Washington: Today - Rain, high near 50, low near 40. The chance of precipitation is 80 per cent today and 20 per cent tonight. Thursday - Partly cloudy, high in the mid 50s.

Maryland and Virginia: Today - Rain, highs from the mid 40s to near 60, lows from the 30s to the mid 40s. Thursday - Partly cloudy, highs from the mid 40s to the mid 50s, lows in the 30s. Thursday - Partly cloudy, highs from the mid 40s to the mid 50s.

Extended Area Forecast for Friday through Sunday: Partly cloudy through the period. There is a chance of some rain in the mountains. Highs will be from the mid 50s to the mid 60s lows in the 40s. Normal Washington temperatures for the period are a high of 44 and a low of 29.

Lower Potomac and Chesapeake Bay: Today - Rain with visibility of more than 5 miles, dropping to less than 2 miles in rain and fog. Wind will be from the south at less than 15 knots, shifting from the southwest tonight. Waves in unprotected waters will be less than 2 feet.

The National Weather Forecast for today - Rain will cover the northwestern corner of the country, from the northern half of the Pacific Coast through the northern half of the Rockies. There will be snow over northern New England, with rain extending from the eastern half of the Great Lakes through southern New England and southward to Florida and eastern Louisiana. Cool or cold temperatures will prevail over most of New England and extreme northern Montana. The remainder of the country will be mostly mild.

Almanac Data for today - Sun rises 7:19 a.m., sets 4:47 p.m.; moon rises 10:28 a.m., sets 9;40 p.m. Tides: high 10:47 a.M., and 11:11 p.m., low 5;11 a.m., and 5;30 p.m. High and low tides at the following locations may be obtained by subtracting the hours indicated from the tides above. Annapolis (1 1/2), Bloody Point Lighthouse (4 1/2), Deale, Md. (4 1/2), Colonial Beach (6), Norfolk (1 1/2); Virginia Beach (1), Solomons 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 p.m. to 3 p.m. period was 14 for the pollutant, sulfur dioxide. Index values between zero and 24 indicate good air quality. When the index exceeds 100 the air is considered very unhealthy and individuals with lung, heart and eye ailments are urged to restrict their activity. The forecast for today indicates that the air quality will be good.

The National Weather Service forecast the Potomac River stage at Little Falls should be near 3.8 feet today. Local Temp., Humidity(TABLE) Time(COLUMN)T.(COLUMN). 12 midnite(COLUMN)38(COLUMN)48 1 a.m.(COLUMN)38(COLUMN)50 2 a.m.(COLUMN)38(COLUMN)48 3 a.m.(COLUMN)37(COLUMN)57 4 a.m.(COLUMN)37(COLUMN)62 5 a.m.(COLUMN)37(COLUMN)64 6 a.m.(COLUMN)37(COLUMN)62 7 a.m.(COLUMN)37(COLUMN)57 8 a.m.(COLUMN)38(COLUMN)55 9 a.m.(COLUMN)40(COLUMN)47 10 a.m.(COLUMN)43(COLUMN)41 11 a.m.(COLUMN)44(COLUMN)38 12 noon(COLUMN)46(COLUMN)35 1 p.m.(COLUMN)48(COLUMN)34 2 p.m.(COLUMN)51(COLUMN)33 3 p.m.(COLUMN)52(COLUMN)35 4 p.m.(COLUMN)52(COLUMN)33 5 p.m.(COLUMN)47(COLUMN)43 6 p.m.(COLUMN)43(COLUMN)49 7 p.m.(COLUMN)41(COLUMN)53(END TABLE) Temperatures ending 8 a.m. (EST) yesterday:(TABLE) City(COLUMN)H.(COLUMN)L. Albany(COLUMN)12(COLUMN)10 Albuquerque(COLUMN)58(COLUMN)24 Amarillo(COLUMN)75(COLUMN)40 Anchorage(COLUMN)10(COLUMN)4 Asheville(COLUMN)47(COLUMN)24 Atlanta(COLUMN)50(COLUMN)41 Atlantic City(COLUMN)33(COLUMN)33 Austin(COLUMN)67(COLUMN)65 Baltimore(COLUMN)38(COLUMN)34 Billings(COLUMN)48(COLUMN)30 Birmingham(COLUMN)55(COLUMN)44 Bismarck(COLUMN)43(COLUMN)10 Boise(COLUMN)49(COLUMN)40 Boston(COLUMN)19(COLUMN)15 Brownsville(COLUMN)75(COLUMN)69 Buffalo(COLUMN)34(COLUMN)15 Burlington(COLUMN)8(COLUMN)5 Casper(COLUMN)44(COLUMN)27 Charleston, S.C.(COLUMN)51(COLUMN)45 Charleston, W Va.(COLUMN)45(COLUMN)38 Charlotte(COLUMN)45(COLUMN)31 Cheyenne(COLUMN)46(COLUMN)23 Chicago(COLUMN)41(COLUMN)38 Cincinnati(COLUMN)39(COLUMN)33 Cleveland(COLUMN)39(COLUMN)34 Columbia, S.C.(COLUMN)50(COLUMN)36 Columbus(COLUMN)37(COLUMN)35 Dal.-Ft. Worth(COLUMN)63(COLUMN)60 Dayton(COLUMN)37(COLUMN)36 Denver(COLUMN)58(COLUMN)20 Des Moines(COLUMN)42(COLUMN)36 Detroit(COLUMN)36(COLUMN)34 Duluth(COLUMN)27(COLUMN)23 El Paso(COLUMN)69(COLUMN)41 Fairbanks(COLUMN)-41(COLUMN)-51 Fargo(COLUMN)22(COLUMN)14 Flagstaff(COLUMN)55(COLUMN)12 Great Falls(COLUMN)46(COLUMN)37 Hartford(COLUMN)18(COLUMN)15 Helena(COLUMN)45(COLUMN)39 Honolulu(COLUMN)86(COLUMN)70 Houston(COLUMN)62(COLUMN)62 Indianapolis(COLUMN)40(COLUMN)37 Jackson, Miss.(COLUMN)63(COLUMN)48 Jacksonville(COLUMN)63(COLUMN)51 Juneau(COLUMN)31(COLUMN)27 Kansas City(COLUMN)45(COLUMN)42 Las Vegas(COLUMN)69(COLUMN)39 Little Rock(COLUMN)49(COLUMN)44 Los Angeles(COLUMN)66(COLUMN)51 ouisville(COLUMN)48(COLUMN)41 Memphis(COLUMN)53(COLUMN)41 Miami Beach(COLUMN)75(COLUMN)74 Midland-Odessa(COLUMN)75(COLUMN)43 Milwaukee(COLUMN)39(COLUMN)34 Mpls.-St. Paul(COLUMN)34(COLUMN)30 Nashville(COLUMN)51(COLUMN)44 New Orleans(COLUMN)65(COLUMN)56 New York(COLUMN)32(COLUMN)27 Norfolk(COLUMN)42(COLUMN)29 North Platte(COLUMN)53(COLUMN)20 Oklahoma City(COLUMN)61(COLUMN)45 Omaha(COLUMN)44(COLUMN)31 Orlando(COLUMN)76(COLUMN)59 Philadelphia(COLUMN)31(COLUMN)29 Phoenix(COLUMN)74(COLUMN)47 Pittsburgh(COLUMN)38(COLUMN)36 Portland, Maine(COLUMN)9(COLUMN)4 Portland, Ore.(COLUMN)52(COLUMN)46 Providence(COLUMN)18(COLUMN)15 Raleigh(COLUMN)42(COLUMN)23 Rapid City(COLUMN)50(COLUMN)28 Reno(COLUMN)46(COLUMN)34 Richmond(COLUMN)40(COLUMN)28 St. Louis(COLUMN)46(COLUMN)44 St. Prbg.-Tampa(COLUMN)76(COLUMN)58 Salt Lake City(COLUMN)50(COLUMN)35 San Antonio(COLUMN)64(COLUMN)61 San Diego(COLUMN)67(COLUMN)55 San Francisco(COLUMN)56(COLUMN)51 San Juan(COLUMN)80(COLUMN)75 St. Ste. Marie(COLUMN)28(COLUMN)25 Seattle(COLUMN)49(COLUMN)45 Shreveport(COLUMN)66(COLUMN)54 Sioux Falls(COLUMN)42(COLUMN)21 Spokane(COLUMN)41(COLUMN)38 Syracuse(COLUMN)25(COLUMN)17 Topeka(COLUMN)46(COLUMN)36 Tucson(COLUMN)73(COLUMN)41 Tulsa(COLUMN)58(COLUMN)52 Washington(COLUMN)40(COLUMN)37 Wichita(COLUMN)54(COLUMN)39(END TABLE)