Mesoscale Precipitation Discussion 0698 NWS Weather Prediction Center College Park MD 853 AM EDT Mon Aug 20 2018
Areas affected...Southeastern AR...Northern MS...Northeastern LA
Concerning...Heavy rainfall...Flash flooding possible
Valid 201250Z - 201850Z
Summary...Ingredients for back-building/training convection are expected to remain in place. Additional flash-flooding is possible.
Discussion...Latest mesoanalysis shows southwesterly flow supporting a plume of deep moisture (PWs 2 to 2.4 inches) across a weak warm front extending southeast well out ahead of a slow-moving cold front that extends from the mid-Mississippi valley back into the southern plains. Ahead of a slow-moving low, the latest RAP shows 850mb winds remaining 20-30kts from the southwest, with comparable to weaker flow aloft -- supporting the potential for back-building/training convection well into the morning hours. The RAP shows this deep moisture, with slow propagation vectors, along with increasing instability through the morning hours. Runoff concerns across this area are heightened by recent heavy rains -- with the most recent NSSL QPE showing 24-hr estimates as high as 3-6 inches along the Arkansas/Mississippi border. Recent runs of the HRRR have been slow to recognize the ongoing trends, particularly along the southern extent of the ongoing convection, where GOES imagery shows cooling cloud tops and where KLZK radar continues to show rainfall rates of 1.5-2 inches.
URGENT - WEATHER MESSAGE National Weather Service Houston/Galveston TX 553 AM CDT Thu Aug 23 2018
...Heat Advisory in Effect...
.A Head Advisory is in effect for the southern half of the area as heat indices climb to 105-110 degrees this afternoon.
TXZ200-210>214-226-227-235>238-300-313-231900- /O.NEW.KHGX.HT.Y.0009.180823T1400Z-180824T0200Z/ Austin-Chambers-Coastal Harris-Colorado-Fort Bend-Inland Brazoria- Inland Galveston-Inland Harris-Inland Jackson-Inland Matagorda- Northern Liberty-Southern Liberty-Waller-Wharton- Including the cities of Alvin, Anahuac, Angleton, Bay City, Baytown, Bellville, Brookshire, Cleveland, Columbus, Dayton, Devers, Eagle Lake, Edna, El Campo, First Colony, Friendswood, Ganado, Hempstead, Houston, League City, Liberty, Mission Bend, Missouri City, Mont Belvieu, Old River-Winfree, Pasadena, Pearland, Pecan Grove, Prairie View, Rosenberg, Sealy, Stowell, Sugar Land, Waller, Weimar, Wharton, and Winnie 553 AM CDT Thu Aug 23 2018
...HEAT ADVISORY IN EFFECT FROM 9 AM THIS MORNING TO 9 PM CDT THIS EVENING...
The National Weather Service in Houston/Galveston has issued a Heat Advisory, which is in effect from 9 AM this morning to 9 PM CDT this evening.
* EVENT...Heat Index of 105 to 110.
* IMPACT...Dangerous heat conditions causing heat related illness.
Take extra precautions if you work or spend time outside. When possible...reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear light weight and loose fitting clothing when possible and drink plenty of water.
To reduce risk during outdoor work...the occupational safety and health administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency - call 911.
Each year...a number of fatalities occur nationwide due to children accidentally being left in vehicles during the summer months. In the past dozen years...500 children have died due to hyperthermia after being left in or gaining access to cars. Never leave children or pets unattended in a vehicle not even for a minute. Remember...beat the heat...check the backseat.