689 FXUS63 KBIS 210905 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 405 AM CDT FRI JUN 21 2013 .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 402 AM CDT FRI JUN 21 2013 THE HIGHLIGHT OF THE SHORT TERM IS SEVERE CONVECTIVE POTENTIAL THIS AFTERNOON THROUGH TONIGHT. THE MAIN QUESTION IS HOW QUICKLY CAPPING WILL BE ERODED TO ALLOW FOR SURFACE BASED CONVECTION THIS AFTERNOON. THE 00 UTC NAM/GFS BUFR SOUNDINGS DO VARY SIGNIFICANTLY IN REGARDS TO THE STRENGTH OF THIS CAPPING...WITH THE GFS HOLDING A STRONG CAP THROUGH THE AFTERNOON...WITH THE NAM SHOWING LITTLE CONVECTIVE INHIBITION BY 18 UTC. THE 03 UTC SREF SOUNDINGS DO SHOW WEAKER CAPPING THAN THE GFS...HOWEVER...THE 00 UTC 4 KM WRF HAS LITTLE AFTERNOON CONVECTION ACROSS THE AREA. THUS...DID LIMIT POPS TO SLIGHT CHANCE OR CHANCE PRIOR TO 00 UTC. SHOULD CAPPING BE ERODED...ML CAPE VALUES OF 2500-3500 J/KG WITH 50 KTS OF DEEP LAYER SHEAR ARE AVAILABLE...WITH VERY LARGE HAIL POSSIBLE GIVEN -10 TO -30 C CAPE VALUES NEAR 1000 J/KG. THE BETTER CHANCES FOR THUNDERSTORMS ARE THIS EVENING AND TONIGHT WITH A POTENTIAL MCS PROPAGATING OUT OF SOUTH DAKOTA WITH THE ARRIVAL OF GREATER UPPER LEVEL FORCING. IN ADDITION TO LARGE HAIL AND DAMAGING WINDS...HEAVY RAINFALL WILL BECOME AN INCREASING THREAT...ESPECIALLY FOR THOSE AREAS IMPACTED BY HEAVY RAINFALL WEDNESDAY AND THURSDAY...WITH PWATS 1.50 INCHES AND K INDEX VALUES OF 35-40 C. .LONG TERM...(SATURDAY THROUGH THURSDAY) ISSUED AT 402 AM CDT FRI JUN 21 2013 THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD ARE THE POTENTIAL FOR CONTINUED HEAVY RAIN AND FLASH FLOODING OVER THE WEEKEND. MODEL CONSENSUS INDICATES AN UPPER TROUGH MOVING INTO THE NORTHERN PLAINS SATURDAY AND SATURDAY NIGHT. BROAD SYNOPTIC LIFT WILL SUPPORT WIDESPREAD SHOWERS AND THUNDERSTORMS...ESPECIALLY LATER IN THE DAY. THE JAMES RIVER VALLEY WILL AGAIN BE UNDER THE GUN FOR ADDITIONAL FLOODING...ALONG WITH ISOLATED SEVERE STORMS. BY SUNDAY...THE UPPER LOW WILL LIFT NORTH WITH THE FOCUS OF SHOWERS AND STORMS ACROSS THE NORTHERN COUNTIES...WHICH WILL DIMINISH SUNDAY NIGHT. SOUTHWEST FLOW WILL PERSIST MONDAY AND TUESDAY WITH RAIN EXPECTED TO BE MORE SCATTERED ACROSS THE STATE. BY THURSDAY...AN UPPER RIDGE WILL BEGIN TO SPREAD INTO WESTERN NORTH DAKOTA. CLOUDS WILL KEEP AFTERNOON TEMPS DOWN MAINLY IN THE 70S OVER THE WEEKEND...FOLLOWED BY NEAR TO SLIGHTLY ABOVE NORMAL TEMPS IN THE LOW 80S BY EARLY TO MID WEEK. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT) ISSUED AT 402 AM CDT FRI JUN 21 2013 FOG AND STRATUS WILL BE POSSIBLE ACROSS MUCH OF WESTERN AND CENTRAL NORTH DAKOTA EARLY THIS MORNING GIVEN THE HUMID AIRMASS IN PLACE AND LIGHT WINDS...WITH MVFR TO IFR CONDITIONS EXPECTED. ISOLATED THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON...WITH A GREATER CHANCE FOR THUNDERSTORMS POST 00 UTC FRIDAY EVENING AS A POTENTIAL COMPLEX OF STRONG TO SEVERE THUNDERSTORMS MOVES NORTHEAST OUT OF SOUTH DAKOTA. && .HYDROLOGY... ISSUED AT 402 AM CDT FRI JUN 21 2013 EXPANDED THE FLASH FLOOD WATCH INTO EMMONS COUNTY GIVEN THE SIGNIFICANT RAINFALL THAT OCCURRED THURSDAY EVENING. MULTIPLE ROUNDS OF STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED FRIDAY THROUGH SUNDAY...WITH ADDITIONAL HEAVY RAINFALL POSSIBLE FOR THOSE LOCATIONS THAT HAVE SEEN SIGNIFICANT RAINFALL AMOUNTS WEDNESDAY NIGHT AND THURSDAY EVENING ACROSS SOUTH CENTRAL NORTH DAKOTA AND THE JAMES RIVER VALLEY. SOILS HAVE LITTLE TO NO CAPACITY TO HOLD ADDITIONAL WATER...ENHANCING RUNOFF AND THE POTENTIAL TO AGGRAVATE THE ONGOING OVERLAND FLOODING ACROSS THE AREA. A COMPLEX OF THUNDERSTORMS WITH HEAVY RAINFALL IS EXPECTED FRIDAY EVENING AND NIGHT...AND AGAIN SATURDAY NIGHT INTO SUNDAY. ADDITIONAL RAINFALL AMOUNTS OF 1 TO 3 INCHES ARE POSSIBLE WITH LOCALLY HIGHER AMOUNTS. && .BIS WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH THROUGH SUNDAY EVENING FOR NDZ023-025-036-037- 046>048-050-051. && $$ SHORT TERM/AVIATION/HYDROLOGY...AYD LONG TERM...RP KINNEY