000 AGUS74 KFWR 071532 HMDFWR HYDROMETEOROLOGICAL DISCUSSION NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX 1032 AM CDT SUN SEP 7 2008 VALID SEPTEMBER 7 THROUGH SEPTEMBER 12 ...METEOROLOGICAL DISCUSSION... ...Hurricane Ike nearing Cuba... ...Unsettled weather forecast for the WGRFC this week... The weather across the WGRFC region will take an unsettled turn this week with several systems impacting the region. Currently, a persistent weak upper level disturbance lingers over northern Mexico, bringing scattered showers and thunderstorms to western Texas and northern Mexico. This disturbance is forecast to track northward across the Texas Panhandle today and tonight and be absorbed into a larger trough of low pressure moving across the central plains. This larger trough is forecast to push a cold front into northern Texas Monday night and Tuesday. The front will provide a focus for shower and thunderstorm development across northern and central Texas Tueday into Thursday. Further west, a trough of low pressure is forecast the deepen over the U.S. west coast Tuesday into Wednesday. The position of the western trough will create a southwest upper level flow pattern over western portions of the WGRFC region. In the eastern Pacific, Tropical Storm Lowell is forecast to track generally northward toward Baja California over the next five days. Mid and upper level moisture from Lowell will be carried over the Mexican interior on the southwest upper flow pattern forecast to develop over the region. Disturbances in this flow, combined with the available moisture, daytime heating, and orographic lifting, will bring an increase in shower and thunderstorm activity to much of western Texas and New Mexico by the middle of the week. Locally heavy rainfall will be possible, especially by the end of the week, due to abundant moisture and the potential for vigorous upper level disturbances moving over the region. Hurricane Ike was located near Great Inagua island in the southern Bahamas late this morning. The current forecast from the National Hurricane Center has Ike moving over Cuba and into the Gulf of Mexico the next couple of days. By Friday morning, Ike is forecast to be in the northern Gulf of Mexico heading in a west northwest direction. If Ike does move across a large portion of Cuba as indicated in the current forecast, significant weakening is likely to occur. However, conditions over the Gulf will allow for restrengthening, and Ike will likely be a strong hurricane as it approaches the Gulf coast. There continues to be significant uncertainty in the longer range guidance as to the eventual track of Hurricane Ike. WGRFC continues to monitor closely this event for impacts to the Texas coast. ...PRECIPITATION FORECAST... For Today into Monday morning, Mean Areal Precipitation (MAP) amounts of 0.25 to 0.50 inch are forecast over far west Texas and south central New Mexico. For Monday into Tuesday morning, MAP amounts of 0.25 to 0.50 inch are forecast over much of central and western Texas, with amounts up to 1.00 inch forecast over a small portions of north central Texas. For Tuesday into Wednesday morning, MAP amounts of 0.25 to 0.50 inch are forecast from east central Texas through the northern Texas Hill Country into western Texas and southeast New Mexico. MAP amounts of 0.25 to 0.50 inch are also forecast over the mountains of northern New Mexico and over Deep South Texas. For Wednesday into Friday morning, MAP amounts of 1.00 to 2.00 inches are forecast from the Big Bend region across northwest Texas. MAP amounts of 0.25 to 0.50 inch are forecast over far west Texas and eastern New Mexico, and from the western Texas Hill Country into north central Texas. Rainfall forecast the last half of the week western Texas will likely generate runoff in the Rio Grande basin. Runoff sufficient to produce significant river rises is possbile as significant river rises are already occurring through the Big Bend region of the Rio Grande due to reservoir discharges from Mexico. Elsewhere, only limited runoff is expected from rainfall forecast the next five days. ...HYDROLOGIC DISCUSSION... ...Rio Grande Basin... ...Moderate Flooding... Reported releases from Luis Leon Reservoir in Mexico on the Rio Conchos will produce minor flooding at Presidio International Bridge (PRST2), moderate flooding at Presidio 5SE (PRDT2), and minor flooding at Lajitas (TGAT2, Castalon (CSTT2), and Johnson Ranch (TELT2). Flooding/higher flows are expected downstream of these points, along the Rio Grande to Amistad. ...Remainder of WGRFC Basins... All rivers throughout the WGRFC area, with the exception of the Rio Grande, are experiencing baseflow conditions. Forecast rainfall over the next 5 days does not pose significant river threats for the majority of the WGRFC region, the exception being the Rio Grande. ...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://www.weather.gov/rivers_tab.php The Flood Potential Outlook can be viewed on our webpage at: http://www.srh.noaa.gov/wgrfc/fop/wgrfcfop.html MPE Precipitation Estimates: http://www.srh.noaa.gov/wgrfc/precip/html/mpe_estimates.shtml National Precipitation Analysis: http://www.srh.noaa.gov/rfcshare/precip_analysis_new.php The forecast rainfall amounts (QPF) can be viewed on our webpage at: http://www.srh.noaa.gov/wgrfc/hydromet/qpf/qpfpage.html The US Drought Assessment: http://www.cpc.noaa.gov/products/expert_assessment/drought_assessment.shtml SHELTON $$