861 FXUS63 KBIS 270008 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 708 PM CDT SUN MAY 26 2013 .UPDATE... ISSUED AT 658 PM CDT SUN MAY 26 2013 UPDATE MAINLY TO REFINE POPS OVERNIGHT...KEEPING THE HIGHER POPS CONFINED MAINLY TO THE WEST AND EVENTUALLY THE CENTRAL COUNTIES LATE. RADAR/VISIBLE SATELLITE IMAGERY INDICATING SOME SHOWERS AND ENHANCED CUMULUS DEVELOPING AROUND HETTINGER AND MOTT. ML CAPES IN THAT AREA ARE AROUND 1500 J/KG...ALTHOUGH DEEP LAYER SHEAR IS RELATIVELY WEAK. STRONG TO SEVERE STORMS ARE CURRENTLY LOCATED WELL WEST OF THE FORECAST AREA IN MONTANA AND WYOMING. SHORT WAVE ENERGY IS EXPECTED TO MOVE INTO THE SOUTHWEST THIS EVENING...AND THE 22Z RUN OF THE HRRR BRINGS STORMS INTO THE SOUTHWEST BETWEEN 02Z-03Z. NOT ANTICIPATING WIDESPREAD SIGNIFICANT SEVERE WEATHER...BUT WILL LIKELY HAVE A FEW STRONGER STORMS TO MONITOR LATER ON. && .SHORT TERM...(THIS EVENING THROUGH MONDAY) ISSUED AT 320 PM CDT SUN MAY 26 2013 FORECAST PROBLEM IN THE SHORT TERM WILL BE THUNDERSTORM CHANCES THROUGH THE PERIOD. OVERALL MODEL TREND HAS BEEN TO LESSEN OR PUSH BACK PRECIPITATION CHANCES ESPECIALLY LATE THIS AFTERNOON AND THIS EVENING. BEYOND THIS THERE IS LITTLE FORECAST CONFIDENCE REGARDING PRECIPITATION TIMING AND PLACEMENT AS MODELS ARE HAVING A HARD TIME RESOLVING THIS IN THE BROAD SOUTHWEST UPPER FLOW. CURRENTLY...MVFR-IFR STRATUS REMAIN ACROSS THE SOURIS TO JAMES RIVER BASINS...WHILE STRATUS HAS DISSIPATED BUT WELL DEVELOPED CU FIELD HAS BROKEN OUT OVER THE WEST AND SOUTH CENTRAL. THIS HAS RESULTED IN TEMPERATURES PUSHING INTO THE LOW TO MID 70S WITH MID 50S DEWPOINT TEMPERATURES FROM WESTERN NORTH DAKOTA INTO EASTERN MONTANA AND NORTHWEST SOUTH DAKOTA. CURRENT SPC ANALYSIS IS SHOWING CAPES OF 1000-1500 J/KG WITH DIMINISHING CIHN OVER THE MONDAK REGION WITH INCREASING LAPSE RATES. CONVECTION HAS RECENTLY INITIATED OVER THE BIGHORNS AND BLACK HILLS. GGW 18Z SOUNDING AND CURRENT LAPS SOUNDING NEAR KOLF INDICATE A NEAR COMPLETE ERODED CAP OVER EASTERN MONTANA. LATEST WATER VAPOR SATELLITE IMAGERY SHOW AN APPROACHING SHORTWAVE TROUGH LIFTING NORTHEAST THROUGH WYOMING WHICH SHOULD HELP TO INITIATE CONVECTION AWAY FROM THE MOUNTAINS. WITH THIS SAID...MODELS ARE NOT POINTING TO STRONG CONVECTION OVER WESTERN AND CENTRAL NORTH DAKOTA THIS AFTERNOON AND EARLY EVENING. GFS/ECMWF BRING BEST CHANCES INTO THE FAR WEST LATE TONIGHT WITH CONVECTION CONTINUING EAST ACROSS THE AREA ON MONDAY. 12 UTC NAM AND 17 UTC HRRR BRING CONVECTION FIRING OFF THE BIGHORNS INTO SOUTHEAST MONTANA BUT THEN SUPPRESS REFLECTIVITIES AS THEY MOVE INTO WESTERN NORTH DAKOTA. 12 UTC HIRES ARW/NMM EAST BOTH POINT MORE TOWARD LATE NIGHT CONVECTION MOVING INTO THE WEST AND LINGERING INTO MONDAY...WITH YET ANOTHER ROUND OF CONVECTION ON MONDAY. FOR NOW WILL LEAN TOWARD SLIGHT CHANCE POPS EAST TO CHANCE POPS WEST THIS EVENING...THEN INCREASING AFTER MIDNIGHT WITH HIGHEST POPS REMAINING IN THE WEST. THEN BASICALLY A BROAD BRUSH OF HIGH CHANCE POPS ON MONDAY DUE TO SO MUCH UNCERTAINTY ON TIMING/PLACEMENT. WITH AFOREMENTIONED SEVERE WEATHER INGREDIENTS WILL KEEP A MENTION OF SEVERE LATE THIS AFTERNOON AND THIS EVENING. IF CONVECTION WOULD DEVELOP AND MOVE INTO WESTERN NORTH DAKOTA...THE GREATEST THREAT WOULD LIKELY BE LARGE HAIL AND VERY HEAVY RAIN CAUSING LOCALIZED FLOODING PROBLEMS. ALTHOUGH SPC SLIGHT RISK DOES INCLUDE A PORTION OF THE FAR SOUTHWEST ON MONDAY...WILL HOLD OFF ON MENTIONING THIS IN THE FORECAST FOR NOW. WILL LET LATER SHIFTS RE-EVALUATE. MODELS DO INDICATE INCREASING 925MB MOISTURE TONIGHT. CONSIDERED ADDING A MENTION OF FOG...BUT THINK THE BIGGEST ISSUE WILL BE LOW STRATUS AND LIFR CEILINGS. COULD SEE SOME MVFR VISIBILITIES BUT WILL HOLD OFF ON ADDING FOG FOR NOW. .LONG TERM...(MONDAY NIGHT THROUGH SUNDAY) ISSUED AT 320 PM CDT SUN MAY 26 2013 A VERY ACTIVE WEATHER PATTERN WILL PERSIST ACROSS THE NORTHERN PLAINS THROUGH MUCH IF NOT ALL OF THE EXTENDED PERIOD. LONG WAVE TROUGH WEST AND RIDGING EAST WILL MAINTAIN SOUTHWESTERLY FLOW ALOFT ACROSS THE DAKOTAS MONDAY NIGHT. SHOWERS AND POSSIBLY SEVERE THUNDERSTORMS WILL BE ONGOING AT THE START OF THE PERIOD MONDAY EVENING AS A STRONG S/WV LIFTS NORTHEAST THROUGH THE REGION. SCALED BACK PRECIPITATION CHANCES TUESDAY/TUESDAY EVENING AS A S/WV RIDGE ADVANCES NORTHEAST THROUGH THE STATE ALONG WITH DRIER AIR INTO MY WEST. SHOWER/THUNDERSTORM CHANCES INCREASE TUESDAY NIGHT AS THE RIDGE CONTINUES OFF TO OUR NORTH AND EAST RESULTING IN FLOW ALOFT TRANSITIONING TO SOUTHWEST ONCE AGAIN...WITH A LEAD IMPULSE MOVING NORTH THROUGH THE WESTERN DAKOTAS. BY WEDNESDAY MORNING THE BASE OF THE WESTERN CONUS TROUGH WILL BE OVER THE SOUTHERN ROCKIES...WHICH IS DEPICTED BY BOTH THE 12Z GFS/ECMWF TO SWING NORTH THROUGH THE CENTRAL PLAINS INTO THE DAKOTAS WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. FOR THURSDAY...THE BASE OF THE TROUGH MORPHS INTO A CUTOFF LOW WHICH MAY LINGER ACROSS THE NORTHERN PLAINS INTO SATURDAY IF THE 12Z ECMWF VERIFIES. THE 12Z GFS IS MORE PROGRESSIVE...WITH THE LOW BECOMING AN OPEN WAVE AND MOVING OVER THE WESTERN GREAT LAKES REGION BY SATURDAY MORNING. BOTH MODEL SOLUTIONS RESULT IN HIGH CHANCES FOR SHOWERS AND THUNDERSTORMS WEDNESDAY-WEDNESDAY NIGHT-THURSDAY...WITH A CHANCE OF STRONG TO SEVERE STORMS AS WELL. FORECAST UNCERTAINTY INCREASES AFTERWARDS FOR FRIDAY THROUGH THE WEEKEND WITH THE ABOVE MENTIONED DIFFERENCES BETWEEN THE GFS/ECMWF. TEMPERATURES WILL AVERAGE NEAR TO SLIGHTLY ABOVE NORMAL EARLY NEXT WEEK...THEN WILL AVERAGE NEAR TO SLIGHTLY BELOW NORMAL FOR THE END OF THE WORK WEEK THROUGH NEXT WEEKEND. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING) ISSUED AT 658 PM CDT SUN MAY 26 2013 SOUTHEAST FLOW WILL CONTINUE THROUGH THE FORECAST PERIOD. THIS WILL KEEP A THREAT OF MVFR-IFR CEILINGS IN THE FORECAST AT ALL TAF SITES. THE PRESENCE OF ABUNDANT LOW LEVEL MOISTURE TONIGHT WILL ALLOW FOR LOWERED CEILINGS DOWN TO IFR-LIFR IN STRATUS AROUND 06-10Z AT ALL SITES...WITH SOME MVFR FOG. BROUGHT A MENTION OF LIGHT RAIN FOR ALL SITES EXCEPT FOR KJMS AFTER 18 UTC..WHERE VCSH WAS MORE APPROPRIATE SINCE THREAT FOR RAIN WILL BE LATER THERE. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...RP KINNEY SHORT TERM...TWH LONG TERM...NH AVIATION...LTH