Point Forecast Matrices

What are the POINT FORECAST MATRICES?
The PFM displays forecast weather parameters in 3, 6, and 12 hour intervals out to 7 days in the future for specific locations.

How to read/interpret the PFM
There are several forecast parameters which appear in the PFM product. Some of these values are forecast in 12 hour intervals while others are forecast in 3 and 6 hour intervals. Listed below is an example of an PFM product and a description of each of its parameters.
DATE FRI 06/13/03 SAT 06/14/03 SUN

UTC 3HRLY 20 23 02 05 08 11 14 17 20 23 02 05 08 11 14 17 20 23 02 05 08 11

CDT 3HRLY 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06



MIN/MAX 69 96 69 89 66

TEMP 89 82 76 69 77 88 94 95 84 76 72 69 75 83 88 88 79 72 69 66

DEWPT 59 61 63 65 66 64 63 61 63 68 68 67 67 68 68 67 67 67 67 66

RH 38 50 66 88 69 44 36 33 50 74 86 99 76 60 52 50 67 83 93 99

WIND DIR SE E SE S S SW S S S E E SE E E E E E E NE N

WIND SPD 10 11 11 13 17 16 10 9 11 16 14 11 12 13 14 14 11 8 5 6

CLOUDS SC SC SC SC SC SC SC SC SC SC BK BK SC SC SC SC SC SC SC SC

POP 12HR 20 30 30 30 40

QPF 12HR 0.13 0.06 0.08 0 0.19

TSTMS S S S S C C C C C C C C C C C C





DATE 06/15/03 MON 06/16/03 TUE 06/17/03 WED 06/18/03 THU 06/19/03

UTC 6HRLY 17 23 05 11 17 23 05 11 17 23 05 11 17 23 05 11 17 23

CDT 6HRLY 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18



MAX/MIN 88 67 89 69 88 70 93 70 92

TEMP 82 87 73 67 83 88 74 69 83 88 75 70 87 92 76 70 86 91

DEWPT 62 59 63 64 64 61 64 65 65 62 62 62 62 62 63 65 65 65

PWIND DIR N NE NE N NE NE NE NE NE

WIND CHAR GN GN GN GN GN GN GN GN GN

AVG CLOUDS SC SC SC SC SC SC SC SC SC SC SC SC SC SC SC SC SC SC

POP 12HR 20 20 20 20 10 10 5 5 5

TSTMS S S S S S S
MAX/MIN. (Alternatively labeled as MIN/MAX for afternoon issuance)
A forecast of maximum or minimum 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.
TEMP
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.
DEWPT
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.
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.
WIND DIR
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.

WIND SPD
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 12 hour period.

Wind Character Codes

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

 

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.

CLOUDS
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 Codes

Code Stands for: Traditional Text Equivalent Percent of Sky Covered with Clouds
CL Clear Clear/Sunny 0-6%
FW Few Mostly Clear/Mostly Sunny 7%-31%
SC Scattered Partly Cloudy/Partly Sunny 32%-69%
BK Broken Mostly Cloudy 70%-94%
OV Overcast Cloudy 95%-100%

 

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 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.

 

 

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 area. 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.

MAX QPF (optional)
The value for MAX QPF value is the estimated maximum amount of precipitation, in inches occurring at any point within the zone(s) during the12-hour period ending at 6:00 a.m. or 6:00 p.m. local time. This amount is presented as either a single value or a range, and is based upon a 75% confidence level of the QPF forecaster(s). MAX QPF is right justified below the hour defining the ending time of the expected precipitation, and is available out to 60 hours.

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.

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 at any point within the zones(s) 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.

Precipitation Type

  Translation:
RAIN Rain
RAIN SHWRS Rain Showers
SPRINKLES Sprinkles
TSTMS Thunderstorms
DRIZZLE Drizzle
SNOW Snow
SNOWSHWRS Snow Showers
FLURRIES Snow Flurries
SLEET Sleet/Ice Pellets
FRZNG RAIN Freezing Rain
FRZNG DRZL Freezing Drizzle

Probability of Precipitation Codes

S Slight Chance <=20%
C Chance 30%-50%
L Likely 60%-70%
O Occasional/periods of 80%-100%
D Definite 80%-100%
   
IS Isolated <=20%
SC Scattered 30%-50%
NM Numerous 60%-70%
EX Extensive 80%-100%

OBVIS
If an obstruction to visibility (OBVIS) is forecast for the zone, 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. In the Figure 19 example, “K” implies that smoke is restricting visibility during the 6-hour period from 3:00 a.m. - 9:00 a.m. EST on Monday 2/12/01. OBVIS is forecast at 3-hour intervals through 60 hours.

Visibility Obstruction Codes

F Fog
PF Patchy Fog
F+ Dense Fog
PF+ Patchy Dense Fog
H Haze
BS Blowing Snow
K Smoke
BD Blowing Dust
VA Volcanic Ash
WIND CHILL
Wind Chill is included seasonally based upon locally defined criteria. The decision on whether to include or exclude these parameters is determined by the local WFO criteria. The Wind Chill is forecast out to 60 hours.
MIN CHILL 6HR
When WIND CHILL values appear in the PFM, a 6-hour minimum wind chill may appear on the following row. These values indicate the minimum wind chill index forecast to occur during the 6-hour period ending at the time indicated at the top of the column. MIN CHILL 6HR is forecast out to 60 hours.



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