WATER VAPOR LOOP SHOWS A SHORTWAVE OVER THE OZARK PLATEAU DROPPING SOUTH/SOUTHWEST AROUND THE PERIPHERY OF AN UPPER LEVEL HIGH THAT REMAINS CENTERED OVER COLORADO. THE SHORTWAVE WILL CROSS THROUGH NORTH CENTRAL TEXAS DURING THE DAY AND PROVIDE WEAK FORCING FOR ASCENT OVER THE REGION. AFTER STRONG SURFACE HEATING...THE AIRMASS OVER THE REGION WILL ONCE AGAIN BECOME UNCAPPED AND UNSTABLE THIS AFTERNOON. THE PRIMARY LIMITING FACTOR FOR RAIN TODAY WILL BE THE LIMITED MOISTURE THROUGH THE DEPTH OF THE TROPOSPHERE...WHICH OFTEN CAUSES CONVECTIVE TOWERS TO STRUGGLE WITHOUT STRONG LIFT. HI-RES MODEL GUIDANCE INDICATES THE NW ZONES MAY BE A SLIGHTLY MORE FAVORABLE AREA FOR CONVECTION THIS AFTERNOON. THIS SEEMS REASONABLE AS THIS AREA WILL BE LOCATED IN THE DIVERGENT LEFT EXIT REGION OF A 50KT UPPER LEVEL JET STREAK...AND THUS HAVE INCREASED POPS TO 20 PERCENT OVER THE NORTHWEST ZONES. WILL KEEP POPS AT 10 PERCENT ELSEWHERE. OTHERWISE ANOTHER DAY MUCH LIKE THE LAST FEW IS EXPECTED WITH LIGHT WINDS AND TEMPS WELL ABOVE NORMAL. THE SHORTWAVE WILL DROP INTO THE LOWER RIO GRANDE VALLEY SUNDAY AND THE UPPER LEVEL HIGH WILL BEGIN TO BUILD INTO THE REGION FROM THE NORTH WITH RISING HEIGHTS AND FALLING PRECIPITABLE WATER. WILL MENTION ISOLATED CONVECTION JUST FOR THE AREA SOUTH OF I-20 SUNDAY AFTERNOON. THE UPPER LEVEL HIGH WILL TRACK EAST ACROSS THE PLAINS SUNDAY AND MONDAY AND BECOME CENTERED OVER THE SOUTHEASTERN UNITED STATES BY TUESDAY. SOUTHEASTERLY FLOW IN THE MID-LOW LEVELS WILL INCREASE TUESDAY AND WEDNESDAY WHICH WILL RESULT IN A SLIGHT COOL DOWN BY MID-LATE WEEK. HOWEVER...TEMPERATURES WILL STILL BE ABOVE NORMAL WITH HIGHS IN THE MID-UPPER 90S AND LOWS IN THE LOW-MID 70S IN RURAL AREAS...BUT UPPER 70S IN URBAN CENTERS. MEANWHILE THE SHORTWAVE THAT DROPS THROUGH THE REGION TODAY WILL CLOSE OFF AND BECOME AN UPPER LEVEL LOW THAT MEANDERS AROUND SOUTH TEXAS AND NORTHEAST MEXICO THIS WEEK. THIS UPPER LOW WILL LIKELY REMAIN TOO FAR SOUTH TO PROVIDE LIFT FOR RAIN CHANCES IN OUR AREA. WILL KEEP THE FORECAST DRY AS MODELS ALSO SHOW PRECIPITABLE WATER VALUES REMAINING BETWEEN 1-1.5 INCHES THIS WEEK. HOWEVER...IF THIS UPPER LOW WERE TO WANDER FARTHER NORTH THAN CURRENTLY FORECAST...WE MAY NEED TO ADD SLIGHT CHANCE POPS TO THE SOUTHERN ZONES. THE UPPER LEVEL HIGH IS FORECAST TO HEAD BACK TO THE WEST BY LATE WEEK AND BECOME CENTERED OVER THE SOUTHERN PLAINS BY THURSDAY. AN UPPER LEVEL TROUGH AND STRONG CANADIAN SURFACE HIGH ARE FORECAST TO DROP INTO THE GREAT LAKES REGION AND AFFECT THE EASTERN U.S. BY NEXT WEEKEND. THE GFS FORECASTS THE WESTERN EDGE OF THIS CANADIAN HIGH TO BACKDOOR INTO THE REGION BY FRIDAY OR SATURDAY. THE ECMWF IS CONSIDERABLY LESS AGGRESSIVE THAN THE GFS WITH THIS COOL DOWN. WHILE WINDS MAY SWING TO THE NORTHEAST BY NEXT SATURDAY...ANY COOL DOWN WOULD BE SUBTLE DUE TO THE WARMING INFLUENCE OF THE UPPER LEVEL HIGH OVERHEAD. GIVEN THAT THE CENTER OF THE CANADIAN SURFACE HIGH WILL REMAIN SO FAR NORTHEAST OF THE REGION...WILL SIDE WITH THE ECMWF FORECAST AND KEEP HIGHS WELL ABOVE NORMAL AND IN THE MID-UPPER 90S FOR FRIDAY AND NEXT SATURDAY. THERE ARE STILL NO STRONG INDICATIONS IN ANY OF THE MODELS FOR OUR FIRST TRUE FALL COLD FRONT.
Posted on: Sat, 07 Sep 2013 14:26:14 +0000
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