445 FXUS63 KBIS 042044 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 344 PM CDT TUE JUN 4 2013 .SHORT TERM...(THIS EVENING THROUGH WEDNESDAY) ISSUED AT 343 CDT TUE JUN 4 2013 THE HIGHLIGHT OF THE SHORT TERM IS CONTINUED HYDROLOGIC IMPACTS FROM MODERATE TO HEAVY RAINFALL THROUGH TONIGHT. SEE THE HYDROLOGIC DISCUSSION BELOW FOR DETAILS. THE 12 UTC GUIDANCE SUITE IS IN GOOD AGREEMENT WITH THE SURFACE LOW ACROSS SOUTHEAST NORTH DAKOTA THIS AFTERNOON PROPAGATING INTO MINNESOTA ON WEDNESDAY. THUS HAVE USED A BLEND OF THE 12 UTC GUIDANCE FOR ALL FIELDS. FOR THIS EVENING PRIOR TO SUNSET...WILL HAVE TO CLOSELY WATCH THE I-94 CORRIDOR EAST OF BISMARCK AND POINTS SOUTH AS A SIMILAR ENVIRONMENT IS SETTING UP AS WAS SEEN LAST NIGHT ACROSS THE SOUTHWEST...FAVORABLE FOR NON-SUPERCELL/LANDSPOUT TORNADOES. THIS AREA HAS SEEN SUNSHINE THROUGH MUCH OF THE DAY...RESULTING IN SURFACE DESTABILIZATION UNDER THE COLD CORE ALOFT. WITH LARGE AMOUNTS OF BOUNDARY LAYER RELATIVE VORTICITY AND LOW LCLS...ANY SURFACE BASED CONVECTION WOULD HAVE THE POTENTIAL TO STRETCH THE ENVIRONMENTAL VORTICITY INTO A POSSIBLE FUNNEL CLOUD OR PERHAPS A WEAK TORNADO. OTHERWISE FOR TONIGHT...DID ADD A MENTION OF PATCHY FOG TO THE WEST WITH UPSLOPE FLOW WITH NEAR SATURATED BOUNDARY LAYER CONDITIONS WHICH PERHAPS RADIATION FOG ACROSS THE NORTHWEST AS SKIES CLEAR AND WINDS BECOME LIGHT TONIGHT. FOR WEDNESDAY ISOLATED TO SCATTERED DIURNALLY DRIVEN SHOWERS ARE POSSIBLE WITH THE COLD TEMPERATURES ALOFT...ESPECIALLY SOUTH OF US HIGHWAY 2. .LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY) ISSUED AT 343 CDT TUE JUN 4 2013 THE FOCUS IN THE LONG TERM WILL BE PRECIPITATION FRIDAY INTO THE WEEKEND. THE 12 UTC GFS AND 12 UTC ECMWF ARE IN GOOD AGREEMENT ON THE UPPER LEVEL PATTERN THE REST OF THIS WEEK INTO EARLY NEXT WEEK. THE LATEST 12 UTC ECMWF HAS ALSO COME INTO BETTER AGREEMENT ON THE TIMING OF THE PRECIPITATION ON FRIDAY WITH PAST GFS MODEL RUNS. THE GFS IS STILL FASTER WITH MOVING THE SHORT WAVE AND FRONTAL BOUNDARY OVER WESTERN NORTH DAKOTA...HOWEVER THE RECENT MODEL AGREEMENT GIVES A LITTLE MORE CONFIDENCE THAT CHANCES FOR PRECIPITATION WILL START FRIDAY LATE AFTERNOON INTO NIGHT IN WESTERN NORTH DAKOTA AND MOVE EAST. MODEL DIVERGENCE ON THIS SYSTEM BEGINS SATURDAY AT 18 UTC WHEN THE GFS DEVELOPS A CUT OFF UPPER LEVEL LOW JUST NORTH OF NORTH DAKOTA...WHILE THE ECMWF DOES NOT DEVELOP A CUT OFF UPPER LEVEL LOW UNTIL THE SYSTEM IS EXITING THE NORTHERN PLAINS AT 12 UTC SUNDAY. DESPITE THIS DIFFERENCE THE MODELS STILL HAVE CHANCES FOR PRECIPITATION LINGERING OVER CENTRAL AND PERHAPS WESTERN NORTH DAKOTA INTO SUNDAY. THE BEST CHANCE FOR THUNDERSTORMS OVER THIS TIME PERIOD WILL BE FRIDAY AFTERNOON AND NIGHT. THE GFS AND ECMWF ARE IN AGREEMENT ON THE POSSIBILITY OF THUNDERSTORMS...HOWEVER SINCE THE GFS BRINGS IN THE FRONTAL BOUNDARY EARLIER ON FRIDAY THAN THE ECMWF THE GFS SOLUTION HAS THE BEST CHANCE FOR STRONG TO SEVERE STORMS. GFS SEVERE PARAMETERS OF DEEP LAYER SHEAR AND SURFACED BASED CAPE ARE ALSO CONSIDERABLY HIGHER THAN THAT OF THE ECMWF FOR FRIDAY EVENING. THIS SITUATION WILL HAVE TO BE MONITORED THE NEXT FEW DAYS...AS HEAVY DOWN POURS FROM THUNDERSTORMS ON THE ALREADY SATURATED SOILS...ESPECIALLY OVER THE SOURIS RIVER BASIN...MAY CAUSE ADDITIONAL FLOODING ISSUES. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON) ISSUED AT 343 CDT TUE JUN 4 2013 WIDESPREAD MVFR TO IFR CONDITIONS IN STRATUS...FOG AND RAIN ARE EXPECTED ACROSS WESTERN AND CENTRAL NORTH DAKOTA THROUGH TONIGHT AS LOW PRESSURE ACROSS SOUTHEAST NORTH DAKOTA SLOWLY MOVES IN WESTERN MINNESOTA. KISN IS EXPECTED TO BE THE FIRST TERMINAL TO BE SUSTAINED IN THE VFR CATEGORY BEGINNING AFTER 03 UTC. && .HYDROLOGY... ISSUED AT 343 CDT TUE JUN 4 2013 AREAL FLOOD ADVISORIES REMAIN IN EFFECT FOR WARD...RENVILLE...MCLEAN...MCHENRY...BOTTINEAU...BURKE AND MOUNTRAIL COUNTIES...WITH THE FLOOD WATCH REMAINING IN EFFECT THROUGH 12 UTC WEDNESDAY FOR ROLLETTE...PIERCE...SHERIDAN...WELLS AND FOSTER COUNTIES. FOR THE WATCH AREA...AN ADDITIONAL ONE TO ONE AND A HALF INCHES OF RAIN WITH LOCALLY HIGHER AMOUNTS IS POSSIBLE AND WILL HAVE TO MONITOR FOR POSSIBLE UPGRADES THROUGH THE EVENING. && .BIS WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH THROUGH WEDNESDAY MORNING FOR NDZ005-013-022-023-025. && $$ SHORT TERM...AYD LONG TERM...MM AVIATION...AYD HYDROLOGY...AYD