446 FXUS63 KBIS 261801 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 101 PM CDT THU SEP 26 2013 .UPDATE... ISSUED AT 101 PM CDT THU SEP 26 2013 GRADIENT FLOW HAS NOT RESPONDED AS PREVIOUSLY EXPECTED. THE SURFACE LOW CONTINUES TO LIFT FARTHER NORTH INTO CANADA THAN HIGH PRESSURE CAN BUILD INTO WESTERN NORTH DAKOTA. THEREFORE...SUSTAINED SURFACE WINDS HAVE ONLY INCREASED TO AROUND 20 KNOTS EARLY THIS AFTERNOON. IN ADDITION...THE LATEST MODEL GUIDANCE CONTINUES TO BACK OFF ON WIND SPEEDS THIS AFTERNOON AS GRADIENT FLOW IS WEAKER THAN PREVIOUSLY EXPECTED. SUSTAINED WIND SPEEDS ARE EXPECTED TO BE UP TO 25 MPH THIS AFTERNOON WITH 35 MPH GUSTS...WHICH IS BELOW WIND ADVISORY CRITERIA. AS A RESULT...DECIDED TO CANCEL THE WIND ADVISORY FOR SOUTHWESTERN INTO NORTH CENTRAL NORTH DAKOTA THIS AFTERNOON. ALSO REMOVED AFTERNOON CONVECTION BASED ON CURRENT RADAR OBS/TRENDS. THE UPDATED PRODUCTS HAVE BEEN SENT. UPDATE ISSUED AT 949 AM CDT THU SEP 26 2013 SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO LIFT NORTH OUT OF NORTH CENTRAL NORTH DAKOTA THIS MORNING. NONE OF THIS ACTIVITY SHOULD BE SEVERE. ALL THUNDERSTORM ACTIVITY WILL BE OUT OF THE CWA BY THIS AFTERNOON. HIGH PRESSURE BUILDING INTO WESTERN NORTH DAKOTA AND LOW PRESSURE LIFTING INTO MANITOBA WILL GENERATE WINDY CONDITIONS ACROSS WESTERN AND NORTH CENTRAL NORTH DAKOTA THIS AFTERNOON. THE LATEST MODEL PROGS HAVE BACKED OFF ON THE SUSTAINED WIND SPEED FORECAST THIS AFTERNOON. HOWEVER...STILL THINK MARGINAL WIND ADVISORY CONDITIONS WILL BE ACHIEVED IN SOME SPOTS. THEREFORE...MAINTAINED THE CURRENT TEMPORAL AND AREAL RESOLUTION OF THE WIND ADVISORY THIS AFTERNOON. THE REMAINING FORECAST ELEMENTS ARE ON TRACK. THE UPDATED PRODUCTS HAVE BEEN SENT. UPDATE ISSUED AT 651 AM CDT THU SEP 26 2013 LOW PRESSURE SITUATED OVER CENTRAL NORTH DAKOTA WITH SCATTERED SHOWERS AND THUNDERSTORMS LIFTING FROM EAST CENTRAL INTO NORTHEAST NORTH DAKOTA...AND SHOWERS EXTENDING BACK INTO CENTRAL NORTH DAKOTA JUST AHEAD OF THE LOW. COLD NORTHERLY FLOW HAS MOVED INTO WESTERN NORTH DAKOTA WITH IFR CLOUDINESS SPREADING EAST ACROSS WESTERN NORTH DAKOTA. UPDATED WEATHER POPS TO MATCH WITH LATEST RADAR IMAGERY...AND EXTRAPOLATING NORTHEAST THROUGH THE MORNING. LIMITED MENTION OF THUNDER TO THE EAST CENTRAL AND FAR NORTH CENTRAL. INCREASED SKY COVER OVER THE WEST THROUGH THE MORNING TO ACCOUNT FOR THE LOW STRATUS. EXPECT THIS TO DISSIPATE BY LATE MORNING AND AFTERNOON WITH STRONG SUBSIDENCE MOVING INTO WESTERN NORTH DAKOTA. && .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 249 AM CDT THU SEP 26 2013 MAIN CONCERN TODAY WILL BE THUNDERSTORMS EARLY THIS MORNING FOLLOWED BY A WIND ADVISORY SOUTHWEST THROUGH NORTH CENTRAL. HAVE UTILIZED A BLEND OF ALL MODELS...BUT SPECIFICALLY THE HRRR FOR AREAL COVERAGE OF PRECIPITATION THIS MORNING AND NAM/GFS FOR THE WIND ADVISORY. THE LATEST WATER VAPOR IMAGERY ALONG WITH SPC MESOSCALE ANALYSIS CONTINUES TO SHOW THE H3 JET STREAK WORKING ITS WAY THROUGH WYOMING AND INTO SOUTH DAKOTA. UPPER DIVERGENCE FIELD ASSOCIATED WITH THE LEFT EXIT REGION CENTERED OVER CENTRAL/NORTHERN NORTH DAKOTA AS ISOLATED THUNDERSTORMS CONTINUE TO ESCALATE UPWARDS. SURFACE LOW PRESSURE IN SOUTHERN SOUTH DAKOTA WILL BEGIN TO MOVE NORTH ALONG A COLD FRONT WHICH IS NOW LOCATED FROM NEAR OXBOW SASKATCHEWAN...SOUTH TO MINOT AND INTO LEMMON SOUTH DAKOTA. AS THE JET STREAK AND UPPER DIVERGENCE FIELD SHIFT FURTHER NORTH THROUGH THE MORNING...THE SURFACE LOW WILL DEEPEN AS IT ENTERS SOUTHERN SASKATCHEWAN THIS AFTERNOON. A TIGHT PRESSURE GRADIENT WILL ENSUE...RESULTING IN A MARGINAL WIND ADVISORY EVENT. WITH SUSTAINED WINDS VERY NEAR 30 MPH AND GUSTS TO 40 MPH OVER A FAIRLY LARGE AREA...DECIDED TO ISSUE A WIND ADVISORY FOR THE SOUTHWEST AND NORTH CENTRAL ZONES. WINDS WILL INCREASE FIRST ACROSS THE SOUTHWEST LATE THURSDAY MORNING...THEN TRANSLATE INTO NORTH CENTRAL BEGINNING IN THE EARLY AFTERNOON. WINDS WILL THEN DIMINISH FROM SOUTH TO NORTH THURSDAY EVENING. AS FAR AS SHOWERS AND THUNDERSTORMS...THERE WILL BE A DIMINISHING EFFECT AS THE SURFACE LOW MOVES FROM SOUTH TO NORTH TODAY. MAIN INSTABILITY WASHES OUT BY 18Z IN THE NORTH AND HAVE ENDED THE THUNDERSTORM THREAT IN THE GRIDDED FORECAST AT THAT TIME. DRY WEATHER COMMENCES CENTRAL AND SOUTH TODAY INTO EARLY TONIGHT. THE NEXT ROUND OF SHOWERS BEGINS IN THE SOUTHWEST EARLY TONIGHT AND GRADUALLY EXPANDS NORTHEAST OVERNIGHT. .LONG TERM...(FRIDAY THROUGH WEDNESDAY) ISSUED AT 249 AM CDT THU SEP 26 2013 THE MAIN FORECAST ISSUE IN THE LONG TERM PERIOD WILL BE PRECIPITATION CHANCES AND PLACEMENT FRIDAY THROUGH SATURDAY MORNING. THERE IS STILL SOME DISAGREEMENT AMONG THE DETERMINISTIC MODELS WITH PRECIPITATION ACROSS NORTH DAKOTA ON FRIDAY. HOWEVER...THERE IS MUCH BETTER AGREEMENT FRIDAY NIGHT INTO SATURDAY MORNING. WE BEGIN THE LONG TERM PERIOD ON FRIDAY WITH AN UPPER LEVEL TROUGH OVER THE NORTHERN AND CENTRAL ROCKIES. SHEARED VORTICITY ALONG THE LEADING EDGE OF THE TROUGH EXTENDS ACROSS EASTERN MONTANA AND WESTERN NORTH DAKOTA. THE ECMWF IS SHOWING A BROAD AREA OF LIGHT TO MODERATE RAIN LIFTING SOUTHWEST TO NORTHEAST ACROSS THE FORECAST AREA...WHILE THE GFS/GEM CONTINUE TO INDICATE TWO SEPARATE AREAS OF PRECIPITATION...ONE OVER THE WESTERN DAKOTAS ASSOCIATED WITH THE UPPER LEVEL TROUGH...AND ANOTHER OVER EASTERN NORTH DAKOTA ASSOCIATED WITH THE SURFACE SYSTEM...AND A DRY SLOT OVER CENTRAL NORTH DAKOTA. DUE TO CONTINUED DIFFERENCES...WILL SETTLE ON A BROAD BRUSH OF CHANCE TO HIGH CHANCE POPS UNTIL THERE IS BETTER MODEL AGREEMENT. EITHER WAY IT WILL BE QUITE COOL AND CLOUDY WITH SCATTERED LIGHT RAIN AND HIGHS MAINLY IN THE 50S. THERE IS BETTER MODEL AGREEMENT AS THE KICKER SHORTWAVE ROUNDS THE BASE OF THE UPPER TROUGH AND LIFTS INTO THE CENTRAL PLAINS FRIDAY NIGHT. STRONG 2D FRONTOGENESIS SETS UP OVER THE EASTERN DAKOTAS FRIDAY NIGHT AS THE SURFACE LOW TRACKS FROM THE CENTRAL PLAINS INTO NORTHERN MINNESOTA BY SATURDAY MORNING. THIS RESULTS IN AN ENHANCED BAND OF DEFORMATION RAIN OVER FAR SOUTH CENTRAL NORTH DAKOTA THROUGH THE JAMES RIVER VALLEY AND INTO EASTERN NORTH DAKOTA. THE RAIN WILL EXIT THE JAMES RIVER VALLEY SATURDAY MORNING WITH CLEARING SKIES OVER WESTERN NORTH DAKOTA. WE WILL NEED TO MONITOR FOR POSSIBLE FROST HIGHLIGHTS ACROSS THE WEST ON SATURDAY MORNING WITH LOWS POSSIBLY FALLING INTO THE MID TO UPPER 30S IF SKIES CLEAR AND WINDS SUBSIDE. UPPER LEVEL RIDGING BUILDS OVER THE AREA THROUGH THE REMAINDER OF THE WEEKEND WITH TEMPERATURES WARMING INTO THE 70S BY SUNDAY AND MONDAY. A QUASI-ZONAL FLOW THEN TAKES SHAPE THROUGH MID WEEK WITH THE STORM TRACK SITUATED NORTH OF THE BORDER. THUS MAINLY DRY CONDITIONS ARE EXPECTED EARLY NEXT WEEK. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON) ISSUED AT 101 PM CDT THU SEP 26 2013 MVFR CIGS WILL GRADUALLY IMPROVE TO VFR FROM SOUTH TO NORTH THIS AFTERNOON. VFR CONDITIONS ARE EXPECTED TO CONTINUE OVER WESTERN AND CENTRAL NORTH DAKOTA TONIGHT. MVFR CONDITIONS WILL SPREAD FROM SOUTHWEST TO NORTHEAST FRIDAY MORNING AS SHOWERS DEVELOP. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...TM SHORT TERM...KS LONG TERM...TWH AVIATION...TM