RSS FeedsIssued by NWS Bismarck, ND
000 FXUS63 KBIS 202046 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 246 PM CST FRI NOV 20 2009 .SYNOPSIS... PERSISTENT NEGATIVE HEIGHT ANOMALIES CENTERED OVER SIBERIA AND ALASKA SHOULD RESULT IN A MORE PROGRESSIVE WEATHER PATTERN ACROSS NORTH AMERICA AS WESTERLIES CRASH INTO WESTERN NORTH AMERICA. SOME COOLER...BUT STILL ABOVE CLIMATOLOGICAL...TEMPERATURES ARE EXPECTED THIS WEEKEND INTO EARLY NEXT WEEK. .SHORT TERM...FRIDAY THROUGH MONDAY NIGHT... CURRENTLY...THERE IS UPPER LEVEL RIDGING ALONG THE FRONT RANGE/HIGH PLAINS WITH A POTENT TROUGH MOVING INTO THE PACIFIC NORTHWEST. AT THE SURFACE...CENTRAL PLAINS HIGH PRESSURE IS SLOWLY SLIDING SOUTHEAST. EXPECT SOUTHERLY WINDS TO CONTINUE OVERNIGHT AND STRENGTHEN DURING THE DAY TOMORROW AS THE PRESSURE GRADIENT TIGHTENS OVER THE REGION AHEAD OF A DEVELOPING SURFACE LOW IN CENTRAL ALBERTA. THE PREVIOUSLY MENTIONED UPPER LEVEL TROUGH MOVES INTO CENTRAL MONTANA ON SATURDAY PUSHING A COLD FRONT THROUGH THE NORTHERN PLAINS. TIMING THIS FEATURE IS THE FORECAST PROBLEM OF THE DAY. THE 12 UTC NAM SLOWED DOWN THE PASSAGE OF THIS COLD FRONT FAR MORE THAN THE SLIGHTLY SLOWER TREND OBSERVED IN THE 12 UTC GFS. BASED ON HPC MODEL DIAGNOSTICS DISCUSSION...GRIDDED FORECASTS FAVORED CONTINUITY BLENDED WITH THE MORE CONSISTENT GFS. LIMITED MOISTURE AVAILABILITY WILL ELIMINATE PRECIPITATION CHANGES WITH THIS SYSTEM. IN THE WAKE OF THE EXITING COLD FRONT A SHORT WAVE RIDGE BUILDS INTO NORTH DAKOTA FOR SUNDAY. TEMPERATES SHOULD BE 10 TO 15F COOLER ON SUNDAY BUT STILL WELL ABOVE AVERAGE. ANOTHER TROUGH APPROACHES WITH ANOTHER...STRONGER...COLD FRONT PASSING THROUGH THE REGION SUNDAY NIGHT INTO MONDAY. MODELS SUPPORT BETTER MOISTURE TRANSPORT...THUS THE CHANCE FOR PRECIPITATION. THE 12 UTC ECMWF/GFS CONTINUE TO DISAGREE ON THE TRACK OF THIS FEATURE. THE GFS IS FARTHER NORTH ALLOWING PRECIPITATION ACROSS WESTERN AND CENTRAL NORTH DAKOTA WHILE THE ECMWF TRACKS THE SYSTEM THROUGH KANSAS AND NEBRASKA WITH LIMITED PRECIPITATION FOR NORTH DAKOTA. .LONG TERM...TUESDAY THROUGH FRIDAY NIGHT... MODELS DEVELOP A STORM CENTER THAT MOVES EAST ACROSS THE ROCKIES IN THE SHORT TERM...AND BY TUESDAY MORNING THE LONG TERM MODELS HANDLE THE PLACEMENT/TIMING OF THE SYSTEM AS IT MOVES EAST/NORTHEAST ACROSS THE CENTRAL PART OF THE COUNTRY. THE GFS IS MORE PROGRESSIVE WITH THE SYSTEM...WHICH PUTS THE LOW CENTER OVER IOWA/WISCONSIN TUESDAY MORNING AND MOVES IT OVER THE GREAT LAKES BY WEDNESDAY MORNING AND INTO HUDSON BAY AREA BY THURSDAY. MEANWHILE THE ECMWF IS SLOWER...WITH THE LOW CENTER OVER NEBRASKA/KANSAS TUESDAY MORNING AND INTO IOWAS BY WEDNESDAY...AND OVER THE GREAT LAKES BY THURSDAY. THE NATIONAL GUIDANCE FAVORS THE CONSISTENCY OF THE ECMWF. BASICALLY KEPT ONLY A SLIGHT CHANCE OF PRECIP ON TUESDAY NIGHT FROM THE PREVIOUS FORECAST PACKAGE. THEN KEPT THE REST OF THE LONG TERM DRY. AFTER THE LOW MOVES TOWARDS HUDSON BAY...RIDGING OVER THE ROCKIES AND PLAINS WILL KEEP A WEST/NORTHWEST FLOW OVER THE NORTHERN PLAINS. TEMPERATURES AT OR ABOVE AVERAGE WITH HIGHS 35 TO 45 AND LOWS IN THE TEENS AND 20S. && .AVIATION... HIGH PRESSURE OVER MINNESOTA AND LOW PRESSURE IN THE LEE OF THE ROCKIES WILL KEEP A SOUTHERLY WIND FLOW ACROSS TAF SITES. A SURFACE TROUGH IS FORECAST TO ENTER WESTERN NORTH DAKOTA AROUND 15Z SATURDAY AND MOVE EAST ACROSS THE STATE. SOUTH WINDS AHEAD AND WEST WINDS BEHIND THE TROUGH. VFR CONDITIONS WITH HIGH CIRRUS CLOUDS THROUGH 12Z SATURDAY...WITH MID CLOUDS AFTER 18Z SATURDAY. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS/SHORT TERM...DC/SCHECK LONG TERM/AVIATION...JV
