AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 345 AM CDT TUE JUN 25 2013 .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 345 AM CDT TUE JUN 25 2013 THE HIGHLIGHT OF THE SHORT TERM IS THE FLASH FLOOD POTENTIAL FROM STRONG TO POSSIBLY SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING. FOR THIS MORNING...ONGOING CONVECTION ACROSS NORTHEAST MONTANA IS EXPECTED TO APPROACH THE NORTH DAKOTA BORDER BY 10 UTC. CURRENT TRENDS HAVE BEEN FOR THESE STORMS TO BE SUB-SEVERE...AND DO NOT ANTICIPATE THEM TO INCREASE TO SEVERE LIMITS AS THEY APPROACH THE BORDER. OTHERWISE FOR TODAY...ISSUED A FLASH FLOOD WATCH FOR NORTHWEST AND CENTRAL NORTH DAKOTA FROM 18-03 UTC THIS AFTERNOON AND EVENING. EXPECT SURFACE DESTABILIZATION ALONG A SURFACE TROUGH ACROSS THESE AREAS THIS AFTERNOON...WITH ML CAPE VALUES OF 2000-3000 J/KG. WEAK DEEP LAYER SHEAR ON THE ORDER OF 20 KTS AT BEST PLACES A LIMIT ON OVERALL ORGANIZATION...AND THUS THE LARGE HAIL AND DAMAGING WIND POTENTIAL. HOWEVER...PWAT VALUES CLIMBING TO 1.5-1.75 INCHES...K INDEX VALUES OF 35-40 C...LCL TO FREEZING LEVEL THICKNESS NEAR 10 KFT AND VERY SLOW STORM PROPAGATION WITH CORFIDI VECTORS OF 5-10 KTS POINT TO AN ELEVATED FLASH FLOOD THREAT FROM SLOW MOVING STORMS IN AN ENVIRONMENT SUPPORTIVE OF EFFICIENT WARM RAIN PROCESSES. BELIEVE THE 00 UTC 4 KM WRF REFLECTIVITY HAS A GOOD HANDLE ON THE POTENTIAL SCENARIO AND IS SUPPORTED BY THE REST OF THE DETERMINISTIC SUITE...IN INCREASING CONVECTIVE COVERAGE AND INTENSITY SIGNIFICANTLY BY 21-22 UTC WITH THE ARRIVAL OF THE UPPER LEVEL WAVE. AS UPPER LEVEL FORCING BECOMES FOCUSED ACROSS EASTERN NORTH DAKOTA AND DRIER AIR IS ADVECTED IN THE WAKE OF THE WAVE...MOST CONVECTION SHOULD BE OUT OF THE CWA BY 06-09 UTC. .LONG TERM...(WEDNESDAY THROUGH MONDAY) ISSUED AT 345 AM CDT TUE JUN 25 2013 LINGERING CONVECTION SHOULD DEPART EASTERN SECTIONS DURING THE DAY ON WEDNESDAY. MODELS ARE IN GOOD AGREEMENT AMPLIFLYING UPPER LEVEL PATTERN WITH RIDGE INTENSIFYING OVER WESTERN HALF OF CONUS AND UPPER LOW CENTERED OVER GREAT LAKES BY END OF WEEK. GENERALLY DRY CONDITIONS EXPECTED WITH THIS PATTERN ALTHOUGH THERE WILL BE SOME PERIODIC LOW POPS WITH OUR AREA ON BACK SIDE OF GREAT LAKES LOW. WITH NORTH/NORTHWEST FLOW IN PLACE THROUGH MOST OF THE EXTENDED PERIOD...TEMPS SHOULD REMAIN NEAR NORMAL WITH HIGHS GENERALLY IN THE LOW 80S AND LOW TEMPS IN THE 50S. SOME DIFFERENCES BETWEEN GFS/ECMWF EARLY NEXT WEEK...THOUGH BOTH HINT AT A MORE PRONOUNCED SHORTWAVE ROTATING AROUND UPPER LOW TOWARD NORTHERN PLAINS BY MONDAY.
Posted on: Tue, 25 Jun 2013 10:18:44 +0000
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