FXUS63 KBIS 110921 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 320 AM CST THU MAR 11 2010 .SHORT TERM...TODAY THROUGH SATURDAY NIGHT THE LARGE BROAD UPPER LEVEL LOW AND IT'S ASSOCIATED SURFACE LOW CONTINUE TO DOMINATE THE WEATHER OVER THE NORTHERN PLAINS TODAY. SATELLITE AND LOCAL RADARS INDICATE ONE MORE UPPER LEVEL SHORT WAVE ROTATING AROUND THE UPPER LEVEL LOW AND INTO THE FORECAST AREA. AT 3 AM CST...RADARS SHOW A LARGE AREA OF PRECIPITATION IN CENTRAL AND EASTERN NORTH DAKOTA WITH THE BACK EDGE SEEMS TO BE IN THE FARGO AREA. ALL THE REPORTING STATIONS IN WESTERN AND CENTRAL NORTH DAKOTA ARE INDICATING LIGHT SNOW. SNOW IS ACCUMULATING IN THE BISMARCK AREA WITH ABOUT 0.1 INCH SINCE LAST HOUR. POTENTIAL ACCUMULATIONS THIS MORNING SHOULD BE NO MORE THAN AN INCH...BUT COULD SEE ISOLATED AREAS WITH AS MUCH A 2 INCHES. IN THE SOUTHWEST THE WINDS HAVE PICKED UP TO 20 TO 30 MPH AND BLOWING AND DRIFTING SNOW COULD BE A PROBLEM. HAVE DECIDED TO EXTEND THE WINTER WEATHER ADVISORY FOR ALL BUT WILLIAMS AND MCKENZIE COUNTIES UNTIL 18Z AS MOTORISTS ARE LIKELY TO BEGIN TRAVEL THIS MORNING WITH CONDITIONS SIMILAR TO YESTERDAY MORNING. A STRONG UPPER LEVEL LOW WILL MOVE ONTO THE WEST COAST TODAY DRIVING A SHORT WAVE RIDGE THROUGH THE ROCKIES AND INTO THE AREA. THIS WILL BRING IMPROVING CONDITIONS TO WESTERN NORTH DAKOTA AS IT COMES UNDER THE INFLUENCE OF THE RIDGE....AFFECTING CENTRAL NORTH DAKOTA TONIGHT AND FRIDAY MORNING. THE CHANCE OF PRECIP WILL DIMINISH IN THE AFTERNOON...AND WITH DAYTIME HEATING...THE SNOW SHOULD BECOME MIXED RAIN WITH LITTLE IF ANY ACCUMULATION. WILL KEEP A SLIGHT CHANCE OF LIGHT SNOW CENTRAL TONIGHT...ENDING IN THE JAMES RIVER VALLEY ON FRIDAY. WILL ALSO ADD PATCHY FOG TO THE WEST TONIGHT AS THE WINDS SHOULD BECOME LIGHT AND THE SKIES SHOULD CLEAR AS A SURFACE HIGH MOVES OVER THE AREA. THE UPPER LEVEL RIDGE SHOULD STAY OVER THE AREA THROUGH THE REMAINDER OF THE SHORT TERM KEEPING ANY CHANCE OF PRECIP LOW. TEMPERATURES SHOULD RETURN TO A NORMAL DIURNAL TREND...ALTHOUGH HIGHS WILL BE GENERALLY BELOW NORMAL DUE TO THE SNOW PACK. .LONG TERM...SUNDAY THROUGH WEDNESDAY... MAIN PROBLEM IN THE DAY 4-5 PERIOD WILL BE TEMPERATURES...WITH POSSIBLE LOW STRATUS AND FOG ISSUES. THE HIGH OVER LOW BLOCKING PATTERN FROM HUDSON BAY INTO THE EASTERN U.S. WILL KEEP ANY SIGNIFICANT SYSTEMS OUT OF THE LOCAL AREA AS WE BEGIN THE DAY 4-5 PERIOD. A WEAK PRESSURE PATTERN WILL PERSIST WITH MEDIUM RANGE MODELS INDICATING HIGH RH REMAINING AT THE LOWER LEVELS OF THE ATMOSPHERE. THIS SHOULD KEEP TEMPERATURES FROM CLIMBING OUT OF THE 30S. HOWEVER...WE SHOULD STILL BE ABLE TO MELT A LITTLE SNOW WHICH WILL IN TURN KEEP THE THREAT OF LOW STRATUS AND FOG IN THE FORECAST. WILL NOT INTRODUCE FOG THIS EARLY BUT WILL BUMP UP SKY COVER TO MOSTLY CLOUDY ON SUNDAY...AND ALSO BUMP UP SKY COVER ON MONDAY. MADE ONLY MINOR ADJUSTMENTS TO TEMPERATURES...KEEPING A SMALL DIURNAL RANGE BOTH SUNDAY AND MONDAY. UPPER RIDGING PUSHES INTO THE NORTHERN ROCKIES LATE ON MONDAY BUT THE GFS IS THE ONLY OPERATIONAL MODEL INDICATING A RETURN FLOW OVER THE AREA. ECMWF AND GLOBAL GEM DEPICT THE SURFACE HIGH ALONG THE MONTANA BORDER WITH LIGHT NORTHERLY FLOW OVER THE REGION. MODELS ARE INDICATING SOME LIGHT QPF ON SUNDAY...MAINLY EAST OF THE CWA. THIS IS ASSOCIATED WITH IMPULSES ROTATING AROUND THE LARGE EASTERN U.S. LOW. WILL KEEP MENTION OF PRECIPITATION OUT OF THE FORECAST FOR NOW. LATE IN THE EXTENDED PERIOD...UPPER RIDGING MOVES OVER THE AREA BY MID WEEK WHICH SHOULD BRING WARMER AND DRIER CONDITIONS TO THE LOCAL AREA. THE RIDGE BREAKS DOWN BY LATE IN THE WORK WEEK WHICH COULD BRING ANOTHER PERIOD OF UNSETTLED WEATHER INTO NEXT WEEKEND. && .AVIATION... SURFACE LOW PRESSURE OVER NORTHERN MISSOURI EARLY THIS MORNING WILL LIFT NORTH INTO IOWA TODAY. THIS WILL CONTINUE TO PUMP MOISTURE INTO THE REGION. A WEAK UPPER LEVEL LOW OVER THE EASTERN DAKOTAS...WITH A SHORTWAVE PUSHING WESTWARD ACROSS EASTERN NORTH DAKOTA IS PRODUCING A BAND OF PRECIPITATION THAT IS MOVING INTO CENTRAL NORTH DAKOTA EARLY THIS MORNING. THIS WILL KEEP PRECIPITATION OVER THE CENTRAL THROUGH MIDDAY. DO NOT THINK THIS BAND WILL MAKE IT ALL THE WAY INTO THE FAR WEST TODAY...BUT WILL LIKELY DISSIPATE OVER THE CENTRAL. COULD SEE SOME VFR CLOUDINESS IN THE WEST LATE TODAY AND TONIGHT...BUT EXPECT MVFR-IFR CIGS CENTRAL AND EAST THROUGH 12Z FRIDAY. NORTHERLY SURFACE FLOW IS EXPECTED ACROSS THE AREA TODAY AND TONIGHT. WINDS TODAY WILL BE HIGHER THAN WE HAVE SEEN IN A WHILE...WITH SOME 15 TO 25 KNOT WINDS ACROSS THE SOUTH. && .HYDROLOGY... SOUTHERN AND WESTERN NORTH DAKOTA HAVE RECEIVED PRECIPITATION ON TOP OF AN ALREADY SUBSTANTIAL SNOW PACK AND THERE WILL BE ADDITIONAL ACCUMULATION TODAY...ALTHOUGH IT SHOULD BE LIGHT. HOWEVER...VERY LITTLE OF THIS PRECIPITATION HAS BEEN MOBILE UPON LANDING ON THE GROUND...EVEN WHERE IT HAS LARGELY BEEN IN THE FORM OF RAIN. MANY AREAS ARE STARTING TO REPORT PONDING OF WATER IN LOW LYING AREAS AND THE TOP OF CREEKS AND RIVERS. WATERSHEDS THAT RECEIVE THE MAJORITY OF THEIR PRECIPITATION THIS WEEK IN THE FORM OF SNOW ARE AT SIGNIFICANTLY LOWER RISK OF NEAR TERM OVERLAND FLOODING AS THE SNOW WILL TAKE LONGER TO MELT AND HOLDS ANY RAIN FROM RUNNING OFF. AREAS..THOUGH...THAT RECEIVED SIGNIFICANT AMOUNTS OF LIQUID PRECIPITATION AND LITTLE SNOW SHOULD BE MORE WATCHFUL OF GENERATING RUNOFF THAT COULD QUICKLY BEGIN TO POND AT PLUGGED CULVERTS AND TOP LOCAL ROADWAYS. THE FORECAST TEMPERATURES FOR THE NEXT SEVERAL DAYS CONTINUE TO SUGGEST VERY LITTLE MELTING OF EXISTING SNOW AND THE RECENT RAIN POSES THE HIGHER RISK OF CREATING OVERLAND FLOODING AS IT BREAKS THROUGH THE ABILITY OF SNOW TO RETAIN IT IN THE RURAL AREAS. && .BIS WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL NOON CST /11 AM MST/ TODAY FOR NDZ010-011-018>022-031>035-040>046. && $$ TSW/TWH