Issued by NWS Bismarck, ND
000 FXUS63 KBIS 291923 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 222 PM CDT SAT AUG 29 2009 .SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT... MAIN FORECAST PROBLEM IN THE SHORT TERM WILL BE PRECIPITATION CHANCES LATE IN THE PERIOD. UNTIL THEN...PLEASANT AND DRY WEATHER EXPECTED. HAVE UTILIZED A NAM/GFS/ECMWF BLEND TODAY. MODELS ARE VERY SIMILAR THROUGH AROUND 60H. BEYOND THIS...THE GFS LOOKS TO BE HAVING PROBLEMS WITH THE HANDLING OF THE UPPER LOW TRAVERSING THE NORTHERN ROCKIES. WHEN COMPARED TO THE OTHER MODEL GUIDANCE...GFS LOOKS TOO FAR SOUTH WITH THE UPPER LOW BEYOND H72. PER PMDHMD THIS IS MAINLY A RESULT OF THE AMPLIFICATION OF THE UPPER RIDGE OVER THE PACIFIC NORTHWEST AND SOUTHWEST CANADA. WILL LEAN MORE TOWARD A NAM/ECMWF SOLUTION IN THE LATTER PERIODS. CURRENTLY...LATEST WV IMAGERY SHOWS A SHORTWAVE DROPPING SOUTH ALONG THE SOUTHERN RED RIVER VALLEY. THIS HAS SPARKED A FEW SHOWERS OVER OUR SOUTHEAST CWA...CURRENTLY FROM ASHLEY TO ELLENDALE. THIS ACTIVITY WILL CONTINUE TO DROP SOUTH AND AT THIS TIME DO NOT EXPECT TO CARRY ANY EVENING SHOWERS. WILL CONTINUE TO MONITOR THOUGH. COOL AND QUIET NIGHT TONIGHT. SUNDAY WILL BE ANOTHER MILD DAY WITH HIGH TEMPERATURES SIMILAR TO...IF NOT A COUPLE DEGREES WARMER THAN TODAY. WINDS WILL BECOME SOUTHEAST ACROSS THE CWA...WITH STRONGEST WINDS IN THE SOUTHWEST...HELPING TO INCREASE TEMPERATURES AND MOISTURE. THIS SOUTHEAST FLOW WILL HELP KEEP TEMPERATURES WARMER SUNDAY NIGHT...ESPECIALLY SOUTH AND WEST. MONDAY AND MONDAY NIGHT...THE 50H LOW BEGINS TO INFLUENCE OUR WEATHER BY THIS TIME...WITH INCREASING SOUTHERLY FLOW BRINGING INCREASING MOISTURE INTO THE REGION. THERMAL RIDGE POKES UP AHEAD OF THE LOW...IN THE FAR WEST MONDAY. WARMER HIGH TEMPERATURES MAY BE TEMPERED A BIT WITH AN INCREASE IN MID AND HIGH LEVEL CLOUDINESS. BY MONDAY NIGHT...INCREASING 85H JET AND INSTABILITY AHEAD OF THE UPPER LOW WILL PROVIDE A CHANCE OF THUNDERSTORMS IN THE WEST. TUESDAY AND TUESDAY NIGHT...THE UPPER LOW MOVES INTO THE DAKOTAS TUESDAY AND TUESDAY NIGHT. HAVE KEPT CURRENT POPS SIMILAR...BUT WE DID PUSH THE CHANCES A BIT FARTHER NORTH AND UPPED THEM IN THE FAR SOUTHWEST. GFS AND EVEN NAM ARE NOT REAL IMPRESSIVE WITH THEIR QPF...GIVEN THE AMOUNT OF MOISTURE THAT SHOULD WORK INTO THE REGION AHEAD OF THE SLOW MOVING UPPER TROUGH. HIGH PWATS MONDAY NIGHT THROUGH TUESDAY NIGHT OVER MAINLY THE SOUTHWEST THIRD OF THE CWA COULD INDICATE SOME HEFTY RAINFALL AMOUNTS. WILL CONTINUE TO MONITOR AND STILL ENOUGH TIME TO INCREASE POPS IF NEED BE. .LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT... THE UPPER RIDGE REMAINS IN PLACE OVER THE ROCKIES AND WESTERN PLAINS WEDNESDAY WITH THE CUTOFF LOW THAT WAS OVER THE DAKOTAS ON TUESDAY EXITING THE REGION. THE LONG TERM MODELS AGREE IN GENERAL ABOUT A LARGE UPPER LEVEL LOW/TROUGH CONTINUING TO DEVELOP OFF THE WEST COAST OF THE US/CANADA...AND LOOKS LIKE THE FIRST IN A SERIES OF SHORTWAVE ENERGY IMPULSES FROM THIS FEATURE WILL REACH THE WESTERN DAKOTAS FRIDAY NIGHT AND HAVE INTRODUCED SMALL CHANCE OF THUNDERSTORMS FRIDAY NIGHT OVER WESTERN NORTH DAKOTA. MORE SHORTWAVE ENERGY CONTINUES INTO SATURDAY AND BEYOND AS THE LOW MOVES EAST ACROSS THE ROCKIES...SO HAVE ALSO INCLUDED SLIGHT CHANCES (FOR NOW) OF THUNDERSTORMS OVER ALL OF WESTERN AND CENTRAL NORTH DAKOTA FOR SATURDAY/SATURDAY NIGHT. SEASONABLE TO SLIGHTLY ABOVE AVERAGE TEMPERATURES FOR THIS 4-DAY PERIOD WITH HIGHS IN THE UPPER 70S/80S AND LOWS IN THE 50S. && .AVIATION... SURFACE HIGH PRESSURE CENTERED OVER THE CENTRAL SASKATCHEWAN/MANITOBA BORDER WITH NORTHERLY/NORTHEASTERLY WINDS OVER THE FORECAST AREA THIS AFTERNOON. CUMULUS FIELD HAS DEVELOPED WITH DAYTIME HEATING WITH BASES OF 4000 TO 6000 FEET. EXPECT CLOUDS TO DISSIPATE BY AROUND SUNSET. WINDS WILL BECOME LIGHT EASTERLY OR CALM AS THE SURFACE HIGH MOVES SOUTH INTO THE RED RIVER VALLEY. EXPECT SOUTHEAST WINDS ON SUNDAY WITH MAINLY CLEAR SKIES. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ TWH/JV
