Glossary for ERF's Daily Fax Forecasts

Sky Conditions

CLDY = Cloudy
Total overcast from fog, low clouds, mid-clouds and high overcast, or a combination of all of these. This depends on the thickness of the cloud cover - 100% of the sky is covered.

M-C = Mostly Cloudy
60-95% of the sky is covered with clouds, low, middle, or high, fog too.

P-C = Partly Cloudy
30-60% of the sky is covered. Low clouds, mid-clouds, or high clouds.

CLR = Clear
Few if any clouds but generally less than 30% coverage. We will call it FAIR or MOSTLY clear if high clouds are present.

We try to pinpoint when these conditions will occur, AM, PM, or all day XX, and at times will give specific hour of arrival or departure. The same holds true with precipitation as well.

Temperature

High = Maximum
Highest of the day, usually arriving by mid-late afternoon or early evening, 4-6 PM. We will use a range from +/- 1.0 to 2.5 degrees, but might be greater if an area is subjected to unusually strong winds, etc. I will use key stations, such as airport temps, PAWS, Agrimet and our own EWIN sites. These will be the basis for the forecasts and for verification. Temps that are forecast should be used as guidelines, but your exact site may be a degree or two different. We try to zero in on each specific subregional forecast.

Low = Minimum
Lowest temps of the day, usually occurring late night or early morning, normally between 4 to 9 AM. We forecast for each subregion separately and attempt to zero in on them the best that we can.

Local
Small dips and low-lying areas within the main regions might see a drop in temperatures that are out of the ordinary. As an example, you might see 23-25 locally when surrounding areas experience 31-35. This is based on our EWIN stations. We will use this mainly for low temps when we know that local frost is likely or when we will see a local value colder than the general forecast minimum value.

Precipitation

RN = Rain
This is for continuous rainfall that lasts longer than 30 minutes at a time. We will try to give specific start and stop times if possible, (usually start time, but end time will be dependent on the showers that follow the rain).

RW = Showers
The on-again, off-again type of intermittent precipitation. You can usually see these coming and going. The type of precipitation associated with cold air aloft, rather unsettled conditions. These can be Few, Light, Sct., Modt, Hvy, and can also include Hail and Thunder. We can also have Snow Showers with Hail and Thunder too.

NN = None
None is the forecast for daylight work hours or for a 24-hour period from 4AM to 4AM the following day. I will also specify if it will be dry AM or PM, or all day
(XX).

Amounts
Rainfall can range markedly from spot to spot or from lower elevations to higher locations. Thus, we try to target the lower area of a specific forecast area, i.e., valley vs. hill, mtns., etc. We try to provide a reasonable range for each area knowing that some spots might be higher, more frequent showers, or lower, fewer showers. We generally see a doubling of rainfall for every 1,000 ft. of elevation gained. It can be 1.5 to 2.0 times that of lower elevations. Amounts in INCHES: tr-1" usually denotes snow amounts for a given area. This is shown below the precip range.

Wind

Winds
Wind speeds are forecast for the day as well as the most dominate wind directions (which will vary from AM to PM). For instance, SW-W might indicate winds early from the SW will vary to the W later in the day. Speeds are in knots (rn.p.h.= 1. 15 x knots). Normally winds increase due to the heating of the sun or in the afternoon. Winter winds can be strong anytime of the day. Gusts = G, A = AM gusts, P = PM gusts.

RH% = Relative Humidity
The highest and lowest RH% of the day based on the forecast high tenip and low temp and associated dew point. These are forecast values and should give you an idea of the amount of moisture in the air. The highest humidity normally occurs at 8 AM, the lowest between 4-8 PM depending on the time of year and associated weather conditions. DEW POINT is the point at which the air becomes totally saturated. At this point, you have 100% RH and usually fog. This is also the theoretical lowest ternp of the day. If Dew Pt. is 32 degrees, then when the air cools to 32 degrees.