast.
DEWPT is located directly below the temperature line.
4. RH:
The relative humidity (RH) is a snapshot of the expected RH for the
same time periods as its corresponding temperature and dew point forecast.
The RH row is located directly below the DEWPT row. RH is available
at 3-hour increments through 60 hours.
5. WIND DIR:
WIND DIR is a snapshot of the expected wind direction forecast to occur
at the indicated hour, using the 8 points of a compass (i.e., N, NE, E,
SE, S, SW, W, NW). If a calm wind is forecast, double zeros (00) will be
listed in place of a wind direction. WIND DIR is located below the hour
to which it refers. WIND DIR is available in 3-hour increments out to 60
hours.
In the 6HRLY block, PWIND DIR is the predominant wind direction
for the zone(s) during the 12-hour period between 6:00 a.m. and 6:00 p.m.,
or 6:00 p.m. and 6:00 a.m. local time. PWIND DIR is valid beyond 60 hours
through Day 7.
6. WIND SPD:
WIND SPD is a snapshot of the sustained wind speed in miles per hour
(MPH) forecast to occur at the indicated hour. If a calm wind is forecast,
double zeros (00) will be listed in place of a wind speed.
WIND SPD is valid in 3-hour increments out to 60 hours.
WIND CHAR codes are used beyond 60 hours through Day 7 of the forecast
and denote the character of the wind for the 12-hour period between 6:00
a.m. and 6:00 p.m., or 6:00 p.m. and 6:00 a.m. WIND CHAR is comprised of
range categories used in conjunction with deterministic wind speeds. Each
range category is equated to a descriptive wind term, i.e., a wind character
to best describe the MAXIMUM SUSTAINED wind speed during the period.
| Wind Character |
Wind Character |
12-hr Maximum Sustained Wind Speed |
| LT |
Light |
<8 mph |
| GN |
Gentle |
8-14 mph |
| BZ |
Breezy |
15-22 mph |
| WY |
Windy |
23-30 mph |
| VW |
Very Windy |
31-39 mph |
| SD |
Strong/Damaging |
>= 40 mph |
6A. WIND GUST:
A wind gust row will appear in the 3HRLY block whenever forecasted
wind gusts exceed the sustained wind speed (WIND SPD) by at least 10 MPH.
WIND GUST is a snapshot valid on the hour indicated at the top of the corresponding
column. WIND GUST is a snapshot of gusts of wind occurring at the indicated
hour and is valid in 3-hour increments through 60 hours.
7. CLOUDS:
The CLOUDS category provides a snapshot of sky coverage during the
indicated hour. CLOUDS is divided into five category codes ranging from
clear to overcast . Each code represents an equivalent percentage of sky
cover in percent. CLOUDS parameter is included in 3-hour time intervals
out to 60 hours. In the 6HOURLY section, AVG CLOUDS is valid for 6-hour
increments beyond 60 hours through Day 7 and indicates the average amount
of all clouds during the 6-hour period ending on the hour indicated at
the top of the column.
| Sky Cover Code |
Sky Cover Expression |
Equivalent Percent Opaque Sky Cover |
| CL |
Clear |
0% to 6% |
| FW |
Mostly Clear/Mostly Sunny |
7% to 31% |
| SC |
Partly Cloudy/Partly Sunny |
32% to 69% |
| BK |
Mostly Cloudy |
70% to 94% |
| OV |
Cloudy |
95% to 100% |
8. POP 12HR:
Probability of Precipitation (POP), is defined as the likelihood, expressed
as a percent, of a measurable precipitation event (1/100th of an inch)
at any given point within the forecast area(s) covered by the AFM/PFM.
The 12HR refers to the 12-hour valid time ending at 6:00 a.m. or
6:00 p.m. local time (0600 or 1800). The POP 12HR value is right justified
in the column beneath the hour defining the ending time of the valid period. POP 12HR is forecast through Day 7.
9. QPF 12HR:
This parameter, quantitative precipitation forecast (QPF) represents
the total amount of liquid precipitation, in inches, expected during a
12-hour period ending at 6:00 a.m., or 6:00 p.m. local time at any point
in the forecast location. The QPF is presented in locally defined ranges, (e.g.,
.10-.24), or single values. The QPF 12HR value is right justified in the
column beneath the hour defining the ending time of the expected precipitation. QPF 12HR is forecast out to 60 hours.
10. SNOW 12HR:
The expected range of total snowfall accumulation (in whole inches)
forecast to occur at the specific point during a 12-hour period ending
at 6:00 a.m. or 6:00 p.m. local time. SNOW 12HR will only appear during
the locally defined winter period. The snow parameter contains 1 to 5 alphanumeric
characters which are right justified in the column below the hour defining
the ending time of the precipitation period. SNOW 12HR may appear as a
one or two digit number (1, 4, 12), or as a specified range (2-4, 8-12).
When no snowfall is forecast during the locally specified winter period,
double zeros (00-00) will appear in the row. Snowfall that is not measurable
(less than 0.1 inch of frozen precipitation) is referred to as a trace.
A trace of snow is depicted by a T. SNOW 12HR is forecast out to
36 hours.
11, 12, and 13. PRECIPITATION TYPE AND CATEGORY:
The PFM may list several types of precipitation. Precipitation
types only appear in the PFM if they are forecast to occur
during the seven day forecast. Precipitation type codes
are listed in the far left column of the PFM. For each type of precipitation
that is forecast, an associated POP. category is specified within the body
of the product. The POP. expression for the indicated precipitation type
is valid at the hour specified by the column header. Precipitation type
expressions are forecast at three hour time intervals out to 60 hours,
then 12-hour time intervals beyond 60 hours through Day 7.
| Code |
Qualifying Term |
POP (%) |
| S |
Slight Chance |
15% to 24% |
| C |
Chance |
25% to 54% |
| L |
Likely |
55% to 74% |
| O |
Occasional/Periods of |
75% to 100% |
| D |
None |
75% to 100% |
| Code |
Areal Term |
Areal Coverage (%) |
| IS |
Isolated |
15% to 24% |
| SC |
Scattered |
25% to 54% |
| NM |
Numerous |
55% to 74% |
| EC |
None (extensive coverage) |
75% to 100% |
| Code |
Areal Term |
Areal Coverage (%) |
| PA |
Patchy |
1% to 24% |
| AR |
Areas |
25% to 54% |
| WD |
Widespread |
55% to 74% |
14. OBVIS:
If an obstruction to visibility (OBVIS) is forecasted, a
row labeled OBVIS will be listed underneath any forecast of precipitation.
If no precipitation is forecast, then OBVIS will be listed under the row
labeled AVG CLOUDS. OBVIS is forecast at 3-hour intervals through 60 hours.
| Code |
Obstruction to Visibility |
| F |
Fog |
| PF |
Patchy Fog |
| F+ |
Dense Fog |
| PF+ |
Patchy Dense Fog |
| H |
Haze |
| BS |
Blowing Snow |
| H |
Haze |
| BS |
Blowing Snow |
| K |
Smoke |
| BD |
Blowing Dust |
| VA |
Volcanic Ash |
15. WIND CHILL and HEAT INDEX:
Wind Chill and Heat Index are included seasonally based upon locally
defined criteria.
The Wind Chill and Heat Index
are forecast out to 60 hours.
16. MIN CHILL 6HR and MAX HEAT 6HR:
When WIND CHILL or HEAT INDEX values appear in the PFM, a 6-hour
minimum wind chill or maximum heat index may appear on the following row.
These values indicate the minimum wind chill/ maximum heat index forecast
to occur during the 6-hour period ending at the time indicated at the top
of the column. MIN CHILL 6HR and MAX HEAT 6HR are forecast out to 60 hours. |
