Washington: Today - Rain, high in 50s, low in 40s. Chance of rain near 100 per cent today, 80 per cent tonight. Saturday - Partly cloudy, high in low 60s.

Maryland and Virginia: Today - Rain, highs mostly in 50s, lows in 40s. Saturday - Rain ending, highs in 50s.

Lower Potomac and Chesapeake Bay: Today - Cloudy with rain likely by afternoon through tonight, visibility from 5 miles or greater to 2 miles or less. Winds should be southerly at 10 to 20 knots today, westerly at 10 to 20 knots tonight.

Extended Area Outlook: For Sunday through Tuesday - Rain likely Sunday night or early Monday followed by fair skies. Highs should average in mid 50s to low 60s, lows in mid 30s to mid 40s. Washington normal temperature range for this time of year is from 52 to 32.

West Virginia: Today - Rain, highs in mids 50s to mid 60s, lows upper 30s to mid 40s. Saturday - Chance of rain, highs in 50s.

The National Weather Forecast for Today - Snow will extend from the northern Rockies through the northern Mississippi Valley and the upper Great Lakes. This will change to rainshowers with occassional thunderstorms through the central Mississippi Valley, east portions of the lower Mississippi Valley, the Ohio Valley and the lower Great Lake, through the Atlantic Coast from North Florida to central New England. Temperatures will be mild over the Atlantic Coastal states through the Ohio Valley and Great Lakes region. Elsewhere, it will remain seasonably cool or cold.

ALMANAC DATA for March 4, 1977: Sun rises 6:37 a.m., sets 6:04 p.m.; moon rises 5:16 p.m., sets 5:01 a.m. Tides: High 6:52 a.m. and 7:17 p.m., low 1:22 a.m. and 1:43 p.m. High and low tides at the following points can be obtained by subtracting the hours indicated from the tides above. Annapolis (3 1/2); Bloody Point Lighthouse (4 1/2); Deale, Md. (4 1/2); Colonial Beach (6); Norfolk (1 1/2); Virginia Beach (1); Solomon's Island (6 1/2); Point Lookout (7).

The Council of Governments' Air Quality Index for yesterday showed the high reading in the Washington area during the 2 to 3 p.m. period was 29 for the pollutant, photochemical oxidants index values between 25 and 49 indicate fair air quality. When the index exceeds 100 the air becomes hazardous and persons with lung, heart and eye problems should restrict their activity. The forecast for today indicates the air quality will improve.

The National Weather Service forecasts that the Potomac River stage at Little Falls will be near 4.3 feet through this morning.

Washington data at 7 p.m. (EST) yesterday: Highest temperature since 7 a.m. yesterday, 60 degrees at 2:50 p.m. Lowest temperature since midnight, 30 degrees at 6:10 a.m. Excess of temperature since March 1, 7 degrees. Deficiency of temperature since Jan. 1, 250 degrees. Record high temperature for today, 80 degrees in 1974. Record low temperature for today, 4 degrees in 1873. Relative humidity: Maximum, 75 per cent at 5 a.m., Minimum, 28 per cent at 1 p.m. 24 hour precipitation, none. Deficiency of precipitation since March 1, .30 inches. Deficiency of precipitation since Jan. 1, 3.21 inches. Highest observed wind since 7 a.m. 16 miles per hour from the S.W. at 12:53 p.m. Peak gust since 7 a.m., 28 miles per hour from the South at 12:00 p.m. Local Temp. Humidity(TABLE) Time(COLUMN)T.(COLUMN)H. 12 mid.(COLUMN)34(COLUMN)67 1 a.m.(COLUMN)35(COLUMN)67 2 a.m.(COLUMN)33(COLUMN)67 3 a.m.(COLUMN)32(COLUMN)69 4 a.m.(COLUMN)32(COLUMN)69 5 a.m.(COLUMN)31(COLUMN)75 6 a.m.(COLUMN)31(COLUMN)69 7 a.m.(COLUMN)31(COLUMN)72 8 a.m.(COLUMN)37(COLUMN)62 9 a.m.(COLUMN)41(COLUMN)55 10 a.m.(COLUMN)44(COLUMN)49 11 a.m.(COLUMN)48(COLUMN)44 12 noon(COLUMN)55(COLUMN)32 1 p.m.(COLUMN)58(COLUMN)28 2 p.m.(COLUMN)58(COLUMN)29 3 p.m.(COLUMN)60(COLUMN)29 4 p.m.(COLUMN)58(COLUMN)36 5 p.m.(COLUMN)58(COLUMN)37 6 p.m.(COLUMN)53(COLUMN)47(END TABLE)