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706 AGUS74 KFWR 271610 HMDFWR HYDROMETEOROLOGICAL DISCUSSION NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX 1109 AM CDT SAT SEP 27 2014 VALID SEPTEMBER 27 THROUGH OCTOBER 2 ...CONVECTIVE ACTIVITY CONTINUES OVER SOUTH TEXAS AND NEW MEXICO FOR THE NEXT COUPLE OF DAYS. ...METEOROLOGICAL DISCUSSION... Convective activity continues in part due to a weak upper low still spinning over southwest Texas. This feature is expected to remain over the area through the weekend until a strong upper level disturbance approaches from the west pushing it eastward. As a result of this upper low lingering around the area, showers and thunderstorms are expected today through tomorrow for the Rio Grande Valley from Lake Amistad south to Brownsville. Rainfall totals are expected to diminish as the atmospheric moisture is reduced as the current system is pushed out of the region by the slowly advancing front. Locally heavy rainfall amounts are possible with some of these convective storms. The upper low will finally begin moving eastward tomorrow providing some temporary relief before the next system affects the region next Thursday. Elsewhere, showers and thunderstorms will continue to affect portions of the Deep South Texas and northern Mexico through this weekend. Convective activity is also expected in southwestern New Mexico with movement to the north and east. No significant flooding is expected over the affected areas, however higher than normal and flashy flows are possible. By early next week, a strong upper level disturbance is expected to approach the region from the west. This will increase rain chances across portions of New Mexico on Monday evening. As the new front arrives Thursday, north and central Texas can expect additional rainfall amounts. As the system advances, updates will be provided as we continue to monitor for any significant changes with the forecast models. ...PRECIPITATION FORECAST... For Today into Sunday morning, Mean Areal Precipitation (MAP) amounts of 0.25 and 0.50 of an inch are forecast over the lower Rio Grande Valley from Lake Amistad downstream to the Gulf of Mexico. Some locally heavier amounts are possible where convective activity is greatest. For Sunday into Monday morning, no significant MAP amounts are forecast for the WGRFC area. For Monday into Tuesday morning, no significant MAP amounts are forecast for the WGRFC area. For Tuesday into Thursday morning, no significant MAP amounts are forecast for the WGRFC area. Drought conditions are slowly improving over Texas and New Mexico. Statewide, New Mexico has no areas of exceptional drought, while less than 2% of Texas remains in exceptional drought. Severe drought conditions are impacting less than 30% of New Mexico and 29% of Texas. Runoff is expected to continue across far west Texas, as well as over southeastern New Mexico for the few days. Runoff leading to significant mainstem river flooding may occur on the Pecos River in addition to flashy rises in southeast New Mexico and west Texas. No significant runoff is expected over the eastern portions of Texas for the forecast period. ...HYDROLOGIC DISCUSSION... ...Rio Grande Basin... ...Minor Flooding... The largest concern in the Rio Grande basin continues to be potential flows from the Rio Conchos out of northern Mexico into the Rio Grande at Presidio. Current forecasts are for minor flood levels at Presidio downstream of the International Bridge (PRST2) and at the weir (PRDT2). At the other end of the Rio Grande, the Rio San Juan in Mexico has seen its lakes filling up over the last month to the point where water is being shifted to lower lakes that aren`t full. Marte Gomez is only 78% full but should see a rapid increase over the next week. No plans for releases into the lower end of the Rio Grande is expected at this time. No significant rainfall is forecast in the Conchos basin for the next five days. WGRFC will continue to monitor the Rio Grande conditions and adjust forecasts accordingly. ...Pecos Basin... Brantley Reservoir continues to hold all inflows and has adequate flood storage available; it will not be making releases until downstream conditions allow for additional flows to pass safely. Lake Avalon continues to slowly spill. Below Avalon, the Pecos mainstem and associated streams and tributaries continue receding nearer to base flow conditions. Red Bluff reservoir continues to spill and slowly fall with pool height of 2829.5 ft; current spill is about 2500 CFS. The reservoir level is expected to decline to near the spillway crest (2827.4 ft) by mid-next week. Downstream of Red Bluff along the Pecos River, flow conditions continue bank full and out of bank down through Pecos where debris jams against railway and highway bridges are retarding the natural flow and causing water to spread out over lower lying areas. The two flood waves generated downstream of Red Bluff, first one from localized, heavy rainfall runoff and the second from Red Bluff spill, is expected to begin showing up further downstream at Girvin (GIVT2) over the weekend. Higher flows are expected through Girvin, but impacts are expected at this time. USGS flood measurements ongoing upstream at Grandfalls (still slowing rising) and planned at Girvin will provide invaluable support to forecast updates. ...Remainder of WGRFC Basins... All other basins are expected to remain near normal flow conditions. ...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 CAZIER $$