National Weather Service United States Department of Commerce

Definitions of MOS Graphical Products

MAX (Maximum) and MIN (Minimum) Temperature

DAYTIME MAXIMUM TEMPERATURE:

The highest temperature that will occur between 8 AM and 7 PM local time during the warm season (9 AM to 7 PM during cool season) in degrees Fahrenheit. Note: Forecasts valid at 0600 UTC apply to the previous day.

NORMAL MAX TEMP:

The normal highest temperature that should occur between 8 AM and 7 PM local time during the warm season (9 AM to 7 PM during cool season) in degrees Fahrenheit.

DEPARTURE FROM NORMAL MAXIMUM:

The difference, in degrees Fahrenheit, between the forecast daytime maximum temperature and the normal daytime maximum temperature.

NIGHTTIME MINIMUM TEMPERATURE:

The lowest temperature that will occur between 7 PM and 8 AM local time during the warm season (7 PM to 9 AM during cool season) in degrees Fahrenheit.

NORMAL MIN TEMP:

The normal lowest temperature that should occur between 7 PM and 8 AM local time during the warm season (7 PM to 9 AM during cool season) in degrees Fahrenheit.

DEPARTURE FROM NORMAL MINIMUM:

The difference, in degrees Fahrenheit, between the forecast nighttime minimum temperature and the normal nighttime minimum temperature.

TMP (Temperature) and DP (Dew Point):

TEMPERATURE:

The temperature, in degrees Fahrenheit, that will occur at the specified time.

DEWPOINT:

The temperature in degrees Fahrenheit to which air must be cooled for saturation to occur. The dewpoint temperature is valid at the specified time.

POP/QPF (Probability of Precipitation/Quantitative Precipitation Amount):

PROB. OF PRECIP. OCCURRENCE ON THE HOUR (1-hr PoPO):

The probability that precipitation of any form (liquid, freezing, or frozen) and any intensity (trace or any amount) will fall at the specified hour.

PROB. OF PRECIP. OCCURRENCE IN A 3-H PERIOD (3h PoPO):

The probability that precipitation of any form (liquid, freezing, or frozen) and any intensity (trace or any amount) will fall in a three-hour period ending at the specified hour.

PROB. OF 0.01" OF PRECIP. (PoP):

The probability that 0.01 inches or more of liquid-equivalent precipitation will fall during the X hour period (usually 6,12, or 24 hours) ending at the specified time.

QPF BEST CATEGORY:

The quantitative precipitation forecast (QPF) category for liquid-equivalent precipitation amount during the X hour period (usually 6,12, or 24 hours) ending at the specified time. Categories are derived from QPF probabilities, and are designed to yield forecasts having desirable skill characteristics.

PROB. OF [Amount ]" OF PRECIP.:

The probability that a given amount (in inches) or more of liquid-equivalent precipitation will fall during the X hour period (usually 6,12, or 24 hours) ending at the specified time.

TSTM (Thunderstorms) and SVR WX (Severe Weather):

PROBABILITY OF THUNDERSTORMS (LTNG):

The probability that a thunderstorm will occur within a 40 km grid box during the X hour period (usually 6,12, or 24 hours) ending at the specified time. A thunderstorm is defined as 1 or more cloud-to-ground lightning strikes.

UNCONDITIONAL PROBABILITY OF SEVERE WEATHER:

The probability that a severe thunderstorm will occur in the X hour period (usually 6,12, or 24 hours) ending at the specified time. A severe thunderstorm is one with wind gusts of 50 kts or greater and/or hail 3/4 inch or more in diameter and/or tornadoes.

WIND (Wind Direction and Speed):

INFLATED WIND SPEED:

The true wind speed (in knots) adjusted to improve forecasts of higher wind speeds. Wind speeds greater than the mean wind speed observed are increased, and wind speeds less than the mean are decreased.

INFLATED MAXIMUM WIND SPEED:

The true maximum wind speed (in knots) in a 12-hour period adjusted to improve forecasts of higher wind speeds. Wind speeds greater than the mean wind speed observed are increased, and wind speeds less than the mean are decreased.

PROB. OF 12H MAX WIND SPEED [Range]:

The probability that the 12-hour maximum wind speed will be in the specified range in knots. (0-12 knots, 13-21 knots, 32+ knots, etc.)

STREAMLINES:

Lines that show the wind flow pattern. Streamlines are useful because they show where surface air converges and diverges.

WIND BARBS:

Standard meteorological method for representing wind speed and direction. The direction the wind is blowing from is represented by a staff or wind direction line. Wind speed (in knots) is denoted by the barbs at the end of the wind direction line (short lines 5 knots; long lines 10 knots). Calm winds are indicated by O's.

CIG (Ceiling Height):

CEILING HEIGHT:

Ceiling height forecast (in feet) valid at the specified time. Unshaded areas represent ceiling heights greater than the largest threshold.

PROB. OF CEILING HGT [Range]:

The probability that the ceiling height is within the range specified (<200 ft, 300-400ft, >12000 ft, etc.) above ground level at the specified time. Ceiling height is the height above ground level of total sky cover greater than 4/8.

CLOUDS (Total cloud amount):

TOTAL SKY COVER:

The total sky cover at the specified time. Unshaded areas represent clear total skies.

PROB. OF TOTAL SKY COVER - CLEAR:

The probability that the total sky cover is 0/8 at the specified time.

PROB. OF TOTAL SKY COVER - SCATTERED:

The probability that the total sky cover is greater than 0/8 and less than or equal to 4/8 at the specified time.

PROB. OF TOTAL SKY COVER - BROKEN:

The probability that the total sky cover is greater than 4/8 and less than 8/8 at the specified time.

PROB. OF TOTAL SKY COVER - OVERCAST:

The probability that the total sky cover is 8/8 at the specified time.

VIS (Visibility):

VISIBILITY:

The horizontal visibility forecast (in miles) valid at the specified time. Unshaded areas represent visibilities greater than the largest threshold.

PROB. OF VISIBILITY [Range]:

The probability that the prevailing visibility at the specified time will be less than (or less than or equal to) the specified range in miles (<= 1/2 mile, <5 miles etc.).

PTYPE (Precipitation Type):

PRECIPITATION TYPE (Ptype Best Category):

The form of precipitation that will fall, given that precipitation occurs.

CONDITIONAL PROB. OF FREEZING PRCP:

Given that precipitation will occur, this is the probability that the precipitation will fall in the form of freezing rain or ice pellets.

CONDITIONAL PROB. OF FROZEN PRCP:

Given that precipitation will occur, this is the probability that the precipitation will fall in the form of pure snow or snow grains.

CONDITIONAL PROB. OF LIQUID PRCP/RAIN:

Given that precipitation will occur, this is the probability that the precipitation will fall in the form of rain or rain and snow mixed.

SNOW (Snowfall Amount):

24H SNOW BEST CATEGORY:

The categorical amount of snowfall during the 24-hour period ending at the specified time. Categories are derived from snowfall amount probabilities, and are designed to yield forecasts having desirable skill characteristics.

POPC (Precipitation Characteristics):

PRECIPITATION CHARACTERISTIC:

The characteristic of precipitation (drizzle, steady, or showers/convection) that will fall, given that precipitation occurs.

COND. PROB. OF DRIZZLE:

Given that precipitation will occur, this is the probability that the precipitation will fall as drizzle.

COND. PROB. OF STEADY PRECIP:

Given that precipitation will occur, this is the probability that the precipitation will fall as steady, stratiform precipitation.

COND. PROB. OF SHOWERS/CONVECTION:

Given that precipitation will occur, this is the probability that the precipitation will fall as showers (convection).