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447 AGUS74 KFWR 221657 HMDFWR HYDROMETEOROLOGICAL DISCUSSION NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX 1156 AM CDT MON AUG 22 2016 VALID AUGUST 22 THROUGH AUGUST 27 ...SOME RAIN WILL CONTINUE THIS WEEK FOR PARTS OF THE WGRFC AREA, BUT THE FOCUS OF HEAVIER RAIN SHIFTS TO THE WEST... ...METEOROLOGICAL DISCUSSION... A cold front has been located over south central Texas the past 24 hours. The presence of the front brought showers and thunderstorms to especially southern Texas the past few days, and some locally very heavy rainfall occurred. This front interacted with an upper atmospheric low pressure system that was located near San Antonio to bring the additional rainfall. This morning the front and the upper air low have started weakening. Since the weather features are weakening the rainfall amounts forecast the next 24 hours are also lower than previous days. Locally heavy rainfall also occurred across portions of south central and southeast New Mexico due to the monsoon. The front in south Texas is beginning to move north as a warm front today. This will assist in pushing the areas of rain back into north Texas through tonight. Heavy rain is not expected. Meanwhile, the upper low which is now near Del Rio is expected to shift back to the west into Mexico, which would increase the rain chances over Mexico southwest of the Texas Big Bend but decrease the rain over south Texas. By Tuesday a high pressure system is forecast to build over the northern Gulf coast into southeast Texas which will suppress rainfall chances across the southeast half of Texas. This ridge will dominate the weather through mid-week and drier weather will prevail into Thursday morning. By the end of the week a low pressure system aloft is forecast to move over the western U.S. Since there will continue to be high amounts of atmospheric moisture present from the eastern Pacific the latter half of this week, diurnal showers and thunderstorms will be possible especially across northwestern and far west Texas into eastern New Mexico. Also by Friday morning, an easterly wave of low pressure may bring a chance for showers to southeast Texas and most of Louisiana. Then by Saturday this wave may produce some rain over the entire eastern third of Texas. But, the heaviest amounts of rain are expected over west Texas and eastern New Mexico from Thursday into Saturday. ...PRECIPITATION FORECAST... For Today into Tuesday morning, Mean Areal Precipitation (MAP) amounts of 0.25 to 0.50 inch are forecast over portions of northern and western Texas, northwestern Louisiana, and parts of southern and extreme northern New Mexico into southern Colorado. MAP amounts of less than 0.25 of an inch are forecast over most of the WGRFC area. For Tuesday into Wednesday morning, MAP amounts of 0.25 to 0.50 inch are forecast over far west Texas, a small part of southeastern New Mexico, northwestern New Mexico and southwestern Colorado. MAP amounts of less than 0.25 of an inch are forecast over the northwest third of Texas, a good part of New Mexico and Colorado, southeast Texas and most of Louisiana. For Wednesday into Thursday morning, MAP amounts of 0.25 to 0.50 inch are forecast over northwestern and far west Texas, northern New Mexico and southern Colorado. MAP amounts of less than 0.25 of an inch are forecast over the northwest third of Texas, most of New Mexico and Colorado, southeast Texas and most of Louisiana. For Thursday into Saturday morning, MAP amounts of 0.25 to 0.50 inch are forecast over the northwestern third of Texas, most of New Mexico, and a good part of Colorado. MAP amounts of 0.25 inch are also forecast over eastern Texas and much of Louisiana. The heaviest rain, with MAP amounts of 1.00 inch, are forecast over west central Texas northwest of Midland TX, and also near Fort Stockton. MAP amounts of less than 0.25 of an inch are forecast over the northwest Texas, the eastern half of Texas, New Mexico, Colorado, and most of Louisiana. After the widespread rain the past seven days over parts of New Mexico and Texas, drought conditions have eased somewhat. The U.S. Drought Monitor has categorized Texas as 29% abnormally dry, with less than 1% in severe drought. Over New Mexico, 88% of the state is abnormally dry, and 24% remains in the moderate drought category. The showers and thunderstorms forecast this week will keep more serious drought conditions from developing over the WGRFC region, while many sections continue drought-free. Since topsoil has become moister, some runoff is possible where the heaviest rain is forecast. However, as the weather dries out some this week most of the runoff will be insignificant across the majority of the WGRFC area. ...HYDROLOGIC DISCUSSION... ...San Antonio Basin... ...Major Flooding... Major flooding continues in the San Antonio River basin as flows from this weekends heavy rainfall move downstream. ...Nueces Basin... ...Moderate Flooding... Heavy rainfall occurred over parts of the Nueces River Basin over the last few days. Moderate flooding is forecast to occur on the middle to lower part of the basin at the Atascosa River near Whitsett (WTTT2) and the Nueces River at Three River (THET2). Higher than normal flows are occurring at a few locations located upstream on the Nueces River, Frio River, and San Miguel creek. ...Rio Grande Basin... ...Minor Flooding... Heavy rainfall occurred a few days ago near Del Rio, Texas. This is causing rises along the Rio Grande River between Del Rio and Laredo. Locations along the Rio Grande near Del Rio (DLRT2) and Eagle Pass (EPPT2) have crested and are currently falling. Downstream, the river is currently near its crest at Columbia Bridge (CBBT2). Further downstream, the Rio Grande is continuing to rise at Laredo (LDOT2), but is expected to crest below moderate flood levels. ...Guadalupe Basin... ...Minor Flooding... Heavy rainfall over the middle Guadalupe Saturday evening into Sunday has caused some rises on the tributaries and lower portions of the basin. Routed flows will push Victoria (VICT2) into minor flood levels this evening with a crest around 25 feet by Wednesday. ...Trinity Basin... ...Minor Flooding... Out of bank to minor flooding continues in the upper West Fork of the Trinity River. Additional significant rainfall is not forecast in the Trinity basin for the next several days. ...Brazos Basin... ...Minor Flooding... Recent rainfall is resulting in out of bank flows and some minor flooding in isolated locations across the Brazos River basin within the Little River, Yegua creek, and Davidson creek watersheds. Further downstream along the mainstem, flows are within action levels from Hempstead to Richmond. Additional significant rainfall is not forecast in the Brazos basin for the next several days. ...Lavaca-Navidad Basin... ...Higher Flow Non-Flood Forecasts... Wet soil conditions and locally heavy rains have caused higher flows along portions of the lower Lavaca-Navidad system. ...Colorado Basin... ...Higher Flow Non-Flood Forecasts... Locally heavy rainfall occurred over the lower Colorado River Basin over the last couple days. This is causing higher than normal flows on the lower mainstem from Bastrop to Wharton. ...Remainder of WGRFC Basins... Rainfall continues across southeast Texas. Additional rainfall is forecast over Texas in the next 5 days. Additional rainfall is forecast across the majority of Texas in the next 5 days - soils are moist and runoff will occur more quickly than typically in August. ...SUPPLEMENTARY GRAPHICAL INFORMATION... The following URLs (all lower case) provide additional graphical information on current and forecast hydrologic conditions, past and future precipitation, and drought and climate forecasts. This information is provided by a variety of National Weather Service, NOAA, and private sector entities. For specific information on river conditions, refer to the AHPS pages from the local NWS offices at: http://water.weather.gov/ahps/ The Flood Potential Outlook can be viewed on our webpage at: http://www.srh.noaa.gov/wgrfc/?n=wgrfcfop The West Gulf River Forecast Center is now on Facebook: http://www.facebook.com/US.NationalWeatherService.WGRFC.gov National Precipitation Analysis: http://water.weather.gov/precip/ The forecast rainfall amounts (QPF) can be viewed on our webpage at: http://www.srh.noaa.gov/wgrfc/?n=wgrfcqpfpage The US Drought Assessment: http://www.cpc.ncep.noaa.gov/products/Drought The latest on Reservoir Information for Texas: http://www.waterdatafortexas.org/reservoirs/statewide STORY $$